The current program for ICF-15 has 90 sessions that are spread across 21 symposia in the Omni Hotel. We have scheduled 13 Plenary and Honor Lectures, over 350 Contributed Presentations, and more than 20 Poster Presentations! Each day of the conference begins with a Plenary/Honor Lecture for all attendees, followed by symposia in parallel sessions and additional content for the day. Please use the overviews of the full-conference and the symposia parallel session schedules shown below to help you plan your visit. To determine when a specific talk is scheduled, use the alphabetized and by symposium lists of all plenary, honor, keynote, contributed, and poster presentations below.
***PROGRAM IN PROGRESS***
Please note that the program and other conference materials are in progress, as we process updates to the schedule. The final set of conference materials, including schedule and other information, is anticipated to be posted here on June 5, 2023. Please return then if you wish to download information for your reference during the conference.
Full Conference Schedule At-A-Glance SCHEDULE AT-A-GLANCE
Symposia Schedule At-A-Glance SYMPOSIA AT-A-GLANCE
List of all Talks and Posters Alphabetized by Presenting Author FULL CONFERENCE- ALPHABETIZED
List of all Talks and Posters Sorted by Symposium FULL CONFERENCE- BY SYMPOSIUM
ICF15 Meeting Rooms at the Omni Hotel ICF15 ROOM MAP
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To access lists of all Plenary, Honor, Keynote, and Contributed Presentations, please use the links above.
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The Conference Schedule shown below is under construction. While the database is complete, the search/sort results are not displaying properly. We will notify participants via email when this problem is fixed.
Sunday Jun 11 2023
10:30 - 18:00 Registration
Conference registration
18:00 - 20:00 Welcome Reception
Welcome Reception for all registered participants and registered accompanying persons
Monday Jun 12 2023
07:00 - 08:00 Registration 1
Registration
08:00 - 08:30 Opening Session
ICF15 Conference Opening Session
08:30 - 10:00 Honor and Plenary Session P1
ICF Opening honor and plenary session P1
08:30 - 09:10
Honor Lecture
ADVANCING MICROSTRUCTURE-SENSITIVE FATIGUE SELECTION AND DESIGN VIA COMPUTATION AND DATA SCIENCE [Honor Lecture]
David McDowellGrand Ballroom E
This work pursues computational micromechanics approaches that define and compute mesoscopic Fatigue Indicator Parameters (FIPs) which serve as surrogate measures of driving forces for fatigue crack formation and microstructurally small crack growth. Attention is focused on constructing the extreme value distributions of FIPs as a function of microstructure to facilitate relative rank-ordering of fatigue resistance of microstructures as a function of thermomechanical process-history for a given alloy composition. Data science correlations are considered as a means to reduce uncertainty associated with model forms and parameters and to accelerate assessment of hot spot FIP distributions used to rank order microstructures. Further extensions in fusing information obtained from such computational strategies with in situ measurements of microstructurally small cracks and AI-enhanced crack detection methods for high cycle fatigue (HCF) are explored.
EXTENDED ABSTRACT
09:15 - 09:55
Plenary Lecture
DEEP LEARNING FROM NATURE AND MACHINES: FRACTURE AND FATIGUE OF ENGINEERED AND BIOLOGICAL MATERIALS [Plenary Lecture]
Subra SureshGrand Ballroom E
This plenary lecture will provide an overview of recent research illustrating how biomimetics, experiments, computational modeling and physics-informed machine learning algorithms synergistically provide unique insights into the deformation, fracture and fatigue characteristics of diverse classes of engineered and biological materials. Specific examples and applications considered here include: fracture and fatigue of compositionally graded nanostructured metals; metallization of diamond by engineering its elastic strain and fracture at nanoscale for applications in microelectronics and energy storage; deformation, failure and fatigue characteristics of human red blood cells with implications for clinical manifestations and human diseases; and design of plant-based materials for self-actuating soft robotics and as substrates for flexible electronics.
EXTENDED ABSTRACT
10:00 - 10:30 Coffee 1A
Coffee Break AM
10:30 - 12:30 Parallel Sessions M1
Parallel sessions symposia M1
10:30 - 12:30 Symp01-M1: Ductile Fracture Under Complex Loading
Organizers: David Wilkinson, Thomas Pardoen, and Amine Benzerga
10:30 - 11:00
Keynote
THE FOURTH SANDIA FRACTURE CHALLENGE - PREDICTING PUNCTURE IN A METAL STRUCTURE [Keynote]
Sharlotte KramerGrand Ballroom A
The fourth Sandia Fracture Challenge (SFC4) investigated the puncture of aluminum structures through comparing various computational predictions to physical experiments. Five teams, internal to Sandia National Laboratories, submitted predictions with mixed success. Qualitatively, many teams were able to predict the deformation and failure modes at the critical velocity for puncture, but the extent of damage was underpredicted by all. Quantitatively, predictions for critical velocity varied widely, though were in the correct order of magnitude. The SFC4 highlighted difficulties in modeling damage and fracture in shear-dominated loading cases.
EXTENDED ABSTRACT
11:00 - 11:20
PREDICTING DUCTILE FRACTURE FOR MIXED MODE OF LOADING USING THE MODIFIED MOHR-COULOMB CRITERION
Diego Felipe Sarzosa BurgosGrand Ballroom A
Reliable and robust fracture prediction tools are necessary for designing and analyzing critical engineering structures. This paper uses a phenomenological damage model to study the fracture response of a pressure vessel steel under complex loading conditions. Details of the experiments and numerical procedures are provided for calibrating and validating the proposed framework for predicting ductile fracture.
EXTENDED ABSTRACT
11:20 - 11:40
MICROMECHANICAL MODELING OF THE COMPETITION BETWEEN TRANSGRANULAR AND INTERGRANULAR DUCTILE FRACTURE
Cédric SénacGrand Ballroom A
In many metallic alloys used in industrial applications, such as precipitation hardened alloys, competition between transgranular and intergranular ductile fracture is observed experimentally. If the latter prevails, material ductility is strongly reduced, which advocates for a comprehensive modeling of this phenomenon. Based on the mechanical homogenization of porous materials, a micromechanical model for intergranular ductile fracture is proposed and used for microstructure-informed investigation of the competition between trangranular and intergranular ductile failure.
EXTENDED ABSTRACT
11:40 - 12:00
COUPLED CRYSTAL PLASTICITY PHASE-FIELD MODEL FOR DUCTILE FRACTURE IN POLYCRYSTALLINE MICROSTRUCTURES
Thirupathi MalothGrand Ballroom A
A wavelet-enriched adaptive hierarchical, coupled crystal plasticity - phase-field finite element model is developed in this work to simulate crack propagation in complex polycrystalline microstructures. The model accommodates initial material anisotropy and crack tension-compression asymmetry through orthogonal decomposition of stored elastic strain energy into tensile and compressive counterparts. The crack evolution is driven by stored elastic and defect energies, resulting from slip and hardening of crystallographic slips systems. A FE model is used to simulate the fracture process in a statistically equivalent representative volume element reconstructed from electron backscattered diffraction scans of experimental microstructures. Multiple numerical simulations with the model exhibits microstructurally sensitive crack propagation characteristics.
EXTENDED ABSTRACT
12:00 - 12:20
A UNIFIED NONLINEAR XFEM-CZM BASED METHODOLOGY TO DEAL WITH DUCTILE FRACTURE
Antonio KaniadakisGrand Ballroom A
The numerical treatment of the whole process of ductile fracture remains a challenging task, particularly when FEM is employed. The main issue regards pathologically mesh dependence of the numerical results, not only in the softening regime but also in the stages of strain localization and further crack propagation. In the literature, non-local approaches are adopted to mitigate these effects but they require a calibrated length scale and mesh refinement, thus being time consuming. This work focuses on the numerical treatment of ductile fracture in metal materials via a three-dimensional unified methodology that combines (i) the GTN model to describe diffuse damage using the standard FEM, the (ii) XFEM to represent the crack and (iii) the coupling of the XFEM with a cohesive zone model to account for the intermediate localization phase. We rely upon the Updated Lagrangian formulation to include large strains and rotations. The methodology, implemented in Abaqus commercial code as a user finite element (UEL), is capable of reproducing numerically the overall response of structures until rupture.
EXTENDED ABSTRACT
14:00 - 14:20
PREDICTING DUCTILE FRACTURE DURING TORSION TESTING USING ELLIPSOIDAL VOID MODEL AND ANALYTICAL MODEL
Kazutake KomoriGrand Ballroom A
Research on ductile fracture under high stress triaxiality has been performed considerably, whereas research on ductile fracture under low stress triaxiality has not been performed sufficiently. In this paper, torsion testing of a bar which is prestrained by drawing is performed using a torsion testing machine, and ductile fracture during torsion testing is predicted using an ellipsoidal void model and an analytical model.
EXTENDED ABSTRACT
10:30 - 12:30 Symp02-M1: JoDean Morrow & Paul Paris Memorial Symposium on Fatigue & Fracture
Organizers: Ashley Spear and Gustavo Castelluccio
10:30 - 11:10
Keynote
MULTIAXIAL FATIGUE BEHAVIOR OF SLM TI6AL4V ALLOY: X-RAY COMPUTED Μ-TOMOGRAPHY ANALYSIS [Keynote]
Carmine MalettaGrand Ballroom B
Crack formation and propagation phenomena in selective laser melting (SLM) Ti-6Al-4V alloy samples were analyzed under combined axial and torsional fatigue loads. In fact, SLM defects lead to a lower fatigue strength and a larger fatigue life variation with respect to to conventionally manufactured parts. Internal defects were captured by X-ray computed μ-tomography (μ-CT) and their evolution was monitored by interrupted fatigue tests. Critical defects were analyzed by the strain intensity factor (SIF) using two differ- ent models based on the Murakami’s method: a modified Smith-Watson and Topper (MSWT) criterion and a virtual strain energy (VSE) criterion. The trend of the crack growth rate was analyzed by the effective defect area at different number of fatigue cycles. The μ-CT data were also used to build finite element models (FEM) of cracked samples to analyze the whole stress-strain distribution in the near crack tip region.
EXTENDED ABSTRACT
11:10 - 11:30
BIAXIAL LOADING IMPACT ON FATIGUE CRACK PROPAGATION IN METALLIC MATERIALS
Rami BouazizGrand Ballroom B
Multiaxial fatigue testing generates curved cracks that are extremely difficult to characterize using standard
compliance based and potential drop-based methods. Therefore, an automated online system was
developed to monitor the crack tips positions in plate cruciform specimens. The system periodically
evaluates the deformation fields at small areas around the crack tips by performing digital image correlation
(DIC) on images obtained by a moving camera triggered at desired phases of the loading cycle. The
displacement field obtained by DIC is fitted by a simple model that specifies the crack propagation direction
and enables it to iteratively find new crack tip positions. Moreover, the model is capable of computing the
crack opening displacements near the crack tip and thus characterizes the local loading. This approach
enables fully automated multiaxial testing with controlled crack length and crack tip loading. The method
was successfully tested on an AA5754 aluminium alloy sheet..Multiaxial fatigue testing generates curved cracks that are extremely difficult to characterize using standard
compliance based and potential drop-based methods. Therefore, an automated online system was
developed to monitor the crack tips positions in plate cruciform specimens. The system periodically
evaluates the deformation fields at small areas around the crack tips by performing digital
EXTENDED ABSTRACT
11:30 - 11:50
BACK TO BASICS FOR THE FATIGUE CRACK GROWTH RATE IN METALLIC ALLOYS
Emiel AmsterdamGrand Ballroom B
The field of fracture mechanics started with Griffith’s energy concept for brittle fracture in 1920. In 1963, Paris et al. used a fracture mechanics’ parameter to introduce an equation for the fatigue crack growth rate in ductile materials and this equation is now commonly known as the ‘Paris law’. However, the Paris law and the semi-empirical models that followed ever since do not fully account for the main intrinsic and extrinsic properties involved with fatigue crack growth in metallic alloys. In contrast, here we introduce a dimensionally correct fatigue crack growth rate equation that is based on the original crack driving force as introduced by Griffith and the presence of plasticity in a metal to withstand crack propagation.
EXTENDED ABSTRACT
11:50 - 12:10
FATIGUE AND DWELL-FATIGUE BEHAVIOR OF A FORGED TI-6AL-4V ALLOY INVESTIGATED BY HIGH-RESOLUTION DIGITAL IMAGE CORRELATION
Fabien BriffodGrand Ballroom B
The present work is dedicated to a comparative analysis of strain accumulation and damage initiation in a forged Ti-6Al-4V alloy subjected to either fatigue or dwell-fatigue condition. To this end, high-resolution digital image correlation analyses were carried out on fatigue specimens interrupted at different number of cycles to clarify the grain-scale strain activity and correlate it with local micro-mechanical features and crack initiation sites.
EXTENDED ABSTRACT
12:10 - 12:30
A DIRECT APPROACH TO FATIGUE CRACK GROWTH UNDER LARGE SCALE PLASTICITY (PRESENTATION IN HONOR OF JODEAN MORROW, UNIVERSITY OF ILLINOIS)
K. S. Ravi ChandranGrand Ballroom B
The major challenge in the mechanics of elastic-plastic fatigue crack growth (FCG) is to find a physically based driving force to correlate the crack growth rates under stress-controlled and strain-controlled conditions. Specifically, a parameter capable of providing a single-valued correlation of crack growth rate, regardless of applied fatigue stress/strain values, is needed. Approaches of the past used either cyclic strain (strain intensity factor) or nonlinear fracture mechanics based (cyclic J-integral, ∆J) parameter, to correlate fatigue crack growth. The latter, however, requires experimental load-deflection curve after every crack length increment and geometry correction factors, which are complex. In the present work, it is shown that a new and physically based approach, based on the cumulative change in the cyclic strain energy of the net-section, is used to successfully correlate fatigue crack growth in a variety of loading elastic-plastic loading situations. The change in the cyclic strain energy is determined analytically from tensile elastic-plastic behavior of material and from the relative sizes of cracked and uncracked sections in the crack plane. Remarkably, excellent correlations of fatigue crack growth data in a variety of specimen geometries and stress/strain levels have been found for both stress- and strain-controlled fatigue conditions.
EXTENDED ABSTRACT
10:30 - 12:30 Symp03-M1: Fracto-emissions in Structural and Seismic Monitoring
Organizers: Alberto Carpinteri and Giuseppe Lacidogna
10:30 - 11:10
Keynote
GYPSUM AND QUARTZ SPECIMENS IN COMPRESSION FAILURE: FRACTO-EMISSIONS AND RELATED STOICHIOMETRIC BALANCES [Keynote]
Alberto CarpinteriGrand Ballroom C
Extensive experimental investigations were conducted on Gypsum and Quartz compression specimens of different sizes. They were brought to complete failure, showing two different failure modalities: (1) Very brittle loading drop for micro-crystalline Gypsum and Quartz; (2) Strain-softening behaviour for macro-crystalline Gypsum. All the tested specimens emitted acoustic and electromagnetic waves and the single events cumulated up to the peak load (Figs.1,2). On the other hand, neutron emissions were evident only for the largest specimens, which are more brittle than the smaller ones [1-4]. The significant chemical composition changes occurred on the fracture surfaces are consistently explainable by the assumption of Low-energy Nuclear Reactions (LENR), both fusion and fission reactions [5-7]. It is the first time that fusion reactions emerge, whereas fission reactions have already explained the results related to other materials like the iron-rich natural rocks [5]. Let us observe that, in the case of macro-crystalline Gypsum, an original correlation seems to appear between mechanical behaviour (strain-softening) and LENR modalities (multi-body fusion reactions).
EXTENDED ABSTRACT
11:10 - 11:30
ACOUSTIC EMISSION AND DAMAGE OF PRE-CYCLED STRUCTURAL STEELS
Ludmila BotvinaGrand Ballroom C
A study of the acoustic characteristics and damage of pre-cycled structural steels F500W, low-carbon steel and 15Cr2MnMoV samples under tension was made. A relationship between the total number of acoustic emission events, the maximum relative damage, and the relative number of preloading cycles, characterized by an exponential relationship has been established.
EXTENDED ABSTRACT
11:30 - 11:50
PERFORMANCE OF 1D-CNN TRAINED WITH AE DATA FOR DAMAGE ESTIMATION IN CONCRETE STRUCTURES
Ninel AlverGrand Ballroom C
In last decades, Acoustic Emission (AE) has gained significant interest as a promising technique for monitoring damage progress in structures. However, the challenging interpretation and time-consuming post-analysis work are the two main problems affecting the performance of the AE method. For this reason, an artificial intelligence-based robust method is considered to be necessary in order to evaluate damage in concrete structures.
In this study, it was aimed to explore the performance of 1D-Convolutional Neural Network (CNN) model to estimate damage using AE signal information from cracking activities. For this, concrete samples having various strength and size under loading were monitored with AE. Afterwards, the model developed by using AE relations and damage information was trained and tested. According to the results, it is seen that 1D-CNN is feasible for damage assessment in structures.
EXTENDED ABSTRACT
11:50 - 12:10
AN ARTIFICIAL INTELLIGENCE-BASED DAMAGE DETECTION MODEL FOR MONITORING REINFORCED CONCRETE STRUCTURES
Ninel AlverGrand Ballroom C
Acoustic emission (AE) has gained much attention in recent years for its effectiveness in non-destructive testing and continuous monitoring of civil infrastructure. As a phenomenon, when structures are loaded, AE sensors mounted on the surface of the structure receive the waves released from the damage and convert it into electrical signals. By analyzing and evaluating these recorded signals, critical information such as type, location, time of origin, size, and orientation of the damage can be identified.
Since the whole process, which includes massive amount of dataset, is time-consuming and needs to be automated, this study aimed to develop an artificial intelligence-based damage detection model that would estimate fracture characteristics of concrete and would be pioneer for application of real-time and automated monitoring of structures, In this scope, failure behavior of concrete samples of various strength and size under loading were monitored with AE. A relationship was established between the load levels and damage status of the specimens with AE features. Afterwards, the model was trained and tested and fracture characteristic results estimated by the artificial intelligence-based model were evaluated to reveal its feasibility.
EXTENDED ABSTRACT
10:30 - 12:30 Symp13-M1: Failure Mechanisms in Advanced Materials and Structures
Organizers: Zengtao Chen, Minghao Zhao, Cunfa Gao, and Stathis E. Theotokoglou
10:30 - 11:10
Keynote
STRONG AND TOUGH FIBROUS HYDROGELS REINFORCED BY MULTISCALE HIERARCHICAL STRUCTURES WITH MULTIMECHANISMS [Keynote]
Huajian GaoDogwood A
Tough natural materials such as nacre, bone, and silk exhibit multiscale hierarchical structures where distinct toughening mechanisms occur at each level of the hierarchy, ranging from molecular uncoiling to microscale fibrillar sliding to macroscale crack deflection. An open question is whether and how the multiscale design motifs of natural materials can be translated to the development of next-generation biomimetic hydrogels. Here, we will discuss a recent work [1] on fabricating strong and tough hydrogel with architected multiscale hierarchical structures using a freeze-casting–assisted solution substitution strategy. The underlying multiscale multimechanisms are attributed to the gel’s hierarchical structures; hydrogen bond–enhanced fibers with nanocrystalline domains; and cross-linked strong polyvinyl alcohol chains with chain-connecting ionic bonds. This study establishes a blueprint of structure-performance mechanisms in tough hierarchically structured hydrogels and can inspire advanced design strategies for other promising hierarchical materials.
EXTENDED ABSTRACT
11:10 - 11:30
MAXWELL STRESS AND ELECTROSTRICTION IN DIELECTRICS AND THEIR IMPLICATIONS FOR FRACTURE MECHANICS
Lennart BehlenDogwood A
In fracture mechanics of smart materials, the influence of electric fields on the propagation of cracks plays a key role. While the piezoelectric effect has been thoroughly investigated in this regard, nonlinear electrodynamic phenomena are oftentimes
disregarded.
As an example, stemming from the microscopic Lorentz force, electrostatic actions manifest themselves macroscopically in terms of surface tractions at discontinuities, body forces caused by graded fields and body couples due to local non-collinearity of electric field and polarization. All three of these manifestations are derived from the Maxwell stress tensor, whose formulation in polarizable matter is still being debated to date [1]. By contrast, electrostriction represents a constitutive effect only inherent to dielectric materials, interlinking mechanical strains with the square of the electric field and polarization, respectively. Due to identical mathematical structures of electrostrictive and Maxwell stresses in isotropic materials, both effects are sometimes treated equivalently.
In this work, these nonlinearities are studied with respect to an elliptic cavity in an infinite dielectric, providing a Griffith crack in the limiting case of a vanishing semi-minor axis. In this context, predominant models of the Maxwell stress tensor are compared and precisely distinguished from electrostriction, ultimately evaluating their individual contributions to crack tip loading.
EXTENDED ABSTRACT
11:30 - 11:50
ENHANCING THE POST-CRACK TENSILE STRAIN CAPACITY OF CEMENT-BASED COMPOSITES USING FIBRILLAR WASTE BYPRODUCTS
Panagiotis DanoglidisDogwood A
The objective of this study is to assess the positive effect of fibrillar waste byproducts, such as biochar, on enhancing the tensile strain capacity and ductile behavior of cementitious composites by evaluating their fracture energy and fracture process zone length through the Work of Fracture Method (WFM). Cementitious mortars enriched using a low amount of biochar of 1 wt% exhibit 100% higher fracture energy over the OPC mortar indicating that the incorporation of the byproduct significantly increases the composite’s ability to absorb strain energy at the post-peak/strain softening area. As indicated by the 1.9x higher characteristic length of fracture process zone, lch, of biochar-mortar, the effective incorporation of the fibrillar byproduct holds a great potential to increase the post-crack tensile strain capacity that leads to a significantly improved ductile behavior of the cementitious composite.
EXTENDED ABSTRACT
11:50 - 12:10
FAILURE MECHANISMS AND STATISTICAL METHOD FOR THE FATIGUE LIFE PREDICTION OF COKE DRUMS
Zihui XiaDogwood A
Coke drums are major production equipment in petroleum refineries. In this presentation, failure mechanisms of the coke drums are analyzed. A statistical fatigue life estimation method is then proposed for the coke drums.
EXTENDED ABSTRACT
10:30 - 12:30 Symp14-M1: Probabilistic Aspects of Fatigue Crack Growth and Fracture: Frameworks, Tools, and Applications
Organizers: R. Craig McClung, James C. Sobotka, and Kai Kadau
10:30 - 10:50
APPLICATIONS OF THE EXTREMELY LOW PROBABILITY OF RUPTURE (XLPR) CODE
Christopher NellisDogwood B
To analyze the integrity of piping components in nuclear power plants (NPPs), the U.S. Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research and the Electric Power Research Institute jointly developed a probabilistic fracture mechanics computer code. The Extremely Low Probability of Rupture (xLPR) code simulates crack initiation and growth from fatigue and stress corrosion cracking (SCC) degradation mechanisms and other aspects of piping component structural integrity. This presentation provides an overview of the NRC staff’s applications of the xLPR code since its public release in 2020 to assist in risk-informed regulatory evaluations of leak-before-break (LBB) analyses for pressurized water reactor piping systems with dissimilar metal welds susceptible to SCC. Potential use of the xLPR code to estimate loss of coolant accident (LOCA) frequencies and to interface with artificial intelligence machine learning (AI/ML) models are also discussed.
EXTENDED ABSTRACT
10:50 - 11:10
XLPR: A PROBABILISTIC CODE FOR FATIGUE AND PWSCC ANALYSIS OF WELD IN NUCLEAR POWER PLANT
Robert KurthDogwood B
The US NRC and EPRI have developed a probabilistic fracture mechanics code through a memorandum of understanding. The code is called xLPR (extremely low probability of rupture) and can be used to evaluate a variety of structural integrity problems dealing with fatigue and primary water stress corrosion cracking (PWSCC) degradation. The code version 2 is now officially released and has been used by both NRC, EPRI and their contractors to perform a series of studies.
EXTENDED ABSTRACT
11:10 - 11:30
FAVPRO: NRC’S 21ST CENTURY REACTOR PRESSURE VESSEL PROBABILISTIC FRACTURE ANALYSIS TOOL
Christopher UlmerDogwood B
Planned and unplanned transients in the operation of a nuclear reactor place stresses on the reactor pressure vessel (RPV) that affect its structural integrity. FAVPRO: Fracture Analysis of Vessels - Probabilistic, is a modern, parallel, object-oriented software tool that can provide high-confidence probabilistic assessments of reactor pressure vessel integrity for any population of flaws and any number of transients, with the goal of risk-informing technical and regulatory decision making. FAVPRO is the successor to the NRC’s FAVOR code with higher solution speeds and new features like automated testing and documentation. The updated tool also includes new embrittlement models and other improvements to align with new fracture mechanics standards.
EXTENDED ABSTRACT
11:30 - 12:00
Keynote
ADAPTIVE MULTIPLE IMPORTANCE SAMPLING FOR STRUCTURAL RISK ASSESSMENT [Keynote]
Harry MillwaterDogwood B
The USAF Airworthiness Bulletin Risk Identification and Acceptance for Airworthiness Determination defines airworthiness in terms of the probability of aircraft loss per flight hour1 with one important component being the aircraft structure. The probability-of-failure of an aircraft component is challenging to compute due to its small size, typically 10-7 or less. As a result, simplified fracture mechanics models are usually used with a small number of random variables. However, these simplifications may lead to an inaccurate probability-of-failure estimate. To address this issue, an adaptive multiple importance sample method was developed that can compute very low probabilities with significant efficiency. This allows one to consider more realistic fracture mechanics models and a larger number of random variables than has been previously possible. The method is adaptive in that it will adjust to the varying relative importance of the random variables for different applications. Convergence is ensured such that the coefficient of variation is below a user-defined threshold. Results to date show efficiency gains of 5 or 6 orders of magnitude over standard Monte Carlo sampling for typical problems of interest. The methodology will be outlined and demonstrated using aircraft example problems.
EXTENDED ABSTRACT
12:00 - 12:20
FRAUCTURE MECHANICS-BASED PROBABLISTIC STRUCTURAL INTEGRITY ASSESSMENT FOR AERO-ENGINE TURBINE DISK
Mauro MadiaDogwood B
Aero-engine turbine disks are safety-relevant components which are operated under high thermal and mechanical stress conditions. The aim of this work is to present part of a fracture mechanics-based probabilistic assessment procedure under development which aims at calculating the critical rotational speed of the turbine disk based on the numerical-analytical solutions and regulations for the failure probability. In particular, the rim-peeling failure mode is considered as case study. A semi-circular surface crack is modelled at the most stressed region at the diaphragm of a turbine disk. In order to design a lab representative specimen, beside the crack driving force, expressed in terms of J-integral, also the constraint to plastic deformation e.g., stress triaxiality, at the crack-tip must be similar for the same crack in the specimen and in the disk. The analytical solutions to calculate the crack driving force for the lab representative specimen are used for the Monte Carlo simulations, the result of which has been assessed in the form of a Failure Assessment Diagram (FAD). The results of the probabilistic structural integrity assessment show good agreement between Monte Carlo simulations and certification values for the disk in terms of expected failure mode and value of the critical speed.
EXTENDED ABSTRACT
10:30 - 12:30 Symp19-M1: Failure Analysis and Prevention
Organizers: Donato Firrao, Erik Mueller, and Pierre Dupont
10:30 - 10:50
FATIGUE FRACTURE ASSESSMENT OF HIGH CARBON STEEL COMPONENTS
Donato FirraoChestnut
Fractographic assessment of fatigue fractures may be difficult if they occur in metallic components characterized by low ductility complex microstructures. In these cases, reconciliation of known fatigue rupture mechanisms with fractographic appearance of fatigue-fractured surfaces is challenging. Special techniques assisted by theory development may be necessary. Fatigue failures in pearlitic steels, such as rail steels, are difficult to analyze and interpret, due to the metallographic microstructure that shows alternate lamellae of ductile ferrite and brittle cementite. Moreover, the task is challenging since their fracture surfaces at room temperature have ductile features, more characteristic of high temperature ruptures. In fact, a brittle to ductile Charpy-V transition curve for rail steels (≈ 0.7% C)indicates that brittle rupture predominates at the lower shelf, which extends up to 40°C ca. Fully ductile upper shelf fracture is reached only at 220°C. Features of their fatigue surfaces are clearly not brittle, but rather ductile, although not fully ductile. Thus, striations, that usually characterize ductile fatigue failures, are not clearly visible because they cannot appear on the brittle carbides, but only on the ductile ferrite lamellae. The examined fatigue fracture surfaces show striations on top of broken, previously necked, ferrite lamellae only at very high magnification.
EXTENDED ABSTRACT
10:50 - 11:10
STATISTICAL FRACTOGRAPHY: THE MISSING LINK BETWEEN FRACTURE MECHANICS AND FAILURE ANALYSIS
Laurent PonsonChestnut
Statistical fractography is a new engineering technique, halfway between data science and failure analysis, that extracts mechanics data encrypted in the fracture surfaces from the statistical analysis of their roughness. Like standard fractographic tools, it provides the failure history (crack direction and initiation, failure mode…) and thus assists traditional expertise. More remarkably, it also measures previously inaccessible data, like (i) the applied mechanical load at failure (stress at initiation, quasi-static and fatigue load amplitude…) as well as (ii) the in-service mechanical properties of the failed material (toughness, failure strength, fatigue resistance…). This information, complementary to the classical metallurgic analysis, are precious to determine the failure root causes, but also for redesigning the failed part. As a result, the technique has now been used for a few years in Europe for determining the root causes of critical in-service failure in the aeronautics, train, automotive and energy sector.
In this presentation, I will show, through use cases, how statistical fractography changes the scope of failure analysis by providing not only the root causes of failure events with unprecedented details but also key information that make failure a keystone for corrective action, (re)design and development of new and more reliable products.
EXTENDED ABSTRACT
11:10 - 11:30
NTSB ACCIDENT INVESTIGATIONS INVOLVING FATIGUE FRACTURES INITIATING FROM SUBSURFACE DEFECTS
Matthew FoxChestnut
The U. S. National Transportation Safety Board has investigated accidents involving fatigue fractures that initiated at subsurface anomalies including (1) a fatigue fracture that initiated from a ceramic inclusion in a turbocharger turbine wheel from a Piper PA-46-350P airplane which contributed to a forced landing, (2) a fatigue fracture of a railcar axle that initiated from a casting void that resulted in a derailment and crude oil explosion, and (3) a fatigue fracture of a high-pressure turbine stage 2 disk on a Boeing 767-300 airplane that initiated from a discrete dirty white spot and resulted in an uncontained engine failure, engine fire, and aborted takeoff. Processes used by the NTSB Materials Laboratory to analyze the fracture mechanisms and characterize the initiating defects will be discussed.
EXTENDED ABSTRACT
11:30 - 11:50
TESTING AND ANALYSIS TO UNDERSTAND AND PREVENT JET FIGHTER MID-FLIGHT ACRYLIC CANOPY FAILURES
Ronald ParringtonChestnut
Polymethylmethacrylate (PMMA) or acrylic transparencies are extensively used for commercial and military aircraft throughout the world. The sudden, mid-flight fractures of acrylic transparencies necessitated the imposition of crippling flight limitations on an entire fleet of jet fighters. This presentation will discuss the failure analysis performed on the jet fighter canopy failures including fractographic analysis, materials testing, stress analysis, and fracture mechanics assessment.
EXTENDED ABSTRACT
10:30 - 12:30 Symp21-M1: Fracture in Polymer-based Materials: Structure-Property Relationships
Organizers: Francesco Baldi, Alicia Salazar, Luca Andena
10:30 - 11:10
Keynote
ROLE OF INTERFACE ON FRACTURE BEHAVIOR OF POLYMER NANOCOMPOSITES [Keynote]
Hung-Jue SueHazelnut
The interfacial region between nanoparticles and polymer matrix can play a significant role in influencing mechanical behavior of polymer nanocomposites. In this research, the fracture behaviors of three sets of model nanocomposite systems with variation in interfacial properties were prepared and investigated. It is found that rigid nanoparticles can serve both as a reinforcing agent and a toughening agent for polymers if the nanoparticle surface is functionalized appropriately.
EXTENDED ABSTRACT
11:10 - 11:30
FRACTURE OF UN-NOTCHED BIAXIALLY COLD ROLLED HIGH DENSITY POLYETHYLENE IN TENSION
Nathan McmullenHazelnut
The fracture surfaces of un-notched tensile specimens prepared from HDPE biaxially rolled at room
temperature and drawn to failure in tension were analyzed using scanning electron microscopy (SEM). The
HDPE sheets were reduced to a thickness of about 80% the initial during the rolling process and the tensile
test was conducted at -40 degrees Celsius and at a strain rate of 100%/min. In comparison to a melt processed sheet of
the same material and thickness, the rolled material exhibited greater work hardening capacity,
homogeneous yield behavior, and improved elongation to failure. The fracture surface manifested in a plane
roughly 45 degrees to the draw direction, and revealed three distinct zones: 1) the damage zone, 2) a fracture
surface associated with slow crack propagation, and 3) a fracture surface associated with rapid crack
propagation. The cross-sectional dimensions of sub-microlayers observed from the fracture surface
suggested that they could have resulted from the affine deformation of spherulitic crystals during the rolling
process.
EXTENDED ABSTRACT
11:30 - 11:50
POLYMERIC MATERIALS TOUGHNESS MEASUREMENT BY STATISTICAL FRACTOGRAPHY
Guillaume De LucaHazelnut
Parts made of polymers play an ever increasing role in many different industries (i.e. aerospace, medical, automobile, etc…), which are attracted by their very interesting material properties. Therefore, there is a need to understand why and how these parts fail to prevent incidents, reduce cost, and move toward a more sustainable approach to the dimensioning of structures made of this type of material. Here, we seek to apply the statistical fractography method to polymers to achieve this goal. This quantitative approach of the field is based on a deep understanding of the non-linear damage mechanisms at play at the crack tip during propagation, and that is expressed through a model used to bridge the measured fracture surface’s roughness and the fracture properties of the material, such as its toughness Kc. We show that our fractographic approach provides reasonable estimate of the fracture toughness, paving the way for the application of statistical fractography to the failure analysis of polymeric parts.
EXTENDED ABSTRACT
11:50 - 12:10
FRACTURE AND FATIGUE OF SELECTIVE LASER SINTERED POLYMERIC LATTICE STRUCTURES
Zoltan MajorHazelnut
Designed cellular lattice structures can be used in many engineering applications. While typically the viscoelastic deformation behavior (stiffness and damping) is utilized in many of these applications, the strength and the fatigue behavior plays an important role for components which are exposed to long-term cyclic loading. Selective laser sintered (SLS) polyamide 12 (PA12) and thermoplastic polyurethane (TPU) materials were investigated in two various lattice structures. A bistable structure based on curved bending beams (BB) and another structure with the combination of bending and torque of the trusses (USF) was designed and produced. To cope with the complexity of the SLS generated structure, three specimen configurations with different printing directions (0° and 90°) were used. To study the bulk behavior cylindrical hollow and notched round-bar specimens, to study the cellular behavior specimens consist of single trusses and knots and specimens contain multiple lattice cells were investigated under both uniaxial and axial/torsional, monotonic and cyclic loading conditions. The monotonic tests provided not only the strength values but relevant material models for subsequent simulations. The cyclic tests were performed at low strains for a comprehensive viscoelastic characterization and at higher strains for fatigue characterization in terms of conventional and strain based S-N curves.
EXTENDED ABSTRACT
12:10 - 12:30
INVESTIGATION OF THE CRACK DEFLECTION/PENETRATION PROBLEM IN EXTRUSION-BASED ADDITIVELY MANUFACTURED POLYMERIC MATERIALS
Christoph WalyHazelnut
Components produced via polymeric additive manufacturing (AM), especially extrusion based methods, possess many weld lines between strands and layers. Thus, the failure of these structures is often dominated either by crack deflection between or crack penetration through individual strands. Two methods to predict the failure mode are those of Cook and Gordan, and of He and Hutchinson. In this work, the applicability of both approaches has been tested on four different polymeric materials. It was observed that the two criteria are quite limited in predicting the correct failure mode. Not only printing temperature also the formation of contact area, the diffusion between the individual strands as well as the resulting morphology of the material were found to play a key role for predicting the crack deflection/penetration problem.
EXTENDED ABSTRACT
12:30 - 14:00 Lunch 1
Lunch Break
14:00 - 16:00 Parallel Sessions M2
Parallel sessions symposia M2
14:00 - 16:00 Symp01-M2: Ductile Fracture Under Complex Loading
Organizers: David Wilkinson, Thomas Pardoen, and Amine Benzerga
14:20 - 14:40
VOID SIZE, SHAPE, AND ORIENTATION EFFECTS UNDER INTENSE SHEARING ACROSS SCALES
Kim Lau NielsenGrand Ballroom A
The present work demonstrates how gradient strengthening at the micron scale affects the macroscopic strain at coalescence under intense shearing conditions. The coalescence mechanism relies on severe flattening, rotation, and elongation of the voids causing severe heterogeneous plastic strain to develop near the voids and in the ligament between voids. These gradients are associated with geometrically necessary dislocations, causing a delay in the coalescence process.
EXTENDED ABSTRACT
14:40 - 15:00
ANALYSES OF DUCTILE FRACTURE USING HUNNY THEORY
Amine BenzergaGrand Ballroom A
We present a theory with a structure that enables analyses of ductile fracture under any type of loading. The theory builds on the standard concept of homogeneous yielding and further proceeds from the concept of unhomogeneous yielding on a (yield) system that depends on the spatial distribution of voids. Depending on the desired level of refinement in analysis, a given simulation employs one or more yield systems with the isotropic limit being reached for an infinite number. We illustrate the predictive capabilities of the theory by considering simulations of three-dimensional crack initiation and growth in a round notched bar, a shear specimen and a compression pin.
EXTENDED ABSTRACT
15:00 - 15:20
1-TO-1 COMPARISON OF SEM-DIC TO CP STRAIN FIELDS OF ULTRATHIN STEEL FILMS TO UNRAVEL PLASTICITY TO DAMAGE INITIATION
Johan HoefnagelsGrand Ballroom A
In advanced high strength steels, crack propagation and fracture is preceeded by damage initiation and propagation, yet, the nature of the plasticity mechanisms leading to damage are debated. To fully unravel the plasticity-to-damage mechanisms, we present a novel integrated experimental-numerical nanomechanical framework for testing ultra-thin specimens, yielding (i) full 3D reconstruction of grain/phase shapes and orientations, (ii) front&rear-sided, high-resolution, microstructure-correlated SEM-DIC strain fields, and (iii) one-to-one comparison to numerical strain fields computed with (advanced) crytal plasticity. Results on martensite ‘bridges’ show that limited plasticity results in martensite damage whereas significant plasticity prevents damage; analysis reveals the key role of ‘substructure boundary sliding’ in martensite on damage initiation.
EXTENDED ABSTRACT
15:20 - 15:40
DEVELOPMENT OF A MICRO-SENT TEST TO DETERMINE TOUGHNESS USING X-RAY SYNCHROTRON TOMOGRAPHY
Yazid MadiGrand Ballroom A
The toughness of a ductile steel (such as API 5L grade X52 vintage) used in the pipeline industry is investigated using a developed micro-SENT specimen. Micro-SENT pre-cracked samples are tested using in-situ X-ray synchrotron-radiation computed tomography (SRCT). The SRCT high resolution technique is used to provide clear images to analyse quantitatively the damage evolution during both crack initiation and crack propagation. Indeed, the crack advance is directly measured during propagation and a J-Δa resistance curve is determined. Finite Element Analysis is also used to analyse the strain fields around the crack tip and to interpret the tomography observations.
EXTENDED ABSTRACT
16:30 - 16:50
INFLUENCE OF LARGE STRAIN REVERSE LOADING ON DYNAMIC STRAIN LOCALIZATION AND FAILURE OF DUCTILE METALLIC RODS
Longhui ZhangGrand Ballroom A
A bespoke real time strain control setup is constructed to apply the reverse loading directly to the gauge section of 304L stainless steel specimen up to a maximum strain level of ±0.16. The subsequent tensile tests of the reverse loaded specimens are performed from quasi-static to high strain rates of 1000 /s. A higher strain reverse loading significantly influences the development of necking instabilities, with smaller strain to necking inception, higher local stress in the necking zone, and higher local strain rate up to failure. An analysis of the local stress-strain relationship indicates that the reverse loaded 304L rod shows good impact energy absorption up to failure, which agrees with the ductile fracture surfaces of the 304L materials with reverse loading.
EXTENDED ABSTRACT
14:00 - 16:00 Symp02-M2: JoDean Morrow & Paul Paris Memorial Symposium on Fatigue & Fracture
Organizers: Ashley Spear and Gustavo Castelluccio
14:00 - 14:40
Keynote
EFFECT OF DYNAMIC EMBRITTLEMENT ON FATIGUE CRACK PROPAGATION MECHANISM AND CRACK GROWTH RATE IN IN718 [Keynote]
Hans-Jürgen ChristGrand Ballroom B
IN718 is a commonly used nickel-base alloy for high temperature applications, e.g., in gas and steam turbines. At elevated temperatures, this and other superalloys are prone to the failure mechanism "dynamic embrittlement". In order to reveal the mechanism of dynamic embrittlement, high-temperature fatigue crack propagation tests were carried out at 650°C applying various dwell times and testing frequencies. Most of the tests were performed in laboratory air, but some experiments were run in vacuum as well, in order to eliminate environmental effects and, hence, to define the reference fatigue crack propagation behavior. Based on the results obtained, a model was developed for the range of test parameters, where intergranular and transgranular areas exist side by side in the fracture surface. This model provides a quantitative mechanismen-related description of the effect of dynamic embrittlement on fatigue crack propagation rate.
EXTENDED ABSTRACT
14:40 - 15:00
FATIGUE CRACK EXTENSION MODE OF 18%NI MARTENSITIC STEEL
Pengxu RenGrand Ballroom B
Martensite is applied as the main structure of high-strength steel to satisfy the demand for lightweight machines. As the fatigue crack extension life takes almost the whole fatigue life, the complex fatigue extension behavior needs to be further studied. This paper is planned to clarify the effect of the hierarchical microstructures and their interfaces on the fatigue extension and the fatigue crack extension mode for the safe and long-lasting use of this material. To achieve the proposal, the rotating bending fatigue tests of 18% Ni martenstic steel was carried out. Fatigue crack behavior and micostrcture near crack path was observed on the specimen surface. The crack extension was found to be discontinuous and was processed by the sub-crack initiation and coalescence with main crack. By the observation of the microstructure around crack path, the observed sub-crack was found to be the inter-granular crack. The proposed reason for the extension process was thought to be the strain localization by the slip along {110} plane and high angle microstructure intrefcae resistance to dislocation motion. Besides, the crack path included inter-granular and trans-granular crack. And the crack extension mode in this material was thought to be damage accumulation mode.
EXTENDED ABSTRACT
15:00 - 15:20
DAMAGE ACCUMULATION MODE FATIGUE CRACK PROPAGATION AND PROPAGATION BEHAVIOR PREDICTION METHOD
Shigeru HamadaGrand Ballroom B
To achieve high-strength steels, their microstructures are complicated. However, with effort, these high-strength steels do not exhibit the fatigue limits expected from their hardness or tensile strength. The low fatigue limit due to inclusions in the steels can be predicted as a fatigue limit problem for metallic materials with small defects. However, the threshold stress intensity factor range of high-strength steel of a long crack is still not as high as expected from the hardness. Currently, there is no clear explanation for this reason. Therefore, the material cannot be used with confidence. The authors propose that this is due to a different crack extension mechanism. In other words, the authors point out the existence of a different mechanism of fatigue crack extension from the generally accepted mechanism of fatigue crack extension due to plastic deformation by alternating slip. Based on the mechanism, the mode of fatigue crack extension is called damage accumulation mode fatigue crack propagation. This name differs from the conventional name focusing on the loading mode, i.e., Modes I, II, and III, and is focused on the extension mechanism. This study discusses a method to predict the fatigue crack propagation behavior.
EXTENDED ABSTRACT
15:20 - 15:40
CRACK TIP ENHANCED CRYSTAL PLASTICITY PHASE FIELD MODEL FOR CRACK PROPAGATION IN TI64 ALLOYS
Kishore Appunhi NairGrand Ballroom B
This work introduces a computational fracture model for Ti64 alloy based on coupled Crystal Plasticity Phase Field model for fracture but also considers the atomistic mechanisms of plasticity at the crack tip. Atomistic simulations are conducted to identify the crack-tip mechanisms of plasticity and the continuum scale phase field model is augmented to account for this. Using the data generated using atomic scale Molecular Dynamic simulations, a functional form describing the evolution of dislocation density nucleating from the crack tip is obtained using Bayesian Inference and Genetic Programming based Symbolic Regression. The effect of nucleated dislocations in crack path and rate of crack propagation is evaluated. The additional plastic strain at the crack tip is also validated with results from Molecular Dynamics.
EXTENDED ABSTRACT
15:40 - 16:00
A GENERALIZED TWO-PARAMETER DRIVING FORCE MODEL FOR SHORT AND LONG FATIGUE CRACK PROPAGATION
Ayhan InceGrand Ballroom B
Numerous different crack growth modeling approaches have been developed to consider the short crack and long crack behaviors by accounting for the stress intensity range-based crack driving forces or the crack closure concept. However, those methods lacked a proper systematic approach to accurately account for the behavior of short cracks. Based on the recent systematic study performed in the authors’ group, a new generalized two-parameter driving force model is proposed to account for crack growth driving forces and corresponding crack growth thresholds to predict both short crack and long crack propagation behaviors. The model predicted crack growth rates are compared with crack growth data set of Ti-6Al-4V titanium and 2024-T3 aluminum alloys. Predicted results show good agreement with experimental crack growth data for these materials.
EXTENDED ABSTRACT
14:00 - 16:00 Symp03-M2: Fracto-emissions in Structural and Seismic Monitoring
Organizers: Alberto Carpinteri and Giuseppe Lacidogna
14:00 - 14:40
Keynote
INTEGRATION OF ELASTIC WAVE VELOCITY INTO BIM OF DAM FACILITY [Keynote]
Tomoki ShiotaniGrand Ballroom C
As for building information modeling (BIM), digital twin of point-clouds of spillway of a rock fill dam is demonstrated. Reproduction of existing structures with point-clouds from still or movie images are shown. Necessary information in addition to the point-clouds such as surface and internal condition of the structure are depicted. Information such as surface deterioration condition as well as internal condition composed of elastic wave velocities, which will be crucially important to realize life-cycle-oriented design, construction, and maintenance, is incorporated into the digital twin. Through the suggested model, overall damage of the spillway is discussed in combination with the pin-point excavations for verification. Through the life cycle of the civil engineering structures roles of elastic wave approaches will be suggestively indicated.
EXTENDED ABSTRACT
14:40 - 15:00
STRUCTURAL HEALTH MONITORING OF FATIGUE BEHAVIOR FOR TI ALLOYS BY DATA ASSIMILATION OF AE
Manabu EnokiGrand Ballroom C
The main purpose of this research is to develop a structural health monitoring method for fatigue behavior of Ti alloys. Experiments were conducted on the effect of microstructure on fatigue behavior at room temperature. Analysis of fracture and deformation behavior using finite element method simulation was also performed. Resutls of AE measurements during fatigue crack initiation and propagation was used to assimilate the mechanical informations using data science methods. For example, a method to directly predict the crack growth rate with variance from the AE measurement results was developed.
EXTENDED ABSTRACT
15:00 - 15:20
ACOUSTIC EMISSION AND ELECTROMAGNETIC MONITORING OF THIN TRC SANDWICH COMPOSITES IN BENDING
Nicolas OspitiaGrand Ballroom C
Textile Reinforced Cementitious (TRC) sandwich composites are innovative materials that combine the loadbearing capacity of TRC facings, with a lightweight core. However, these materials may fail under early interlaminar debonding, substantially reducing the load-bearing capacity of the composite. For this reason, thin TRC sandwich composites are subjected to three-point bending test, and monitored with Acoustic Emission (AE), and millimeter wave (MMW) spectrometry.
EXTENDED ABSTRACT
15:20 - 15:40
APPLICATION OF ACOUSTIC EMISSION TESTING IN ORDER TO UNDERSTAND MODE I FRACTURE PROCESS IN STEEL FIBRE REINFORCED CONCRETE
Vidya Sagar RemalliGrand Ballroom C
This article presents characteristics of acoustic emissions (AE) generated during the mode I fracture process in steel fibre reinforced concrete (SFRC). Three-point bend SFRC specimens were tested in the laboratory by following EN-14651-2005 guidelines. A 2D planar location was adopted to mount the four 57 kHz resonant-type AE sensors on the test specimen to record the generated AE. The number of AE events reduced with the increase in the steel fiber content under the same experimental conditions. The fracture process zone (FPZ) was divided into major damage zone comprised of AE events with (i) high peak amplitude, (ii) low information entropy (iii) longer AE waveform duration. The major damage zone was located ahead of the notch tip very closely. AE testing is a useful testing method to study the fracture process in SFRC.
EXTENDED ABSTRACT
15:40 - 16:00
INVESTIGATION OF THE MECHANICAL PERFORMANCE OF THE UNSATURATED POLYESTER/CENOSPHERE SYNTACTIC FOAMS USING ACOUSTIC EMISSION TECHNIQUE
Vimalathithan Paramsamy KannanGrand Ballroom C
Cenospheres are special class of filler materials, commonly used in preparing lightweight structural
composites. They are hollow and thin-walled microspheres which entraps inert gas inside them. Composite
materials filled with thin-walled microspheres are known for their energy absorption properties and
improved mechanical performances. Such class of materials are known as syntactic foams. In this study,
unsaturated polyester composites are prepared by adding different compositions of cenospheres as fillers.
The influence of cenospheres on the mechanical performance of unsaturated polyester syntactic foams are
investigated. The acoustic emissions due to the failure of the syntactic foams under mechanical loading are
studied. Acoustic emission signals are recorded using a piezoelectric transducer and are analysed in their
time domain, frequency domain, and time-frequency domain. Different acoustic emission features of the
recorded signals are compared with the mechanical test results. The fracture behaviour of the syntactic
foams is, thus, investigated using the acquired acoustic emission signals.
EXTENDED ABSTRACT
14:00 - 16:00 Symp13-M2: Failure Mechanisms in Advanced Materials and Structures
Organizers: Zengtao Chen, Minghao Zhao, Cunfa Gao, and Stathis E. Theotokoglou
14:00 - 14:40
Keynote
NUCLEATION AND GROWTH OF CRACKS IN ELASTOMERS [Keynote]
Krishnaswamy Ravi-ChandarDogwood A
We explore fracture nucleation and propagation within a transparent polydimenthylsiloxane elastomer using the “poker-chip” specimen. Global measurements are correlated with optical visualization at high spatial and adequate temporal resolution to identify the sequence of events; this is augmented with interrupted tests and x-ray computed tomography scans to probe the three dimensional geometry of the nucleation and growth of cracks. The experimental results are used to identify the different types of response, ranging from growth of surface cracks, to interior nucleation and growth of a single crack, to a completely nucleation dominated response. The dependence of the response on the specimen constraint, characterized by the specimen thickness, is explored through simulations within a finite deformation framework; a preliminary criterion for nucleation of cracks under multiaxial loading is proposed.
EXTENDED ABSTRACT
14:40 - 15:00
BRITTLE FAILURE IN HYBRID STEEL-GLASS BEAM-COLUMN JOINT PROTOTYPE. EXPERIMENTAL INVESTIGATION AND NUMERICAL MODELLING.
Mirko PejatovicDogwood A
A small-scale hybrid glass beam-column connection prototype is tested in order to assess its rotational characteristics and post-fracture performance. To simulate fracture process in glass, possibility of using two numerical Finite Element (FE) approaches is explored and the results are compared to the experimental findings focusing on the connections failing in a brittle manner.
EXTENDED ABSTRACT
15:00 - 15:20
A MODE-III CRACK WITH SURFACE EFFECT IN A MAGNETOELECTROELASTIC MEDIUM
Keqiang HuDogwood A
In this paper, the contribution of surface effect to the anti-plane deformation of a magnetoelectroelastic medium weakened by a crack is investigated. The surface magnetoelectroelasticity is incorporated by using the extended surface/interface model of Gurtin and Murdoch. The mixed boundary value problem of the mode-III crack is formulated by using a continuous distribution of screw dislocations and the dislocations of electric potential and magnetic potential on the crack, and the problem is finally reduced to solving a system of coupled Cauchy singular integro-differential equations, which can be numerically solved by the decoupling and collocation methods. The results show that the stresses, eldctric displacements and magnetic induction near the crack tips exhibit the logarithmic singularity when the surface effect is considered. When there is no surface effect on the crack face, the classical square-root singularity of the near crack-tip fields can be observed.
EXTENDED ABSTRACT
15:20 - 15:40
ROLE OF WIRE ASPECT RATIO AND CRACK ASPECT RATIO ON FRACTURE BEHAVIOR OF WIRE SPECIMEN
Apoorv VermaDogwood A
Accurate stress intensity factor (SIF) solutions for cylindrical specimens with different wire aspect ratios and crack aspect ratios are required to determine the fracture toughness of rods and wires. The mode I geometric factor solutions of various crack configurations in a cylindrical fracture specimen in tension have been determined using liner elastic fracture mechanics. Finite element analysis (FEA) is applied to compute this as a function of wire aspect ratio (𝐻/𝐷), crack aspect ratio (𝑎/𝑏), and relative crack depth (𝑎/𝐷). It is found that the geometric factor is independent of wire aspect ratio for shallow cracks but has a major influence for deeper cracks. Also, the geometric factor is higher for concave cracks which facilitates the crack propagation. The mechanistic causes of the same are explained. Fracture toughness measurements on polymethylmethacrylate (PMMA) were carried out for the experimental validation of the solutions. The application of these solutions to fracture toughness measurements at the micro- and nanoscale, particularly in ceramic fibers and high strength metallic wires, is discussed.
EXTENDED ABSTRACT
15:40 - 16:00
MULTISCALE TOUGHENING MECHANISM IN HYBRID FIBER REINFORCED CEMENT-BASED NANOCOMPOSITES
Panagiotis DanoglidisDogwood A
In this study a thorough evaluation of the toughening mechanism in cement-based nanocomposites reinforced with hybrid networks of carbon nanofibers (CNFs) and polypropylene microfibers (PPs) took place. The critical values of fracture toughness/stress intensity factor, KIC, were experimentally determined on prismatic notched specimens of nano and micro scale fiber reinforced cementitious composites using the two parameter fracture model (TPFM). The post-crack energy absorption capacity of the hybrid-composites was assessed by evaluating the dimensionless toughness index, I20, calculated through linear elastic fracture mechanics (LEFM) tests. The addition of CNF/PP networks at low volume fractions of about 0.1 vol% in cementitious matrix results in a significant improvement in the KIC (85-240%) and 1.6 – 10x higher I20 compared to the CNF or PP reinforced materials. Relative to the single-scale fiber reinforcement, the synergy between the nano- and micro- scale fibers results in a multi-scale crack arresting distinctively increasing the toughening effect in the hybrid fiber-cementitious mortar nanocomposites.
EXTENDED ABSTRACT
14:00 - 16:00 Symp14-M2: Probabilistic Aspects of Fatigue Crack Growth and Fracture: Frameworks, Tools, and Applications
Organizers: R. Craig McClung, James C. Sobotka, and Kai Kadau
14:00 - 14:30
Keynote
PROBABILISTIC FRACTURE MECHANICS FOR HEAVY-DUTY GAS TURBINE ROTOR OPERATIONS IN THE ENERGY SECTOR [Keynote]
Christian AmannDogwood B
We present probabilistic fracture mechanics methodologies and applications from an energy industry perspective. Topics include probabilistic fracture mechanics for heavy-duty rotating equipment, including gas turbine rotor disks, probabilistic modeling of forging flaw crack nucleation, modeling of non-destructive inspection capabilities, and probabilistic crack propagation from low-cycle fatigue-initiated cracks. We will present relevant new design and service applications in which reliable risk quantification and minimization are paramount. We will also illustrate how the developed Monte Carlo scheme harnesses the power of high-performance computing, including Graphics Processing Unit (GPU) utilization, to enable a fast computational turn-around time for the millions of individual fatigue crack growth calculations needed to resolve the low-risk requirements.
The presented methods pave the way for a fast and reliable robust risk quantification of power plant components and systems, including probabilistic digital twins, and support power plants' efficient, reliable operation. These methods are essential for the energy transition, including intermittent renewable energy sources such as wind turbines and photovoltaic systems, where the start-up flexibility of gas turbines is a crucial requirement.
EXTENDED ABSTRACT
14:30 - 15:00
Keynote
A SOFTWARE FRAMEWORK FOR PROBABILISTIC FATIGUE CRACK GROWTH ANALYSIS OF METALLIC COMPONENTS [Keynote]
Craig McclungDogwood B
A comprehensive software framework has been developed for probabilistic fatigue crack growth (FCG) analysis of safety-critical metallic components. The framework has been implemented in a computer code called DARWIN® (Design Assessment of Reliability With INspection). DARWIN determines the probability of fracture for a component as a function of operating cycles, with and without inspection, by integrating finite element (FE) geometries, stress, and temperature analysis results; fracture mechanics models; material anomaly data; probability of anomaly detection; and uncertain inspection schedules with a user-friendly graphical user interface (GUI). The framework can accommodate anomalies occurring anywhere in the volume of the component (such as material voids or inclusions) or anomalies occurring only on the surface of the component (such as manufacturing or maintenance damage).
EXTENDED ABSTRACT
15:00 - 15:30
Keynote
PROLOCA 7.1 A PROBABILISTIC FRAMEWORK FOR FATIGUE ANALYSIS OF ALUMINUM AND WELD STEEL STRUCTURES [Keynote]
Robert KurthDogwood B
PROLOCA 7.1 is a probabilistic fracture mechanics (PFM) cods developed for the analysis of damage initiation and growth up to the point of structural failure. The PROLOCA (PRObability of Loss Of Coolant Accident) code was formulated to address nuclear piping and was based on past probabilistic analyses of fatigue in aircraft. These methods were integrated into a code, PROLOCA 2.0 originally developed under NRC contract [1], which was developed for nuclear piping analyses. Since that time, PROLOCA was continually improved under contract to an international team of regulators and operators. In this paper we examine some of the key differences between PROLOCA and other frameworks for fatigue analyses. Examples of the application of PROLOCA to dissimilar metal welds and aircraft damage tolerance are given to demonstrate the extremely low risk of failure with and without inspections and leak detection
EXTENDED ABSTRACT
15:30 - 16:00
Keynote
PROBABILISTIC STRUCTURAL INTEGRITY ASSESSMENT OF WELDED JOINTS [Keynote]
Mauro MadiaDogwood B
The fatigue assessment of welded joints requires several input data, which can be subdivided into three categories: geometry, material and loading. The number of input data depends essentially on the complexity of the models employed and on the level of accuracy of the analysis. It is common practice to use safety factors in design to account for the scatter of the input parameters. Nevertheless, overly-conservative factors lead often to unrealistic estimations of fatigue life. This work presents a fracture mechanics-based model for the structural integrity assessment of welded joints under constant amplitude fatigue loading, in which the local geometry at the weld toe and the fatigue crack growth properties are considered statistically distributed. The approach is validated against a large number of experimental data.
EXTENDED ABSTRACT
14:00 - 16:00 Symp19-M2: Failure Analysis and Prevention
Organizers: Donato Firrao, Erik Mueller, and Pierre Dupont
14:00 - 14:20
STUDY OF NEW GREEN INHIBITOR FOR PROTECTION AGAINST CORROSION IN PIPE STEEL TRANSPORTATION
Hadj Meliani MohammedChestnut
Several inhibitors extracted from medicinal plants were analyzed. The results showed that the green inhibitor based on some plants is the better anti-corrosion product for API X52 and X70 steels in the 1M solution of hydrochloric acid compared to commercial inhibitors used by oil companies in transport and storage. In this new project, we set the following objectives: to provide sufficient convincing scientific evidence to replace synthetic inhibitors that are very expensive and toxic to humans and the environment; to open a new line of research, promising to develop a new family of inexpensive inhibitors from bio-sources, and to offer the new products for protection against corrosion in different branch of industry. This project has a triple result: to fight against corrosion, to valorise the natural resource and to propose an effective product against corrosion at very competitive cost. Creating an enterprise to make the inhibitor is an evident sequel"
EXTENDED ABSTRACT
14:20 - 14:40
INVESTIGATION AND REMEDIATION OF A COMPLEX FAILURE OF A HIGH-STRENGTH STEEL FAN MIDSHAFT FROM A GENX ENGINE
Erik M MuellerChestnut
On July 28, 2012, a Boeing 787-8 airplane experienced a loss of thrust in the right GEnx turbofan engine during a pre-flight, low speed taxi test at Charleston International Airport in Charleston, South Carolina. Inspection of the engine revealed the forward end of the fan midshaft had separated, causing the low-pressure turbine rotor to shift aft, damaging that section of the engine. A detailed investigation performed by the NTSB and General Electric found the fan midshaft on the GEnx engine had separated from an environmentally assisted cracking mechanism under static load. Cracking was predicated by an intricate and previously undetected reaction between the fan midshaft ultra-high strength steel, the dry film lubricant, and the assembly aid. This investigation explored multiple and fundamental aspects of the fan midshaft, including manufacturing, assembly, design, and loading. From the investigation, a non-destructive inspection was developed and employed throughout the fleet with multiple changes to the assembly of the GEnx engine to prevent future reoccurrences.
EXTENDED ABSTRACT
14:40 - 15:00
A NEW ORIGINAL SCHEME FOR PREVENTING NOWADAYS MODERN MACHINE DESIGN FAILURES
Pierre DupontChestnut
Traditional classical design methodologies consider (or do not consider at all) the question of the “delivery” at the latest stages of the overall machine design project. Most of the machine design projects are nowadays highly time-dependent, volatile and uncertain. Due to the nature of the design process itself (Inverse iterative problem with a large number of constraints to be satisfied) a new form of “design failure” occurs : the come up with a given satisfactory design iteration that is not available within the requested delivery time intervals of the overall project.
The current article intends to present a design methodology in 8 steps that organizes the overall machine design process in a way to avoid this problem.
EXTENDED ABSTRACT
15:00 - 15:20
MUZZLELOADER FAILURE ANALYSES
Mohammed Naziru IssahaqChestnut
Muzzleloading rifles (also known as “muzzleloaders”) can be safe and enjoyable firearms for shooting and hunting if handled properly. There are a number of muzzleloader constructs such as inline, flint lock and percussion. These firearms operate on the ignition of black powder propellant or approved substitute charge. There are a number of mechanisms that can be utilized to ignite the powder (e.g. primers, percussion caps, etc.); once the powder is ignited, the pressure builds up rapidly and then decreases as the projectile moves down the barrel and the volume of the gas behind the projectile increases. If circumstances arise that impede the motion of the projectile, such as an obstruction, then a marked over-pressurization event may occur causing ductile fracture of the barrel. Often, the location of the fracture(s) and the deformation of the barrel provide clues as to the type of obstruction. In this study, we investigate several examples of obstructions causing over-pressurization events that led to ductile fracture of the barrels.
EXTENDED ABSTRACT
15:20 - 15:40
ON THE GHISLENGHIEN'S DISASTER, BELGIUM, JULY 2004 : A DRAMATIC PIPELINE'S (S) ... CRA ... (TCH) ... CK ?!
Pierre DupontChestnut
On early morning of July 30, 2004, in GHISLENGHIEN's industrial area, Belgium, a worker of one of the industry field company informs the Fire Department (FD) of a potential gaz-leak problem within the fully new company's building. FD and the Gaz Distribution Company arrive quickly on site for checking any potential leakages ... at 8h56 AM, a large explosion occurs spreading a 120 [m] height fire gerb, visible 15 [km] away, blasting building's debris over 6 [km] all around, leading to shock wave felt 20[km] farer. A large heavy portion (~11 [m], many tons) of 1 of the 2 large scale (DN 800 and DN 1000), 80 bars high pressure natural gaz pipeline bridging the gas terminal of ZEEBRUGGE (100 [km] more in the North) to France has just been blown out nearly 200[m] away ... the intense heat felt up to 2 [km] around subsequent to the explosion makes 23 deaths & 132 injuries (mainly burned at different degrees)... This talk reviews the events and main probable disaster's causes (2nd-most critical accident in Belgium after the 1956's "Le bois du Cazier" (262 deaths). The speech wants also to put in evidence the "human factor" in terms of communication.
EXTENDED ABSTRACT
14:00 - 16:00 Symp21-M2: Fracture in Polymer-based Materials: Structure-Property Relationships
Organizers: Francesco Baldi, Alicia Salazar, Luca Andena
14:00 - 14:20
THERMAL AND VOID VOLUME FRACTION PROFILES IN 3D FOR A DENT SPECIMEN OF NEAT AND GLASS OF SYNTACTIC POLYPROPYLENE MATERIALS
Lucien LaiarinandrasanaHazelnut
Glass of syntactic polypropylene (GsPP) is used for thermal insulation of subsea pipelines. This contribution displays the temperature and deformation fields in 3D on Double Edge Notched Tensile (DENT) specimens, made of both polypropylene (PP) matrix and GsPP. The influence of the microstructural and the thermal changes in the notched section on the load versus crack opening displacement curve is analyzed. The definition of the crack initiation in relation to a critical void volume fraction is discussed
EXTENDED ABSTRACT
14:20 - 14:40
FEM MODELING ON SCRATCH BEHAVIOR OF MICRO-PATTERNED POLYMER SURFACE
Sumit KhatriHazelnut
Polymers are inherently scratch-sensitive due to their low resistance to deformation. Surface patterning is a viable strategy to achieve better scratch performance. In this paper, we model the scratch behavior of micro-patterned surfaces using FEM simulation by employing the powerful coupled Eulerian-Lagrangian approach. The effect of two different pattern types on the scratch behavior of polycarbonate was studied and validated with available experimental results. Results support the use of patterned surfaces in improving scratch performance.
EXTENDED ABSTRACT
14:40 - 15:00
FULL PMMA KINETIC LAW OF FRACTURE: FROM QUASI-STATIC TO DYNAMIC REGIME
Vincent FournierHazelnut
This study uses digital image correlation for the extraction of the stress intensity factor of PMMA in quasi-
static and dynamic regime. The area quantification induced by the cracking of PMMA is a major focus of
this work. Created surface resulting from crack propagation was measured over the entire length of test
pieces. At approximately 0.6 c R , the amount of fracture surface created is higher than twice the projected
fracture surface on the average fracture plane, close to the “mirror” zone. Kinetic laws representing K ID and
G ID according to the crack speed are thus compared with those from the literature by considering dynamical
effects induced by rapid crack propagation. The dynamic fracture energy must be considered as a function
of created surface since the microcrack branching velocity has been reached.
EXTENDED ABSTRACT
15:00 - 15:20
MEASUREMENT AND FE-MODELING OF THE EFFECTS OF STRESS TRIAXIALITY ON THE NECK INITIATION AND FAILURE OF HIGH-DENSITY POLYETHYLENE
Md Shafiqul IslamHazelnut
This study analyses the tensile deformation of neck i.e localization initiation, propagation and failure of injection-moulded polymer composed of high-density polyethylene (HDPE) as a function of initial stress triaxiality. Three different specimen geometries namely i) Simple tension, ii) Plane strain and iii) Shear specimens were punched from injection-moulded HDPE plates and tested experimentally in uniaxial tension to induced different stress triaxialities. Based on the major-minor strain paths from digital image correlation (DIC) measurements stress triaxiality has been calculated. It is challenging to follow the stochastic pattern at larger local strain in DIC and hence the strain at failure has been measured using orthogonal grid lines on the specimen surface. Strains at neck-initiation and failure at three different stress triaxialities for injection-moulded HDPE in two material orientations were implemented in finite lement model. ISIGHT with Abaqus was used for calibration of hardening behaviour, triaxiality dependent neck initiation and failure.
EXTENDED ABSTRACT
15:20 - 15:40
DISK-SHAPED COMPACT TENSION & COMPACT TENSION TESTS ON QUASI-BRITTLE THICK CELLULAR STRUCTURAL ADHESIVE: EXPERIMENTAL AND NUMERICAL ANALYSES
Maxime WettaHazelnut
This paper deals with fracture mechanics analysis to study and understand the effect of density on the crack initiation resistance of a thick cellular structural adhesive. Disk-shaped compact tension and compact tension samples of two different densities have been fractured and analyzed. The crack opening has been stabilized making possible the crack growth resistance curve computation. The behavior of the material has then been shown to be quasi-brittle. A numerical simulation of the tests using finite elements and virtual crack closure technique has been performed to extract the evolution of an equivalent elastic crack length associated to the measurable sample elastic stiffness decrease along the test. The resistance curve has then been estimated by applying the equivalent linear elastic fracture mechanics.
EXTENDED ABSTRACT
15:40 - 16:00
DUCTILE FAILURE OF A PLASTICIZED POLYVINYLCHLORIDE DURING AIR BAG DEPLOYMENT
Cristian OvalleHazelnut
The present work addresses the ductile fracture process of a plasticized Polyvinylchloride (PVC), constituting the skin of the dashboard, with the goal of ensuring the security of passengers for the automotive industry. Clamped single edge notch bending (SENB) specimens were used to characterize the mechanisms of crack initiation and propagation for the studied material. The ductile failure of the plasticized PVC, by using fracture mechanics tools, was characterized thanks to the exploitation of the experimental database associated with finite element simulation of the crack propagation.
EXTENDED ABSTRACT
16:00 - 16:30 Coffee 1B
Coffee Break PM
16:30 - 18:00 Parallel Sessions M3
Parallel sessions symposia M3
16:30 - 18:00 Symp01-M3: Ductile Fracture Under Complex Loading
Organizers: David Wilkinson, Thomas Pardoen, and Amine Benzerga
16:50 - 17:10
ELEVATED TEMPERATURE DYNAMIC DEFORMATION OF AISI 321 AUSTENITIC STAINLESS STEEL
Mostafa ShazlyGrand Ballroom A
In the present work, the dynamic compression behaviour of austenitic steel AISI 321 is obtained at elevated temperatures up to 750 oC using the Split Hopkinson Pressure Bar. The material showed strain rates sensitivity in the range from quasi-static up 6200 s-1. The role of strain-induced martensite transformation on strain-hardening was studied. The % of the strain-induced martensite was found to depend on the test temperature and amount of strain. In the dynamic regime,~ 2800-5000 s-1, the amount of %transformed strain-induced martensite depended only on the test temperature and not the strain rate. This indicated that the strain-induced martensite transformation did not contribute to the drop in the rate of strain hardening at intermediate strain rates of ~2800 s-1 at elevated temperatures and its increase at higher strain rates of 5000 s-1. The Johnson-Cook material model was fitted to the obtained results and model constants were obtained using two different fitting approaches.
EXTENDED ABSTRACT
10:30 - 10:50
A GURSON-TYPE LAYER MODEL FOR DUCTILE POROUS SOLIDS CONTAINING ARBITRARY ELLIPSOIDAL VOIDS WITH ISOTROPIC AND KINEMATIC HARDENING
Francois RoubaudGrand Ballroom A
Extensions of Gurson’s model for porous ductile materials have been done by Madou and Leblond (2012) for general ellipsoidal cavities made of rigid-plastic materials, and Morin et al. (2017), for spherical voids with rigid-hardenable matrices. The aim of this work is to provide a homogenized criterion for porous ductile materials incorporating both void shape effects and isotropic and kinematic hardening. A sequential limit-analysis is performed on an ellipsoidal representative volume made of some rigid-hardenable material, containing a confocal ellipsoidal cavity. The overall plastic dissipation is obtained by using the velocity field proposed by Leblond and Gologanu (2008) and that satisfies conditions of homogeneous strain rate on an arbitrary family of confocal ellipsoids. The heterogeneity of hardening is accounted for by discretizing the cell into a finite number of ellipsoids between each of which the quantities characterizing hardening are considered as homogeneous. The model is finally assessed through comparison of its predictions with the results of micromechanical finite element simulations. The numerical and theoretical overall yield loci are compared for various distributions of isotropic and kinematic pre-hardening with a very good agreement.
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16:30 - 18:00 Symp02-M3: JoDean Morrow & Paul Paris Memorial Symposium on Fatigue & Fracture
Organizers: Ashley Spear and Gustavo Castelluccio
16:30 - 17:00
Keynote
INFRARED TEMPERATURE MEASUREMENT AND X-RAY TOMOGRAPHY FOR INTERNAL FATIGUE CRACK MONITORING DURING ULTRASONIC FATIGUE TESTS [Keynote]
Thierry Palin-LucGrand Ballroom B
The observation of fatigue cracks in the gigacycle fatigue regime is very difficult because they are very often initiating and propagating in the core of the specimens. This paper presents a methodology for detecting and monitoring internal fatigue cracks during ultrasonic fatigue tests. Using both the heat source located in the reverse cyclic plastic zone at the crack tip and the 3D geometry of the crack (from X-Ray tomography), finite element analysis is done to solve the heat transfert problem. This allow us to related the internal crack growth rate and the temperature field evolution versus time at the surface of the specimen. This proposed method has been successfully applied on specimens in cast aluminum alloy.
EXTENDED ABSTRACT
17:00 - 17:20
THERMO-MECHANICAL FATIGUE CRACK GROWTH INVESTIGATION FOR CAST AUSTENITIC STAINLESS STEEL
Zeineb MeskineGrand Ballroom B
This paper describes a complete experimental program and its numerical counterpart to investigate and predict failure analysis (crack initiation and propagation) of a cast 1.4837 heat-resistant austenitic stainless steel commonly used for automotive turbochargers. Fatigue crack growth analysis is the focus of this paper considering both isothermal and anisothermal loading for both experimental and finite element analysis. On this basis fatigue crack growth rate model is derived accounting for complex interaction of large levels of plasticity and subsequent crack closure.
EXTENDED ABSTRACT
17:20 - 17:40
CRYSTAL PLASTICITY MODELING OF FATIGUE CRACK GROWTH IN STAINLESS STEEL
Ting ZhuGrand Ballroom B
Predicting the crack behavior under monotonic and cyclic loading is essential for an accurate assessment of the reliability of engineering structures. This work is concerned with the deformation fields in crack tip grains and their effects on fatigue crack growth rates under cyclic loading. We develop a cyclic crystal plasticity finite element (CPFE) model to characterize the mechanical behavior of 316L stainless steel. The deformation fields in crystal grains near crack tips under monotonic and cyclic loading are studied for two crack tip grain orientations using CPFE simulations. The CPFE results under monotonic loading are consistent with previous theoretical and experimental results. The CPFE results under cyclic loading match those from cyclic J2 plasticity finite element (JPFE) simulations. Based on the accumulated plastic work, cyclic CPFE simulations predict the fatigue crack growth rate as a function of stress intensity factor. The predicted Paris law exponent is consistent with the experimental value. This work demonstrates a new CPFE approach to predict both the deformation field and fatigue crack growth rate in metal alloys. This approach may be further generalized to investigate the time dependent crack growth that can be strongly influenced by the crystallographic effects of crack tip grains.
EXTENDED ABSTRACT
17:40 - 18:00
DEVELOPMENT OF THE NOVEL MIXED MODE ULTRASONIC FATIGUE TEST SYSTEM BASED ON FREQUENCY RESPONSE FUNCTION AND DYNAMIC MODAL ANALYSIS
Longguan JinGrand Ballroom B
In case it is important to characterizze the ultra-high fatigue behaviors of a metal, ultrasonic fatigue tests can be considered due to high test frequences. Moreover, it is quite important to understand the ultra-high fatigue life of metals under multi-axial stress status practically. This research demonstrates how to develop a novel mixed mode ultrasonic fatigue test system based on Frequency Response Function and Dynamics Modal Analysis, and the compatibility of the fatigue system is validated by experiments.
EXTENDED ABSTRACT
16:30 - 18:00 Symp03-M3: Fracto-emissions in Structural and Seismic Monitoring
Organizers: Alberto Carpinteri and Giuseppe Lacidogna
16:30 - 17:10
Keynote
RECENT ADVANCES IN ULTRASOUND MONITORING OF CRACKING AND SELF-HEALING OF CONCRETE [Keynote]
Dimitrios AggelisGrand Ballroom C
Elastic waves have been long used for structural integrity evaluation of concrete materials and structures. Ultrasonic parameters are well related to crack density, deterioration of the elastic modulus, even empirical characterization of the strength. Recently, several ultrasonic studies have emerged also in the field of repair monitoring. Manual repair actions or self-healing strongly contribute to the sealing of the crack, and the regain of the mechanical properties. However, the restoration cannot be evaluated in a non-destructive manner, especially in-situ. Ultrasonic parameters exhibit strong sensitivity to the degree of filling of a single crack or of a distributed system of cracks, while they also have the capacity to monitor the self-healing process, due to the increase of elastic modulus of the healing compounds in the crack volume. The present abstract intends to give an overview of the recent developments in the field of ultrasound as a means of fracture and repair characterization. Through-the-thickness wave transmission, ultrasonic mapping, surface waves as well as air-coupled applications are reviewed as standalone methods or in conjunction with simulations in the framework of an optimal material assessment after fracture and consequent repair.
EXTENDED ABSTRACT
17:10 - 17:40
Keynote
EXPERIMENTAL ANALYSIS BY ACOUSTIC EMISSION ON FULL-SCALE PC DECK BEAMS AFTER 50 YEARS OF SERVICE [Keynote]
Giuseppe LacidognaGrand Ballroom C
The AE technique is highly adopted for the structural integrity assessment of materials as well as large-sized structures (buildings, bridges, etc.) due to its ability to offer information on their stability conditions. This paper presents a loading test on a prestressed concrete (PC) full-scale beam. It was taken from a bridge built in Turin (Italy) in 1970 and dismantled in 2018 for urban redevelopment works. The efficacy of the AE technique for determining the progression of damage is confirmed by the observed relations between the measured strain and the recorded AE activity.
EXTENDED ABSTRACT
16:30 - 18:00 Symp13-M3: Failure Mechanisms in Advanced Materials and Structures
Organizers: Zengtao Chen, Minghao Zhao, Cunfa Gao, and Stathis E. Theotokoglou
16:30 - 17:00
Keynote
THEORETICAL, EXPERIMENTAL AND COMPUTATIONAL STUDY THE OFF-AXIS ELASTIC CONSTANTS, FRACTURE AND STRENGTH OF UNIDIRECTIONAL FIBER COMPOSITE [Keynote]
Efstathios TheotokoglouDogwood A
In this work a theoretical/analytical, computational and experimental study of unidirectional glass-fiber reinforced epoxy composites is carried out. The concept of boundary interphase is used in order to determine the elastic constants of the composite. A finite element analysis is adopted in order to correlate with the derived theoretical values of the elastic constants. Finally, these results are compared with experimental findings obtained from tensile experiments performed on composites of the material used in order to predict the fracture of composites.
EXTENDED ABSTRACT
17:00 - 17:20
USING ANALYTICAL APPROACH FOR CALCULATING LOCALIZED STRESS FIELD NEAR CENTRAL SLIT CRACK IN AMORPHOUS MATERIAL AT ATOMISTIC SCALE
Ashish SinghDogwood A
The localized stress field helps in predicting the crack initiation and its growth in fracture mechanics. At an atomistic scale, a localized stress field has been calculated by virial theorem for anisotropic materials. However, there is still confusion regarding its validation and comparison, as its origin differs from continuum stress. Moreover, finding the localized stress field at the atomic site for amorphous materials are complicated and tedious by the virial approach due to the presence of different elements at disordered positions. Therefore, there is a need to develop a method which does not have there drawbacks. The present work has developed an analytical approach to calculate localized stress fields at an atomistic scale. First, the stress field calculated with this method has been validated in crystalline materials like silicon with virial and finite element (FEM) results. As this method validates linear elasticity near the crack tip. The same localized approach has been used in silica to validate stress field with FEM result. The proposed method in the present work can be used under mixed-mode conditions to study crack initiation and its growth in amorphous solids.
EXTENDED ABSTRACT
17:20 - 17:40
MECHANICS OF INTERACTION OF GROWING CRACK WITH GRAIN BOUNDARY IN BICRYSTAL SOLIDS
Sunil Kumar DuttaDogwood A
Molecular Dynamics (MD) simulations have been carried out to understand the mechanics of crack
interaction with Grain Boundary (GB) under different scenarios. Specifically, different stages of a growing
crack, like crack growth initiation and arrest at GB have been studied. The study was done by evaluating
the Stress Intensity Factor (SIF) using near-tip stress field at each of these stages i.e. crack growth initiation
and arrest at GB. To perform this simulation, an understanding of rotation transformation has been applied
to form an aluminum bi-crystal.
EXTENDED ABSTRACT
17:40 - 18:00
LONG-TERM PERFORMANCE OF POST-INSTALLED CONCRETE SCREWS
Andrea Carolina Oña VeraDogwood A
Concrete screws are a type of anchor used in structural and non-structural applications in uncracked and cracked concrete. The load transfer is based on mechanical interlock between the threads and concrete. Like all anchor products, they undergo rigorous testing during product assessment which at the moment does not cover the sustained load behavior. This investigation aims at studying the sustained-load behaviour of concrete screws by performing a series of tensile tests. Short-term tests were first performed from which the ultimate load capacity of the screws was determined. Long-term tests were then performed at different load levels, selected as a function of the short-term capacity. The time to failure and displacements were recorded throughout each test. The resulting experimental data was used to generate time-to-failure curves and fit the regression models that are currently used for the long-term assessment of chemically bonded anchors. Finally, the predicted long-term capacity for a 50-year lifetime is presented and compared to adhesive anchors.
EXTENDED ABSTRACT
16:30 - 18:00 Symp14-M3: Probabilistic Aspects of Fatigue Crack Growth and Fracture: Frameworks, Tools, and Applications
Organizers: R. Craig McClung, James C. Sobotka, and Kai Kadau
16:30 - 17:00
Keynote
PROBABILISTIC CRITICAL FLAW SIZE ASSESSMENTS IN THE CIRCUMFERENTIAL WELDS OF LAYERED PRESSURE VESSELS [Keynote]
Matthew KirbyDogwood B
The National Aeronautics and Space Administration (NASA) operates approximately 300 aging, carbon steel, layered pressure vessels (LPVs) that were designed and manufactured prior to ASME Boiler and Pressure Vessel (B&PV) code requirements. Fitness-for-service assessments and traditional evaluations of these non-code vessels is a challenge due to unique uncertainties that are not present in code vessels, such as missing construction records and the use of proprietary materials in construction. Furthermore, many of the steels used in these non-code vessels are at a risk of cleavage fracture at low temperatures within the operating temperature ranges of the NASA sites where these vessels are installed. Additionally, the stress state in critical regions of the LPVs, such as the longitudinal seam welds and circumferential welds, is uncertain due to weld residual stresses (WRS), geometric discontinuities, and stress concentrations in weld connections. In order to guide non-destructive evaluation (NDE) and assessment of the circumferential welds and account for uncertainties in these non-code LPVs, probabilistic critical initial flaw size (CIFS) and critical crack size (CCS) analyses were performed for eleven locations of interest within the head-to-shell and shell-to-shell circumferential welds of three demonstration LPVs.
EXTENDED ABSTRACT
17:00 - 17:20
INTERMITTENCY IN FATIGUE CRACK GROWTH AND FATIGUE STRIATIONS
Tero MäkinenDogwood B
The fatigue crack growth rate exhibits apparent self-similarity as it grows as a power of the stress intensity factor (the Paris–Erdogan law). We have studied the fatigue crack growth in two aluminum alloys (Al-1050 and Al-5005) using optical methods and found that the crack tip advances in an intermittent way, characterized by a power-law distribution of crack tip jump sizes. The exponent of the distribution is around two – higher than what is usually observed in avalanching systems – and there is a cutoff that increases with increasing crack velocity. If the generally accepted one-to-one correspondence between the crack tip advancement per cycle and the fatigue striation lines on the fracture surface holds, one should expect a similar distribution for the striation line spacings. We have performed post-mortem fractography using scanning electron microscopy and, by automatically tracking the striation spacings, we indeed see a similar power-law distribution with a cutoff and an exponent around two.
EXTENDED ABSTRACT
17:20 - 17:40
TOWARDS HIGH THROUGHPUT FATIGUE CHARACTERIZATION
Grant WestDogwood B
While the advance of experimental and computer modeling techniques has continued to push mechanistic understanding and predictive modeling capabilities forward, the capability to generate fatigue data has been almost stagnant. Fatigue engineering and research efforts often operate in a data starved modality (considering the highly stochastic nature of fatigue failures). This impedes attempts to effectively use modern machine and statistical learning tools for fatigue performance prediction, both within standard prognosis frameworks, and integrated computational materials engineering (ICME) frameworks.
This presentation will report on our exploration for opportunities to improve the throughput of fatigue testing machines utilizing the expanded design space offered by technological advancement, e.g., computer aided drawing and manufacturing, data acquisition and computer modeling, and robotic automation. Following our review, we will present two concepts for uniaxial high throughput fatigue testing, with the goal of improving fatigue throughput by ~100x while conforming to popular test standards. Our progress towards this goal, and ultimately the prospects for achieving it, will be presented by sharing the results of multiple design-build-test iterations.
EXTENDED ABSTRACT
17:40 - 18:00
A LOADING HISTORY AGNOSTIC FREE ENERGY BASED FRACTURE CRITERION
Alex ArzoumanidisDogwood B
Rather than energy release rate, the proposed framework starts from the energy function itself. Instead of strain energy density, it considers the change in volume-specific free energy density from mechanical deformation. The free energy function must capture strain induced orthotropy, known to be critical for polymers but also important for metals plasticity. To capture strain induced orthotropy, free energy is defined in terms of principal strains and by separating deformation into dilatational and distortional contributions. The separation does not utilize deviatoric strain. Rather, it leverages a new distortional strain definition and the new concept of orthotropic dilataion, enabling clean separation to large strain.
The proposed framework clarifies how a generalized Maxwell model spring-dashpot mechanical analog cleanly interperets the First and Second Laws of Thermodynamics. A transition state theory based nonlinear viscoelastic (NLVE) model is mated to the Maxwell model. Nonlinear Maxwell springs feature an instability in their constitutive law, providing a viscoelastic failure criterion. Embedding the instability into the springs in an NLVE model provides a failure criterion that accommodates complex temperature histories, rate dependence, and self generated heat from cyclic loading.
EXTENDED ABSTRACT
16:30 - 18:00 Symp16-M3: Residual Stress in Fatigue and Fracture
Organizers: Thomas J. Spradlin, Michael R. Hill, Casey E. Gales, and Dale L. Ball
16:30 - 17:00
A TEST METHOD TO MEASURE THE EFFECTS OF RESIDUAL STRESS DURING AN FCG TEST
Mark JamesHickory
Residual stress in material can pose significant challenges during material characterization, especially during fatigue crack growth testing at relatively low values of applied DK, where even modest amounts of residual stress can bias the crack growth rate data. This paper discusses a recent test method that can be used during standard compliance-based fatigue crack growth testing to measure the stress-intensity factor, Kres, caused by the residual stress in a test specimen. This data can then be used to partition residual stress effects from the fatigue crack growth data, a necessary step to understand true material performance before introducing residual stress formally into the structural design process. Positive results have motivated an effort to standardize the method as a non-mandatory appendix in ASTM E647.
EXTENDED ABSTRACT
17:00 - 17:30
ACCOUNTING FOR RESIDUAL STRESS IN FATIGUE CRACK GROWTH RATE TESTS: VALIDATION OF RESIDUAL STRESS INTENSITY FACTOR MEASUREMENTS
Michael HillHickory
Fatigue crack growth rate (FCGR) test data are a key to ensuring structural safety by design and inspection, but residual stress in test specimens can lead to significant (and unknown) bias in FCGR data. In turn, biased FCGR data confound estimates of structural capability for fielded systems. The paper will describe an experimental method for measuring the residual stress intensity factor as a function of crack size, Kres(a), during FCGR tests and provide data for validation. Further test data show that simultaneous measurements of FCGR and Kres(a) enable residual stress bias to be removed from FCGR test data.
EXTENDED ABSTRACT
17:30 - 18:00
RELAXATION OF RESIDUAL STRESS IN WELDED PLATES DURING LONG LIFE FATIGUE LOADING
Casey GalesHickory
The presence of residual stresses affects the fatigue response of welded components. In the present study of a thick welded cantilever specimen, residual stresses were measured in an as-welded A36 steel sample and in a sample subjected to a long history of bending loads where minimal local plasticity is expected at the fatigue hot-spot weld toe. Extensive XRD measurements describe the residual stress state in a large region in front of the weld toe both in an untested as-welded sample and in a sample subjected to a long load history that generated an estimated 0.001 strain amplitude at the stress concentration zone at the weld toe. The results show that such a test will moderately alter the welding induced residual stresses. Fatigue life prediction methods need to be aware that such alterations are possible and incorporate the effects of such cyclic stress relaxation in life computations.
EXTENDED ABSTRACT
16:30 - 18:00 Symp21-M3: Fracture in Polymer-based Materials: Structure-Property Relationships
Organizers: Francesco Baldi, Alicia Salazar, Luca Andena
16:30 - 16:50
No workshops in this session.
18:00 - 19:00 Exhibition
Exhibition
19:00 - 20:00 ICF Executive Committee
ICF Executive Committee Meeting
Tuesday Jun 13 2023
07:00 - 08:30 Registration 2
Registration
08:30 - 10:00 Honor and Plenary Session P2
Plenary session P2
08:30 - 09:10
Plenary Lecture
THE PATH TO HIGH FORMABILITY AND DAMAGE TOLERANCE IN 3RD GENERATION HIGH STRENGTH STEELS [Plenary Lecture]
David WilkinsonGrand Ballroom E
3rd Generation (3G) Steels with strengths well above 1GPa has opened up new opportunities for vehicle lightweighting. For many applications high strength must be coupled with sufficient ductility to withstand impact during a crash or forming operations. For stretch forming applications ductility can be adequately characterized by the tensile elongation. However, for forming operations involving bending or out of plane deformation it is the true ductility, i.e. the true strain at fracture, that represents the critical parameter. For some 3G steels true ductility can be remarkable, with fracture strains up to 0.8. This appears to be due to a combination of factors that provide damage tolerant microstructures in these materials. Two primary mechanisms involve grain refinement and TRIP effects, while the mechanical homogeneity of the phases also plays a significant role. With regard to the latter, Figure 1 illustrates the effect in a DP1300 steel to which V has been added. In the V-modified steel the strength of the martensite has been lowered while the ferrite is stronger. This reduction in micromechanical heterogeneity reduces the strain gradient across M-F interfaces making damage nucleation more difficult. The result is a factor of two increase in true ductility.
EXTENDED ABSTRACT
09:15 - 09:55
Plenary Lecture
HYDROGEN EMBRITTLEMENT IN STEELS AND HIGH ENTROPY ALLOYS [Plenary Lecture]
William CurtinGrand Ballroom E
In spite of considerable experimental study, the mechanisms and understanding of Hydrogen embrittlement in metals remain open. No approaches are able to predict embrittlement conditions in austenitic steels without fitted inputs. New experiments on fcc high entropy alloys, such as CoCrFeMnNi, present an additional paradox, absorbing more H than Ni or austenitic 304 stainless steel (SS304) but being more-resistant to embrittlement. Here, a new theory of embrittlement in fcc metals is presented based on the role of H in driving an intrinsic ductile-to-brittle transition at a sharp crack tip. Hydrogen at the crack tip reduces the decohesion energy and prevents dislocation emission/blunting, and both are needed for embrittlement. The theory quantitatively predicts a critical room-temperature H concentration above which an alloy is embrittled. Using first-principles DFT to compute the relevant alloy properties including H absorption, good agreement with available experiments for the transition concentration is found for the alloys SS304, SS316L, CoCrNi, CoNiV, CoCrFeNi and CoCrFeMnNi. The theory rationalizes why CoNiV is the most-resistant alloy and why SS316L is more resistant than the HEAs CoCrFeNi and CoCrFeMnNi. The theory thus opens a path toward computationally-guided discovery of embrittlement-resistant alloys, although limitations and challenges are discussed.
EXTENDED ABSTRACT
10:00 - 10:30 Coffee 2A
Coffee Break AM
10:30 - 12:30 Parallel Sessions Tu1
Parallel sessions symposia Tu1
10:30 - 12:30 Symp01-Tu1: Ductile Fracture Under Complex Loading
Organizers: David Wilkinson, Thomas Pardoen, and Amine Benzerga
10:50 - 11:10
A NON-LOCAL GURSON MODEL WITH TWO FRACTURE-MECHANISM ASSOCIATED LENGTH SCALES: SUPPORTED BY NUMERICAL ANALYSES AND EXPERIMENTS
Shuyue WangGrand Ballroom A
An extension of Gurson’s porous plasticity model capable of preventing pathological strain localization, and describing crack initiation and propagation under both shearing and tension is investigated. This paper separates the progression of shear failure and flat dimple rupture based on the assumption that these two failure mechanisms are governed by different characteristic length scales, a deviatoric and a dilatational length scale, respectively. A set of numerical analyses is presented which brings out the effects of these length scales on the development of e.g. cup-cone and slant fracture. Guided by the outcome of the numerical study, a set of tests has been designed and carried out for calibration of these length scales.
EXTENDED ABSTRACT
11:10 - 11:30
ASSESSMENT OF EXISTING OFFSHORE GAS TRANSIMISSION PIPELINES IN TERMS OF DUCTILE FRACTURE CONTROL USING A MODELING FRAMEWORK
Reiner TrautmannsbergerGrand Ballroom A
A modeling framework is established to describe running ductile fracture in vintage API grade X52 offshore pipelines. For the structural model, the plasticity and ductile fracture properties were characterized by various laboratory scale tests. Tensile tests up to strain rates of 1000 1/s were performed to calibrate the strain rate dependent plasticity model. Using notched tensile specimens with a wide range of stress states, a hybrid experimental-numerical procedure was performed to determine the parameters of a ductile fracture (FL) model. The material model was successfully verified against the instrumented Battelle Drop-Weight Tear (BDWT) test results. The decompression of the CO2-rich gas mixture was described by the GERG-2008 equation of state and implemented as an idealized pressure decay model to reduce the computational cost. Finally, the established modeling framework provides a valuable tool for investigating and evaluating ductile fracture propagation and arrest behavior in the vintage offshore pipelines.
EXTENDED ABSTRACT
11:30 - 11:50
FLOW AND FRACTURE OF AUSTENITIC STAINLESS STEELS AT CRYOGENIC TEMPERATURES: EXPERIMENTS AND SIMULATIONS
Pilar Fernandez-PisonGrand Ballroom A
Austenitic stainless steels at cryogenic temperatures show an evolving microstructure. In the undeformed state the microstructure is fully austenitic, yet the material straining leads to strain-induced martensite transformation resulting in a biphasic microstructure. In this work, we study the influence of martensitic transformation on the ductile fracture behavior of AISI 304L and AISI 316LN austenitic stainless steels at cryogenic temperatures.
EXTENDED ABSTRACT
11:50 - 12:10
ESTIMATING PLASTICITY AND DUCTILE DAMAGE MODEL PARAMETERS FOR S355-S690 STEEL FROM MILL TEST CERTIFICATE DATA
Wei Jun WongGrand Ballroom A
Accurate finite-element simulation of the fracture of metals requires the calibration of plasticity and fracture modelling parameters based on mechanical tests on the material. Depending on the complexity of the model, each different material that is modelled requires a number of non-standard tests followed by a calibration process. This paper derives relationships between mill test certificate data and the plasticity and damage model parameters for S355-S690 steel in order to enable the quick application of generally representative plasticity and damage models to these steels without the need for repeated manual calibration of each material. The relationships are obtained by regression analysis between a database of 2597 mill test certificate results (of tensile and Charpy tests) and a parametric finite element study in which the parameters of a Hollomon-type stress-strain model and the Modified Mohr-Coulomb damage model were varied.
EXTENDED ABSTRACT
10:30 - 12:30 Symp02-Tu1: JoDean Morrow & Paul Paris Memorial Symposium on Fatigue & Fracture
Organizers: Ashley Spear and Gustavo Castelluccio
10:30 - 11:10
Keynote
CONSTITUTIVE MODELING OF ALLOYS UNDER HIGH TEMPERATURE LOW-CYCLE AND THERMAL- MECHANICAL FATIGUE: A KEY ISSUE IN COMPONENT DESIGN [Keynote]
Fabien SzmytkaGrand Ballroom B
Dissipated plastic energy is a convenient and widely used criterion to assess the life of components experiencing high temperature low-cycle fatigue and thermal-mechanical fatigue. However, component design relies on efficient and accurate constitutive models. Elasto-viscoplastic models are enriched using dislocation density as an internal variable to account for recovery or overaging effects in precipitate strengthened alloys. Examples are shown for components made of cast iron, welded stainless steels and cast aluminum alloys.
EXTENDED ABSTRACT
11:10 - 11:30
FATIGUE ANALYSIS WITHOUT CYCLE COUNTING: SUBCYCLE FATIGUE CRACK GROWTH AND EQUIVALENT INITIAL FLAW SIZE MODEL
Yongming LiuGrand Ballroom B
Threshold and near-threshold fatigue crack growth (FCG) is critical for the total life prediction as majority of time is spent in this regime. The proposed study includes the fatigue crack growth near-threshold in the time-based subcycle model for fatigue life prediction under arbitrary loading conditions. A novel fatigue-life prediction methodology combining a subcycle fatigue crack growth analysis and equivalent initial flaw size (EIFS) concept is proposed. A previously developed time-based subcycle fatigue crack growth model is extended to near threshold regime and under multiaxial loadings. A new temporal kernel function to include intensity factor corresponding to near threshold region is proposed. The multiaxial load scenario is considered for mixed-mode FCG using a critical plane approach. Model predictions under arbitrary are compared with experimental data from open literatures and internal testing. Most of the predicted fatigue life results lie with error factor range of 2, which shows a good prediction for fatigue life.
EXTENDED ABSTRACT
11:30 - 11:50
PROPOSAL OF FATIGUE DESIGN METHOD FOR STRUCTURAL DISCONTINUITES CONSIDERING STRES GRADIENT
Masahiro TakanashiGrand Ballroom B
This paper discusses a method that focuses not only on peak stresses but also on stress gradients to rationalize fatigue design using a low-alloy steels. First, fatigue strength reduction ratios are associated with stress gradients rather than stress concentration factors. Next, to verify the stress gradient method, fatigue tests were conducted on hole-notched specimens. Finally, the fatigue life was predicted, considering the stress gradient at the notch root. The predicted atigue lives agreed well with the experimental results. It was confirmed that the fatigue life can be predicted more accurately than the conventional peak stress method.
EXTENDED ABSTRACT
11:50 - 12:10
EFFECT OF PRE-ACCUMULATED PLASTIC STRAIN ON STRESS CORROSION CRACKING AND FATIGUE LIFE OF STEELS; EXPERIMENT AND MODELING
Amir AbdelmawlaGrand Ballroom B
Steel structures may experience localized plastic strains, arising from wide range of service anomalies. Regions of accumulated plastic strain are more prone to accelerated stress corrosion cracking and reduced fatigue life. In this work, we systematically analyzed the intergranular corrosion (IGC) under combined oscillatory mechanical loading and active electrochemical environment in a specially designed experimental apparatus. Loading cycles were design to mimic both the low amplitude high frequency vibration loads and the low frequency-high amplitude structural duty cycles. Electrochemical potentials were maintained for active dissolution in moderately alkaline carbonate-bicarbonate solutions and under pre-accumulated plastic strain of 0-4%. We observed grain boundary softening, directly arising from vacncies formed by silicon oxidation. Triangular wedges were formed and correlated with the level of the accumulated plastic strains and the load profile. A three-dimensional elasto-plastic continuum damage mechanics model is developed to account for both, the pre-accumulated plastic strain, and the induced elasto-plastic fatigue strains to accelerate the evolution of damage accumulation. Upto 90% of life reduction is observed with 4% of pre-accumulated plastic strain. These findings can be used to advance the understanding of the combined effect of damage and corrosion on the remaining fatigue life of energy materials.
EXTENDED ABSTRACT
10:30 - 12:30 Symp05-Tu1: Hydrogen Embrittlement and Environmentally Assisted Cracking
Organizers: Jesus Toribio, Chris San Marchi, and Joseph Ronevich
10:30 - 10:50
EXPLORING THE PHNOMENOLOGY AND GOVERNING MECHANISMS FOR THE LOADING RATE DEPENDENCE OF ENVIRONMENTALLY ASSISTED CRACKING IN STRUCTURAL ALLOYS
James BurnsGrand Ballroom C
While literature indicates that the applied loading rate (dK/dt) can affect environmentally assisted cracking (EAC) behavior, the quantification of dK/dt dependencies and mechanistic understanding of why the applied dK/dt influences EAC remain limited. In this study, a slow-rising stress intensity (K) framework was utilized to measure EAC kinetics over dK/dt ranging from 0.2 to 20 MPa√m/hr in Beta-C Ti, AA7075-T651, AA5456-H116, Monel K-500, 304L SS, Pyrowear 675, and Custom 465-H900 stainless steel immersed in 0.6 M NaCl at applied potentials known to promote modest EAC susceptibility. Results demonstrate that the crack growth rate (da/dt) exhibits two characteristics regimes of behavior with increasing dK/dt across multiple alloys. In particular, a ‘plateau’ regime where da/dt is independent of dK/dt was observed for elevated dK/dt, while a ‘linear’ regime where da/dt linearly scales with dK/dt was noted for slow dK/dt. These findings are analysied in the context of stress- and strain-controlled failure criteria and the environmentally modified Ritchie-Knott-Rice criteria for crack advance. The implications of these findings on recent testing standardization efforts for HEAC are then discussed.
EXTENDED ABSTRACT
10:50 - 11:10
COMPARISON OF LINEAR-ELASTIC FRACTURE AND ELASTIC-PLASTIC FRACTURE OF FERRITIC STEELS IN GASEOUS HYDROGEN
Chris San MarchiGrand Ballroom C
There is a common misperception that exposure to gaseous hydrogen makes construction steels brittle. Reality, however, is more nuanced. Whereas very high-strength steels can display characteristics of brittle fracture, low- to medium-strength steels remain ductile in gaseous hydrogen. Typical pressure vessel steels (e.g., quench and tempered Cr-Mo and Ni-Cr-Mo steels) and line-pipe steels (e.g., low-carbon steels) remain sufficiently ductile that fracture measurements do not satisfy the requirements of standardized linear elastic fracture mechanics. Generally, for steels with tensile strength 1,000 bar. This presentation reviews the requirements of linear elastic and elastic plastic fracture testing in the context of fracture tests in gaseous hydrogen that have been reported in the literature.
EXTENDED ABSTRACT
11:10 - 11:30
HYDROGEN EMBRITTLEMENT SUSCEPTIBILITY OF L485MB PIPELINE STEEL AND WELD THROUGH TENSILE TESTING WITH DIFFERENT STRESS TRIAXIALITIES
Laura De PueGrand Ballroom C
With the ambition to reuse existing pipelines for hydrogen transport and/or storage, the industry is looking for ways to timely and reliably evaluate pipeline steels and welds for their hydrogen embrittlement sensitivity. A L485MB steel and weld are screened in this work, based on ex-situ tensile testing of hydrogen-charged specimens. Additionally, the effect of notches to generate stress triaxiality in tensile specimens is investigated . The paper reveals differences in the hydrogen embrittlement sensitivity of different materials, at different stress triaxiality levels.
EXTENDED ABSTRACT
11:30 - 11:50
REVISITING THE DISC TEST METHOD FOR THE STUDY OF HYDROGEN EMBRITTLEMENT IN STEEL
Luciano SantanaGrand Ballroom C
The ISO 11114 standard describes the disc test (method A) for selecting materials resistant to hydrogen embrittlement. However, the disc-shaped specimen geometry specified by this standard usually fails in the clamping area, making the test analysis more difficult. This work suggests two new sample geometries to obtain the disc rupture outside the clamping area.
EXTENDED ABSTRACT
11:50 - 12:10
EFFECTS OF TESTING RATE ON HYDROGEN-ASSISTED FRACTURE OF FERRITIC STEELS
Joseph RonevichGrand Ballroom C
Conventional wisdom suggests hydrogen-assisted fracture occurs principally at slow testing rates as hydrogen requires time to diffuse to the region of elevated stress, such as the crack tip. The effects of testing rate were examined on ferritic-based steels by performing fast rate fracture tests in gaseous hydrogen at testing rates spanning four orders of magnitude.
EXTENDED ABSTRACT
10:30 - 12:30 Symp08-Tu1: Beyond Similitude: Role of Multiscale Heterogeneity in Fracture Prognosis
Organizers: Ashley Spear and Gustavo Castelluccio
10:30 - 11:10
Keynote
SIMILITUDE A BASIC CORNERSTONE FOR THE ANALYSES OF CRACK PROPAGATION [Keynote]
Reinhard PippanWalnut
The similitude concept in fracture mechanics is the base for the understanding the size and loading condition dependent or independent crack propagation resistance. In the present overview few selected examples for monotonic and cyclic loading will be presented and underlying mechanisms are discussed.
EXTENDED ABSTRACT
11:10 - 11:30
COMPETITION BETWEEN INTERGRANULAR AND TRANSGRANULAR FAILURE IN ALUMINUM ALLOY: EXPERIMENTS AND CRYSTAL PLASTICITY MODELING
Mark JhonWalnut
Aluminum alloys commonly used in airframe structures have been observed to show orthotropy in fracture when processed through hot rolling or extrusion, while other properties such as yield are more isotropic. Fracture orthotropy is likely due to a competition between damage accumulation within the grains by void growth and cleavage along the grain boundaries. Analysis of the fracture surface indicates varying degrees of dimpled regions (indicating damage by void growth) and quasi-brittle flat regions coinciding with the grain boundary (indicating grain boundary failure). To help determine structure-property relations in such materials, this paper describes a computational model for fracture in ductile polycrystals accounting for both the damage mechanisms. The model is validated by comparing with experiments on a high strength aluminum alloy, AA2139.
EXTENDED ABSTRACT
11:30 - 11:50
USING DEEP LEARNING TO PREDICT MICROSTRUCTURALLY SMALL FATIGUE CRACK GROWTH PARAMETERS IN POLYCRYSTALLINE MATERIALS
Vignesh Babu RaoWalnut
The ability to rapidly predict the growth behavior of microstructurally small cracks (MSCs) has the potential to significantly advance fracture-based designs and structural prognosis. The difficulties associated with characterizing or predicting MSC growth using experimental and numerical techniques preclude the applicability of such techniques in industrial design approaches, despite their potential benefits. Here, we propose a framework to accelerate high-fidelity MSC growth predictions using deep-learning algorithms, viz. , convolutional neural networks (CNNs). The primary research aim is to train CNNs to predict the rules governing MSC growth and to subsequently apply the trained CNNs to make rapid forward predictions of local crack extension given microstructural neighborhood information along a crack front. The training data are acquired from a large number of “virtual” MSC growth observations enabled by high-fidelity finite-element-based simulations. The MSC-growth-simulation framework, data-extraction strategies, and application of deep-learning algorithms for data-driven model development will be presented, and the resulting advantages will be demonstrated.
EXTENDED ABSTRACT
11:50 - 12:10
FORWARD AND INVERSE ANALYSIS OF TENSILE PROPETIES OF DUAL-PHASE STEELS
Takayuki ShiraiwaWalnut
This study proposed a forward analysis method to predict tensile strength and total elongation by considering the three-dimensional microstructure of dual-phase steels. By repeating the forward analysis, an inverse analysis was performed to search for a microstructure with higher tensile properties. The optimal microstructures found by the inverse analysis were consistent with conventional materials engineering findings, demonstrating that the proposed inverse analysis method is effective in solving the structure-properties linkages in the inverse direction.
EXTENDED ABSTRACT
10:30 - 12:30 Symp09-Tu1: Fatigue and Fracture of Additively Manufactured Materials
Organizers: Bo Chen, Nagaraja Iyer, and Filippo Berto
10:30 - 10:50
PREDICTING MICROSTRUCTURE-SENSITIVE FRACTURE BEHAVIOR IN AM IN625 USING A DAMAGE-ENABLED ELASTO-VISCOPLASTIC FFT FRAMEWORK
Ashley SpearGrand Ballroom E
In this work, we use a large-strain elasto-viscoplastic fast Fourier transform (LS-EVPFFT) code enhanced with a continuum damage mechanics model to predict failure response of a subcontinuum mesoscale tensile specimen in the context of the National Institute of Standards and Technology (NIST) 2022 Additive Manufacturing Benchmark (AM-Bench) Challenge. In the Challenge, participants were provided with data from X-ray computed tomography and electron backscattered diffraction (EBSD) for an AM IN625 sample and asked to predict stress and strain response and locations of necking and fracture. To account for uncertainty in the subsurface microstructure, we instantiated 10 semi-synthetic microstructures using a Potts model in a modified version of the open-source software SPPARKS. While all 10 models maintain identical surface grain structure, surface roughness, and internal porosity, their subsurface grain structures vary due to randomness in the microstructure-generation procedure. Results from the blind predictions using the LS-EVPFFT framework are compared to the experimental results. Lessons learned are discussed.
EXTENDED ABSTRACT
10:50 - 11:10
EFFECTS OF PROCESS CONDITIONS AND MICROSTRUCTURE ON THE FATIGUE AND FRACTURE OF AM IN718 UNDER
Alexander CaputoGrand Ballroom E
Additive manufacturing (AM) dramatically increases the design freedom for difficult to machine alloys like IN718. For turbine applications for aerospace and energy, additional freedom in component design allows for lightweighting and better cooling efficiency. This study seeks to elucidate and model the effects of porous and crystallographic microstructural elements on the fatigue life and fracture behavior of AM IN718 through X-ray computed tomography (XCT), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) of specimens tested under high temperature high cycle fatigue.
EXTENDED ABSTRACT
11:10 - 11:30
MICROSTRUCTURE-PROPERTY PREDICTIONS AND MULTISTAGE FATIGUE LIFE PREDICTION OF HOLE RESTORATION COUPONS USING AFSD
Jim LuaGrand Ballroom E
Military aircrafts operate frequently in a highly corrosive environment. Corrosion in aluminum aircraft structures with holes and adhesive-bonded lap joints promotes multi-site cracking, which can lead to failure of major aircraft components. To expedite and facilitate the corrosion repair process, an emerging solid-state process, additive friction stir deposition (i.e. AFSD) is applied for the hole restoration followed by the fatigue performance evaluation. Because of the friction stir induced material flow of the deposited and substrate materials, the resulting microstructure and its associated properties are position-dependent. The weak metallurgical bond at the bottom of the repaired hole coupon can promote a crack initiation under cyclic loading and the total life consists of crack initiation, short crack growth, and long crack propagation. This paper describes the use of a multiphysics modeling approach to characterize the process-driven properties evolution and to evaluate the effects of a kissing bond on the total life of hole restoration coupons.
EXTENDED ABSTRACT
11:30 - 11:50
SHORT CRACK GROWTH BEHAVIOR OF IN718 UNDER HIGH TEMPERATURE CONDITIONS IN CONSIDERATION OF PLASTICITY INDUCED CRACK CLOSURE
Timo BruneGrand Ballroom E
The behavior of short fatigue cracks under high temperature conditions is of significant importance for lifetime predictions and defect assessment of components in aircraft and gas turbine applications. The cyclic R(esistance) curve provides a possibility to describe phenomenologically the crack growth behavior below the long crack threshold. Within this paper experimentally determined cyclic R-curves of the nickel based alloy IN718 for varying load ratios (Rσ = -1, 0 and 0.5) at 650 °C are compared to each other. Furthermore, an approach supporting a mechanism-based understanding of the cyclic R-curves, taking plasticity induced crack closure (PICC) into account, is developed. Finite element analysis is used to estimate the amount of PICC in the short crack regime. For a systematic investigation of the impact of different ductility properties on short crack behavior, results from an additively and two conventionally (cast and wrought) manufactured material variants of IN718 are part of the investigations.
EXTENDED ABSTRACT
11:50 - 12:10
MICROSTRUCTURALLY INFORMED HIGH-VELOCITY IMPACT EXPERIMENTATION ON ADDITIVELY-MANUFACTURED METALLIC MATERIALS
Juan Carlos Nieto-FuentesGrand Ballroom E
This work presents a flexible experimental setup to study dynamic fragmentation of additively-manufactured metallic materials using two different configurations: (i) rapid axial penetration of thin-walled tubes, and (ii) rapid radial expansion of rings. In the first approach, the experiment consists of a light-gas gun that fires a conical nosed cylindrical projectile that impacts axially on a thin-walled cylindrical tube fabricated by 3D printing. The diameter of the cylindrical part of the projectile is approximately twice greater than the inner diameter of the cylindrical target, which is expanded as the projectile moves forward, eventually breaking into fragments. In the second approach, using a similar technique, a ring is inserted over a high-ductility tube, which expands after penetration by the conical projectile, pushing the metallic ring radially outwards, ultimately breaking into multiple fragments. The experiments have been performed for impact velocities ranging from 180 m/s to 390 m/s. A salient feature of this work is that we have characterized by X-ray tomography the porous microstructure of selected specimens before and after testing. Moreover, two high-speed cameras have been used to film the experiments and thus to obtain time-resolved information on the mechanics of formation and propagation of fractures.
EXTENDED ABSTRACT
12:10 - 12:30
CRACK GROWTH-BASED FATIGUE-LIFE PREDICTION OF ADDITIVELY MANUFACTURED MATERIALS
Mohammadbagher MahtabiGrand Ballroom E
In this study, a plasticity-induced crack closure model, FASTRAN, was used to predict the fatigue life of Inconel 718, 17-4 precipitation hardening (PH) stainless steel (SS), and Ti-6Al-4V alloys fabricated via additive manufacturing (AM) systems. Results indicated that in the presence of large defects (e.g., lack-of-fusion defects), the total fatigue life of AM specimens is dominated by crack growth. Results indicated that variations in the fatigue lives of specimens in machined and as-build surface conditions can be predicted based on the characteristics of AM process-induced defects and surface profile. Effect of build orientation on fatigue life was also captured based on the size of defects projected on a plane perpendicular to the loading direction. In addition, maximum valley depth of the surface profile can be used as an appropriate parameter for the fatigue-life prediction of AM specimens in their as‐built surface condition.
EXTENDED ABSTRACT
10:30 - 12:30 Symp11-Tu1: Finite Fracture Mechanics: Theoretical Aspects, Numerical Procedures, and Experimental Applications
Organizers: Vladislav Mantič, Pietro Cornetti, Dominique Leguillon and Pedro Camanho
10:30 - 11:10
Keynote
3D FINITE FRACTURE MECHANICS UNDER MODE I LOADING: THE FLAT ELLIPTICAL CRACK [Keynote]
Pietro CornettiDogwood B
In recent years, the Finite Fracture Mechanics approach, originally proposed by Leguillon in 2002, has been applied successfully to several material and geometrical configurations. However, up to now, most of the applications were restricted to two-dimensional geometries. In the present paper, we provide an insight to a simple yet challenging three-dimensional case, namely the flat elliptical crack. Results are provided in analytical form.
EXTENDED ABSTRACT
11:10 - 11:50
Keynote
ON THE DIFFICULTY OF IMPLEMENTING THE COUPLED CRITERION TO PREDICT GLASS FRACTURE [Keynote]
Dominique LeguillonDogwood B
Glass is an extremely brittle material that behaves almost perfectly linear elastic until it fractures. The linear-elastic fracture mechanics (LEFM) approach described by Griffith’s energy criterion is typically used to explain failure from a pre-existing crack like defect. However, LEFM reaches its limits in explaining failure processes at general stress concentration points and implementing the Coupled Criterion (CC) to take over is a tricky task. This mainly because it requires the knowledge of the tensile strength of the material which is a parameter not easy to characterize in glass. It is in general defined through a statistical law and relies strongly with surface flaws. The general aim of this work is to give an overview of the current understanding of glass tensile strength.
EXTENDED ABSTRACT
11:50 - 12:10
MODELING OF GLASS MATRIX COMPOSITES BY THE COUPLED CRITERION AND THE MATCHED ASYMPTOTICS APPROACH. THE ROLE OF A SINGLE PLATELET.
Sara Jiménez AlfaroDogwood B
The fracture toughness of glass can be increased by introducing a second constituent with high modulus, strength and/or ductility. Among others, a very attractive solution for industrial proposes is the borosilicate glass/Al2O3 platelet composite. Hence, in this work different toughening mechanisms in this composite are analysed from the point of view of the Coupled Criterion, together with the Matched Asymptotics approach.
EXTENDED ABSTRACT
12:10 - 12:30
ON-LINE TOOL FOR ANALYSIS OF SINGULAR STRESSES AND DISPLACEMENTS IN ANISOTROPIC MULTI-MATERIAL CORNERS
María De Los Ángeles Herrera GarridoDogwood B
A Python code based on a semianalytic procedure for the analysis of singular stress and displacement fields in anisotropic multi-material corners in generalized plane strain is developed. Open and closed (periodic) multi-material corners formed by isotropic, transversely isotropic or anisotropic materials with perfectly bonded interfaces or in frictionless or frictional sliding contact are considered. Many kinds of boundary conditions as free, clamped, displacement allowed or not in any given direction, and frictionless or frictional sliding contact are covered. This computational tool may help researchers who need to know the singularity exponents and the singular eigenfunctions for stresses and displacements for a corner, e.g., to improve or check their numerical results by FEM, or to verify their analytic formulas of eigenequations developed for specific stress singularity problems. With the aim of sharing this useful tool, it has been made available on research group website, where the user can introduce the corner problem parameters and the corner singularity problem is solved by a high-performance computing server.
EXTENDED ABSTRACT
10:30 - 12:30 Symp13-Tu1: Failure Mechanisms in Advanced Materials and Structures
Organizers: Zengtao Chen, Minghao Zhao, Cunfa Gao, and Stathis E. Theotokoglou
10:30 - 11:10
Keynote
NON-FOURIER HEAT CONDUCTION AND NONLOCAL THEORY, RECENT PROGRESS AND APPLICATION IN THERMAL FRACTURE ANALYSIS [Keynote]
Zengtao ChenDogwood A
Non-Fourier heat conduction theories have recently been introduced to thermal stress analysis to account for the wave-like behavior of heat conduction under extreme thermal environments, such as high temperature gradient, extremely low temperature, or heat transport in heterogenous microstructures. When considering the highly localized heating process in laser manufacturing, nonlocal heat conduction needs to be included in the heat conduction equation. Combined non-Fourier, nonlocal thermoelastic theories revealed new phenomena in thermal stress analysis of cracked structures. This presentation summarizes some recent progress in thermal fracture analysis using nonlocal, non-Fourier thermoelastic theories.
EXTENDED ABSTRACT
11:10 - 11:30
USING A HIERARCHY OF POROSITY TO IMPROVE THE FRACTURE TOUGHNESS OF METAMATERIALS
Kaitlynn FitzgeraldDogwood A
Mechanical metamaterials have been quickly growing in popularity based on their lightweight, multifunctional properties. One of the factors limiting their widespread adoption in weight baring applications, however, is their poor fracture toughness compared to bulk materials. Arrestor planes have been added to gyroid surface metamaterials and solid beams to manipulate the path of a propagating crack and improve the fracture toughness. The arrestor planes used a hierarchy of porosity interacting with the features inherent in the gyroid topology to direct propagating cracks into natural features that served to arrest the crack. This methodology was tested in both brittle polymer and stainless steel with toughening ranging from 22% to 300% depending on material.
EXTENDED ABSTRACT
11:30 - 11:50
THE IMPACT OF MULTIAXIALITY ON THE STATIC AND FATIGUE FRACTURE OF CARBON/EPOXY POLYMER COMPOSITES
Kalliopi-Artemi KalteremidouDogwood A
Polymer composites can be used in a plethora of applications, creating lightweight and durable structures. Their anisotropy together with the complexity of the laminate structure can lead to multiaxial stress states within the material, which can significantly affect the fracture process. In this work, carbon/epoxy laminates with different stacking sequences, and consequently different stress states, are tested under static and fatigue conditions. It is demonstrated that multiaxiality plays a crucial role in the fracture process and that shear stresses create severe damage conditions within the material.
EXTENDED ABSTRACT
10:30 - 12:30 Symp16-Tu1: Residual Stress in Fatigue and Fracture
Organizers: Thomas J. Spradlin, Michael R. Hill, Casey E. Gales, and Dale L. Ball
10:30 - 11:00
UNCERTAINTY QUANTIFICATION IN RESIDUAL STRESS AFFECTED FATIGUE CRACK GROWTH LIFE
Dale BallHickory
In recent years a number of studies have been performed in which the impact of residual stress on structural performance, especially fatigue performance, has been evaluated both experimentally and analytically. These efforts are leading to an emerging paradigm in which residual stresses are represented explicitly in structural design, analysis, manufacturing and sustainment calculations. In order for this new approach to be become minimally viable, it is necessary to be able to quantify both the residual stresses in the structural component in question, and the impact that those residual stresses have on component strength and life. However, to achieve general acceptance, especially for critical applications in which the presence of the residual stress directly impacts whether or not the component will meet its design requirements, deterministic quantification alone may not be sufficient; it may be necessary to quantify the uncertainties in both the residual stresses and the resulting fatigue lives.
EXTENDED ABSTRACT
11:00 - 11:30
CHARACTERIZING THE PHYSICS OF TAPER-LOK FASTENER HOLES TO SUPPORT B-1 SUSTAINMENT
Robert PilarczykHickory
Taper-Lok fasteners provide great benefit to fatigue performance but create a complex scenario for analysis to fully account for its effects. The interference due to the oversized tapered fastener introduces tensile hoop stress around the hole and compressive radial stress that combine with applied loading to effectively reduce stress amplitude and improve fatigue performance. The combination of the stress due to interference, applied stress, and the likelihood of plastic deformation near the hole results in a complicated scenario for damage tolerance analysis. The objective of this work was to develop an analytical approach to support explicit incorporation of the physics of a Taper-Lok fastener installation for B-1 critical locations. The work included experimental measurements and finite element predictions of residual stress utilizing manufactured coupons and aircraft excised structure. A comprehensive fatigue crack growth test program was conducted to obtain validation data using coupons representative of wing rear spar and wing carry-through lower cover control points. The analytical approach and validation data developed in this work are discussed in detail.
EXTENDED ABSTRACT
11:30 - 12:00
RESIDUAL STRESS RELAXATION IN INCONEL718 COLD EXPANDED HOLE UNDER LOADING AT ELEVATED TEMPERATURE
Moad FatmiHickory
The cold expansion process is widely used in industry in order to introduce compressive residual stresses around fastener holes, up to 2 mm beneath the surface. These compressive residual stresses are beneficial since they will prevent crack initiation from the surface and decrease subsequent crack growth rates. However, residual stress relaxation may occur due to the thermomechanical loading of the area. This study aims to investigate residual stress relaxation under thermo-mecanical cyclic loads.
EXTENDED ABSTRACT
12:00 - 12:25
FATIGUE LIMIT PREDICTION OF AISI4140 STEEL WITH COMPRESSIVE RESIDUAL STRESS CONSIDERING THE LOCAL YIELDING OF COMPRESSIVE RESIDUAL STRESS LAYER
Motoaki HayamaHickory
The effect of compressive residual stress on the fatigue limit was investigated using fatigue tests on specimens with and without compressive residual stress. The results demonstrated that the fatigue limit of AISI4140 steel with compressive residual stress can be predicted using the fatigue limit diagram, considering the local yielding of the compressive residual stress layer.
EXTENDED ABSTRACT
10:30 - 12:30 Symp21-Tu1: Fracture in Polymer-based Materials: Structure-Property Relationships
Organizers: Francesco Baldi, Alicia Salazar, Luca Andena
10:30 - 10:50
THE IMPACT OF CURING TIME AND MOLD TEMPERATURE ON THE FATIGUE BEHAVIOR OF NITRILE BUTADIENE RUBBER
Tobias GehlingHazelnut
To complement the present research results in the field of fatigue and fracture in elastomers, an analysis of the influence of curing time and mold temperature on the fatigue properties of a carbon black-filled industrial NBR compound was carried out. There was a significant difference in the crack growth rate with respect to the different manufacturing conditions.
EXTENDED ABSTRACT
10:50 - 11:10
ENVIRONMENTAL STRESS CRACKING RESISTANCE (ESCR) OF RECYCLED PP (RPP) FROM AND FOR YOGURT CUPS
Paul FreudenthalerHazelnut
Recycling of plastic packaging waste is a promising approach towards a circular economy due to the high amount used and the short application time. This paper uses the concept of environmental stress cracking resistance (ESCR) to investigate the fatigue behavior of recycled yogurt cup materials. As test environments air and oil where chosen, where the latter imitates the fatty structure of yogurt. Therefore, four fractions of manually sorted post-consumer polypropylene yogurt cup waste was shredded to flakes and washed with different temperatures and media. Additionally, one of these fractions was blended with varying amounts of virgin pipe material. Furthermore, the reference material, which is currently used for yogurt cups was tested for comparison. Various influences of the fatigue tests were detected, which are a more pronounced influence of oil than of air, especially for recyclates but also for virgin materials and a significant improvement of the recyclates which were blended with a pipe grade material.
EXTENDED ABSTRACT
11:10 - 11:30
STRUCTURAL STUDY OF AP-HTPB COMPOSITE UNDER IMPACT LOADING
Mahavir SinghHazelnut
The impact response of a composite material is dependent on its microstructure. This study examines the effect of particle size and impact velocity on the temperature rise and strain rate in a composite material containing Ammonium Perchlorate (AP) crystals and Hydroxyl-terminated polybutadiene (HTPB) binder by combining computational and experimental work. Samples of AP-HTPB composite, with AP crystal sizes of 200 and 400 μm, respectively, are impacted at velocities ranging between 5-10 m/s. A volume fraction of 70-80% AP is maintained in each sample.
EXTENDED ABSTRACT
11:30 - 11:50
SEAWATER DEGRADATION IN POLYMER-BASED COMPOSITE SANDWICH STRUCTURES.
Norman Osa-UwagboeHazelnut
Thanks to their advantageous low weight-to-strength factor, fiber-reinforced plastic (FRP) sandwich structures have increasingly been used for various marine applications such as boats and underwater vessels. This paper focuses on experimental analysis of the effect of seawater degradation on flexural and tensile performances of glass- and carbon-fiber-reinforced sandwich panels.
EXTENDED ABSTRACT
11:50 - 12:10
INFLUENCE OF AGEING ON THE STRUCTURAL INTEGRITY OF CARBOXYL-TERMINATED POLYBATUDIENE SOLID ROCKET PROPELLANT
Alicia SalazarHazelnut
The operability of a composite solid propellant is compromised by the presence of cracks, with origin in natural or mechanical ageings. These cracks may cause uneven burning of the propellant leading to a malfunction of the motor or in the worst scenario an overpressure burst. The propellants are characterised by an heterogeneous microstructure, due to many distinct components with very complex and different mechanical performance. Nevertheless, the mechanical behaviour of these propellants is mainly controlled by the elastomeric matrix, the properties of which exhibit a strong time dependence. Therefore, this paper uses Viscoelastic Fracture Mechanics analysis to establish the influence of the mechanical and oxidative ageings on the structural integrity of a booster composite solid propellant, based on a carboxyl-terminated polybutadiene binder reinforced with ammonium perchlorate oxidizer particles.
EXTENDED ABSTRACT
12:10 - 12:30
IN-SITU EXPERIMENTAL INVESTIGATION OF FATIGUE CRACK PROPAGATION MECHANISMS IN POLYMER ELECTROLYTE MEMBRANE OF FUEL CELL UNDER OVERLOADING EFFECT
Wei LiHazelnut
The fatigue crack growth mechanisms in polymer electrolyte membranes of fuel cell are investigated under single overload conditions. In-situ SEM testing and in-situ optical microscopy testing combined with digital image correlation technique are conducted. The results show that the residual stress dominates the fatigue crack growth after the application of small overload cycle leading to subsequent fatigue crack growth retardation while larger overload cycle causes crack tip sharpening, resulting in fatigue crack growth retardation reduction or even acceleration.
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12:30 - 14:00 Lunch 2
Lunch Break
14:00 - 16:00 Parallel Sessions Tu2
Parallel sessions symposia Tu2
14:00 - 16:00 Symp01-Tu2: Ductile Fracture Under Complex Loading
Organizers: David Wilkinson, Thomas Pardoen, and Amine Benzerga
14:00 - 14:20
EFFECT OF HPT PROCESSING ON FRACTURE BEHAVIOUR OF MARAGING STEELS
Kevin JacobGrand Ballroom A
Maraging steels are a class of precipitation hardened steels wherein different micro-mechanisms of deformation such as planar slip, interaction with coherent/incoherent precipitates, and reverted austenite affecct the overall mechanical behavior of the material. High-pressure-torsion (HPT) processing introduces a large density of dislocations that form sub-grain boundaries within the refined nano-scale structure, leading to changes in precipitate morphology compared to hot-rolled maraging steels. The impact of such nanostructuring on the deformation and fracture micro-mechanisms is being reported for the first time using in-situ characterization techniques along with transmission electron microscopy and atom probe tomography analysis, in this study. Digital image correlation has been used to quantify the full field strain maps in regions of severe strain localization as well as to determine the fracture toughness through critical crack tip opening displacements.
EXTENDED ABSTRACT
14:20 - 14:40
DUCTILE FRACTURE OF SS-304L MICROTUBE UNDER COMBINED AXIAL FORCE AND INTERNAL PRESSURE
Yannis KorkolisGrand Ballroom A
The fracture behavior of the stainless-steel SS-304L is assessed by loading microtubes of 2.38 mm diameter under combined axial force and internal pressure, using a custom apparatus. The force/pressure ratio is controlled in the experiments, to generate different biaxial stress paths that are proportional or nearly proportional. The results from the experiments are used to calibrate the non-quadratic anisotropic yield function Yld2004-3D. Then, finite element (FE) models of the microtubes are created after incorporating the anisotropic material modeling framework, and compared with the experiments to establish their fidelity. The FE models are then used to probe the fracture behavior under the proportional loading. The failure modes of the microtubes are different depending on the stress state being axial- or hoop-stress-dominant. It is found that the structural instabilities that precede necking are different and appear at different levels of strain. The strains at the onset of fracture, as determined by probing the FE model, reveal significant fracture anisotropy, that can be possibly also attributed to the specimen geometry, beyond the material processing.
EXTENDED ABSTRACT
14:40 - 15:00
MODELING OF THE ELASTO-PLASTIC BEHAVIOR OF HSLA X140 STEEL: EFFECT OF PRE-STRAIN AND TRIAXIALITY
Asmae ElochiGrand Ballroom A
In this work, a comprehensive experimental campaign is conducted to investigate the effect of pre-strain on the mechanical properties of X140 steel used in high performance threaded connections. Mechanical tests are used to characterize the plastic and fracture behavior of the material. Smooth tensile (ST), notched tensile (NT), plane strain (PE) and shear tests (STC) were performed. Cyclic tension-compression tests are used to characterize kinematic hardening. Initially qualified as isotropic, this material showed an anisotropic behavior after undergoing a pre-strain expansion as its plastic flow becomes loading direction dependent. This pre-strain effect is well reproduced using a phenomenological modeling combining isotropic and kinematic hardening contributions with a Hosford’s criterion.
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15:00 - 15:20
MICRO-STRUCTURAL DAMAGE ANALYSIS FOR PREDICTING THE EFFECT OF LOADING PATH ON DUCTILITY OF TWO-PHASE STEELS
Hiroto ShojiGrand Ballroom A
The purpose of this study is to predict the effect of loading path on ductility of two-phase steels based on micro-structural damage analyses. A micro-structural damage model that consists of 3D micro-structural FE-model and ductile damage model is proposed. Isotropic / kinematic hardening model is introduced for considering the mechanical behavior of Bauschinger effect. The effective damage concept for considering micro-scopic behavior of Bauschinger effect which is dislocation behavior in loading path change is introduced into the damage model. Two types of ferrite-pearlite two-phase steels with different volume fraction of pearlite, and ferrite and pearlite single-phase steels are used. Tensile tests using micro-tensile specimen extracted orthogonal to pre-strained direction from tensile pre-strained round-bar specimens are conducted. Ductility is increased due to loading path change, and the effect is greater in the case of higher volume fraction of pearlite. The mechanism of the effect is analyzed by numerical simulation based on the proposed micro-structural damage model. It is presented that the improvement of ductility by loading path change is caused by micro-structural heterogeneity, delay of necking due to mechanical behavior of Bauschinger effect, and non-effective plastic strain for damage evolution due to micro-scopic behavior of Bauschinger effect.
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15:20 - 15:40
STRAIN EVOLUTION AND DAMAGE DEVELOPMENT DURING TIGHT-RADIUS BENDING OF ADVANCED HIGH STRENGTH STEELS
Nizia Mendes-FonsecaGrand Ballroom A
Improved vehicle fuel efficiency and driving safety requirements have promoted the development of Advanced High Strength Steels (AHSS) in the last few decades. The mechanical performance of AHSS is commonly characterized by the product of the ultimate tensile stress and total elongation. However, tensile elongation is not suitable for predicting the performance of a material under complex forming operations. This work aims to investigate the effect of the steel microstructure on bending performance and to make a parallel between strain partitioning and damage nucleation in tension and bending.
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15:40 - 16:00
THE INFLUENCE OF TRANSFORMATION INDUCED PLASTICITY IN THIRD-GENERATION ADVANCED HIGH STRENGTH STEELS
Concetta PelligraGrand Ballroom A
Considerable research has been invested in developing thin sheet Advanced High Strength Steels (AHSSs) and to metastabilize phases at ambient temperatures; however, little has been done to determine the extent to which the transformation from austenite to martensite (TRIP), can suppress/delay damage. The damage processes that lead to fracture in AHSSs are complex and understanding them requires a careful assessment of the strain partitioning amongst the phases, the evolution of microstructure with strain and how damage accumulates in the form of voids and microcracks. This can only be accomplished by applying a range of methodologies tracked as deformation proceeds, including micro-Digital Image Correlation (µDIC), Electron Backscattered diffraction (EBSD), X-ray microtomography (µXCT) and synchrotron-sourced High Energy X-ray diffraction (HEXRD). Such experiments have also been applied to notched specimen to further understand the response of AHSSs at different states of stress. Data will be presented on a range of ultrahigh strength AHSSs with and without TRIP-assistance (dual phase (DP), quench & partition (Q&P), and Medium-Mn steels). The data suggests that grain refinement, TRIP and decreased mechanical heterogeneity amongst phases can be used to suppress damage. It remains a challenge to quantify these effects separately, opening new avenues for experimental and modeling investigations.
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14:00 - 16:00 Symp02-Tu2: JoDean Morrow & Paul Paris Memorial Symposium on Fatigue & Fracture
Organizers: Ashley Spear and Gustavo Castelluccio
14:00 - 14:30
Keynote
MONITORING FATIGUE DAMAGE IN HYPOEUTECTIC AL-SI CASTINGS WITH VARYING MICROSTRUCTURE CHARACTERISTICS [Keynote]
Ulrich KruppGrand Ballroom B
Due to their low density, good recyclability and producibility of complex net shapes, cast aluminium alloys are promising candidates for many demanding applications in mobility, power generation and machinery. The inherent microstructure inhomogeneity is the most striking challenge in placing cast Al alloys in cyclically loaded components. Therefore, obtaining a quantitative understanding of the correlation between casting process, microstructure parameters (dendrite arm spacing (DAS), size and shape of (i) the eutectic silicon, (ii) the gas porosity, and (iii) the shrinkage porosity) and fatigue properties (fatigue limit, fracture mechanical data) is the aim of the present study. The adjustment of these microstructure parameters by tailored casting systems and fatigue testing revealed that the fatigue limit increases and the threshold of the stress intensity range Delta K th decreases with decreasing DAS (microstructure refinement). Microscopic in-situ-tracking of fatigue damage yields a detailed understanding of the fatigue mechanisms that will be the basis of a numerical short crack modeling approach in the future.
EXTENDED ABSTRACT
14:30 - 14:50
CRYSTALLOGRAPHIC ORIENTATION ANALYSIS OF FATIGUE CRACK SURFACE FROM AA7050 SAMPLES WITH MULTI-STAGE AGING TREATMENTS
André CarvalhoGrand Ballroom B
The retrogression and re-aging (RRA) and interrupted aging heat treatments (T6I4 conditions) lead to a bimodal microstructure feature within the 7050-aluminum alloy. Microstructural effects have a strong influence on fatigue crack nucleation and short crack growth via the activation of competing mechanisms operating during fatigue crack nucleation. Electron Back Scatter Diffraction (EBSD) technique permits the study of the effects of fatigue-induced crystal defects on the crack path and the pre-existing defect structure. Furthermore, few studies have explored the potential of multi-stage aging treatments on the fatigue crack nucleation paths using the EBSD technique. The purpose of this study is to elucidate the role of the microstructure on small fatigue crack crystallography in samples of RRA, T6I4-65 and T7451 conditions made from AA 7050. Fatigue crack surface crystallography will be determined near the vicinity of crack initiation sites and within the early crack growth regime using focused ion beam (FIB) surface preparation combined with electron back-scattered diffraction (EBSD). All the small fatigue cracks were initiated at the bore-hole surfaces on the gage length of specimen geometry, i.e., double-edge notches with two 4.8 mm diameters. The bore-hole surfaces of samples were electropolished prior to fatigue loading to remove bore-hole surface machining damage.
EXTENDED ABSTRACT
14:50 - 15:10
ORIENTATION-DEPENDENT FATIGUE ASSESSMENT OF TI6AL4V MANUFACTURED BY L-PBF
Luca PatriarcaGrand Ballroom B
The fatigue behaviour of as-built parts produced by means of Laser-Powder Bed Fusion process (L-PBF) is primarily influenced by the presence of stress raisers on the surface, whose morphology strongly depends on the relative orientation between the surface and the build direction. This study aims to shed light into the factors representing the surface morphology that correlate with the fatigue performance of L-PBF Ti6Al4V specimens manufactured in different orientations. A fracture mechanics model based on measurable roughness parameters was employed for the prediction of the fatigue properties in both the finite life and endurance limit regions.
EXTENDED ABSTRACT
15:10 - 15:30
FUNCTIONAL FATIGUE PROPERTIES OF TINIZRSN BIOCOMPATIBLE SHAPE MEMORY ALLOY
Wael AbuzaidGrand Ballroom B
Functional fatigue degrades the superelastic properties of shape memory alloys under cyclic loading. In the presence of geometric stress concentrations, the local stress fields are amplified resulting in local accumulation of irrecoverable strains and consequently loss of functionality. For the biocompatible TiNbZrSn system, grain size and solution treatment temperature play a major role in affecting the level of pseudoelastic strains and their evolution upon cycling. These aspects are quantitatively investigated in this work. Dogbone tensile specimens and samples with drilled circular holes are considered in this work and full field strain measurements are employed to quantitatively evaluate the localization in response leading to loss of functionality.
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14:00 - 16:00 Symp05-Tu2: Hydrogen Embrittlement and Environmentally Assisted Cracking
Organizers: Jesus Toribio, Chris San Marchi, and Joseph Ronevich
14:00 - 14:20
MODELING OF STRESS CORROSION CRACK INITIATIONS OF POLYETHYLENE PIPE TRANSPORTING CHLORINATED WATER
Byoung-Ho ChoiGrand Ballroom C
Stress corrosion cracking is one of the long-term failure mechanism of thermoplastic pipes when exposed to the oxidative agents, such as the chlorinated water. In this paper, the stress corrosion crack initiation model was suggested based on the diffusion of chlorinated water with oxidation, combining with the energy analysis by cracking. The multiple micro cracking, which is a dominant feature in stress corrosion cracking failure, was successfully simulated by the proposed model.
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14:20 - 14:40
MODDELING OF INTERGRANULAR STRESS CORROSION CRACKING MECHANISM THROUGH COUPLING OF SLIP-OXIDATION AND COHESIVE ZONE MODEL
Michal Sedlak MosessonGrand Ballroom C
A finite element model was proposed for intergranular stress corrosion cracking modelling (IGSCC). The model is based around a moving integration point formulation which enables the model to track the oxide, dissolution, and crack tip. The formulation is introduced in the cohesive element. The model also relies on an electrochemical model, based on the slip-oxidation model and a diffusion model. The model is dependent on the plastic strain rate and creep strains for oxide rupture to evaluate the effect of creep and plastic strain on crack growth and oxide thickness in IGSCC.
EXTENDED ABSTRACT
14:40 - 15:00
INTEGRATED MODELING OF STRESS CORROSION CRACKING IN SUPERALLOYS
Gustavo CastelluccioGrand Ballroom C
The reliability of turbine blades is strongly dependent on the humidity, contamination, stress, and temperature to which they are exposed during operation. In many cases, cracks initiate simultaneously at multiple locations, which can result in crack arrest (shielding) or (coalescence). This presentation will explore an integrated computational and experimental approach that evaluates crack interaction in CMSX-4 superalloy using C-Ring tests with a layer of contaminant salt exposed to 550C. A phase-field model calculates the diffusion of species and reduces the material critical energy release rate accordingly. The model, which is parameterised to enable cracking above a threshold stress, predicts the critical crack spacing that results in shielding or coalescence. In addition, the integration of X-Ray microscopy (XRM) characterisation with FEM modelling demonstrates univocally the role of crack interaction in stress corrosion cracking. We conclude discussing the value of integrating models and experiments to understand complex failure mechanisms.
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15:00 - 15:20
IN-SITU CORROSION SMALL PUNCH TEST ON STRESS CORROSION CRACKING WITH DIGITAL IMAGE CORRELATION
Kuo YuanGrand Ballroom C
A small punch test (SPT) setup has been designed to allow monitoring the initiation and propagation of stress corrosion cracking (SCC) with digital image correlation (DIC). This paper reports the design of the setup, the method of accelerating the corrosion progress and correlation of the stress corrosion cracks.
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15:20 - 15:40
COUPLED CORROSION AND FATIGUE EFFECTS IN REINFORCED CEMENT CONCRETE MEMBERS USING MULTI-PHYSICS APPROACH
Vivek VishwakarmaGrand Ballroom C
Coupled corrosion fatigue causes the reinforced concrete structures to fail prematurely, leading to a brittle type of failure. In this paper, numerical simulation using commercially available FE solvers has been performed to understand the behavior of reinforced cement concrete members under the coupled effects of fatigue and corrosion.
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14:00 - 16:00 Symp08-Tu2: Beyond Similitude: Role of Multiscale Heterogeneity in Fracture Prognosis
Organizers: Ashley Spear and Gustavo Castelluccio
14:00 - 14:40
Keynote
INVESTIGATION OF HIERARCHICAL POROUS STRUCTURES USING PHASE-FIELD FRACTURE MODELING INFORMED BY MOLECULAR DYNAMICS SIMULATION [Keynote]
Pania NewellWalnut
The mechanical integrity of hierarchical porous structures depends on their pore morphology. To investigate the role of pore morphology on the mechanical and fracture behaviors of these complex systems, a multi-scale approach has been proposed. This paper shows how molecular dynamics simulations provide the means to extract material properties at the atomistic scale to further inform phase-field fracture technique at the continuum scale in an attempt to understand the mechanical response of these porous materials.
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14:40 - 15:00
FRICTIONAL CRACK GROWTH INITIATION IN A NATURAL ORTHOTROPIC QUASI-BRITTLE SOLID
Sailendu BiswalWalnut
The frictional crack is extensively observed in natural phenomena like earthquake fracture, fracture at rock
fault line and in fracture of other geological materials. The contact between the flaw faces alters the stress
field in comparison to the stress field in an open condition or when not in contact. The crack growth
initiation in an open condition have been investigated sufficiently in literature. However, the frictional crack
or closed crack in an anisostropic medium has hardly been addressed. The naturally occurring biological
materials such as bone, wood, cartilage, etc. are anisotropic as well as quasi-brittle in nature. Considering
the vital application of these naturally occurring composites, it calls for a thorough investigation. The
current research work performs compression test on wood with an embedded central pore for different
contact surface conditions and orientation of pore. In addition to that, it carries out numerical simulation of
crack growth initiation and propagation using cohesive zone model (CZM) considering quasi-brittle nature
of wood. Further, it verifies the applicability of classical fracture criteria for friction crack propagation in
wood.
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15:00 - 15:20
MICROSCALE DISCRETE ELEMENT SIMULATION OF SHOCK WAVE PROPAGATION IN PLASMA SPRAYED CERAMICS
Vincent LongchampWalnut
The macroscopic behavior of plasma sprayed zirconia coatings is greatly affected by their microstructure, and phenomena that occur at this scale, such as micro-craking and cracks closure. The present study investigates the effect of micro-porosities and micro-craking on compressive waves mitigation, material compaction, and macroscopic fracture. A procedure to generate 3D digital twins that faithfully represents the microstructure is developped using the discrete element method (DEM) and analysis of scanning electron microscope (SEM) images. Static and dynamic compressive loadings are applied to 3D and 2D twins to identify their macroscopic behavior. Local damage mechanisms and their influence on the waves mitigation and the macroscopic damage are observed and discussed related to the current knowledge in the literature.
EXTENDED ABSTRACT
15:20 - 15:40
REGULARIZATION OF DAMAGE AND FAILURE USING A NON-LOCAL HARDENING VARIABLE IN AN EULERIAN FORMULATION OF INELASTICITY
Martin KroonWalnut
It is known that damage or inelastic softening can cause an ill-posed problem leading to localization and mesh-dependence in finite element simulations. Here, a nonlocal hardening variable is introduced in a finite deformation Eulerian formulation of inelasticity. This nonlocal variable is defined over an Eulerian region of nonlocality, which is a sphere with radius equal to a characteristic length, defined in the current deformed geometry of the material. The influence of the nonlocal hardening variable is studied using an example of a plate that is loaded by a prescribed boundary displacement causing formation of a shear band. Predictions of the applied load vs. displacement curves and contour plots of the total distortional deformation of the plate and the hardening variable are studied. It is shown that the characteristic material length controls the structure of the shear band developed in the plate.
EXTENDED ABSTRACT
15:40 - 16:00
UNRAVELING THE INTERMITTENCY OF DAMAGE EVOLUTION FOR PREDICTING THE FAILURE OF QUASI-BRITTLE SOLIDS
Ashwij MayyaWalnut
We study the intermittent damage evolution preceding compressive failure using a non-local damage model accounting for material disorder and long-range elastic interactions. Our theoretical predictions are successfully compared with experiments carried on a model elasto-damageable 2D solid where damage evolution is tracked at both the global and local scale. Finally, we show how our understanding of these failure precursors can be harnessed for predicting the remaining lifetime of structures under compression.
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14:00 - 16:00 Symp09-Tu2: Fatigue and Fracture of Additively Manufactured Materials
Organizers: Bo Chen, Nagaraja Iyer, and Filippo Berto
14:00 - 14:20
INFLUENCE OF THE CONTOUR PARAMETER IN MICROSTRUCTURE DUALITY AND FRACTURE INITIATION IN NON-COMBUSTIBLE MAGNESIUM ALLOYS FABRICATED BY LASER POWDER BED FUSION
Bryan ProanoGrand Ballroom E
Non-combustible Mg alloy components fabricated by laser powder bed fusion in as-built conditions have an average ultimate tensile strength (UTS) of 320 MPa, a significantly larger value than its casting counterparts, which present an average UTS of 200 MPa. In addition, it was determined that stable crack extension always starts at the outer surface due to the coarsened microstructure regions present in the area. Therefore, this paper will use fracture mechanics to predict the UTS value by determining the size of the coarsened microstructure region and considering it as a surface crack with the √area parameter. Then, by using a fixed fracture toughness value, the UTS will be predicted. Furthermore, a processing parameter known as contour, which is used for remelting the outer surface of the specimen, can also smoothen the microstructure and potentially increase the UTS value. Results showed that the √area of the surface crack responsible for fracture was 730 μm for the no-contour specimen and 630 μm for a contour specimen. Subsequently, using Murakami’s theory, the predicted UTS is 320 MPa and 345 MPa respectively. Finally, tensile testing was performed to confirm the prediction, showing similar results with an average deviation of 2.9%.
EXTENDED ABSTRACT
14:20 - 14:40
EVALUATION OF STRENGTH CHARACTERISTICS FOR NON-COMBUSTIBLE MAGNESIUM ALLOY PRODUCTS FABRICATED BY LASER POWDER BED FUSION UNDER AS-BUILT CONDITION
Taeseul ParkGrand Ballroom E
It is difficult to evaluate fracture toughness according to ASTM standards for non-combustible magnesium alloy fabricated by Laser Powder Bed Fusion (LPBF) in as-built conditions. The reason is its microstructure duality between inner and outer surfaces. The microstructure duality can be eliminated by heat treatment. However, heat treatment reduces the strength of the material by around 11%. Therefore, heat treatment was not performed. In addition, the greatest advantage of LPBF is maximized when it can be used immediately without post-processing. Therefore in this study, the as-built condition was targeted. In the case of non-combustible Mg products, the mechanical properties of the inner and outer microstructures have a non-negligible difference. The difference is expected to affect the fracture behavior, so it is important to consider the difference in microstructure in strength evaluation. Therefore, this paper explains why ASTM standards are difficult to apply to non-combustible magnesium products fabricated by LPBF in as-built conditions with their microstructure differences. Furthermore, the alternative methods for measuring the fracture toughness of metals fabricated by the LPBF in as-built conditions with these characteristics are introduced and discussed.
EXTENDED ABSTRACT
14:40 - 15:00
REDUCING LOW CYCLE FATIGUE LIFE SCATTER OF ADDITIVE MANUFACTURED ALSI10MG USING LASER SHOCK PEENING
Garrett PatakyGrand Ballroom E
Additive manufactured (AM) alloys are still prone to critical manufacturing flaws, such as gaseous bubble entrapment. These defects can lead to early crack initiation reducing fatigue life and increasing scatter, especially when near surface. This research investigated the effect of femtosecond laser shock peening (FLSP) on the fatigue life of AM AlSi10Mg. Due to the low penetration of the FLSP, fatigue life remained consistent between treated and untreated specimens. Of equal importance though, the scatter was found to be reduced in the FLSP treated samples. From the high resolution DIC results, the average strain per grain in the untreated specimens showed a higher increase of strain from initial loading to final fracture as compared to the FLSP samples. Implementing the use of FLSP onto AM materials could lead to more consistent fatigue life despite the presence of porosity, leading to a path of easier certification and improved confidence in their behavior.
EXTENDED ABSTRACT
15:00 - 15:20
COMPUTATIONAL MODELING FOR IDENTIFYING VOIDS IN ADDITIVELY MANUFACTURED AL-SI10-MG
Nha Uyen HuynhGrand Ballroom E
Additive manufacturing (AM) is a quicker and more cost-effective technique to produce complex parts that can perform similar to or better than conventionally manufactured parts. However, due to the dissimilar microstructure compared to conventional parts, there is a lack of understanding in the physical and mechanical response of AM alloys under different loading conditions and strain rates, and thus the suitability of using AM parts is uncertain. Notably, the presence of voids in AM metal alloys is more prevalent. By developing a computational model that can represent plasticity and track fracture initiation at the void sites in AM alloys such as Al-Si10-Mg, the failure response can be predicted. Therefore, the objective of this research is to use in-situ micro-computed tensile testing to identify individual voids or networks of voids that are likely to cause fracture initiation in an AM Al-Si10-Mg alloy.
EXTENDED ABSTRACT
15:20 - 15:40
FINITE ELEMENT MODELLING IN PREDICTING THE EFFECT OF DEFECTS ON STRESS CONCENTRATION AND FATIGUE LIFE OF L-PBF ALSI10MG ALLOY
Raj DasGrand Ballroom E
The elastic-plastic finite element analysis is performed to obtain the stress field around pores and evaluate their resultant effects on fatigue life for L-PBF (Laser Powder Bed Fusion) produced AlSi10Mg alloy. The stress field is calculated for both single and multiple pore models, where stress concentration is evaluated as a function of the pore location and its size. A multi-scale finite element (FE) model is proposed based on the inherent porosity data from Computed Tomography (CT) to predict the overall fatigue life with high (90%) accuracy. The predicted fatigue life (cycles) are calculated using the rainflow counting algorithm in fe-Safe software using the stress-strain data obtained from the proposed FE model developed using the Abaqus software. Using the proposed model, it is possible to generate S-N curves for any loading condition for a given porosity characteristic (porosity density and average pore size).
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14:00 - 16:00 Symp11-Tu2: Finite Fracture Mechanics: Theoretical Aspects, Numerical Procedures, and Experimental Applications
Organizers: Vladislav Mantič, Pietro Cornetti, Dominique Leguillon and Pedro Camanho
14:00 - 14:40
Keynote
ON FFM/PFM FAILURE CRITERIA FOR METALS UNDERGOING SSY - NEW INSIGHTS AT V-NOTCHED TIPS [Keynote]
Zohar YosibashDogwood B
Structures made of steel alloys may fracture at V-notch tips at which a small plastic zone usually evolves. Failure criteria for predicting fracture loads for such quasi-brittle alloys, as a function of the V-notch opening angle are very scarce and have not been validated, to the best of our knowledge, by a set of experimental observations. Neither the FFM coupled criterion (FFMCC) for brittle fracture, nor two phase-field models (the classical AT1 for brittle materials and a ductile version) could predict the increase of the crack nucleation force observed in the four-point bend (4PB) experiments performed on AISI 4340 specimens as the opening angle increased. Extension of the FFMCC to account for the small plastic zone and further 4PB experiments on a new steel alloy (H13) are being considered to improve the failure criterion.
EXTENDED ABSTRACT
14:40 - 15:20
Keynote
CRACK DEFLECTION AT CURVED INTERFACES. A FINITE FRACTURE MECHANICS ANALYSIS [Keynote]
Israel GarcíaDogwood B
Curved weak interfaces present promising advantages to be implemented as crack arrestors in structures designed under the tolerant-design principles. Among other advantages, they neither add extra weight nor affect significantly to the global stiffness of the structural element, in contrast with other crack arrestors. To be employed as crack arrestor, it is key that the interface can deviate the crack. If the crack penetrates across the interface, the effect of the weak interface as crack arrestor is canceled. In view of this, this work studies how to set the interface parameters to promote the crack deviation along the interface. In particular, following the dimensional analysis of the problem, the effect of three significant dimensionless parameters is studied: interface to bulk fracture toughness, interface to bulk tensile strength and the interface curvature radius normalized with the material characteristic length. The study is carried out using the Coupled Criterion of the Finite Fracture Mechanics.
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15:20 - 15:40
FINITE FRACTURE MECHANICS VERSUS PHASE FIELD: A CASE STUDY ON THE CRACK ONSET FROM CIRCULAR HOLES UNDER BIAXIAL LOADING CONDITIONS
Arturo Chao CorreasDogwood B
The phenomenon of brittle crack onset stemming from a circular hole embodied in a biaxially loaded infinite plate is herein investigated. Three different approaches are used to determine the biaxial safety domains: Finite Fracture Mechanics, Cohesive Zone Model and Phase Field. In particular, the original formulation of Finite Fracture Mechanics (FFM) proves to be consistently more optimistic than its averaged-stress variant (FFM-avg); likewise, both agree in predicting the existence of a region in the loading space where failure is governed by the energy condition. Besides, failure predictions according to Dugdale’s Cohesive Zone Model (CZM) prove to be fairly close to those by FFM, whereas the differences between CZM and FFM-avg result more noticeable. Lastly, the Phase Field model of fracture is implemented paying special attention to the choice of the energy decomposition, being herein implemented two relevant options: No-Decomposition and No-Tension decomposition. In particular, the latter showcases reasonable agreement with FFM (and CZM), thus rendering it a solid contender for its use in applications in which combined tension-compression stress states appear, such as in the dynamic failure of brittle materials.
EXTENDED ABSTRACT
15:40 - 16:00
MECHANICS OF THE INTERACTION OF TWO PARALLEL, SIMULTANEOUSLY GROWING CRACKS USING LEFM
Sachin YadavDogwood B
Experiments and numerical simulations studied the mechanics of two interacting colinear and offset cracks. Quasi-static experiments were carried out on acrylic sheets to determine the crack growth direction in the specimens with double parallel cracks or a single crack. The Finite Element Method (FEM) was adopted to calculate stress intensity factors at the crack tips. The interaction and influence of crack growth and direction of propagation with various geometries of cracks and their positions were discussed. This interaction is observed through a change in the propagation directions of crack tips. As the cracks grow, the SIF at the crack tip continuously increases. When the cracks are very close, SIF sharply increases for the colinear case. Crack growth behavior is observed, and the stress intensity factor is calculated at each step of crack growth for both cracks. The interaction effect on the crack path during propagation in simulation is predicted by the Maximum Tangential Stress (MTS) criterion. Some experiments are conducted to validate the analysis results. Comparisons are also made with experiments conducted under this study.
EXTENDED ABSTRACT
14:00 - 16:00 Symp16-Tu2: Residual Stress in Fatigue and Fracture
Organizers: Thomas J. Spradlin, Michael R. Hill, Casey E. Gales, and Dale L. Ball
14:00 - 14:25
VALIDATION OF WELD RESIDUAL STRESS FINITE ELEMENT PREDICTIONS FOR USE IN NUCLEAR REGULATORY APPLICATIONS
Michael BensonHickory
Weld residual stresses (WRS) are an important driver of primary-water stress corrosion cracking (PWSCC) in nuclear reactor piping, and thus can have an large influence on crack growth predictions. Consequently, it is important to be able to accurately predict WRS using finite element (FE) modeling. This study describes a proposed procedure for the validation of WRS predictions in nuclear primary piping systems using 2D axi-symmetric FE models.
EXTENDED ABSTRACT
14:25 - 14:50
FATIGUE CRACK GROWTH IN ELECTRON BEAM WELDMENTS
Simon MckendreyHickory
As the UK fleet of power plants changes technology from Advanced Gas Cooled Reactors to Light Water Reactors (LWR), the fatigue life of structural components in the primary coolant loop becomes of high interest. This is because of cyclic loading of LWRs caused by solid-liquid interactions which are less prominent in gas cooled reactors. Concurrently, modern welding techniques such as electron-beam (EB) welding are of great interest in LWR designs thanks to their benefits such as the ability to be automated, smaller heat affected zones and less material complexity as they can be deployed with no filler material (Horne et al., 2019). A common focus in studying weld fracture is the weld toe; this is because it has been observed that cracks often initiate in this region typically due to higher expected carbide deposition within the heat affected zone acting as stress concentrators. As EB welds have very narrow heat affected zone, the expected region in which cracks may initiate, is less obvious. This work compares three crack initiation sites taken from a modern reactor material (stainless steel 316L) pipe containing a circumferential EB butt weld and evaluates the fatigue crack growth rate (FCGR) within the linear region of the
EXTENDED ABSTRACT
14:50 - 15:15
DETERMINATION OF WELDING RESIDUAL STRESSES IN TUBULAR JOINTS WITH MULTI-PASS WELDS
Le WangHickory
Tensile residual stresses caused by welding potentially lend to detrimental consequences on the structural integrity and durability of tubular joints in the engineering field. This paper presents the experimental and numerical investigations to determine the welding residual stresses in X-tubular joints. This paper describes a new modeling approach to establish the finite element model of the tubular joint with a multi-pass weld to simulate the welding process with multiple welding passes and analyses the welding residual stresses. Assisted by the non-destructive residual stress measurement by the X-ray diffraction approach, the numerical results realized by the proposed modeling approach and the thermal-mechanical simulation method agree well with the X-ray diffraction measurement.
EXTENDED ABSTRACT
15:15 - 15:40
FATIGUE PERFORMANCE ASSESSMENT OF A QUENCHED ALUMINUM COMPONENT WITH PROCESS INDUCED RESIDUAL AT DIFFERENT DIPPING ANGLES
Jim LuaHickory
Quenching is a heat treatment process for the rapid cooling of a metallic workpiece in water, oil or air to obtain certain desired material properties. The accurate determination of resulting residual stress and distortion of a large aerospace aluminum part is challenging due to the nature of fast transient thermal process that includes the coupling of thermal, metallurgical, and mechanical interactions. The use of heat transfer coefficients (HTCs) in empirical tools requires an extensive testing matrix to calibrate these HCTs based on measured temperature data at selected locations of the workpiece. The use of a thermal multi-phase FSI tool is essential for the rational design of the flow rate quenchant with agitation to reduce the quenching residual stress by decreasing the thermal gradient from the center of the work piece to the surface. Given the temperature and phase profiles predicted from the Fluid Structure Interaction (FSI) based heat transfer module, a residual stress and distortion prediction module is developed by including fields mapping, temperature and phase dependent property evolution, and a user-defined material model for Abaqus. The fatigue performance of a quenched T-stiffener is evaluated in the presence of quenching induced residual stress under different dipping orientations.
EXTENDED ABSTRACT
15:40 - 16:05
STUDIES OF CRACK GROWTH AND FRACTURE DRIVEN BY WELD RESIDUAL STRESS FIELDS
Bud BrustHickory
Subcritical crack growth of nuclear components is a current concern in operating light water nuclear reactors. Weld residual stresses (WRS) can drive stress corrosion crack growth, affect fatigue crack growth, lead to reheat cracking issues if the components are operated in the creep regime, and can affect the fracture response of components. This paper provides several examples where crack growth, driven by weld residual stress fields, has led to safety concerns in several nuclear components. This is especially true for the dissimilar metal welds that are present in most PWR reactors. Mechanical mitigation examples are also discussed which are used to reduce the WRS fields or alter them to compression which can mitigate stress corrosion cracking.
EXTENDED ABSTRACT
14:00 - 16:00 Symp21-Tu2: Fracture in Polymer-based Materials: Structure-Property Relationships
Organizers: Francesco Baldi, Alicia Salazar, Luca Andena
14:00 - 14:40
Keynote
INFLUENCE OF TEMPERATURE AND TESTING MEDIA ON FATIGUE CRACK GROWTH PERFORMANCE OF POLYETHYLENE TESTED VIA CRACKED ROUND BAR SPECIMEN [Keynote]
Paul J. FreudenthalerHazelnut
Static loading test methods to characterize the resistance against slow crack growth use surfactants to shorten testing times. In comparison, the cracked round bar test method uses cyclic loading but no accelerating media and/or temperatures. To allow for a comprehensive knowledge on the effect of media influence, this research investigates the effect of air as well as deionized water with and without surfactant on the crack growth performance of blow-molding polyethylene in cracked round bar experiments at various temperatures. As also seen in literature, first test results show a crack growth decelerating effect of surfactant in cyclic tests at an elevated temperature. Ongoing tests will show the temperature dependency of these effects.
EXTENDED ABSTRACT
14:40 - 15:00
REACTIVE TELECHELIC POLYETHERIMIDE TOUGHENED TETRAFUNCTIONAL EPOXY
Hengxi ChenHazelnut
Highly crosslinked multifunctional epoxy resins possess superior properties, like high Tg, modulus, chemical resistance, etc, yet they are brittle due to their high crosslink density. It is desired that toughness improvements should not compromise other properties, including mechanical, thermal properties, and processability. Here, reactive polyetherimide containing amine functional end groups with two different molecular weights and loading levels were incorporated in tetraglycidyl diamino diphenyl methane tetrafunctional epoxy resin to study their structure-property relationship.
EXTENDED ABSTRACT
15:00 - 15:20
FRACTURE CHARACTERIZATION OF DUCTILE POLYMERS: RECENT APPLICATIONS OF THE LOAD SEPARATION CRITERION
Francesco BaldiHazelnut
For ductile polymers, the development of sound relationships between material structure and fracture response calls for the use of robust testing methodologies able to measure properties that describe the different processes occurring during fracture. The most common testing methods used with these materials appear inadequate, and there is a need to examine new approaches. This paper describes the most recent applications of the load separation criterion (LSC) in the fracture characterization of ductile polymers: the testing procedures are introduced and some representative results shown.
EXTENDED ABSTRACT
15:20 - 15:20 Symp21-Tu2-4
RUPTURE OF HYDROGELS
John BassaniHazelnut
Hydrogels are soft, highly deformable materials with applications ranging from soft actuators to natural and synthetic biomaterials. The rupture of hydrogels generally involves very large deformations that can be strongly coupled to the fluid flow. In this paper, a modified J-integral (J*) is used to calculate the critical energy release rate utilizing either a critical stretch criterion or the measured overall force-extension relation for a SENT specimen of a fibrin gel, which is the primary stress-carying component of blood clots.
EXTENDED ABSTRACT
16:00 - 16:30 Coffee 2B
Coffee Break PM
16:30 - 18:00 Honor and Plenary Session P3
Plenary session P3
16:30 - 17:10
Plenary Lecture
INTERFACE NANOSTRUCTURES AND MECHANISMS CRITICAL FOR FATIGUE [Plenary Lecture]
Huseyin SehitogluGrand Ballroom E
Interfaces are the most inconspicuous and yet the most profound influencers of material behavior by far. They are capable of imparting large enhancements in fatigue-resistance and increase in failure strength, authoritatively dictating performance in several domains spanning biomedical devices, energy-harvesting, aeronautics, and space exploration. The enhancements in safety and performance fundamentally rests on a foundation of materials where metal fatigue is alleviated by materials design. A gaping scientific void debarring such a development is the lack of understanding of the two most fundamental interfaces in functional materials: Twin Boundaries (TBs) and Habit Planes (HPs). The current talk will address this void, explaining nanostructures and evolutionary mechanisms of these interfaces under external stimuli at multiple scales. This understanding will further be catapulted by the development of a suite of novel, ab-initio, fully-predictive microstructural models from the nano- to the meso-scale, explaining the key interface characteristics responsible for fatigue. Such an approach will advance knowledge on TBs, topological nanostructure of the HP, reveal their interplay in fatigue-damage mechanisms and establish tailorable design targets to alleviate fatigue. Such an approach dealing with large number of TBs and materials with varying compositions in the thousands require research that is devoid of empiricism and transcend
EXTENDED ABSTRACT
17:15 - 17:55
Plenary Lecture
THE FAILURE OF ADHESIVE LAYERS: FROM FAST FRACTURE TO STRESS CORROSION [Plenary Lecture]
Norman FleckGrand Ballroom E
Adhesive joints are increasing used in engineering components, particularly in the bonding of dissimilar materials. This talk focuses on deformation and failure mechanisms of a sandwich joint: brittle fracture in elastic layers, ductile failure by cohesive zone modelling, diffusion-controlled attack of an interface and toughening of an adhesive layer by the presence of micro-architectured reinforcement.
EXTENDED ABSTRACT
18:00 - 19:00 Exhibition and Poster Session
Exhibition and Poster Session
18:00 - 19:00
Poster
FRACTURE BEHAVIOUR OF HPT PROCESSED MARAGING STEEL 250 [Poster]
Kevin JacobGrand Ballroom D1-D2
Maraging steels are a class of precipitation hardened steels wherein different micro-mechanisms of deformation such as planar slip, interaction with coherent/incoherent precipitates, and reverted austenite controls the overall mechanical behavior of the material. High Pressure Torsion (HPT) processing adds to this complexity by pumping in a large density of dislocations that form sub-grain boundaries and cellular structures, leading to changes in precipitate morphology and stability upon ageing. This results in a drastic change in the deformation accommodation mechanism. While these steels are known to display high fracture toughness in the hot rolled condition (hereafter referred to as: as-received), this study reports for the first time their KIC values after deformation processing, including the effect of grain size refinement, dislocation density and texture induced anisotropy. To accomplish these measurements in the small volume discs that are produced by HPT, small-scale clamped beam bend geometries were utilized for the first time. KIC measurements were carried out for both cases in the unaged, peak-aged and over-aged conditions. DIC strain mapping has been made use of to quantify the crack tip opening displacement and process zone evolution ahead of the crack tip.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
FULL FIELD MEASUREMENT OF SHOCK COMPRESSION DEFORMATION ACROSS THE CRYSTAL BINDER INTERFACE USING TIME RESOLVED RAMAN SPECTROSCOPY [Poster]
Mahavir SinghGrand Ballroom D1-D2
In applications requiring high velocity interactions of energetic materials, the shock response of the crystal-binder interface is of great importance. We demonstrate a technique for capturing the high localized deformation of the crystal-binder interface using time resolved Raman spectroscopy at nanosecond intervals. A bi-crystal interface of polydimethylsiloxane (PDMS) sandwiched between sucrose crystals is used in the method, with the sample as a whole put on a glass surface and impacted from the opposite end. Aluminum cylindrical flyers with thicknesses of 25-50 um and diameters of 1 mm were accelerated utilizing the Laser Induced Projectile Impact Test (LIPIT) to create high velocity shock compression loads. The velocity of the projectiles was determined using heterodyne photon doppler velocimetry (het-PDV) and ranged from 0.5 to 1.5 km/s. Full field measurements of the 532nm Raman spectroscopic response were acquired using an in-house designed laser array configuration with 27 discrete laser subsets. The pressure and temperature distributions over the interface were calculated using the pre-calibrated peak shifts of the sucrose CH and CH2 bonds. The highly localized deformation generated by pressure and temperature rise as the shock front travels across the interface were measured in-situ by the time resolved Raman spectroscopic response. The results showed
EXTENDED ABSTRACT
18:00 - 19:00
Poster
GRAIN BOUNDARY SLIDING AND INTRAGRANULAR SLIP MEASUREMENT IN-SITU DURING CREEP [Poster]
Benjamin ElbrechtGrand Ballroom D1-D2
Creep in future long-term space technology materials is a critical concern due to the duration of potential missions to Mars and beyond. Structural and skin components in long-term mission spacecraft will undergo creep deformation and eventual failure if not designed to be sufficiently creep resistant. The microstructural deformation mechanisms that control the creep behavior must be understood to intelligently inform the design of new creep resistant alloys and enhance those already in service. Using lightweight single phase β Ti alloys, an analysis tool was developed to measure grain boundary sliding (GBS) and intragranular slip in-situ via a Heaviside function-based algorithm. The data needed for the analysis tool includes an electron backscattered diffraction generated microstructural map and high-resolution digital image correlation (HRDIC) strain fields. This testing technique advances the state of the art by facilitating in-situ measurement of these microstructural deformation mechanisms without the need to interrupt creep testing and introduce unwanted thermic cyclic effects. Proof-of-concept experiments utilizing this analysis tool on a single phase β Ti alloy in room temperature creep rapidly identified the dominant deformation mechanism to be intragranular slip and glide creep without the need for destructive and expensive post-mortem testing.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
SIMULATING FRACTURE AND POST-FRACTURE RESPONSE OF WELDED COLUMN SPLICES [Poster]
Aditya JhunjhunwalaGrand Ballroom D1-D2
Pre-Northridge moment frames with PJP Welded Column Splices (WCS) are highly vulnerable to brittle fracture much before the connection develops the strength of the upper connected column due to the inherent crack-like flaw (unfused region of the weld) and the low toughness of the weld material. Given that the consequences of fracture are catastrophic and that retrofitting these splices can be highly disruptive to building operations, accurately estimating their fracture risk is of great importance. To achieve this, a probabilistic quantification of splice fracture is necessary, along with tools that simulate splice fracture and post-fracture response in a global frame assessment framework.
A framework to probabilistically assess the fracture strength of these splices is presented which addresses shortcomings of previous research and performance assessment guidance that do not consider key mechanistic or statistical effects. A new element model (in OpenSees), which is informed by the fracture mechanics-based estimates of splice strength and existing material models in OpenSees, is developed to simulate the splice fracture and post-fracture response. Application of the new splice element in assessment of a 20-story building to scaled ground motions is demonstrated.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
AN INVESTIGATION OF LODE EFFECTS ON DUCTILE FRACTURE [Poster]
Joshua HerringtonGrand Ballroom D1-D2
Ductile fracture is affected by the state of stress, which is commonly described by two parameters, stress triaxiality and Lode parameter. While the effects of triaxiality are well known, the effect of the Lode parameter are uncertain. This uncertainty results in particular from the difficulty to vary the Lode parameter at controlled triaxiality. Recent experiments by the authors suggest that the Lode parameter does indeed affect ductile fracture to some extent. The aim of this work is to analyze the mechanisms behind these apparent effects of the Lode parameter.To accomplish this, an advanced multi-surface porous-plasticity model that accounts for both homogeneous and inhomogeneous yielding is used in an Abaqus Umat to simulate proportional loading of a single integration point. Within this modeling framework, the effect of Lode parameter is inherently captured through the competition between the two main modes of inhomogeneous yielding: internal necking and internal shearing of the intervoid ligament. The ability of this constitutive formulation to capture the effects of the Lode parameter that were observed in experiments is examined.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
RAPID FATIGUE CHARACTERIZATION OF ADDITIVELY MANUFACTURED POLYMER COMPOSITES USING INFRARED THERMOGRAPHY. [Poster]
Pharindra PathakGrand Ballroom D1-D2
High cycle fatigue (HCF) in composite structures leads to damage accumulation and associated stiffness
degradation, which are challenging to quantify. This work uses a medium wave infrared to monitor selfheating in chopped carbon fiber/acrylonitrile butadiene styrene specimens subjected to tension-tension
fatigue loading. An innovative rapid testing protocol that correlates the generated full-field temperature
maps and stiffness degradation data has been developed providing a comprehensive understanding of
material behavior under cyclic loading. Results contribute to the fundamental understanding of HCF in
composite materials and develop more accurate predictive models for fatigue life. Rapid testing has allowed
correlating process parameters with the microstructure and structural integrity of additively manufactured
(AM) composites.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
STRONG AND TOUGH FIBROUS HYDROGELS REINFORCED BY MULTISCALE HIERARCHICAL STRUCTURES WITH MULTIMECHANISMS [Poster]
Huajian GaoGrand Ballroom D1-D2
Tough natural materials such as nacre, bone, and silk exhibit multiscale hierarchical structures where distinct toughening mechanisms occur at each level of the hierarchy, ranging from molecular uncoiling to microscale fibrillar sliding to macroscale crack deflection. An open question is whether and how the multiscale design motifs of natural materials can be translated to the development of next-generation biomimetic hydrogels. Here, we will discuss a recent work [1] on fabricating strong and tough hydrogel with architected multiscale hierarchical structures using a freeze-casting–assisted solution substitution strategy. The underlying multiscale multimechanisms are attributed to the gel’s hierarchical structures; hydrogen bond–enhanced fibers with nanocrystalline domains; and cross-linked strong polyvinyl alcohol chains with chain-connecting ionic bonds. This study establishes a blueprint of structure-performance mechanisms in tough hierarchically structured hydrogels and can inspire advanced design strategies for other promising hierarchical materials.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
FRACTURE PROPERTIES OF MULTIDIMENSIONAL CARBON-BASED MATERIALS [Poster]
Abigail EatonGrand Ballroom D1-D2
We perform steered molecular dynamics tensile studies [1] on carbon-based low dimensional materials including carbyne, cyclo[18]carbon, carbon nanotubes, and hybrid structures. We study the response of these materials to quantify the maximum stress, strain, and force required for fracture. We then use density functional theory to study the electron density distributions at different strains in low-dimensional materials to validate the molecular dynamics fracture predictions. This study predicts the fracture and mechanical properties of carbon-based low dimensional materials that will help with applications such as nanodevices and nanocomposites.
[1] Eaton, A. L., Fielder, M., and Nair, A. K., 2022, "Mechanical and thermal properties of carbon-based low-dimensional materials," MRS Bulletin, 47, pp. 1001-1010.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
UNUSUAL STRESS SERRATIONS AND PLC BANDS IN HIGH MANGANESE AUSTENITIC FE-MN-C TWIP STEEL [Poster]
Lihe QianGrand Ballroom D1-D2
Deformation twinning and dynamic strain aging (DSA) are two major phenomena occurring in Fe-Mn-C twinning-induced plasticity (TWIP) steels. DSA is manifested with serrated plastic flow, with stress serrations appearing on stress-strain or stress-time curves. TWIP steels, especially Fe-Mn-C TWIP steels, show apparent serrated plastic flow. However, the stress serrations and associated Portevin-Le Chatelier (PLC) band behavior of such steels reported in several publications, especially at very low strain rates, are not consistent. This paper is to investigate the serrated plastic flow and the spatio-temporal behaviors of PLC bands in a Fe-Mn-C TWIP steel at very low strain rates, by means of in-situ tensile tests, in conjunction of digital image correlation (DIC) technique.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
OPTIMIZATION OF NANOPOROUS METALLIC ACTUATORS BY COMBINING MULTISCALE CALCULATIONS AND MACHINE LEARNING [Poster]
Sheng SunGrand Ballroom D1-D2
Nanoporous materials (NMs) in electrolytes can achieve approximately 1% deformation under low operating voltages of about 1 V, making them promising for use in artificial muscles. The multi-field and multi-scale nature of the NM electrochemical actuator makes simulation-based optimization extremely challenging. A computational framework was developed that combines joint density functional theory (JDFT), surface eigenstress model, symbolic regression, finite element methods (FEM), and surrogate modeling to perform both concurrent and sequential multi-scale calculations. Specifically, JDFT calculations were performed on Au thin films to obtain in-plane strain as a function of charge density and film thickness. The surface eigenstress and surface Young's modulus of the Au nanofilm were then determined by fitting the surface eigenstress model to the JDFT data. Additionally, symbolic regression was used to obtain the constitutive equation of surface eigenstrain versus surface charge density, which realized macroscale FEM calculations. Finally, a mapping scheme was established between a given sequence of numbers and a particular structure of nanoporous Au, which allowed for the employment of Gaussian process regression surrogate models. These surrogate models were employed to accelerate the evaluation of actuation strain and effective Young’s modulus, and hence enable the exploration of the entire design space.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
COMPETITION BETWEEN NECKING AND PRE-CUT PROPAGATION IN FRACTURE OF HIGH-DENSITY POLYETHYLENE REVEALED BY TIME COURSES OF STRAINS [Poster]
Shengwang HaoGrand Ballroom D1-D2
High-density polyethylene pipes are widely used in pressure pipe applications such as water and gas transportation, but both necking and pre-crack effects are still poorly understood. This paper presents experimental observations to highlight strain field evolutions to necking and effects of pre-crack on strain field evolutions in a high density polyethylene material deformed in tension through analyzing spatial distributions of time histories of strains. Necking and its growth along the tension direction dominate the failure behavior of the intact specimen. Necking and crack propagation are both observed in the pre-cut specimen, but the crack propagation eliminates the necking propagation along the tension direction. Energy releases from positions outsides the crack zone lead to the macroscopic load-displacement curve deviates from the trend of the intact specimen. These findings present new recognitions on strain fields evolving to necking and failure induced by the pre-crack that are significant for designing of theoretical models and simulations of polymeric materials and structures.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
IN-SITU HEALING OF STATIC AND FATIGUE CRACK IN THERMOSET FIBER-REINFORCED COMPOSITES I [Poster]
Nilesh VisheGrand Ballroom D1-D2
In this study, static fracture experiments under mode-I and mixed mode loading, and fatigue testing under mode-I loading were carried out on double cantilever beam (DCB) specimens, and subsequent healing of the delamination was investigated. Thermoplastic healants dispersed in a thermoset CFRP composite were used to perform the healing, triggered through brief heating in an oven. It was observed from the test results that delaminations can be healed efficiently and the healing was found to be repeatable. As a result of healing, significant crack closure was observed and the fatigue crack growth rate was considerably reduced. These findings can be helpful in extending the service life of laminated composites.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
TRANS-SCALE PROPERITES OF PRECURSORY ACCELERATING DEFORMATION IN CATASTROPHIC FAILURE OF UNIAXIALLY COMPRESSED SANDSTONES [Poster]
Shengwang HaoGrand Ballroom D1-D2
The power law acceleration has been validated as an effective method for predicting catastrophic failure time, however, the precursory acceleration distribution in local monitoring signals is still unclear. This paper experimental results to show the variable properties of durations, onset times and critical power law exponents of precursory accelerating deformation with monitoring positions and sizes. Our results declare that precursory strain acceleration at different positions and size windows can provide consistent and stable prediction that agree well with the actual failure time. Our findings suggest that there is an optimal size and monitoring position that present earlier alarm and higher accurate prediction, because of heterogeneity of precursory accelerations in amplitudes and durations.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
INFLUENCE OF PRINT PARAMETERS ON FRACTURE RESPONSE OF PLAIN AND FIBER-REINFORCED 3D-PRINTED BEAMS [Poster]
Avinaya TripathiGrand Ballroom D1-D2
While much attention has been given to developing concrete mixtures for digital manufacturing (3D printing) and their associated rheological and mechanical properties, selecting appropriate printing parameters is also crucial for extrusion-based layered manufacturing. This paper explores the impact of layer height, a key parameter affecting rheology requirements, print quality, overall printing time, and interlayer bonding, on the flexural strength and fracture properties of 3D printed beams. This study investigates three-layer heights (LH) (5, 10, and 15 mm) corresponding to 25, 50, and 75% of the nozzle diameter (ND) (20 mm). The results show that smaller layer heights are more beneficial for both unreinforced and fiber-reinforced 3D printed mortars, despite the longer printing times and increased number of interfaces. Furthermore, adding a small amount of steel fiber reinforcement mitigates the adverse effects of weak interfaces on bulk properties. On average, flexural strengths are 30-40% higher, and fracture toughness and crack tip opening displacement are almost 30% higher than plain mixtures. The study employs strain energy release rates, digital image correlation, and optical images/micrographs to explain crack propagation in layered 3D printed mortars under unnotched four-point and notched three-point bending.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
AN INTEGRATED APPROACH TO DIGITAL IMAGE CORRELATION APPLIED TO A NOVEL THREE ACTUATORS FRETTING FATIGUE RIG [Poster]
Filipe Da Rocha ChavesGrand Ballroom D1-D2
This poster showcases a novel three-actuator fretting fatigue rig that features a horizontal contact orientation. The machine is equipped to conduct tests under lubrication and enables independent control of all loads in terms of intensity and angle phase. To validate this new rig, we performed fretting fatigue tests on a Ti-6Al-4V alloy couple in a cylinder-plane configuration, instrumented with an integrated approach to digital image correlation.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
FRACTURE OF MULTI-PRINCIPAL ELEMENT ALLOYS [Poster]
David CookGrand Ballroom D1-D2
Yield strength and fracture toughness are often mutually exclusive properties in metals and their alloys. The CrCoNi-based face-centered cubic (fcc) multi-principal element alloys (MPEAs) are known to possess extraordinary high fracture toughness that is enhanced at cryogenic temperatures; however, their relatively low yield strengths limit their engineering applications. This study investigates the role of sub-grain cellular structures in CrCoNi introduced by laser powder bed fusion (LPBF) that enhance its strength, with small compromise to the fracture toughness.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
FRACTURE PROPERTIES OF TETRAGRAPHENE UNDER MIXED MODE LOADING [Poster]
Elnaz HaddadiGrand Ballroom D1-D2
Tetragraphene (TG) is a quasi-2D semiconductor carbon allotrope composed of hexagonal and tetragonal rings and shows metallic or semiconducting behaviors. This study uses molecular dynamics (MD) simulations to understand fracture properties of triple-layered TG sheets with two different structures under mixed mode I and II loading using the Tersoff–Erhart potential. We investigate the effect of crack edge chirality, loading phase angle, and temperature on the crack propagation path and critical stress intensity factors.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
APPLICATION OF CONCURRENT ATOMISTIC-CONTINUUM COUPLING TO STUDY FRACTURE IN POLYMER NANOCOMPOSITES [Poster]
Sankha Subhra AdityaGrand Ballroom D1-D2
Nanoparticles have been used to improve the fracture toughness of polymer composites. Understanding the nanoscale mechanisms that promote enhanced toughness is critical to tailoring such material properties, and Molecular Dynamics (MD) simulations have been extensively used for this purpose. However, our ability to model real-life macroscale cracks purely using MD simulations is limited by the large length and time scales involved. Therefore, concurrently coupling continuum models such as Finite Element Method (FEM) with MD can potentially circumvent the length-scale issue and help provide insight into these basic failure mechanisms. The objective of this paper is to use a state-of-the-art concurrent atomistic-continuum coupling technique to study the nanoscale crack-tip behavior of a macroscale crack in a thermosetting resin and demonstrate its potential to study macroscale fracture in nanocomposites materials.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
STUDY ON THERMOMAGNETIC COUPLING FRACTURE OF HIGH TEMPERATURE SUPERCONDUCTOR MULTILAYER STRUCTURES [Poster]
Shenghu DingGrand Ballroom D1-D2
Most studies on the fracture of bulk or ribbon superconductors are based on superconducting critical state models that do not consider temperature changes. Most of the research objects of the thermal-mechanical-electric-magnetic model only focus on the distribution of magnetic field current and stress, while the thermal-mechanical-electric-magnetic model with cracks is rarely involved. The research in this paper will be based on a generalized critical state model that considers both temperature and magnetic field effects to investigate the effects of thermal and magnetic effects on cracks in superconducting structures.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
THREE-DIMENSIONAL SIMULATIONS OF DUCTILE FRACTURE UNDER ARBITRARY LOADINGS [Poster]
Vigneshwaran RadhakrishnanGrand Ballroom D1-D2
A complete constitutive theory is presented to enable ductile fracture simulations under complex loadings that may involve shear-dominated stress states or even negative triaxialities. The yield criteria accounting for various forms of anisotropy is supplemented with evolution equations to complete the constitutive theory formulation. State-of-the-art ductile fracture theory can only be fully exploited when a robust implementation enabling structural computations is available. This work set out to address the latter within a multisurface framework. A complete constitutive theory of plastic porous materials incorporating homogeneous (HY) and multiple (n) unhomogeneous yieldings (UY), named HUNnY is developed. The capabilities of the new formulation and its implementation are demonstrated by simulating fracture in tension, fracture in shear of top hat specimen and fracture by shear banding. The predictive theory promises to completely change our understanding of some of these most challenging problems that remained elusive for decades.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
EFFECTS OF SERVICE AGE ON THERMAL-MECHANICAL FATIGUE OF A 2.25CR-1MO STEAM HEADER [Poster]
Michael ZimnochGrand Ballroom D1-D2
Understanding the remaining life of a component is critical to maintaining safe operation and is necessary for budgeting repairs. This paper uses Finite Element Analysis to predict the performance of a steam header under realistic loading scenarios, comparing the difference between life expectancies of service-aged material to that of virgin material.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
CRACK GROWTH UNDER THERMO-MECHANICAL FATIGUE IN NICKEL CAST ALLOYS [Poster]
Karl Michael KraemerGrand Ballroom D1-D2
This poster presentation summarizes the results from several projects in this field conducted at the TU Darmstadt to identify and describe the various influences on crack growth under thermo-mechanical fatigue (TMF) loading. The activation of damage mechanisms under TMF loading and interactions between them are dependent of the temperature cycle and the respective load phasing. Depending on the type of loading (force- vs. strain-control), contrary influences of the phase shift on the TMF crack growth rates are found. To describe crack growth under creep-fatigue and TMF conditions, the linear accumulation model ‘O.C.F.’ was developed - based on the contributions of fatigue, creep and oxidation to crack growth per load cycle. This model is capable to reproduce the effects of time-dependent damage, different load ratios and TMF phase shifts, as well as component geometries. The model’s linear formulation allows assessing the dominant driver of crack growth at each stage of an experiment. These predictions are compared with fractographic investigations and in-situ observations of crack paths to identify the mechanisms of crack growth under different TMF load cycle forms.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
A HYBRID MODEL OF DUCTILE FAILURE ACCOUNTING FOR STRAIN HARDENING [Poster]
Sahil WajidGrand Ballroom D1-D2
Existing ductile failure models such as the Gurson-Tvergaard-Needleman (GTN) model as well as more recent physics-based models (for instance, the Benzerga-Leblond coalescence model from 2014) were all derived for perfectly plastic porous materials using classical limit analysis, with plastic flow in the matrix being described by J2 flow theory. When extended heuristically to hardenable materials, these models do not account for the heterogeneity of plastic strain in the matrix, and are unable to capture the effect of hardening on the evolution of porosity, the primary damage variable.
This work uses “sequential limit analysis” (SLA) to first derive a hardening-sensitive void coalescence criterion for a cylindrical cell containing a coaxial cylindrical void of finite height, by discretizing the intervoid ligament into a finite number of shells in each of which the quantities characterizing isotropic hardening are considered to be homogeneous. Next, this new criterion is combined with a recently formulated hardening-sensitive void growth criterion (also derived using SLA) to obtain a hybrid model of ductile failure. The new constitutive formulation’s ability to remedy the two aforementioned shortcomings of existing models is examined, and a set of finite-element micromechanical unit cell calculations is used to further assess the model's predictive capabilities.
EXTENDED ABSTRACT
18:00 - 19:00
Poster
FLOWFORMING TO IMPROVE THE FATIGUE LIFE OF IMPLANTS? [Poster]
Mohamed Akram MechterGrand Ballroom D1-D2
An analysis of the fatigue performance of 316L stainless steel bar drilled and tapped is performed. The effect of flow drilling and flow tapping on the material microstructure, microhardness and fatigue life is compared to the characteristics of conventional cutting processes.
The hardness recorded at the surface of flow formed holes is 62% higher than that of the raw material. In addition, grains are refined and plastically deformed by the flow processes.
Four-points bending fatigue tests were performed at 3 stress amplitudes and with a stress ratio of 0.1. The results revealed no significant differences in fatigue life for tests performed bending moment is equal to 75% and 60% of the yield bending moment. Nevertheless, when the maximum bending moment applied was limited to 50% of the yield bending moment, the specimens containing holes manufactured by the cutting endure more cycles. Fractographic observations revealed, for both specimens, that the failure initiated from the thread beneath the surface of maximum tensile stress. On the fracture surfaces of flow processed specimens, cracks initiated from the discontinuities observed at the peak of threads. In addition, secondary cracks are observed at the thread roots where to material is hard and the grains are refined.
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19:00 - 20:00 ICF Business Meeting
ICF business meetings
Wednesday Jun 14 2023
07:00 - 08:30 Registration 3
Registration
08:30 - 10:00 Honor and Plenary Session P4
Plenary session P4
08:30 - 09:10
Presidential Lecture
FRACTURE AND THE LIMITATION IT PLACES ON TECHNOLOGY: FROM LITHIUM-ION BATTERIES TO MEDICAL IMPLANTS [Presidential Lecture]
Robert McMeekingGrand Ballroom E
New technologies often bring along new fracture issues as they develop, or they place a renewed focus on some existing aspects of fracture. For example, electronic packaging, as it developed as a technology, led to a renewed focus on fracture caused by thermal stresses and thermal expansion mismatch. It also required much research on cracks at the interface between two materials, layered systems and channel and mud cracking. More recently, the development of lithium-ion batteries caused extensive work on fracture due to lithiation swelling in electrode storage particles and on crack-like lithium filament growth in solid electrolytes. Medical implants require much attention to fatigue fracture in their design, and utilization of some materials including Nitinol has brought forward new research on fatigue failure and its mechanisms. The highly variable human physiology causes the implants to be in diverse conditions and environments, leading to a renewed focus on reliability engineering for fatigue failure.
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09:15 - 09:55
Plenary Lecture
DOMAIN KNOWLEDGE-GUIDED MACHINE LEARNING AND CASE STUDIES OF METAL OXIDATION [Plenary Lecture]
Tong-Yi- ZhangGrand Ballroom E
This presentation first briefly introduces the concept of materials/mechanics informatics, which integrates machine learning with materials/mechanics science and engineering to accelerate materials/mechanics, products and manufacturing innovations. Then, this presentation reports a domain knowledge-guided machine learning strategy and demonstrates it by studying the oxidation behaviours of ferritic-martensitic steels in supercritical water and oxidation behaviours of FeCrAlCoNi based high entropy alloys (HEAs) at high temperatures. This strategy leads to the development of formulas with high generalization and accurate prediction power, which are most desirable to science, technology, and engineering.
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10:00 - 10:30 Coffee 3A
Coffee Break AM
10:30 - 12:30 Parallel Sessions W1
Parallel sessions symposia W1
10:30 - 12:30 Symp01-W1: Ductile Fracture Under Complex Loading
Organizers: David Wilkinson, Thomas Pardoen, and Amine Benzerga
10:30 - 10:50
A MODIFIED J-Q CONSTRAINT APPROACH TO ASSESS EFFECTIVE NOTCH FRACTURE TOUGHNESS
Nicolas LarrosaGrand Ballroom A
This paper uses a modified constraint-based fracture mechanics approach to estimate the effective notch fracture toughness . A modified J-Q constraint correction approach is proposed to evaluate the role of the notch tip acuity on the severity of the stress field accounting for two main characteristics, i.e. spread and maximum stress dependence of notch tip acuity. The methodology uses standard pre-cracked specimen toughness and the constraint-based approach in BS7910/R6 procedures to estimate mean values of notch fracture toughness. Experimental notch tests for S355 specimens at -140oC show good correlation with the model predictions
EXTENDED ABSTRACT
10:50 - 11:10
FRACTURE ANALYSES OF THIN-DUCTILE MATERIALS USING CRITICAL CTOA AND TWO-PARAMETER FRACTURE CRITERION
James NewmanGrand Ballroom A
The critical crack-tip-opening angle or displacement (CTOA/CTOD) fracture criterion is one of the oldest fracture criteria applied to metallic materials. Improved computer-aided photographic methods have been developed to measure CTOA during the fracture process; and elastic-plastic, finite-element analyses (ZIP2D) with a constant CTOA and a plane-strain core have been used to simulate fracture of laboratory specimens. The fracture criterion has been able to link the fracture of laboratory specimens to structural applications. This paper analyzes fracture of cracked thin-sheet 2219 aluminum alloy over an extremely wide range in width, crack-length-to-width ratio, and applied loading. The results from the critical CTOA fracture analyses on the thin-sheet material showed that the stress-intensity factor at failure (KIe) was linearly related to the net-section stress (Sn), as predicted by the Two-Parameter Fracture Criterion (TPFC).
EXTENDED ABSTRACT
11:10 - 11:30
CHARACTERIZATION AND NUMERICAL SIMULATION OF DUCTILE CRACK INITIATION AND PROPAGATION IN CT SPECIMENS OF DIFFERENT SIZES MACHINED FROM A 316L THICK PLATE
Sihan ChengGrand Ballroom A
Measuring fracture toughness for ductile materials requires the specimen size to be large enough for the tests to be valid. The higher the toughness is, the larger the specimen must be. This paper uses experimental and numerical approaches to study the fracture behavior of as-received and aged 316L(N) steel and the effect of the size and thickness of the specimens on the evaluated toughness.
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11:30 - 11:50
APPLICATION OF A NOVEL UNIFIED PARAMETER ON CHARACTERIZING IN-PLANE AND OUT-OF-PLANE CRACK-TIP CONSTRAINTS FOR AL7075 T651 SEN(B) SPECIMENS
Zeng ChenGrand Ballroom A
Crack-tip constraint can have a significant effect on fracture toughness. A loss of crack-tip constraint can cause an increase in fracture toughness. In this paper, a novel unified constraint parameter λ based on the plastic strain energy was proposed to quantify the crack-tip constraint level. The application of this parameter for assessing the in-plane and out-of-plane constraints of Al7075 T651 alloy SEN(B) specimens was investigated with a series of fracture bending experiments and numerical modelling.
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11:50 - 12:10
FRACTURE MODELLING AND ANALYSIS OF MULTIPLE SITE CRACKS IN PLATES UNDER LATERAL PRESSURE
Zeljko BozicGrand Ballroom A
Results of experimental and finite element study on fracture behavior of damaged thin plate specimens subjected to lateral pressure are presented. Plate specimens with a single crack or an array of collinear cracks were tested applying lateral pressure load by using a specially designed experimental setup. The elastic plastic fracture mechanics concept (EPFM) was employed in FE analyses, as large scale yielding occurred in ligaments of fractured specimens. The critical J-integral and crack tip opening displacement (CTOD) values associated with fracture onset were inferred from finite element simulation results. Assessed critical pressure loads for considered plate specimens were compared with experimentally obtained results and a good agreement was ob-served.
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10:30 - 12:30 Symp02-W1: JoDean Morrow & Paul Paris Memorial Symposium on Fatigue & Fracture
Organizers: Ashley Spear and Gustavo Castelluccio
10:30 - 10:50
NUMERICAL ANALYSIS OF ROLLING CONTACT FATIGUE CRACK GROWTH ON CURVED RAILWAY TRACKS
Wenyi YanGrand Ballroom B
In this study, numerical analyses were conducted to investigate the non-proportional mixed-mode RCF crack growth behaviour in the presence of severe longitudinal, lateral and spin creepages. The whole procedure combined multi-body dynamic simulation (MBDS) and the extended finite element method (XFEM) in an indirectly coupled way. Attempts were also made to modify the FaStrip theory to obtain traction distributions based on elastoplastic contact pressures which were then applied in an XFEM model to predict surface crack growth directions. Parametric studies were also conducted to further quantify the influence of different creepage combinations on both crack growth directions at rail surface and crack growth rate at crack tips. It is concluded that the increase of either of the three creepages can significantly influence the phase and magnitude of stress intensity factor histories, albeit to different extents.
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10:50 - 11:10
FATIGUE TESTING FOR COATINGS: A SYSTEMATIC APPROACH USING MICRO-IMPACT TESTING ON TIN
Abdalrhaman KokoGrand Ballroom B
A practical and systemic method to quantify coatings’ fatigue strength has been outlined and tested on titanium nitride (TIN) coating using multi-cycle and multi-load micro-impact testing with a spherical indent.
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11:10 - 11:30
FATIGUE OF HUMAN RED BLOOD CELLS IN HEALTH AND DISEASE
Ming DaoGrand Ballroom B
Human red blood cells (RBCs) are responsible for delivering oxygen to the organs and tissues from the lungs. During its lifespan, an RBC needs to squeeze through the smallest openings (i.e., smallest capillaries and splenic interendothelial slits) in the human body many times, and go through repeated hypoxia-normoxia cycles. Using our established microfluidic platform, we have shown that both mechanical fatigue and hypoxia-normoxia fatigue (through hypoxia-normoxia cycles) may cause significant mechanical degradation of RBCs. The results are compared between healthy RBCs and sickle cell disease (SCD) RBCs, and provide underlying mechanisms for a much shorter lifespan of SCD RBCs.
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10:30 - 12:30 Symp05-W1: Hydrogen Embrittlement and Environmentally Assisted Cracking
Organizers: Jesus Toribio, Chris San Marchi, and Joseph Ronevich
10:30 - 10:50
ENVIRONMENTAL STRESS CRACKING RESISTANCE OF HIPS UNDER CYCLIC LOADING USING CRACKED ROUND BAR SPECIMENS
David MittermayrGrand Ballroom C
The service life of polymers depends strongly on their loading conditions and the environment surrounding them. Prolonged contact of a polymer with an oily or fatty environment increases the tendency of crazing and thus shorten the service life. The objective of this paper was to investigate two different high-impact polystyrene polymers (HIPS) in terms of their environmental stress cracking resistance (ESCR) in air and sunflower oil environments by cyclic testing. It was shown that the HIPS grade with bigger rubber particles, even though it has lower short-term mechanical performance in tensile modulus, yield strength, and notched impact strength, is preferrable in terms of ESCR and should be used in fatty environment applications.
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10:50 - 11:10
RECENT NATURAL GAS PIPELINE ACCIDENTS INVOLVING HYDROGEN INDUCED CRACKING
Michael BudinskiGrand Ballroom C
Recently, the National Transportation Safety Board (NTSB) has investigated two natural gas pipeline accidents that occurred due to hydrogen induced cracking. This presentation reviews the findings.
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11:10 - 11:30
FATIGUE DESIGN SENSITIVITIES OF STATIONARY TYPE 2 HIGH-PRESSURE HYDROGEN VESSELS
John EmeryGrand Ballroom C
Common manufacturing processes for type 2 high-pressure hydrogen storage vessels use a surrogate measure of the desired residual stress, e.g., target strain on the external surface or target internal pressure. The critical value of these measures is chosen to impart residual stress sufficient to achieve a certain fatigue performance for the targeted operational pressure cycling and with given assumptions about the liner and overwrap geometry and materials. This paper uses computational simulation to study the sensitivities of fatigue performance to associated design specifications and assumptions.
EXTENDED ABSTRACT
11:30 - 11:50
MECHANICAL CHARACTERIZATION AND DEFECT ANALYSIS OF NATURAL GAS PIPELINE STEEL TOWARDS HYDROGEN INJECTION
T.E.F. SilvaGrand Ballroom C
Repurposing of natural gas infrastructure towards hydrogen injection implies its mechanical viability assurance. This study focuses on the structural integrity assessment of vintage steel API 5L Grade B (used in natural gas infrastructure), especially in what concerns the ductility loss due to hydrogen embrittlement and its effect on common damage occurrence, such as plain denting.
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11:50 - 12:10
SUBCRITICAL CRACK GROWTH IN HIGH-PRESSURE HYDROGEN AND HYDROGEN WITH OXYGEN IMPURITY
Robert WheelerGrand Ballroom C
In this study, the effects of oxygen content on hydrogen environment-assisted cracking are studied for several pipeline and commercial steels. Characterizing the effects of low oxygen impurities in hydrogen gas on subcritical crack growth in high pressure hydrogen environments can help inform fracture mechanics-based design and evaluate if oxygen can be utilized to mitigate hydrogen effects over long timescales.
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12:10 - 12:30
CRACK GROWTH-BASED FATIGUE LIFE PREDICTION FOR AGING PIPELINE STEEL IN HYDROGEN WITH PRE-EXISTING CORROSION
Kaushik KethamukkalaGrand Ballroom C
Using existing pipeline infrastructure for hydrogen transport is under prime focus nationwide and globally. As a result, several studies were conducted under gaseous and electrochemically charged hydrogen environments. However, most existing studies focused on virgin material degradation under a hydrogen environment but did not include the effect of pre-existing damage due to aging, such as corrosion. This study focuses on a hydrogen-assisted fatigue crack growth model that can capture the growth rate behavior for various line pipe steels at various operating conditions. Pre-existing corrosion (both general material loss and pitting) effects are naturally included as surface irregularities in the form of roughness. Modified stress intensity factor solutions for surface roughness and crack growth kinetics function are integrated for fatigue life prediction. Model predictions are validated with collected experimental data from the open literature. Several future research directions are recommended based on the current findings.
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10:30 - 12:30 Symp08-W1: Beyond Similitude: Role of Multiscale Heterogeneity in Fracture Prognosis
Organizers: Ashley Spear and Gustavo Castelluccio
10:30 - 11:10
Keynote
QUANTIFYING THE EFFECT OF FIBER BRIDGING ON MODE I QUASI-STATIC AND FATIGUE TESTING [Keynote]
Leslie Banks-SillsWalnut
This investigation focuses on mode I delamination propagation in a unidirectional (UD) carbon fiber reinforced polymer (CFRP) composite laminate. Delamination propagation in this type of material may be accompanied by fiber bridging, a phenomenon where fibers from one face of the delamination cross over to the other face, such that the fibers are simultaneously pulled from both faces, thus, bridging the delamination. This increases the material's apparent resistance to further propagation of the delamination. This phenomenon occurs mostly in beam-type test specimens commonly used to characterize failure of composite materials, but does not generally occur in structures with the exception a few structures such as rotor blades. The aim of this investigation is to quantify the effect of fiber bridging for quasi-static and fatigue testing of DCB specimens so as to eliminate it from the fracture and fatigue delamination propagation properties.
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11:10 - 11:30
ANALYSIS OF RIGID CURVED INCLUSION EMBEDDED IN A SOFT MATRIX: EXPERIMENTAL INSIGHTS
Swapnil PatilWalnut
The role of fiber curvature in short-fiber thermoplastics can be explored by studying a rigid curved inclusion embedded in an epoxy matrix. Although inclusion enhances global stiffness, it also acts as a source of stress singularity, which leads to failure. The current study employs the 2D digital image correlation (DIC) technique to obtain full-field strain fields over a rigid curved inclusion embedded in a soft matrix. The experiment is performed on a rigid curved inclusion specimen subjected to remote tensile loading of 350N. The experimentally obtained strain field is verified using the finite element technique, and a good match is observed. Finally, the stress intensity factor is defined for the rigid curved inclusion, and it is estimated along with the geometric correction factor.
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10:30 - 12:30 Symp09-W1: Fatigue and Fracture of Additively Manufactured Materials
Organizers: Bo Chen, Nagaraja Iyer, and Filippo Berto
10:30 - 10:50
IMPACT OF MICRO AND MESOSTRUCTURE ON THE FAILURE RESISTANCE OF LASER POWDER BED FUSION-PROCESSED MATERIALS
Bernd GludovatzGrand Ballroom E
Engineering materials processed using additive manufacturing (AM) techniques such as laser powder bed fusion (LPBF) often exhibit unique microstructures and defects that must be controlled to obtain peak performance in mechanical properties and as such a level of damage-tolerance that cannot be achieved in cast alloys. However, our understanding of how processing conditions control micro- and mesostructure and, in turn, mechanical performance, particularly regarding failure resistance, is weak. Furthermore, heat treatments that have been designed to achieve peak performance in cast alloys are often not optimized for alloys that have been processed using AM techniques. Here, we report our work on the effect of processing parameters such as layer thickness, hatch spacing, and scan strategy on crack resistance curve (R-curve) behavior in different orientations of LPBF-processed AlSi10Mg and correlate mechanical performance with meso- and microstructural features such as melt pool arrangement, cell morphology, grain size, grain orientation, and texture. Compared to that we show how heat-treatments impact fracture resistance as well as their anisotropy in two orthogonal orientations in an LPBF-processed 18Ni-300 maraging steel.
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10:50 - 11:10
PREDICTING SURFACE ROUGHNESS IN METALLIC ADDITIVELY MANUFACTURED PARTS USING MACHINE LEARNING
Nagaraja IyyerGrand Ballroom E
A melt pool geometry-based approach is developed to predict surface roughness in metal additively manufactured parts for a range of processing parameters. It is shown that surface roughness on a particular facet can be estimated by stacking melt pools along the facet, extracting their outer contour and applying the necessary transformations. To be able to predict surface quality of various processing parameters in a reasonable time frame, a machine learning framework is developed. This framework is trained over melt pool data generated by high-fidelity FE simulations.
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11:10 - 11:30
ANALYSIS OF FATIGUE CRACK GROWTH WITH OVERLOAD EFFECTS THROUGH T-STRESS
Ghita Bahaj FilaliGrand Ballroom E
Fatigue crack is a major concern to all industries for safety reasons. Fatigue life predictions for structural components such as railways or turbine disks are based on fracture mechanics analysis. Such components are inevitably submitted to underloads or overloads. The aim of this paper is to provide a DIC-BASED experimental analysis of overload 2D fatigue cracks using higher order terms in the Williams’ series expansion.
The prediction of the fatigue life of these components is often based on crack propagation calculations. However, overloads and underloads perturb steady state fatigue crack growth conditions and affect the growth rates by retarding or accelerating growth. The application of overloads generates complex effects on the crack behavior which induce delays that are difficult to predict. The mechanisms that have been proposed to explain retardation after tensile overload include, e.g. residual stress, crack closure and plasticity ahead of the crack tip.
In this work, based on DIC we use full-field measurements to obtain LEFM crack tip features (Stress Intensity Factor and T-stress). Therefore, with these crack tip features, we propose to analyze the T-stress effect on the crack growth propagation.
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10:30 - 12:30 Symp11-W1: Finite Fracture Mechanics: Theoretical Aspects, Numerical Procedures, and Experimental Applications
Organizers: Vladislav Mantič, Pietro Cornetti, Dominique Leguillon and Pedro Camanho
10:30 - 11:10
Keynote
THE THEORY OF CRITICAL DISTANCES TO MODEL THE STATIC STRENGTH OF ADDITIVELY MANUFACTURED CONCRETE/POLYMERS CONTAINING MANUFACTURING DEFECTS/VOIDS [Keynote]
Luca SusmelDogwood B
The present paper deals with the use of the Theory of Critical Distances to model the detrimental effect of manufacturing defects and voids in 3D-printed concrete/polymers subjected to static loading. The validity and robustness of the proposed approach is assessed against a large number of experimental results that were generated by testing 3D-printed specimens of both concrete and polylactide (PLA) containing manufacturing defects/voids. The sound agreement between experiments and predictive model makes it evident that the Theory of Critical Distances is not only a reliable design approach, but also a powerful tool suitable for guiding and informing effectively the additive manufacturing process.
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11:10 - 11:50
Keynote
SINGULAR ELASTIC SOLUTIONS IN CORNERS AND CRACKS WITH SPRING BOUNDARY CONDITIONS WITH VARYING STIFFNESS [Keynote]
Vladislav ManticDogwood B
Singular elastic solutions in corners and cracks with spring boundary conditions with varying spring stiffness are studied. First, a novel analytic procedure is developed for the antiplane strain case. Then, some general observations obtained are checked for the plane strain case by using a FEM code. Finally, applications of these observations in a suitable computational implementation of the Coupled Criterion of Finite Fracture Mechanics are discussed.
EXTENDED ABSTRACT
11:50 - 12:10
FEM IMPLEMENTATION OF THE COUPLED CRITERION BASED ON MINIMIZATION OF THE TOTAL ENERGY SUBJECTED TO A STRESS CONDITION TO PREDICT MIXED MODE CRACK ONSET AND GROWTH
Karthik Ambikakumari SanalkumarDogwood B
A numerical procedure predicting crack onset and growth in a mixed mode in brittle materials is developed using the Coupled Criterion of Finite Fracture Mechanics (CCFFM), which assumes crack advances by finite steps and requires both stress and energy conditions are fulfilled. The Principle of Minimum Total Energy subjected to a Stress Condition (PMTE-SC) is implemented by a load-stepping algorithm, minimising the total energy change due to a crack advance allowed by the stress criterion. A simple implementation of PMTE-SC in FEM code Abaqus considers cracks geometrically modelled as topological discontinuities in the FEM mesh, with cracks introduced explicitly during the discretisation of the domain, the crack faces coinciding with the element edges. Several numerical examples are solved for mixed-mode crack onset and propagation.
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12:10 - 12:30
MODELING HYDRAULIC FRACTURE INITIATION OF A NOTCH-FREE WELLBORE IN ANISOTROPIC ROCKS
Mahsa SakhaDogwood B
In this study, we address hydraulic fracture initiation from a notch-free wellbore subjected to compressive in-situ stresses, where the wellbore is situated in an anisotropic host rock with transversely isotropic properties. To capture the three unknown parameters, i.e. the initial crack length, orientation, and the fluid pressure at initiation in anisotropic formations, we extend the mixed criterion proposed for isotropic rock formations in the literature. The mixed criterion requires that both stress and energy conditions at the initiation point are met. To do so, we calculate the fracture energy through the displacement discontinuity method (DDM), where the kernel matrix appropriate to the geometry of the problem (i.e. an infinite plane with a circular hole) is adopted for a transversely isotropic formation. To evaluate the reliability of our formulation at any degree of material anisotropy, the crack emanating from the wellbore is simulated by the finite element method, and consequently the energy dissipated between the cracked and crack-free states is measured. While the two methods are in agreement, the results unravel the systematics of how the competition between the material anisotropy and the differential in-situ stresses determines the initiation parameters.
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10:30 - 12:30 Symp15-W1: Advanced Computational Methods in Fracture
Organizers: P.R. Budarapu, M.K. Pandit, A.K. Pradhan, S. Natarajan, T. Rabczuk
10:30 - 11:00
Keynote
PERIDYNAMIC MODELING OF CRACKING AND DEGRADATION IN CHARRING AND NON-CHARRING MATERIALS DURING ABLATION [Keynote]
Erdogan MadenciHickory
Polymers and ceramics are preferred materials for ablative Thermal protection systems (TPS) owing to their superior thermal and mechanical properties. Based on their degradation mechanism in the presence of heat, they can be classified as non-charring and charring. In non-charring materials, the material degradation is limited to the surface and can be caused due to chemical reactions or thermomechanical erosion. During this process, the volume of the initial material changes; however, the density of the material remains constant. However, a charring ablative undergoes internal decomposition leading to the formation of char, release of pyrolysis gases, and deterioration in material properties. This study presents a 3D coupled thermo-chemo-mechanical peridynamic (PD) model to simulate the pyrolysis process and crack propagation of charring materials and degradation in non-charring materials due to aerodynamic heating.
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11:00 - 11:20
A PERIDYNAMIC FATIGUE MODEL BASED ON TWO-PARAMETER REMAINING-LIFE FORMULATION
Ayhan InceHickory
In this paper, a new two-parameter remaining-life concept is introduced in the development of a peridynamic fatigue model. Based on the proposed remaining-life concept, the R-ratio effect is accounted for in the crack growth simulations by applying two independent controlling parameters of cyclic bond strain and maximum cyclic strain in the peridynamic remaining-life governing equation. The validation of the model is performed by assessment of correlation between predicted and experimental crack growth data for 2024-T3 aluminum alloy at various R-ratio loading conditions. The model predicted results show a good agreement with experimental crack growth data.
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11:20 - 11:40
FAST INFERENCE OF CRACK TIP POSITION AND STRESS INTENSITY FACTORS FROM DISPLACEMENT DATA
Swati GuptaHickory
Fracture prognosis and characterization efforts require knowledge of crack tip position and the configurational driving force acting on the crack. Here, we present an efficient numerical approach to determine these characteristics under a consistent theoretical framework from displacement data. The novel approach utilizes the separable characteristics of the asymptotic linear elastic fracture mechanics model to expedite the search for crack tip position and is particularly useful for noisy displacement data.
The importance of accurately locating crack tip position is assessed when quantifying the crack driving force from observed displacements. The proposed separability approach for quickly inferring crack tip position is introduced, setting the stage for subsequent assessment of the utility of the separability approach. Comparing to the widely-used displacement correlation approach, we examine performance in cases involving bad starting guesses, noise, and non-conformance with the asymptotic linear elastic fracture mechanics model, e.g. inelastic material behavior and finite geometries. We envision our proposed separability method and the associated code that has been made freely available to be of use to those doing experiments (involving digital image correlation) and simulations where the crack tip position is not explicitly defined, e.g. finite elements with damage models and atomistic simulations of crack growth.
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11:40 - 12:00
LEAST SQUARES METHOD FOR MODE III SIF CALCULATION
Jorge G. DiazHickory
The paper presents an experimental approach to determine the stress intensity factors (SIF) of cracks subjected mode III fracture mode. The proposed scheme fits displacement data to Williams series for cracks solving the equations by the overdeterministic Least Squares Methods (LSM). An example is presented for a tube with a through-crack under axial and cyclic torque loading where displacement field measurements were taken with the Digital Image Correlation (DIC) technique. The experimentally determined mode III SIF with the proposed method are compared with respective values found using crack opening displacement (COD) equations. It is concluded that the proposed LSM method agrees with COD measurements but exhibiting less noisy results.
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12:00 - 12:20
SIMULATING CRACK CLOSURE WITH COHESIVE ZONE ELEMENTS DURING CRACK GROWTH
Shanhu LiHickory
Closure and the cohesive effect at crack fronts/surfaces play key roles in simulating crack growth. In this paper, fracture analysis method has been coupled with finite element remeshing techniques to automatically insert cohesive zone element on crack surfaces when cracks propagate, and then multiple cohesive zone models are compared and discussed. This feature has been implemented in Ansys Mechanical MAPDL so that customers are capable of accurately analysing crack growth in a more general background.
EXTENDED ABSTRACT
12:30 - 14:00 Lunch 3
Lunch Break
14:00 - 16:00 Parallel Sessions W2
Parallel sessions symposia W2
14:00 - 16:00 Symp05-W2: Hydrogen Embrittlement and Environmentally Assisted Cracking
Organizers: Jesus Toribio, Chris San Marchi, and Joseph Ronevich
14:00 - 14:20
NUMERICAL ANALYSIS OF HYDROGEN DIFFUSION AROUND THE NOTCH UNDER CYCLIC LOADING WITH AN OVERLOAD
Toshihito OhmiGrand Ballroom C
Hydrogen embrittlement is known to be induced by a local increase in hydrogen concentration in materials. Therefore, it is important to elucidate the mechanism of hydrogen concentration behavior, which is the cause of hydrogen embrittlement, to prevent hydrogen embrittlement. One of authors proposed a numerical analysis method that couples stress analysis using the finite element method and hydrogen diffusion analysis using the finite difference method. This analysis has clarified that there is the effect of loading waveforms on hydrogen concentration behavior. In this study, hydrogen diffusion concentration behavior analysis under fatigue conditions with an overload was performed, and it was shown that hydrogen concentration may be enhanced by an overload.
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14:20 - 14:40
MATERIAL DISSOLUTION AT THE CRACK TIP
Mingjie ZhaoGrand Ballroom C
Despite a long-documented history of environmental effects, an understanding of the controlling mechanisms remains clouded. At fault are several challenges. First, multiple mechanisms can act simultaneously, e.g., dissolution, oxide fracture, oxide formation, material redeposition, and hydrogen embrittlement. Second, the scale of the material separation process on which the environment acts is atomistic, inhibiting direct observation. Considering these challenges, atomistic modeling can serve as a powerful probe to illuminate the mechanisms governing environmental effects and providing a means to study the material separation processes under the action of isolated mechanisms. Here, we report on the results of atomistic simulations specifically constructed to illuminate the role of material dissolution at the tip of a long crack. In cases of both brittle and ductile materials, we find that material dissolution can free arrested cracks. Beyond this, we find material dissolution to play a dole role, accelerating crack growth in the cases of brittle materials under sub-critical loading and accelerating crack tip blunting in the case of ductile materials. We find the result to be largely independent of loading magnitude and type, i.e. static vs fatigue. In total these results provide guidance for the development of continuum scale crack growth rules.
EXTENDED ABSTRACT
14:40 - 15:00
THREE-DIMENSIONAL ANALYSIS ON HYDROGEN-RELATED INTERGRANULAR CRACK PROPAGATION IN MARTENSITIC STEEL
Akinobu ShibataGrand Ballroom C
This study investigated three-dimensional propagation behavior of hydrogen-related intergranular crack in martensitic steel by X-ray computed tomography and FIB-SEM serial sectioning. Macroscopic analysis using X-ray computed tomography revealed that the crack morphology exhibited more continuous in the hydrogen-charged specimen. Through FIB-SEM serial sectioning, we found that the crack-tip blunting and ductile rupture of un-cracked ligaments were associated with a certain grain boundary segment in the uncharged specimen. In the case of hydrogen-related intergranular crack propagation, even very fine low-angle grain boundary segments (sub micro-meter size) could act as obstacles to crack propagation. Based on the results, we can propose that misorientation of each grain boundary segment has a large influence on local crack arrestability of intergranular crack propagation.
EXTENDED ABSTRACT
15:00 - 15:20
EFFECTS OF CRACK TIP STRESS RELAXATION ON SUBCRITICAL CRACK GROWTH IN SILICATE GLASSES: THRESHOLD AND STOCHASTICITY
Scott GrutzikGrand Ballroom C
Silicate glass is a non-equilibrium material and as such evolves over time to reduce internal energy through thermally activated structural rearrangement. This statement is perhaps especially true in the highly stressed region around a crack tip. At the atomistic scale, structural changes to accommodate crack growth or to mediate stress relaxation become indistinguishable. Here, we present a simple expression for static fatigue threshold using slow crack growth power law parameters and a structural relaxation time scale. Using subcritical crack growth data from the literature and measured threshold data, this model is demonstrated for soda lime silicate glass. In addition, we discuss the impact of crack tip relaxation on statistical lifetime prediction and evolution of flaw populations.
EXTENDED ABSTRACT
15:20 - 15:40
MODELING OF HYDROGEN EMBRITLLEMENT USING MIXED NONLOCAL FINITE ELEMENTS
Daniella Lopes PintoGrand Ballroom C
Industrial power generation and transmission structures are designed to have a service life of 40 years. Knowledge of the evolution of material behavior over long periods of time is therefore crucial to ensure the safety and reliability of these facilities. Due to the continuously increasing power demand, new energy sources are needed. As part of the decarbonization of these sources, hydrogen will play an important role as an energy vector. However, hydrogen can easily diffuse in materials, inducing premature failure with reduced ductility and toughness. This phenomenon, called hydrogen embrittlement (HE), is a complex mechanism which combines mechanical and chemical loadings. Therefore, this work presents a strategy to simulate HE by the finite element method integrating plasticity and damage coupled to hydrogen diffusion. Since damage is highly dependent on local stresses and hydrostatic pressure mixed formulations in displacement, pressure and volume variation have been proposed to control volumetric locking. To represent ductile rupture, the Gurson-Tvergaard-Needleman (GTN) model based on an implicit gradient nonlocal formulation with two internal lengths is considered, which allows regularizing void growth and strain-controlled nucleation. All the implementations and simulations have been carried out using the Z-set software.
EXTENDED ABSTRACT
14:00 - 16:00 Symp06-W2: Microstructures and Fracture in Advanced Materials
Organizers: Tong-Yi Zhang, Chad Landis, Weiqiu Chen, Ralf Müller, and Jie Wang
14:00 - 14:40
Keynote
CRACK TIP TRANSFORMATION ZONE MORPHOLOGY IN SMA MATERIALS WITH TRANSFORMATION SOFTENING [Keynote]
Chad LandisGrand Ballroom A
The pseudoelastic effect due to martensitic transformation in polycrystalline shape memory alloys is simulated with a phenomenological constitutive model based on a kinematic hardening framework with a gradient enhancement to regularize moving austenite-to-martensite boundaries that arise in softening materials. This constitutive modeling framework introduces a length scale within the theory which has yet to be deteremined experimentally. Calculations are presented for the evolution of the transformation zone around a stationary crack tip. The calculations uncover the interplay between the length scale associated with the size of the transformation zone around the crack tip and the material length scale inherent to the consistutive model. The calcualtions show that localized “fingers” or “needles” of deformation emenate from the transformation zone at a specific level of the applied stress intensity, which provide a comparison to experimental observations that then can be used to quantify the sie of the material length scale.
EXTENDED ABSTRACT
14:40 - 15:00
EFFECT OF STRAIN RATE AND REFORMED AUSTENITE ON MECHANICAL PROPERTIES OF AISI 415 STAINLESS STEEL
Aidin BarabiGrand Ballroom A
Hydraulic turbine blades are exposed to cyclic loading which favors formation and propagation of fatigue cracks. Due to different in-service loading regimes, the crack tip is subjected to a range of strain rates. The present study proposes an experimental investigation of the mechanical properties of a 13%Cr-4%Ni martensitic stainless steel at strain rates (ε ̇) ranging from 4.7E-6s-1 to 6E-2s-1. The ε ̇ was chosen to simulate plastic deformation rate at the crack tip for load cycles frequency ranging from 0.3 to 35 Hz. Two heat treatments were applied to the alloy to obtain a martensitic microstructure containing 2% and 20% of reformed austenite (RA). For the sample containing 2% of RA, increasing ε ̇ resulted in a difference in yield strength (σ_y) and ultimate tensile strength (UTS) of 10% and 7%, respectively. As for the sample containing 20% of RA, an increase in the RA content had no significant effect on the σ_y strain rate sensitivity. On the other hand, it reduced the UTS strain rate sensitivity to 1%. These results indicate that σ_y is strain rate sensitive for both tested microstructure. Results also show that presence of RA increased 23% the uniform elongation as compared to microstructure containing
EXTENDED ABSTRACT
15:00 - 15:20
FROM CONTINUUM TO QUANTUM MECHANICS STUDY ON THE FRACTURE OF NANOSCALE NOTCHED BRITTLE MATERIALS
Yabin YanGrand Ballroom A
The fracture of nanoscale notched brittle materials is investigated using the multi-scale analysis of cohesive zone modeling and first-principles calculations based on the notched nano-cantilever bending experiment. first-principles calculations are performed to investigate the inherent fracture properties of single-crystal silicon from atomic and electronic viewpoints. The fracture surface energy and critical bond length for the break of atomic bonds during the fracture are compared with the cohesive energy and failure length parameter, which indicates that the consumed energy is an effective linkage to quantify the fracture of brittle materials at different scales.
EXTENDED ABSTRACT
15:20 - 15:40
MICROMECHANICAL MODELING OF THE FRACTURE PROCESS IN ADVANCED METAL SANDWICH PLATES USING FFT-BASED HOMOGENIZATION
Felix BödekerGrand Ballroom A
The fracture behavior of the complex core material of Hybrix sandwich plates was investigated by micromechanical modeling using FFT-based homogenization. A method for generating virtual Representative Volume Elements (RVEs) based on experimental observations was developed and the homogenization results were compared to experiments in peel mode I. The applicability of micromechanical simulations to the optimization of fracture properties of the Hybrix core is discussed.
EXTENDED ABSTRACT
15:40 - 16:00
NUMERICAL MODELING OF SPALLING PHENOMENON ON ALUMINA BY DISCRETE ELEMENT METHOD.
Luc BremaudGrand Ballroom A
The numerical Discrete Element Method (DEM) approach has already proven its legitimacy to represent the behaviour of brittle or quasi-brittle materials such as ceramics at quasi-static regime. The present study investigates the DEM approach in reproducing the dynamic behaviour of an AL23 ceramic under dynamic spalling tests. Elastic microscopic parameters of the DEM model are calibrated using quasi-static uniaxial tensile tests in order to match the macroscopic elastic behaviour of an AL23 ceramic. The DEM model is then used to simulate the stress waves propagation, interactions and fracture mechanisms generated during spalling damage tests. Rear face velocity profiles have been measured and compared to the numerical results. The strain-rate sensitivity of the spalling stress of AL23 ceramic has been observed experimentally. The anisotropic DFH (Denoual-Forquin-Hild) damage model is implemented in DEM to take into account the strain rate sensitivity. Several methods to manage anisotropy in DEM are tested.
EXTENDED ABSTRACT
14:00 - 16:00 Symp08-W2: Beyond Similitude: Role of Multiscale Heterogeneity in Fracture Prognosis
Organizers: Ashley Spear and Gustavo Castelluccio
14:00 - 14:40
Keynote
EXAMINING SUB-GRAIN DRIVING FORCES FOR SMALL CRACK GROWTH [Keynote]
William MusinskiWalnut
High energy X-ray diffraction microscopy (HEDM) techniques and micro-computed tomography were combined with in-situ cyclic loading to examine the evolution of sub-grain-level fatigue crack growth within a Ni-base superalloy at room temperature. A focused-ion beam notch was introduced within the specimen to concentrate damage within the characterized microstructure region of interest. The test specimen was subjected to fatigue cycling with pauses for periodic micro-computed tomography and HEDM measurements to characterize the sporadic growth of the crack front and grain-level strains ahead of the crack front. The HEDM data was used to instantiate a crystal plasticity finite element model and compared to experimentally determined grain-level strains, sub-grain reorientation, and crack path.
EXTENDED ABSTRACT
14:40 - 15:00
PREDICTING MICROSTRUCTURALLY SENSITIVE FATIGUE-CRACK PATH IN WE43 MAGNESIUM USING HIGH-FIDELITY NUMERICAL MODELING AND THREE-DIMENSIONAL EXPERIMENTAL CHARACTERIZATION
Brian PhungWalnut
Microstructurally small fatigue-crack growth in polycrystalline materials is highly three-dimensional due to sensitivity to local microstructural features (e.g., grains). One requirement for modeling microstructurally sensitive crack propagation is establishing the criteria that govern crack evolution, including crack deflection. Here, a high-fidelity finite-element modeling framework is used to assess the performance and validity of various crack-growth criteria, including slip-based metrics (e.g., fatigue-indicator parameters), as potential criteria for predicting three-dimensional crack paths in polycrystalline materials. The modeling framework represents cracks as geometrically explicit discontinuities and involves voxel-based remeshing, mesh-gradation control, and a crystal-plasticity constitutive model. The predictions are compared to experimental measurements of WE43 magnesium samples subject to fatigue loading, for which three-dimensional grain structures and fatigue-crack surfaces were measured post-mortem using near-field high-energy X-ray diffraction microscopy and X-ray computed tomography. Findings from this work are expected to improve the predictive capabilities of numerical simulations involving microstructurally small fatigue-crack growth in polycrystalline materials.
EXTENDED ABSTRACT
15:00 - 15:20
EFFECT OF LOCAL HETEROGENEITY ON FRACTURE DRIVING FORCES
Gustavo CastelluccioWalnut
Traditional fracture theories infer the local crack growth driving forces by surveying the mechanical response far from the crack. Although this approach has successfully predicted fracture by assuming isotropic and homogeneous materials, local heterogeneity such microstructural heterogeneity can affect fracture response. This presentation will evaluate the differences between the local and far field driving forces using different microstructure-sensitive modelling approaches. We will demonstrate the effects of grain size and crystallographic orientation gradients on crack tip blunting and microplasticity variability. We will also explore the role of microstructures as a buffer between the local and far fields considering the propagation of uncertainty from constitutive models into fracture prognosis. To conclude, we will discuss the implications for traditional experimental methods based on far field measurements smearing out important crack tip variability.
EXTENDED ABSTRACT
15:20 - 15:40
CONSIDERATIONS ON THE R-CURVE OF HUMAN CORTICAL BONE
Glynn GallawayWalnut
Human bone presents several factors which complicate the evaluation of fracture. Several toughening mechanisms protect humans from health complications, but also contribute to a unique 3D crack geometry. In this study, we combine 3D imaging, in-situ loading (in air and with a waterbath), and computational analysis for the interpretation of the toughness measurements of human cortical bone in the aging human population.
EXTENDED ABSTRACT
14:00 - 16:00 Symp09-W2: Fatigue and Fracture of Additively Manufactured Materials
Organizers: Bo Chen, Nagaraja Iyer, and Filippo Berto
14:00 - 14:20
HIGH CYCLE FATIGUE OF AM PRODUCED HOT WORK TOOL STEEL
Dimitrios NikasGrand Ballroom E
Additive manufacturing as a mean to produce near net shape components of metal alloys has evolved in many commercial applications during the last decade. Still, development of additive processes and alloy grades requires new research knowledge. In the present study focus is on advanced high strength martensitic steels and fatigue properties. They are used in demanding tooling and high performance applications where high strength and toughness, both static and dynamic, are required. Fatigue strength and failure defect distributions of one AISI H13 AM grade and one corresponding ingot cast and forged grade have been characterized and modelled.
EXTENDED ABSTRACT
14:20 - 14:40
ON THE MECHANISTIC ORIGINS OF THE INCREASED HYDROGEN ENVIRONMENT-ASSISTED CRACKING SUSCEPTIBILITY OF AM 17-4PH STEEL
Zachary HarrisGrand Ballroom E
Literature results indicate that the hydrogen environment-assisted cracking susceptibility of additively manufactured (AM) 17-4PH steel fabricated using laser powder bed fusion is increased relative to comparable wrought 17-4PH. This study seeks to understand the mechanistic origins of this increased susceptibility through a detailed examination of near-crack deformation, alloy microstructure, and hydrogen-metal interactions. Based on these data, it is determined that sub-micrometer porosity present in the AM material provides a primary contribution to the degradation in HEAC resistance. The mechanistic basis for the influence of porosity is considered in the context of an existing model for HEAC. The implications of these findings on the broader AM community are then discussed.
EXTENDED ABSTRACT
14:40 - 15:00
ENVIRONMENTAL CRACKING OF ADDITIVELY MANUFACTURED 316L STAINLESS STEEL
Michael RoachGrand Ballroom E
The widespread use of 316L stainless steel for applications requiring increased corrosion resistance has motivated interest in leveraging additive manufacturing (AM) for in-service production of replacement components. However, while a large number of studies have examined the effect of AM processing parameters on yield strength and fracture toughness, detailed assessments of the environment-assisted cracking (EAC) susceptibility of AM alloys are limited. The objective of this study is to compare the corrosion fatigue and stress corrosion cracking behavior of AM and wrought 316L with similar yield strengths in aqueous chloride environments at temperatures ranging from 293 to 358 K. As built material will be compared with cold drawn bar, and hot isostatic pressed (HIP) material will be compared with plate in the annealed state to minimize the effect of different yield strength between material form. Differences in microstructure and build-introduced stresses are correlated with EAC performance, thereby providing mechanistic insights into the factors governing EAC behavior of AM 316L. In particular, the influence of build direction, residual stresses, texture, and compositional heterogeneities are all assessed.
EXTENDED ABSTRACT
15:00 - 15:20
DEFECT STATISTICS AND FRACTURE INITIATION MECHANISMS IN AS-BUILT AND HEAT-TREATED ADDITIVE MANUFACTURED 17-4 STEEL
Ravi KiranGrand Ballroom E
Defects in additively manufactured metals are detrimental to the manufactured components. Due to the rapid melting and solidification during printing, a non-homogeneous microstructure is typical in the metal specimens additively manufactured using laser powder bed fusion. The present study aims to understand the fracture initiation mechanism in as-built and heat-treated additively manufactured 17-4 stainless steel. To this end, 17-4 stainless steel unnotched and notched specimens additively manufactured using direct metal laser sintering were used. Solution annealing and subsequent aging were performed as the post-heat treatment of the stainless steel test specimens. Postmortem fractography using scanning electron microscopy (SEM) of the fracture surface and micro-computed tomography (micro-CT) of the test specimens before and after fracture revealed that the large coalesced microvoids with sizes greater than 120 µm significantly influence the ductile fracture initiation in the additively manufactured steel specimens.
EXTENDED ABSTRACT
14:00 - 16:00 Symp11-W2: Finite Fracture Mechanics: Theoretical Aspects, Numerical Procedures, and Experimental Applications
Organizers: Vladislav Mantič, Pietro Cornetti, Dominique Leguillon and Pedro Camanho
14:00 - 14:40
Keynote
V-NOTCHED COMPONENTS UNDER TORSIONAL FATIGUE LOADING [Keynote]
Alberto SaporaDogwood B
Finite Fracture Mechanics (FFM) is applied to assess the brittle or quasi-brittle failure initiation at sharp V-notches under torsional loading. By assuming that failure is shear stress governed, the approach is developed in the fatigue framework. The analysis includes a discussion on the calibration of the material properties, and the comparison with experimental data available in the literature.
EXTENDED ABSTRACT
14:40 - 15:20
Keynote
MULTIPLE DELAMINATIONS PREDICTION ON ILTS SPECIMENS BY AN ABAQUS IMPLEMENTATION OF THE COUPLED CRITERION OF FFM AND LEBIM [Keynote]
Luis TavaraDogwood B
Inter-Laminar Tensile Strength (ILTS) test uses L-shaped composite coupons with laminas having different orientations. To model multiple delaminations that occur in ILTS specimens a quite general formulation of the Coupled Criterion of Finite Fracture Mechanics (CCFFM) with the Linear Elastic-perfectly Brittle Interface Model (LEBIM) is applied.
EXTENDED ABSTRACT
15:20 - 15:40
STUDY OF INTRA- AND INTER-LAMINAR DAMAGE INTERACTIONS IN LAMINATED COMPOSITES USING FINITE FRACTURE MECHANICS
Jean VereeckeDogwood B
Composite laminates are widely used in aerospace industry overall for their mass-to-performance ratio. In this context, the storage of cryogenic propellant is subject to numerous studies, in which the composite must ensure a sealing function. However, the permeability is strongly related to the damage state of the laminate and heterogeneities at micro and meso scales make their damage behavior hard to predict. Among all damage mechanisms, transverse cracks and microdelamination are particularly interesting. Indeed, their coalescence through the laminate thickness is likely to generate leakage paths. Experimental observations often show that the transverse cracking bifurcates either in microdelamination at ply interfaces or in additional transverse cracks in adjacent plies. The Finite Fracture Mechanics (FFM) demonstrated its relevance in the prediction of crack propagation but it relies on a presupposed path. In this context, two scenarios, microdelamination at transverse crack tips and transverse cracking in adjacent plies are studied with FFM in order to identify the preferred mechanism regarding some material properties (limit strength, energy release rate…) and geometrical parameters (thickness, orientation…). In addition to the cracking scenario and morphology, FFM will also provide information on cracking rates with the aim of predicting the overall damage state of the laminate.
EXTENDED ABSTRACT
15:40 - 16:00
FATIGUE LIFE PREDICTIONS OF NOTCHED COMPONENTS BASED ON FINITE FRACTURE MECHANICS
Amir Mohammad MirzaeiDogwood B
A new fatigue criterion is proposed to assess the lifetime of notched components by developing Finite Fracture Mechanics (FFM). Wohler’s curves for a plain and a notched sample are used for the calibration of the model parameters, and theoretical predictions are validated against experimental data taken from the literature.
EXTENDED ABSTRACT
14:00 - 16:00 Symp15-W2: Advanced Computational Methods in Fracture
Organizers: P.R. Budarapu, M.K. Pandit, A.K. Pradhan, S. Natarajan, T. Rabczuk
14:00 - 14:30
Keynote
DYNAMIC FRACTURE BEHAVIOR OF LAYERED COMPOSITE AGAINST MULTIPLE PROJECTILE IMPACT LOADING [Keynote]
Sobhan PattajoshiHickory
A layered composite comprising of reinforced concrete, steel plates, and boulder-mixed soil are used as a bunker which can safely protect military personnel against multiple projectile impacts. This paper uses computational methods (Ansys AUTODYN) for the fracture to check the structural integrity of the layered target against projectile impact.
EXTENDED ABSTRACT
14:30 - 14:50
COMPUTATIONAL INVESTIGATION OF DYNAMIC FRACTURE BEHAVIOR OF MULTI-LAYERED STRUCTURES AGAINST MULTIPLE BALLISTIC IMPACTS
Shashwat KapoorHickory
Since, the protection of military structures against ballistic impacts is of grave concern. Protective structures made up of homogeneous concrete or fiber-reinforced concrete might not be sufficient to resist repeated ballistic impacts. Therefore, there is a need to develop and analyze functionally graded layered composite structures with varying material properties. Additionally, conducting experimental studies on such full-scale layered composite structures is extremely time-consuming and expensive. Analysis of such structures by developing a computational framework will provide realistic solutions. Hence, multi-layered structures comprising reinforced concrete, boulder-mixed soil, shredded rubber, and hot-rolled steel plates are proposed for bunkers which can safely protect military personnel against repeated ballistic impacts. The investigation presents the development of finite element models using ABAQUS–EXPLICIT to study the dynamic fracture behavior and to check the structural integrity of the multi-layered structures against ballistic impacts.
EXTENDED ABSTRACT
14:50 - 15:10
APPLICATION OF CONCURRENT ATOMISTIC-CONTINUUM COUPLING TO STUDY FRACTURE IN POLYMER NANOCOMPOSITES
Sankha Subhra AdityaHickory
Nanoparticles have been used to improve the fracture toughness of polymer composites. Understanding the nanoscale mechanisms that promote enhanced toughness is critical to tailoring such material properties, and Molecular Dynamics (MD) simulations have been extensively used for this purpose. However, our ability to model real-life macroscale cracks purely using MD simulations is limited by the large length and time scales involved. Therefore, concurrently coupling continuum models such as Finite Element Method (FEM) with MD can potentially circumvent the length-scale issue and help provide insight into these basic failure mechanisms. The objective of this paper is to use a state-of-the-art concurrent atomistic-continuum coupling technique to study the nanoscale crack-tip behavior of a macroscale crack in a thermosetting resin and demonstrate its potential to study macroscale fracture in nanocomposites materials.
EXTENDED ABSTRACT
15:10 - 15:30
FRACTURE OF HIGHLY ELASTIC AND COMPOSITE MATERIALS AT COMPRESSION ALONG NEAR-SURFACE CRACK IN CASE OF SMALL DISTANCE BETWEEN FREE SURFACE AND CRACK
Mykhailo DovzhykHickory
In this paper, the nonclassical problems of fracture mechanics for a near-surface crack in the case of small distances between a free surface and a crack plane was investigated. To solve this problem the numerical analytical procedure was proposed. As an example, numerical research for highly elastic material with Bartenev-Khazanovich potential, and composite material was conducted. Also, the applicability of the «beam approximation» for these materials was investigated.
EXTENDED ABSTRACT
15:30 - 15:50
RECENT ADVANCEMENTS AND APPLICATIONS IN DEVELOPMENT OF SMART CRACK GROWTH SIMULATION
Guoyu LinHickory
SMART (Separating, Morphing, Adaptive and Remeshing Technology) is a finite element based crack growth simulation framework[1] recently developed in the ANSYS Mechanical Solver. Crack representation is essential for FE based fracture and crack growth simulation. The ability to control the mesh and ensure mesh quality at remeshing are essential for robust and accurate crack growth prediction. In this paper several examples and benchmarks are presented to demonstrate the effectiveness and validity of the SMART framework for complex crack propagation simulation. We will then present the latest technological advancements in SMART development related to meshing control with special focus on meshing refinement and coarsening, and adaptive crack initiation.
EXTENDED ABSTRACT
14:00 - 16:00 Symp17-W2: Damage, Fracture, and Fatigue of Composites
Organizers: Raj Das and Rhys Jones
14:00 - 14:20
INTERFACE CRACK OR DELAMINATION: WHEN & WHERE TO INITIATE? HOW TO PROPAGATE & HOW BIG AREA TO ATTAIN?
Zheng-Ming HuangChestnut
After inserting a matrix, secondary layer in between the two adjacent primary layers of the bimaterial, the overall load causing the weakest secondary layer element to fail can be even bigger than the bimaterial’s strength. The stresses in the element must be untrue. In this paper, two modifying coefficients (MCs) are applied to modify the stresses, which are then substituted into a strength failure equation of the matrix. If it is fulfilled, the failed secondary layer element is deleted, and an interface crack occurs within the two adjacent primary layer elements. Continued in this way step by step, all of the interface failure information is available without iteration. Only the critical displacements at the peak loads of a DCB (double cantilever beam) and an ENF (end notched fracture) tests are required as inputs in addition to the material properties of the two primary layers and the secondary layer.
EXTENDED ABSTRACT
14:20 - 14:40
EXPERIMENTAL AND NUMERICAL STUDY ON THE DELAMINATION BEHAVIOUR OF INTERLEAVED COMPOSITES WITH AUTOMATED TAPE LAYING
Huifang LiuChestnut
Automation of composite materials manufacturing is an important pre-requisite to upscaling the manufacturing without diminishing quality of the end-products. In this research, interleaved composites have been manufactured by modified skip tow automated tape laying (ATL) process, where each tape can cross many tapes multiple times. This tape architecture has been shown previously to reduce delaminations through the internal/inherent crack arresting features. Here, Single Leg Bending (SLB) experiments were carried out to study the delamination behaviour of the interleaved composites under quasi-static loading. It was found that, following from delamination initiation, the crack plane propagated with a new crack regularly deviating/migrating away from the primary inter-tapes crack plane towards other inter-tapes interfaces due to the gaps, misorientations and interleaves between the tapes. The multiple delaminations fracture toughness was qualified by the compliance calibration (CC) method in which the fracture toughness was theoretically calculated by crack length back-calculated specimen compliance, and was also numerically modelled by accounting for large-scale fibre bridging. Moreover, both optical microscopy and X-ray computed tomography were performed to examine defects in the specimens before testing and damage after testing. It was observed that the generation of multiple cracks was heavily depended on the local lay-up structure. This suggests
EXTENDED ABSTRACT
14:40 - 15:00
EFFECT OF PROCESS-INDUCED DEFECTS ON MODE I BEHAVIOR OF PMCS: RANDOM DEFECTS VS. CONTROLLED DEFECTS
Joseph GunstChestnut
With advances in composite manufacturing, the need to establish process-microstructure-property relations remains an ongoing challenge. Effective property predictions, including damage tolerance behavior of advanced composites, often requires explicit modeling of defects and investigating the onset and propagation of damage. The high porosity level is a more commonly encountered defect in heterogeneous composite materials. The current work uses the cohesive zone modeling (CZM) approach adapted for explicit defects in the crack path within a finite element (FE) numerical framework. Random and controlled pore distributions have been modeled and numerically compared. Experimental efforts toward creating controlled pores in the crack path are ongoing. The execution of the current approach will enable better material behavior predictions for advanced composite materials.
EXTENDED ABSTRACT
15:00 - 15:20
SCALE EFFECTS IN THE POST-CRACKING BEHAVIOUR OF CNT-EPOXY COMPOSITES: PREDICTING CRACK JUMPS AND DUCTILE-TO-BRITTLE TRANSITIONS
Federico AccorneroChestnut
The scale effects on the global structural response of fibre-reinforced brittle-matrix specimens subjected to bending are discussed in the framework of Fracture Mechanics by means of the Updated Bridged Crack Model (UBCM). This analytical model assumes the composite as a bi-phase material, in which both the brittle matrix and the reinforcing fibres contribute to the global toughness. In particular, the bridging mechanism of the reinforcing layers can be described by an appropriate cohesive softening constitutive law, which takes into account the progressive slippage of the fibre inside the matrix. In addition, the discontinuous phenomena, i.e., crack jumps (snap-back) and snap-through instabilities, which experimentally characterize the post-cracking behaviour of the composite, can be captured in a quantitative way. Furthermore, UBCM predicts different post-cracking regimes depending on two dimensionless numbers: the reinforcement brittleness number, NP, and the pull-out brittleness number, Nw. Finally, UBCM simulations of non-smooth crack evolutions are compared to experimental results reported in the scientific literature, in which carbon nanotube-epoxy specimens are tested in bending.
EXTENDED ABSTRACT
15:20 - 15:40
THERMAL BEHAVIOR DURING FRACTURE OF HYBRID EPOXY/CNT/GNP COMPOSITES
Julkarnyne M Habibur RahmanChestnut
This work reports the distinct thermal signatures during failure of epoxy-based nanocomposites comprised of multi-walled carbon nanotubes (MW-CNTs) and graphene nanoplatelets (GNPs). These fillers individually alter the material properties, but their synergy dramatically improves mechanical performance and other multifunctionality. CNT/epoxy, GNP/epoxy nanocomposites are fabricated and compared with the mixed GNP/CNT/epoxy hybrid nanocomposites containing the same weight percentage. Temperature profiles during tension tests have been observed using an infrared thermography (IR) camera yielding distinctive temperature profiles.
EXTENDED ABSTRACT
15:40 - 16:00
DETECTION OF MODE I INTERLAMINAR CRACK IN CNF DOPED GFRP LAMINATES USING ELECTRICAL IMPEDANCE TOMOGRAPHY
Akash DeepChestnut
Electrical impedance tomography (EIT) is an emerging structural health monitoring tool for self-sensing composites using the piezoresistive effect. This work presented a novel methodology to detect interlaminar crack or delamination developed during mode I loading in carbon nanofillers doped glass fiber reinforced polymer (GFRP) composites using EIT. DCB specimens were fabricated with 1 wt% carbon nanofillers (CNF) doped GFRP laminates to produce interlaminar crack under mode I loading. The boundary voltage datasets, obtained from electrodes mounted on top and bottom surface of the specimen, were used to solve the EIT inverse problem to get the reconstructed conductivity change map. This methodology demonstrated that interlaminar cracks can be successfully detected using EIT.
EXTENDED ABSTRACT
16:00 - 16:30 Coffee 3B
Coffee Break PM
16:30 - 18:00 Parallel Sessions W3
Parallel sessions symposia W3
16:30 - 18:00 Symp05-W3: Hydrogen Embrittlement and Environmentally Assisted Cracking
Organizers: Jesus Toribio, Chris San Marchi, and Joseph Ronevich
16:30 - 16:50
FRACTURE TOUGHNESS CHARACTERIZATION OF HIGH STRENGH MARTENSITIC STEELS SUBJECTED TO HYDROGEN
Armin HalilovicGrand Ballroom C
High strength steels that are subjected to hydrogen may experience environmentally assisted degradation. These types of steels exhibit a loss of load bearing capacity. This paper presents a numerical-experimental method for screening materials’ susceptibility subjected to hydrogen. In this work it is found that hydrogen needs time to diffuse into the material and time to cause degradation. It is seen in this work that experimental fracture mechanics combined with cathodic polarization is an excellent choice to obtain reproducible results as well as a screening method of materials sensitivity to hydrogen embrittlement. An environmentally driven transition from high to low toughness was observed in a rather narrow range of loading rates. In this range, it was also observed that the hydrogen degradation may be mitigated by crack growth leaving less time for the degradation process to occur and a rise in toughness
EXTENDED ABSTRACT
16:50 - 17:10
IN-SITU NEUTRON IMAGING AND MODELING OF HYDROGEN EMBRITTLEMENT IN HIGH STRENGTH STEELS
David LindblomGrand Ballroom C
A new experimental method to investigate hydrogen assisted cracking is presented in this paper. By combining electrochemical pre-charging, fracture mechanics and neutron imaging it is possible to get large experimental data which can give insight into the local fracture process zone. Furthermore, it can be used to calibrate FEM-models which considers crack propagation, embrittlement, and H diffusion from a moving stress field.
EXTENDED ABSTRACT
17:10 - 17:30
HYDROGEN EMBRITTLEMENT BEHAVIOR OF A 1.5 GPA CLASS DUAL-PHASE STEEL
Rama Srinivas VaranasiGrand Ballroom C
In the current work, using tensile tests, we evaluate the hydrogen embrittlement behavior of a 1.5 GPa dual-phase (DP) steel consisting of ~75% martensite. Contrary to previous studies of DP steel with ultimate tensile strength (UTS) ≤1.2 GPa, a predominant brittle fracture is observed in the DP steel in the absence of hydrogen. Conventionally, in the absence of hydrogen, ferrite is reported to arrest cracks, resulting in a ductile fracture. However, ferrite undergoes {100} brittle cleavage cracking. Furthermore, the morphology of the martensite crack is found to have an influence on ferrite {100} cleavage cracking. The micro-mechanisms are presented in detail. Subsequently, we investigated the effect of hydrogen on the degradation of tensile properties. Hydrogen caused a significant deterioration of UTS, from 1.5 GPa to 0.9 GPa. The damage mechanisms of hydrogen-induced fracture are discussed in detail.
EXTENDED ABSTRACT
17:30 - 17:50
FRACTURE TOUGHNESS OF ZIRCALOY-4 CLADDING IN CASE OF DELAYED HYDRIDE CRACKING
Pierrick FrancoisGrand Ballroom C
Spent nuclear fuels are stored after their use in reactors. Dry storage can favor the appearance in the fuel rod cladding of a mechanical-chemical phenomenon referred to as Delayed Hydride Cracking (DHC). DHC is divided into three iterative steps: (i) diffusion of hydrogen in solid solution; (ii) precipitation of this hydrogen into hydrides; (iii) brittle fracture of hydrides. To assess the risk of occurrence of this phenomenon, the fracture toughness is determined by calculating the stress intensity factor below which DHC is not observed (KIDHC) based on an experimental procedure and a numerical model.
EXTENDED ABSTRACT
16:30 - 18:00 Symp06-W3: Microstructures and Fracture in Advanced Materials
Organizers: Tong-Yi Zhang, Chad Landis, Weiqiu Chen, Ralf Müller, and Jie Wang
16:30 - 17:00
Keynote
THE JUMPING DIELECTRIC BREAKDOWN BEHAVIOR INDUCED BY CRACK PROPAGATION IN FERROELECTRIC MATERIALS: A PHASE FIELD STUDY [Keynote]
Jie WangGrand Ballroom A
Ferroelectric materials often experience fracture and dielectric breakdown under large mechanical and/or electrical loadings. These two failure behaviours can affect each other and may lead to new phenomena. In the present study, a new type of jumping dielectric breakdown are predicted during the crack propagation in ferroelectric materials by using a phase field model with multiple order parameters. The driving force for the jumping dielectric breakdown induced by crack propagation is analysed based on the concept of configurational force. It is found that the jumping dielectric breakdown is attributed to the competition between the crack propagation and the breakdown initiation at the moving crack tip. The breakdown pattern is related to the polarization domain structure and thus greatly influenced by the applied electric field and the crack boundary conditions. Further, the jumping breakdown associated with possible mechanical degradation on the material can change the driving and resistant forces for the crack propagation. The present work not only suggests a novel dielectric breakdown behaviour during crack propagation but also provides new insights into the coupling failure of ferroelectric materials.
EXTENDED ABSTRACT
17:00 - 17:20
TOUGHNESS AND FATIGUE CRACK GROWTH MECHANISMS OF WC-CO CERAMIC-METAL COMPOSITES: A COMPARATIVE STUDY USING CONTROLLED SMALL INDENTATION FLAWS AND LONG THROUGH-THICKNESS CRACKS
Luis LlanesGrand Ballroom A
Crack growth mechanics and mechanisms under both monotonic and cyclic loading are investigated in a WC-Co cemented carbide by using small and long cracks, both of them artificially introduced by indentation and cyclic compression of unnotched and notched specimens respectively. Agreement and discrepancies on fracture toughness and fatigue crack growth behavior are discussed and rationalized, on the basis of the similitude evidenced in toughening and fatigue degradation mechanisms for both crack types, by taking into account the residual stress field arising after indentation in the unnotched specimens.
EXTENDED ABSTRACT
17:20 - 17:40
STRUCTURE EVOLUSTIONS AND MECHANICS OF MATERIALS DURING ELECTROCHEMCIAL ION INSERTION
Kaikai LiGrand Ballroom A
Electrochemical ion insertion plays an important role in secondary batteries like lithium ion batteries and sodium ion batteries. Electrochemical ion insertion involves coupled ion-electron transfer and usually causes crystal/electronic structure changes as well as chemical stress/strain of the host materials. This presentation discusses the crystal and electronic structure evolution of CeO2, MoS2, and RuO2 during electrochemical lithium/sodium ion insertion, and the chemical strain of graphite during lithium ion insertion. The electrochemical lithium insertion as an effective method to improve the electrocatalytic performance of RuO2 will also be introduced.
EXTENDED ABSTRACT
17:40 - 18:00
HIGH QUALITY GROWTH AND ADHESION ENERGY MEASUREMENT OF BILAYER GRAPHENE ON SAPPHIRE
Kenneth LiechtiGrand Ballroom A
One bottleneck in integrating graphene in the next generation of microelectronics devices is the efficient and effective transfer of graphene from its growth substrate to the substrate that is targeted for device fabrication. Dry transfer offers the potential for a relatively fast manufacturing process with minimal contamination of and damage to graphene. The paper describes the development of a chemical vapor deposition process for growing graphene on sapphire rather metal. It also demonstrates that graphene can be dry transferred to another substrate via a polymer carrier by exploiting rate and mode-mix dependent interfacial fracture.
EXTENDED ABSTRACT
16:30 - 18:00 Symp10-W3: Small Scale Specimen Testing
Organizers: V. Jayaram, Raghu V. Prakash, N Jaya Balila, Robert Lancaster, Bernd Gludovatz, and Dan Gianola
16:30 - 17:10
Keynote
RELATING NANOSCALE STRUCTURE AND PROPERTIES TO MACROSCALE FRACTURE TOUGHNESS FOR BULK METALLIC GLASSES [Keynote]
Jamie KruzicGrand Ballroom B
Bulk metallic glasses (BMGs) can range from exceptionally tough to brittle depending on their structural state; however, quantifying their structure-property relationships has been an unresolved challenge. Our findings revealed that local hardness variations within the BMG microstructure strongly affect the fracture behavior. Moreover, the hardness heterogeneities are controlled by the size and volume fraction of FCC-like medium-range order (MRO) clusters. We have proposed a model of ductile phase softening whereby relatively soft FCC-like MRO clusters sit in a matrix of harder icosahedral dominated ordering, while micropillar compression testing has revealed how the activation of these clusters into shear transformation zones can be negatively affected by oxygen impurities which in turn lower the fracture toughness.
EXTENDED ABSTRACT
17:10 - 17:30
IN SITU SEM HIGH-THROUGHPUT CYCLIC TESTING OF FREESTANDING THIN FILMS
Alejandro BarriosGrand Ballroom B
This work presents a small-scale high-throughput technique to characterize the cyclic behavior of freestanding thin films. The technique consists of the microfabrication of a Si carrier composed of an array of grips and freestanding dogbone thin films and of the automated in situ Scanning Electron Microscope (SEM) fatigue testing of the microfabricated carrier. The Si carrier functions as a nanomechanical testing device in which multiple dogbones can be simultaneously and independently tested under the same applied mechanical conditions. As a proof-of-concept, the fatigue behavior of nanocrystalline Al thin films was investigated. The technique allows for the simultaneous evaluation of crack nucleation and propagation across the fatigue life of several dogbones, facilitating the understanding of deformation mechanisms in nanocrystalline metals and providing statistically significant data. This technique reduces total testing time by orders of magnitude and allows for the investigation of the stochastic variability in fatigue failure. The current technique can be further expanded to account for different materials, new geometries and different loadings modes.
EXTENDED ABSTRACT
17:30 - 17:50
UNDERSTANDING FATIGUE DAMAGE PROGRESSION IN A STRUCTURAL STAINLESS STEEL THROUGH CYCLIC BALL INDENTATION TESTING
Raghu V. PrakashGrand Ballroom B
Understanding fatigue damage progression and estimating remaining life of dynamically loaded components has been a major challenge for several safety critical in-service components. Towards this, a few small specimen fatigue test methods are available, such as, cyclic ball indentation, cyclic small punch test and cyclic bulge test etc. Cyclic ball indentation has the potential to be deployed in-situ during plant maintenance to record fatigue response of localized spots. The method uses a spherical indenter of 1/16” (~1.58 mm) diameter which applies cyclic compression-compression loading on the material at selected location and monitors the load-displacement response continuously to identify failure event due to fatigue.
To capture a complete picture of this, controlled experiments using carefully prepared dog bone fatigue specimens of SS 304 have been conducted. The dog bone specimen is fatigue cycled under tension-tension uni-axial loading till failure, with Acoustic Emission (AE) signature capture during fatigue cycling. the fatigue cycling is interrupted periodically and cyclic ball indentation tests are carried out again at some locations of gage length to identify failure life cycle data of fatigue cycled specimen through displacement sensing and hysteresis area. Data obtained from cyclic ball indentation is then correlated with loss of stiffness.
EXTENDED ABSTRACT
17:50 - 18:10
DETERMINING THE RATE-CONTROLLING, GRAIN-BOUNDARY-MEDIATED MECHANISMS IN ULTRAFINE GRAINED AU AND AL FILMS
Olivier PierronGrand Ballroom B
The active grain boundary (GB) mediated mechanisms in ultrafine grained (ufg) Au and Al metallic films, and the extent to which they dictate plastic flow kinetics, are investigated in this work. The approach consists of a synergistic integration of in situ transmission electron microscopy (TEM) deformation experiments, nanomechanical testing, and transition state theory based atomistic modeling, in order to provide a linkage between GB-mediated dislocation processes and their deformation kinetics. The in situ TEM nanomechanical testing experiments are employed to simultaneously identify plastic deformation mechanisms, obtain key details, and measure the sample-level true activation volume in ufg thin films. The activation of relevant GB mediated dislocation mechanisms is modeled using the atomistic free-end nudged elastic band (FENEB) method as a function of representative, experimentally observed GB characters and local stress. Proper integration of experiments (sample-level true activation volume) and atomistic simulations (activation volumes of dislocation processes) to determine strength/rate-controlling mechanisms requires linking the applied stress to the local stress. To that end, a model of grain-size-dependent activation volume previously developed by Conrad is extended to account for the competition between various GB mediated mechanisms.
EXTENDED ABSTRACT
16:30 - 18:00 Symp15-W3: Advanced Computational Methods in Fracture
Organizers: P.R. Budarapu, M.K. Pandit, A.K. Pradhan, S. Natarajan, T. Rabczuk
16:30 - 17:00
Keynote
ADVANCED CRACK TIP FIELD QUANTIFICATION USING DIGITAL IMAGE CORRELATION, MACHINE LEARNING, AND INTEGRAL EVALUATION [Keynote]
David MelchingHickory
We use higher-order Williams coefficients from full-field displacement data obtained by digital image
correlation (DIC) to approximate complex crack tip fields with simpler expressions. The methodology is
based on invariant path integrals and machine-learned crack detection. We demonstrate the framework for
fatigue crack growth experiments of aluminium alloys and compare the results to matching finite element
simulations.
EXTENDED ABSTRACT
17:00 - 17:20
AN AUTOMATED PROCESS FOR SOLVING DUCTILE DAMAGE PARAMETER SELECTION USING MACHINE LEARNING AND FINITE ELEMENT ANALYSIS
Patrick G. MonganHickory
In this work we show how a machine learning algorithm based on a Bayesian optimization framework can be used in conjunction with finite element analysis to autonomously select parameter values for a ductile damage model representative of experimental test data.
EXTENDED ABSTRACT
17:20 - 17:40
SINGULAR INTEGRAL EQUATION FOR SOLVING COHESIVE CRACK PROBLEM FOR INITIALLY RIGID TRACTION-SEPARATION RELATION
Gaurav SinghHickory
In case of an initially rigid traction-separation cohesive relation, the total potential energy is not differentiable. This makes the use of variational operator over it questionable. Therefore, the accurate application of FEM is mathematically doubtful. The present work bypasses this issue by modelling the cohesive crack problem as a singular integral equation and solving it using Chebyshev polynomials.
EXTENDED ABSTRACT
17:40 - 18:00
BIOCHEMOMECHANICAL FRACTURE MECHANICS MODEL FOR DORSAL CLOSURE IN DROSOPHILA EMBRYOGENESIS
Xiqiao FengHickory
Dorsal closure is an essential developmental process of Drosophila embryogenesis, during which the ectoderm fuses the two sides of a gap into a complete ectodermal epithelium. A multiscale fracture mechanics model that involves active contractions of filopodial and lamellipodial protrusions is established to elucidate the biochemomechanically coupled mechanisms in the dorsal closure. The results agree well with relevant experiments.
EXTENDED ABSTRACT
16:30 - 18:00 Symp17-W3: Damage, Fracture, and Fatigue of Composites
Organizers: Raj Das and Rhys Jones
16:30 - 17:00
Keynote
DELAMINATION RESISTANCE IN RANDOM AND ALIGNED CNF-GFRP MULTISCALE STRUCTURAL COMPOSITES [Keynote]
Naresh DatlaChestnut
The improvement in mode-I interlaminar fracture toughness of glass fiber reinforced polymer (GFRP) laminates was explored in detail while carbon nanofibers are used as reinforcements with the epoxy matrix. Fracture tests with double cantilever beam (DCB) laminates were used to characterize the mode-I interlaminar fracture toughness and traction separation parameters. The mode-I traction separation parameters for delamination were identified for control laminates as well as for the CNF-GFRP DCB laminates. The effect of through thickness CNF alignment on interlaminar fracture toughness as well as on the traction separation parameters was also investigated. FE simulation was performed using the experimentally obtained TSLs to predict the load-displacement responses of control GFRP, random and aligned CNF-GFRP DCB laminates.
EXTENDED ABSTRACT
17:00 - 17:20
NOVEL SERR-CONTROLLED ENVIRONMENTAL FATIGUE TEST METHODOLOGY FOR ADHESIVE-BONDED LAMINATES
Gabriel RiedlChestnut
In this paper a novel environmental fatigue test methodology is presented, in which the strain energy release rate (SERR) was controlled during the cyclic experiment at an elevated temperature in humid air. Therefore, an electrodynamic testing machine equipped with a custom-built environmental chamber along with a compatible calculation and controlling software package was used. To determine the crack length based on force and displacement data a compliance-based calibration method was implemented. SERR values were deduced for individual load cycles employing an user defined control channel. The control channel allows for definition of a specific starting point (e.g., 10 J/m²) and an increase rate (e.g., +5 J/m² after 50,000 cycles). By holding the SERR constant over many cycles confidence bands were deduced for the measured crack propagation rates accounting for measurement uncertainties. To corroborate the novel methodology, experiments were conducted on double cantilever beam laminates bonded with soft adhesives in both, a SERR and a displacement controlled mode.
EXTENDED ABSTRACT
17:20 - 17:40
HEALING OF LAMINATED COMPOSITES AFTER STATIC AND FATIGUE DELAMINATION
Nilesh VisheChestnut
In this study, static fracture experiments under mode-I and mixed mode loading, and fatigue testing under mode-I loading were carried out on double cantilever beam (DCB) specimens, and subsequent healing of the delamination was investigated. Thermoplastic healants dispersed in a thermoset CFRP composite were used to perform the healing, triggered through brief heating in an oven. It was observed from the test results that delaminations can be healed efficiently and the healing was found to be repeatable. As a result of healing, significant crack closure was observed and fatigue crack growth rate was considerably reduced. These findings can be helpful in extending the service life of laminated composites.
EXTENDED ABSTRACT
17:40 - 18:00
INFLUENCE OF THE RANDOMNESS OF FIBER DISTRIBUTION ON THE DISPERSION OF FATIGUE RESPONSE IN STEEL FIBER REINFORCED CONCRETE USING MICRO-COMPUTED TOMOGRAPHY
Álvaro Mena-AlonsoChestnut
In this work, the dispersion in the flexural fatigue behavior of steel fiber reinforced concrete is studied. For this purpose, the random distribution of the fibers inside the specimens is analyzed by means of micro-computed tomography. The results reveal that fibers are better positioned in some specimens than in others, which partially explains the scatter of the results. In particular, fiber density or average height around the crack plane show a strong correlation with fatigue life.
EXTENDED ABSTRACT
18:00 - 19:00 Exhibition and NSF Mixer
Exhibition and NSF Mixer
19:00 - 20:00 ICF Council
ICF Council meeting
Thursday Jun 15 2023
07:00 - 08:00 Registration 4
Registration
08:30 - 10:00 Honor and Plenary Session P5
Plenary session P5
08:30 - 09:10
Plenary Lecture
NONINVASIVE DIAGNOSIS OF BLOOD VESSEL DISEASES RELATED TO VISCOELASTIC DETERIORATION OF BLOOD VESSEL WALL [Plenary Lecture]
A.T. YokoboriGrand Ballroom E
Studies of the strength deterioration of blood vessel were conducted under in vitro pulsatile pressure conditions. Furthermore, as an application of this results to the non destructive inspection, an algorithm of noninvasive diagnosing blood vessel diseases was established by detecting the acceleration response of blood vessel wall under pulsatile conditions, which estimates viscoelasticity of blood vessel wall characterized by our proposed parameter of I*. This method and theory were shown to be used to predict coronary artery disease by the clinical research. Furthermore, this method was applied to detect non-invasively the existence of aneurysm based on chaos theory. In this research, by dividing frequencies that compose the frequency of the pulsatile velocity of blood vessel wall into low and high frequency regions and conducting attractor analyses of the trajectory of pulsatile blood vessel wall, the possibility of accurate selective detection of blood vessel diseases such as mechanical deterioration of blood vessel wall ( low frequency region) and morphological change of blood vessel wall that are aneurysm (high frequency region) was indicated. In this lecture, close link of mechanical behavior of blood vessel wall with clinical disease of blood vessel is conducted.
EXTENDED ABSTRACT
09:15 - 09:55
Plenary Lecture
CRITICAL CONCERNS AND CHALLENGES IN FRACTURE AND FATIGUE ASSESSMENTS OF CORROSION RESISTANT ALLOY (CRA) PIPES WITH DISSIMILAR WELDMENTS: SUBSEA APPLICATIONS AND BEYOND [Plenary Lecture]
Claudio RuggieriGrand Ballroom E
The presentation will provide an overview of recent progress and challenges in fracture and fatigue assessments of corrosion resistant alloy (CRA) pipes having dissimilar weldments, with a particular focus on marine risers and subsea infrastructure. Despite advances in existing technology, there are still restrictions imposed by the use of new materials, more hostile environment and extreme loading conditions to obtain lighter and more cost-effective structures without compromising operation safety and environment protection. Clearly, there is a need of developing improved technological capabilities in connection with innovative and advanced procedures for fracture and fatigue assessments of critical components for subsea applications to ensure more reliable and fail-safe operations of the infrastructure for production and transportation of oil and gas in deep water offshore hydrocarbon reservoirs.
EXTENDED ABSTRACT
10:00 - 10:30 Coffee 4A
Coffee Break AM
10:30 - 12:30 Parallel Sessions Th1
Parallel sessions symposia Th1
10:30 - 12:30 Symp04-Th1: Brittle Fracture: 100 years After Publication of Griffith’s Theory
Organizers: Claudio Ruggieri, and Laszlo Toth
10:30 - 10:50
REVISITING LOCAL APPROACHES TO CLEAVAGE FRACTURE: AN OVERVIEW OF PROGRESS AND CHALLENGES FOR ENGINEERING-LEVEL APPLICATIONS
Claudio RuggieriGrand Ballroom C
This paper provides an overview of recent progress in probabilistic modeling of cleavage fracture phrased in terms of a local approach to fracture (LAF) and the Weibull stress concept. Emphasis is placed on the incorporation of plastic strain effects into the probabilistic framework by approaching the strong influence of constraint variations on (macroscopic) cleavage fracture toughness in terms of the number of eligible Griffith-like microcracks which effectively control unstable crack propagation by cleavage. Some recent results based on a modified Weibull stress model to predict specimen geometry effects on Jc-values for pressure vessel grade steels are summarized in connection with an engineering procedure to calibrate the Weibull stress parameters. These results are compared against corresponding fracture toughness predictions derived from application of the standard Beremin model. Finally, the robustness of LAF methodologies, including specifically the Weibull stress approach, is critically examined along with a discussion of key issues and challenges related to engineering applications in fracture assessments of structural components.
EXTENDED ABSTRACT
10:50 - 11:10
EVOLUTION OF GRIFFITH’S CONCEPT FROM 1921 TO THE PRESENT
Tamás FeketeGrand Ballroom C
The presentation will briefly review the history of the development of fracture mechanics from 1921 to the present, including the evolution of its basic concept. Arguments will be made that Griffith's basic concept, properly implemented in the context of modern non-equilibrium thermodynamics, remains valid.
EXTENDED ABSTRACT
11:10 - 11:30
GRIFFITH FRACTURE THEORY FOR THE SIZE EFFECT ON STRENGTH OF BRITTLE MATERIALS
K. S. Ravi ChandranGrand Ballroom C
The scale- or the size-dependence of mechanical strength in many brittle materials appears to follow a ‘universal law,’ of the form: strength proportional as:L^-n or V^-n, where n is a number, L is the length and V is the volume of the specimen or structure. Broadly known as the “size-effect” in geology, civil engineering, mining and materials science, this behavior determines the strength of large structures such as ice sheets, rock formations, coal pillars in mines and concrete beams and columns in civil infrastructure. As of now, there is no reliable scientific basis or theory to explain the size effect or for determining a reliable value of ‘n’. This has been the missing link in strength of materials for nearly a century since the Griffith’s crack theory Here, we show that the change in net-section strain energy, due an initial crack in a structure, and its dissipation within a crack layer of finite thickness, leads to the necessary and sufficient physical basis to explain the size-dependence of strength as L^-0.5. Further, size-independence of strength is explained simultaneously when the crack layer volume approaches the specimen volume.
EXTENDED ABSTRACT
11:30 - 11:50
LOCAL APPROACH TO CORRELATE CLEAVAGE FRACTURE TOUGHNESS WITH MICROSTRUCTURE OF STEEL
Mitsuru OhataGrand Ballroom C
This study proposes a new fracture model to correlate cleavage fracture toughness with microstructure of steel having bainitic structure with/without M-A constituent based on the Local Approach. In this model, a new fracture parameter to predict fracture toughness is derived through the proposal of microstructural characteristic of the material to control fracture toughness and on the basis of weakest link theory assumed Griffith crack. The material properties required for applying the fracture model are microstructural properties, those are 1) representative volume and 2) maximum size distribution of micro-crack nuclei, 3) mechanical properties and 4) effective energy release rate of matrix material. The applicability of the theoretical fracture model is demonstrated by experiments for upper bainitic steel with different microstructural morphology. This model can correlate materials properties which are microstructural and mechanical properties with fracture toughness.
EXTENDED ABSTRACT
11:50 - 12:10
MACRO CLEAVAGE ENERGY TO MICRO BOND BREAKING MECHANISMS- SHORTER IS TOUGHER
Dov ShermanGrand Ballroom C
Fracture of brittle solids is ultimately executed by atomistic-scale, discrete, and ultrafast bond-breaking mechanisms along the crack path. Here, we show new fracture behavior and properties of brittle materials, based on macroscopic fracture cleavage experiments of silicon crystal specimens and atomistic-scale semi-empirical model for bond-breaking mechanisms along the curved crack front, to relate micro to macro in fracture.
EXTENDED ABSTRACT
12:10 - 12:30
FAILURE OF THERMALLY SPRAYED 7YSZ COATINGS UNDER CYCLIC BENDING
Praveen KumarGrand Ballroom C
In this talk, we will describe damage accumulation and failure of free-standing micro-cantilevers made of 7YSZ coatings during cyclic bending in a nanoindentation system in both, the as-sprayed condition as well as after low-temperature thermal cycling up to 700 oC while attached to the substrate. The technique has been established as a means of tracking elastic modulus, hysteresis/creep, and fracture behavior as a function of coating densification during isothermal treatment at high temperatures. In contrast, low-temperature thermal cycling is designed to simulate operating conditions during which crack healing and sintering, which are known to lead to stiffening, are minimal. The load-displacement curves typically display hysteretic behavior with an increasing permanent residual displacement (ratcheting) after each cycle which increases with an increase in load, accompanied by a reduction in stiffness that is characteristic of damage accumulation. Failure appears to result from the formation of macrocracks after a critical amount of ratcheting. The number of mechanical cycles to failure reduces with the number of prior thermal cycles and with increasing maximum load/stress. Thus, mechanical cycling can act as a proxy for thermal cycling in evaluating progressive damage accumulation in TBCs.
EXTENDED ABSTRACT
10:30 - 12:30 Symp06-Th1: Microstructures and Fracture in Advanced Materials
Organizers: Tong-Yi Zhang, Chad Landis, Weiqiu Chen, Ralf Müller, and Jie Wang
10:30 - 11:00
Keynote
FRACTURE OF 2D RANDOM POROUS MEDIA PHASE FIELD MODELING AND MACHINE LEARNING [Keynote]
Xiangyu LiGrand Ballroom A
The study of fracture process of random porous media in pore scale is critical to understand theirs macroscopic failure behaviors. However, measuring the material properties or computing the mechanical response in both experiments and numerical simulation methods is different because of the heterogeneity and complexity of pore structure. In this study, a novel computational framework is proposed to simulate and predict fracture behavior by virtue of the phase field method and machine learning. The fracture process of one-cut Gaussian random field model is systematically calculated by phase field method, and the size effect of macro fracture is revealed in pore structure. The fracture behaviors observed in the experiments and simulations are remarkably similar to each other. A machine learning method is developed to further capture the regularities between the statistical parameters of the structure and the fracture behaviors. By combination the convolution neural network and generative adversarial networks the fracture load and crack propagation path can be predicted well. Through tuning the input data, it is proved that the mechanical variables before crack initiation determine the final fracture state. The computational framework developed in study provides an efficient and accurate solution scheme to the fracture problem of complex random materials.
EXTENDED ABSTRACT
11:00 - 11:30
Keynote
ADVANCES IN NECKING-ASSISTED CONTROLLED FRAGMENTATION BY COMPOSITE COLD DRAWING [Keynote]
Dong LiGrand Ballroom A
Fracture of materials has been regarded as the major danger to structures and is to be avoided in design, manufacture and maintenance. However, the application of classical cold drawing technique to advanced composites consisting of brittle semiconductor/glass/2D materials and ductile polymers prone to necking enables controlled fragmentation of the target component, resulting in structured patterns in micro- down to nano- scales. The controlled fragmentation can thus be taken advantage of to produce microstructures in large scale. Mechanism of controlled fragmentation and key parameters for tuning fragment size are revealed through theoretical modeling, experiment and finite element analysis. Effects of the addition of a sacrificial layer/capping layer on fragment size to improve capability of the cold drawing technique will also be discussed.
EXTENDED ABSTRACT
11:30 - 11:50
PHASE FIELD MODELING OF COUPLING EVOLUTION OF POLARIZATION, FRACTURE, AND DIELECTRIC BREAKDOWN IN FERROELECTRIC MATERIALS.
Yong ZhangGrand Ballroom A
Ferroelectric materials have attracted increasing attention due to their distinguished electromechanical performance. As two main failure behaviors, fracture and dielectric breakdown may occur simultaneously in ferroelectric materials. Understanding the coupling evolution of polarization, fracture, and dielectric breakdown is crucial for the application of ferroelectric materials under complex electromechanical environments. A phase field model was developed to investigate the coupling evolution behavior of polarization, fracture and dielectric breakdown in ferroelectric materials subjected to both mechanical and electrical loadings. Driving forces for fracture and dielectric breakdown were analysed based on the generalized configurational forces. The phase field simulations showed that dielectric breakdown can be induced by the concentrated electric field at impermeable crack tips. At the same time, the dielectric breakdown can influence the stress distribution around the crack tip as well as the driving force for crack propagation. The attraction of fracture to breakdown path and the deflection of breakdown to fracture path were observed during the coupling evolution of fracture and breakdown. The developed model framework can be employed to investigate more complex coupling failure behaviours of ferroelectric and dielectric materials.
EXTENDED ABSTRACT
11:50 - 12:10
FATIGUE DAMAGE MODELLING OF ALUMINIUM ALLOY POLYCRYSTALS CONTAINING INTERMETALLIC PHASES
Manon LengletGrand Ballroom A
The objective of this work is to model fatigue damage of the aluminium alloy AA2139 at the microscopic scale. It combines an experimental campaign and numerical simulations for a complete modelling of the alloy. Special attention is given to the reproduction of the alloy grain morphology and crystallography. Moreover, intermetallic phases are preferred sites for fatigue crack initiation in this alloy. Therefore, a method for taking into account the alloy microstructural complexity including the presence of intermetallic phases is presented. Finally, a fatigue damage model using a fatigue indicator parameter (FIP) is considered for the introduction of a crack and its propagation in simulations.
EXTENDED ABSTRACT
12:10 - 12:30
GRIFFITH FRACTURE IN VISCOELASTIC ELASTOMERS DONE RIGHT
Oscar Lopez-PamiesGrand Ballroom A
Strikingly, "pure-shear" fracture tests have repeatedly shown that fracture nucleation in (common hydrocarbon and other types of) viscoelastic elastomers occurs at a critical stretch that is independent of the stretch rate at which the test is carried out. In this Letter, we demonstrate that this remarkable --- yet overlooked --- experimental finding implies that the Griffith criticality condition that governs nucleation of fracture from large pre-existing cracks in viscoelastic elastomers can be written in fact as an expression not in terms of an elusive loading-history-dependent critical tearing energy T_c, as ordinarily done, but as one exclusively in terms of the intrinsic fracture energy G_c of the elastomer.
EXTENDED ABSTRACT
10:30 - 12:30 Symp09-Th1: Fatigue and Fracture of Additively Manufactured Materials
Organizers: Bo Chen, Nagaraja Iyer, and Filippo Berto
10:30 - 11:00
Keynote
RESISTANCE TO FRACTURE AND FATIGUE IN ADDITIVELY MANUFACTURED ALLOYS [Keynote]
Punit KumarGrand Ballroom E
Ti-6Al-4V fabricated by the laser powder bed-fusion (LPBF) process consists of metastable α' microstructure and columnar prior β grain (PBGs) mesostructures. These micro-and mesostructures adversely affect fracture toughness (KIc) in as-built conditions. After an optimized post-processing heat-treatment, the KIc of LPBF Ti-6Al-4V improves by ⁓104%; however, the anisotropy in KIc persists due to preferential crack growth along the columnar PBGs. In another LPBF fabricated β Ti-alloy, Ti41Nb, the crack tortuosity from the mesostructures formed by compositional segregation improves the KIc by ⁓80%. These results demonstrate extrinsic toughening in AM alloys. While such toughening from mesostructures enhances AM alloys' reliability, the processing-induced defects present in them, i.e., porosity, significantly reduce their high cycle fatigue (HCF) resistance. Therefore, in the second part of the present study, the HCF life of 316L and 17-4 PH steels produced by the binder jet printing process was investigated. The hot isostatic pressing (HIP) was employed on these steels to improve their HCF life. The HCF life of HIPed 17-4 PH steel is comparable to their conventionally manufactured counterparts; however, in 316L, HIP fails to improve fatigue life. Based on these findings, the microstructural origin for fracture and fatigue resistance in AM alloys are discussed.
EXTENDED ABSTRACT
11:00 - 11:20
VERY HIGH-CYCLE FATIGUE BEHAVIOR OF ADDITIVELY MANUFACTURED TI-6AL-4V USING ULTRASONIC FATIGUE MACHINE AND SELF-HEATING TESTING.
Grégoire BrotGrand Ballroom E
Accelerated characterization of high-cycle fatigue properties is necessary in order to enable the optimization of parameters of additive manufacturing processes such as LPBF (Laser Powder Bed Fusion). Therefore, two accelerated characterization methods are applied and compared on Ti-6Al-4V samples produced using the LPBF process. The first method uses an ultrasonic fatigue machine and the second one determines the fatigue limit using self-heating testing. To study the interactions between the material and the accelerated testing methods, fatigue tests are carried out on different grades of Ti-6Al-4V-LPBF differing by their microstructure or their porosity. Three grades have the same microstructure but different porosity levels and three grades have different microstructures with the same porosity. Both properties showed a strong impact on VHCF strength and affected the mechanisms at fatigue crack initiation.
EXTENDED ABSTRACT
11:20 - 11:40
ANALYSIS OF POROSITY EFFECTS ON SPALL FAILURE OF ADDITIVELY MANUFACTURED 316L SS
Taylor SloopGrand Ballroom E
Additive manufacturing (AM) allows for tuning of mechanical properties for unique functionalities, and stainless steel is a prime candidate for use in many applications due to its high strength, ductility, and corrosion resistance. AM fabricated 316L stainless steel samples with intentionally random pore placement are compared to samples with known pore placement to study the interaction of the shock wave with individual and grouped pores. Velocity profiles were obtained using photon doppler velocimetry (PDV) probes placed strategically along the location of the known pores to understand the limits of local influence for the known pores. Post-mortem characterization of soft-recovered samples using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) was performed to investigate the strain accommodation around pores. It was observed that shock wave fronts are highly dispersed and slow as they propagate through the pore due to strain accommodation around individual pores. As a result, there is shifting of the spall plane away from the impact face. This slow wave front propagation also results in slow rise time and lack of velocity plateau in the collected velocity profiles when areas with pores were probed.
EXTENDED ABSTRACT
11:40 - 12:00
FAILURE CHARACTERIZATION IN 17-4PH STAINLESS STEEL ACROSS MULTIPLE MANUFACTURING METHODS
Brian FuchsGrand Ballroom E
Accurate models of additively manufactured (AM) materials require extensive mechanical testing for proper calibration and verification/validation. The process-structure-property relationships in 17-4PH stainless steel from multiple manufacturing modes were examined via mechanical testing across several strain rates and post-mortem characterizations of the fracture surfaces and microstructure. Under all manufacturing modes and testing conditions, optical and scanning electron microscopy showed ductile failure characteristics. Higher porosity concentration (determined by density measurement) resulted in lower ultimate strength in cast samples; the pores often acted as crack initiation points. Strain-rate dependence and failure modes were also affected by process-dependent anisotropy in the microstructure, which was quantified through electron backscatter diffraction (EBSD) imaging. This data will be used to inform models of failure in the 17-4PH for multiple manufacturing forms.
EXTENDED ABSTRACT
10:30 - 12:30 Symp10-Th1: Small Scale Specimen Testing
Organizers: V. Jayaram, Raghu V. Prakash, N Jaya Balila, Robert Lancaster, Bernd Gludovatz, and Dan Gianola
10:30 - 11:10
Keynote
11:10 - 11:30
IN SITU TRANSMISSION ELECTRON MICROSCOPY STUDY OF NANOMECHANICAL DEFORMATION AND ATOMIC-SCALE FRACTURE IN HIGH ENTROPY ALLOYS
Qi ZhuGrand Ballroom B
Intergranular fracture plays an important role in polycrystalline materials including high entropy alloys, but the atomic scale fracture mechanisms of individual grain boundaries (GBs) are still not fully understood. In this work, we selectively investigate the fracture behaviors of individual GBs in a single-phase face-centered cubic CoCrFeNi high entropy alloy via in situ transmission electron microscopy (TEM) nanomechanical testing supported by molecular dynamics (MD) simulations. With this set up, the classic mode I crack propagation along GBs can be dynamically visualized and quantitatively analyzed.
EXTENDED ABSTRACT
11:30 - 11:50
EFFECTS OF IRRADIATION DAMAGE LEVELS ON ACTIVATION VOLUME AND DEFORMATION MECHANISMS IN IRRADIATED GOLD THIN FILMS USING IN SITU TEM STRAINING
Lina DazaGrand Ballroom B
The plastic deformation mechanisms of ultrafine-grained gold thin films (average grain size ~150 nm) irradiated with 2.8 MeV Au+ ions at three different levels (0.1, 1 and 5 dpa) have been studied using quantitative in-situ transmission electron microscopy (TEM) nanomechanical testing. This technique allows for the simultaneous observation and comparison of the active deformation mechanisms, measurement of mechanical properties and true activation volume. Some of the observed deformation mechanisms include dislocation nucleation at grain boundaries (GB), dislocation pinning/de-pinning at irradiation induced defects, and stress-induced GB migration. During the early stages of deformation, dislocation nucleation and GB migration occur simultaneously. However, the dense populations of irradiation-induced defects prevent transgranular dislocation motion. As the deformation levels increase, GB migration leads to defect-free zones which then provide avenues for unimpeded dislocation glide. The true activation volume increases from ~10b3 in unirradiated specimens, to ~22b3 in irradiated specimens at 1dpa, for flow stresses ranging from 400 to 550 MPa. The experimentally measured activation volume values are compared with values determined from atomistic simulations (grain size ~10 nm) for different unit dislocation processes to determine the controlling deformation mechanism, using Conrad’s model that provides a Hall-Petch-type relationship of grain size dependent activation volume.
EXTENDED ABSTRACT
11:50 - 12:10
QUANTIFICATION OF INTERFACE STRENGTH OF A THIN FILM USING A NEW MICROCANTILEVER GEOMETRY.
Eloho OkoteteGrand Ballroom B
Interfaces failure occurs not only in structural materials but also in functional material systems including systems for energy conversion and storage. Such failures lead to degradation of mechanical and functional properties, such as battery capacity or electrical conductivity. In bulk scale, there are various experimental methods to investigate the interface strength and its failure mechanisms, for instance, peeling test, superlayer test, or indentation test. One of the disadvantages of these approaches is that it can be applied only to relatively thick coatings [1,2]. Small-scale mechanical testing is a powerful tool for studying interface properties because it can quantify micro- and nanometer-sized thin films, and individual interfaces of interest can be tested by isolating them using focused ion beam (FIB). Single and double cantilever beams have been used to investigate fracture/delamination properties of single interfaces [3,4], however, these methods are prone to experimental imperfections arising from testing geometries.
In this talk, we propose a new in situ scanning electron microscope (SEM) microcantilever design that provides reliable and quantitative interface toughness. In addition, the optimized geometry can promote a pre-notch (or crack) to propagate in a stable manner, which is important to generate a natural crack front without FIB-induced damage/artifacts.
EXTENDED ABSTRACT
12:10 - 12:30
EVALUATING THE INTERFACIAL TOUGHNESS OF GAN-ON-DIAMOND USING BLISTERING METHOD WITH NANO-INDENTATION
Dong LiuGrand Ballroom B
An improved analysis of the interfacial toughness using nanoindentation induced blistering of thin films on stiff substrates is demonstrated on GaN-on-diamond. The Hutchinson-Suo analysis requires accurate measurement of blister dimensions, conventionally measured using 2-D line-scans from 3-D topographical maps. The new meteorology overcomes shortcomings of this technique by fitting the 3-D analytical solution of a clamped Kicrchoff plate to the topological map of the blister. This allowed for quantification of interfacial toughness of smaller blisters in GaN-on-diamond, previously assumed invalid for analysis due to inadequacies of the line-scan analysis. Three samples were investigated and found to have interfacial toughness ranging from 0.6–1 J m−2. Additionally, the relationship between residual stress in the GaN and interfacial toughness was investigated using photoluminescence spectroscopy. In all cases, the GaN was found to be under increased compression at the diamond interface by up to -0.81 GPa, although no correlation with interfacial toughness was observed.
EXTENDED ABSTRACT
10:30 - 12:30 Symp12-Th1: Phase-Field Models of Fracture
Organizers: Israel Garcia, Fabian Welschinger, and Vladislav Mantic
10:30 - 11:10
Keynote
A PHASE FIELD FATIGUE MODEL FOR COMPLEX LOADING SITUATIONS [Keynote]
Sikang YanDogwood B
The phase field method for fracture mechanics has drawn a lot of attention in the past decade because of its simple formulation and easy implementation. Recently, the phase field model is also applied for fatigue fracture for a uniform loading. However, there is still a lack of studies on how to consider complex loading cases in the phase field fatigue model. In this work, we extend the phase field model for non-uniform loading situations by combing it with the rainflow counting algorithm.
EXTENDED ABSTRACT
11:10 - 11:30
NUMERICAL ASSESSMENT OF PHASE-FIELD APPROACH IN WESTERGAARD’S PROBLEM UNDER MIXED MODE LOADING
Diego Infante-GarciaDogwood B
Assessment of phase-field numerical errors to classical Griffith’s theory is essential to obtain feasible solutions which do not require an excessive computational cost. This work analyses the phase-field fracture approach to Westergaard’s problem in terms of crack growth initiation under mode I and mixed mode I+II loading conditions.
EXTENDED ABSTRACT
11:30 - 11:50
A PHASE FIELD MODEL FOR DAMAGE NUCLEATION IN GEOPOLYMER COMPOSITES
Reshmi Maria JoseDogwood B
Multi-scale models have been greatly appreciated due to their ability to precisely correlate the microstructure properties with the macroscopic properties of materials. With an aim to verify the structural integrity of geopolymer composites, the microscopic cracks nucleating from the matrix and preexisting pores and the effect on their macroscopic fracture toughness are studied using a computational framework of phase field (PF) in the finite element (FE) context. To assess the effect of random distribution of voids, the representative volume element (RVE) of the composite microstructure is generated using a take and place algorithm. The elastic properties of the composites are obtained by Mori-Tanaka and Self-consistent homogenization schemes. The RVE is then used to simulate a plate under tension to study the damage initiation and propagation in geopolymer composites. The PF model investigates the crack nucleation and branching from the already-existing voids in the composites. A qualitative validation of the approach by means of crack patterns is also presented.
EXTENDED ABSTRACT
11:50 - 12:10
COUPLING CRYSTAL PLASTICITY WITH PHASE FIELD FRACTURE FOR CREEP DAMAGE FORMATION ANALYSIS IN AUSTENITIC AND FERRITIC STEELS
Michael SalviniDogwood B
Accurate modelling and prediction of both statistical trends in damage formation and damage site initiation
is critical in both the design, microstructure optimization and lifetime management of components and
welded joints for nuclear power stations. This paper presents a coupling between a strain-gradient based
crystal plasticity formulation and a phase field fracture model to predict damage initiation sites, damage
propagation and void initiation statistics that match electron microscopy experimental results for grain
boundary damage from a 316H stainless steel creep test specimen. The interplay between the grain
misorientation and the presence of carbides at the grain boundaries is investigated. A range of novel
variations are incorporated into this approach that can isolate damage from varying mechanisms, including
slip, creep, and contributions from plastic or elastic deformation within the simulated microstructure. The
local effect of carbides, forming on specific grain boundary types, on void cavitation is included by using
a misorientation-dependent critical energy release rate. The direct comparison with electron backscatter
diffraction experiments clarifies what the most important damage mechanisms are and the quantitative
fracture energy reduction as a function of carbide density. The extension of this model to ferritic steel
microstructures is also explored.
EXTENDED ABSTRACT
12:10 - 12:30
A VERSATILE PHASE-FIELD FRACTURE MODEL FOR POLYMER COMPOSITES: CAPTURING THEIR MULTI-FACETED FRACTURE BEHAVIOR VIA GRADED INTERPHASES
Paras KumarDogwood B
Accurate modeling of fracture in polymer nano-composites entails the consideration of numerous complex phenomena including the branching and coalescence of multiple cracks. This contribution employs a graded interphase enhanced phase-field fracture approach (PFF-GI) to capture a wide spectrum of experimentally observed fracture behaviors including particle debonding. Herein the overall fracture response of the composite material is controlled via the degree of grading, i.e. continuous variation in material properties, within an interphase region of finite thickness around the filler particle.
EXTENDED ABSTRACT
10:30 - 12:30 Symp15-Th1: Advanced Computational Methods in Fracture
Organizers: P.R. Budarapu, M.K. Pandit, A.K. Pradhan, S. Natarajan, T. Rabczuk
10:30 - 11:00
Keynote
REDEFINED J-INTEGRAL AND J-INTEGRAL RANGE DELTA-J AS FINITE STRAIN ELASTIC-PLASTIC CRACK PARAMETERS [Keynote]
Hiroshi OkadaHickory
The summary of applications of redefined three-dimensional J-integral and J-integral range Delta-J are presented in this paper. The redefined fracture parameters were derived with a rigorous consideration on energy dissipation into a small volume in the vicinity of the crack front. It can be seen as a rigorous extension of two-dimensional T_ε^*-integral to three-dimensional problem. The equation formulations are briefly presented in this paper. Then, their applications will be presented in the conference.
EXTENDED ABSTRACT
11:00 - 11:20
THE VIRTUAL ELEMENT METHOD FOR EFFICIENT CRACK TIP LOADING ANALYSIS AND CRACK GROWTH SIMULATION
Kevin SchmitzHickory
To precisely model crack growth, accurate calculations of crack front loading and crack deflection angles are essential. These calculations require solutions of the underlying boundary value problems (BVPs), which are typically obtained by applying numerical methods, e.g., the finite element method (FEM). However, since accuracy and computational cost of the analyses are in general competing aspects, compromises often have to be made in order to generate satisfactory results in acceptable times. In contrast, the use of more efficient methods, both for the solution of the BVP as well as for the subsequent crack tip loading analyses, can substantially lower the computational effort while maintaining desired accuracies. The virtual element method (VEM) is a fairly new discretization scheme for the numerical solution of BVPs, and can be interpreted as a generalization of the FEM. Since the VEM can handle arbitrary polytopal meshes in a straightforward manner, it provides a higher degree of flexibility in the discretization process than the FEM, which turns out to be profitable in terms of both computing times and accuracy. This holds in particular for the simulation of crack growth in 2D and 3D, sparing adaptive re-meshing or the construction of discontinuous element shape functions.
EXTENDED ABSTRACT
11:20 - 11:40
3D FRACTURE MECHANICS ANALYSIS OF THERMOMAGNETOELECTROELASTIC ANISOTROPIC SOLIDS ACCOUNTING FOR CRACK FACE CONTACT WITH FRICTION
Roman KushnirHickory
Thermal expansion of the material usually causes existing cracks to close, resulting in the requirement to consider contact problems. The latter are complicated since one should consider the contact of crack faces accounting for sliding, friction, and unknown contact area. This study tries to solve this task by development of the 3D boundary element approach with iterative solver, which can determine the contact zone, sliding of crack faces and account for friction between them. Moreover, multifield materials and various thermal, mechanical, electric and magnetic boundary and contact conditions can be considered.
EXTENDED ABSTRACT
11:40 - 12:00
CYCLIC EFFECTIVE NEAR-FIELD LOADING BASED ON THE DOMAIN INTEGRAL METHOD
Florian GarnadtHickory
This paper presents a modification of the domain integral method for cyclic loading and crack closure to compute the cyclic effective J-Integral as a near-field loading parameter. The path-dependency of the solution is discussed for different reference states of the field quantities in a cycle. It turns out that refering to the crack opening time point the cyclic effective J-Integral is path-independent for a domain outside the active plastic zone. The validity of this procedure is discussed by comparison with a global energy approach and theoretical field solutions for the J-controlled zone.
EXTENDED ABSTRACT
12:00 - 12:30
Keynote
MULTIPHYSICS ANALYSIS OF PHOTOVOLTAIC SOLAR CELLS [Keynote]
Pattabhi BudarapuHickory
The physics of power generation on photovoltaic solar cells is complex, involving multiple fields. In this study, the performance characteristics of Silicon based solar cells are investigated considering mechanical, therma, electrical and chemical fields through a finite element (FE) analysis. A fully coupled thermo-mechanical-electrostatic-chemical relations for a deformable semiconductor are planned to be developed by combining the thermodynamically consistent formulation of the interaction between electric field and polarizable matter with the carrier charge transportation. A functional form of free energy considering the energies due to all the above-mentioned fields will be defined, through which the constitutive relations can be derived. As a result, the influence of the densities of electrons and holes can be coupled to the mechanical equilibrium. Therefore, the FE analysis can be finally extended to estimate the I-V characteristics of a p-n junction. Furthermore, each node of such three dimensional finite element is estimated possesses 14 degrees of freedom, leading to a total of 112 degrees of freedom per element.
EXTENDED ABSTRACT
10:30 - 12:30 Symp18-Th1: Mechanical Behavior in Nuclear Materials
Organizers: Dong Liu, Filippo Berto, and Robert O. Ritchie
10:30 - 11:10
Keynote
MECHANISTIC UNDERSTANDING OF IRRADIATION ASSISTED STRESS CORROSION CRACKING [Keynote]
Gary WasWalnut
Irradiated austenitic alloys are susceptible to degradation in high temperature water by irradiation assisted stress corrosion cracking (IASCC). This paper will provide a mechanistic understanding of the IASCC process to date, incorporating the most recent observations and experimental results.
EXTENDED ABSTRACT
11:10 - 11:30
CORROSION FATIGUE OF HOLLOW SPECIMENS IN SIMULATED LWR WATER ENVIRONMENT
Mustafa SubasicWalnut
Pipe systems in nuclear power plants are subjected to cyclic thermal and mechanical loads from mixing points between hot and cool water and mechanically induced vibrations. The light water reactor (LWR) water environment flowing through the pipes at 300 °C with an internal pressure of 120 bars has a detrimental effect on the fatigue lives of the pipe systems. In this study, an experimental setup has been developed and designed to assess the corrosion fatigue lives of hollow specimens subjected to an alternating uniaxial cyclic load and simulated LWR water environment simultaneously. The corrosion fatigue tests have been conducted for both boiling water reactor (BWR) and pressurized water reactor (PWR) water environments.
EXTENDED ABSTRACT
11:30 - 11:50
EFFECT OF TENSION HOLD IN CREEP-FATIGUE CRACK PROPAGATION IN NI-BASE SUPERALLOYS: TRANSITION FROM CRACK RETARDATION TO ACCELERATION
Shiyu SuzukiWalnut
Effect of tension hold on crack propagation under subsequent fatigue loading during creep-fatigue crack propagation (CFCP) in single crystal (SC) and wrought Ni-base superalloys was investigated by conducting crack propagation tests with single tension hold applied during pure fatigue loading. Fatigue crack retardation occurred after the tension hold in the SC superalloy, whereas both retardation and acceleration occurred in the wrought superalloy depending on stress intensity factor, K. The retardation and acceleration were attributed to enhanced crack closure due to creep deformation and grain boundary (GB) embrittlement due to oxygen diffusion, respectively. Transition from the retardation to the acceleration was rationalized based on a comparison between sizes of residual compressive stress field and GB embrittlement area.
EXTENDED ABSTRACT
11:50 - 12:10
EVALUATING THE SENSITIVITIES OF AISCC SUSCEPTIBILITY IN STAINLESS-STEEL NUCLEAR WASTE STORAGE CANISTERS FOR DEVELOPMENT OF A LIFETIME PREDICTION MODEL
Sarah BlustWalnut
Spent nuclear fuel (SNF) is currently stored across the US in passively cooled stainless steel dry storage canisters (DSC). Due to the design of the DSC, aerosols from the outside environment are able to deposit on the stainless-steel canisters. Over time the deposited aerosols will deliquesce on canisters to form concentrated salt brines resulting in localized corrosion, which when coupled with the high residual stress around welds can lead to stress corrosion cracking (SCC). The scope of the work presented is to investigate the boundaries of SCC to varying sensitivities such as environmental factors, microstructure variability, and material composition. These sensitivities will allow for recommendations to be made for canister monitoring and which variables are of the greatest concern for SCC of the DSCs. The data generated will be used in probabilistic FM predictions of AISCC growth for lifetime management of DSC. These predictions will inform a framework to quantify and manage a risk-based ranking of storage sites.
EXTENDED ABSTRACT
12:30 - 14:00 Lunch 4
Lunch Break
14:00 - 16:00 Parallel Sessions Th2
Parallel sessions symposia Th2
14:00 - 16:00 Symp04-Th2: Brittle Fracture: 100 years After Publication of Griffith’s Theory
Organizers: Claudio Ruggieri, and Laszlo Toth
14:00 - 14:20
NEW MODEL FOR BRITTLE FRACTURE ASSESSMENT UNDER COMBINED STRESS FIELD BASED ON THE LOCAL APPROACH
Kazuma ShimizuGrand Ballroom C
This study proposes the new fracture model to assess the fracture toughness under complex loading mode subjected to cracked component on the brittle fracture toughness assuming combined stress state in plastic zone near crack-tip. This model newly considers non-linear energy release rate named Local-J as the elastic-plastic local fracture driving force for micro-crack nucleus in plastic zone. The effect of 3-dimentioinal combined stress state on local-J, which is different from the effect on the linear elastic energy release rate for Griffith crack, is formulated as the Local-J equivalent stress by conducting numerical analysis of unit-cell including a penny-shaped crack. Based on weakest link theory assuming this new model under combined stress field, Extended Weibull stress is derived as a new fracture parameter for cracked component. The characteristics of the proposal model is examined by predicting the critical load for pure mode II or III from fracture toughness assumed under pure mode I load. Fracture toughness assessed by this new model under mode II or III load is smaller than that assessed by conventional model. This result of numerical analysis implies the possibility of rational assessment of the effect of loading mode by applying the new model.
EXTENDED ABSTRACT
14:20 - 14:40
INFLUENCE OF HETEROGENEITY ON FAILURE PROBABILITY BASED ON WEAKEST LINK MODELING
Daniela V. KleinGrand Ballroom C
Brittle failure by transgranular and intergranular mechanisms is commonly addressed by probabilistic methods based on the weakest-link concept. For homogeneous materials this approach is straightforward and well established. Different methods have been proposed in the past to incorporate the presence of heterogeneities, e.g. due to welding or segregated zones. A key issue in this context is the length that characterizes variations in the heterogeneous microstructure in relation to a representative size of the zone where brittle fracture typically has been observed to occure, i.e., fracture process zone (FPZ). Here, a new approach for weakest-link modelling of heterogeneous materials is proposed that accounts for the interplay between the different scales.
EXTENDED ABSTRACT
14:40 - 15:00
STATISTICAL SIMULATION OF FRACTURE TOUGHNESS IN SEGREGATED RPV STEEL USING DEEP-LEARNING-BASED RANDOM FIELD GENERATION AND HIGH-FIDELITY FEA MODELING
Regis KenkoGrand Ballroom C
Charpy impact tests are used in the nuclear industry to certify forging processes. However, the results of these tests may exhibit a strong variability in the context of large metal parts manufactured by Framatome. Preliminary studies have shown that the steel is highly heterogeneous at the millimeter scale in certain areas of forged parts. These heterogeneities are surmised to be the main cause of the variability observed in the results of impact tests. The aim of this study is to qualify and numerically quantify the effect of these heterogeneities on the distribution of fracture energies thanks to an innovative computational approach featuring deep learning to generate 3D realizations of the mechanical properties from sparse experimental results, and high-fidelity modeling of brittle fracture in heterogeneous Charpy specimens.
EXTENDED ABSTRACT
15:00 - 15:20
USING MIXED FINITE ELEMENTS AND REMESHING TO ASSESS BRITTLE FAILURE USING THE BEREMIN MODEL
Jacques BessonGrand Ballroom C
A computational strategy to evaluate the Weibull stress for the Beremin model
is proposed to simultaneously solve problems caused by volumic locking and extreme element
distortion at the crack tip. It is based on the use of mixed elements and remeshing. It is shown that
a single simulation can be used to evaluate the Weibull stress for any range for the CTOD at failure.
EXTENDED ABSTRACT
15:20 - 15:40
COUPLING OF A GRADIENT-ENHANCED GTN MODEL TO THE BEREMIN MODEL FOR THE SIMULATION OF DUCTILE-TO-BRITTLE TRANSITION
Jacques BessonGrand Ballroom C
Ductile-To-Brittle transition modeling for ferritic steels used in the nuclear industry has been studied for years. This paper proposes a two-step coupled modeling representing ductile crack growth thanks to a gradient-enhanced GTN model and applying a modified Beremin model to evaluate the probability of failure of CT specimens at -50°C.
Both models have been calibrated separately at temperatures where there is no coupling. Beremin model is first studied at low temperature. It is shown that the model could be applied to different geometries. GTN model is then calibtrated at -20°C. The identified GTN model could be transferred to lower temperatures. Finally the coupling is studied.This work emphasizes the necessity of a special treatment of the stress field resulting from the GTN model to compute the Weibull stress and the use of a modified Beremin model accounting for the void volume fraction.
EXTENDED ABSTRACT
15:40 - 16:00
PERIDYNAMIC MODELING OF DYNAMIC FRACTURE OF B4C IN A SPLIT-HOPKINSON PRESSURE BAR
George GazonasGrand Ballroom C
The dynamic fracture of a brittle ceramic, B4C, is investigated using our in-house split-Hopkinson pressure bar (SHPB), and Sandia’s peridynamics simulation code, PERIDIGM. In order to study the dynamics of this particular SHPB, the initial boundary value problem (IBVP) is solved for a 1-D impact in which a finite striker bar collides with the front face of a stationary incident bar bonded to a specimen of finite thickness, with the back face of the specimen bonded to another finite transmission bar; this is the classic SHPB experiment. Laplace transform domain solutions are numerically inverted to the time domain using a modified Dubner-Abate-Crump algorithm. The new IBVP solutions for particle velocity in the SHPB composed of maraging steel bars, and B4C specimen, are used to verify the commercial FE codes COMSOL and ABAQUS, and PERIDIGM. Subscale SHPB simulations are conducted using PERIDIGM on jacketed/unjacketed B4C specimens with a critical stretch failure condition proportional to the ceramic’s critical energy release rate, Gc; also investigated is the effect of initial defect populations governed by, Weibull, uniform random, and Bobaru critical stretch distributions, on the ceramic failure behavior. Computationally expensive full-scale PERIDIGM simulations are also currently underway to compare with the subscale simulation results.
EXTENDED ABSTRACT
14:00 - 16:00 Symp06-Th2: Microstructures and Fracture in Advanced Materials
Organizers: Tong-Yi Zhang, Chad Landis, Weiqiu Chen, Ralf Müller, and Jie Wang
14:00 - 14:30
Keynote
I-INTEGRAL FOR MAGNETO-ELECTRO-ELASTIC MATERIALS WITH RESIDUAL STRAIN [Keynote]
Hongjun YuGrand Ballroom A
Magneto-electro-elastic (MEE) materials generally consist of piezoelectric and piezomagnetic constituent phases so that the residual strain often occurs during the manufacturing process. The distributed residual strain and complex interfaces between constituents cause a great challenge to the fracture analysis of MEE materials. Considering the effect of the residual strain, this paper develops an interaction integral (I-integral) method for the extraction of the fracture parameters of an impermeable crack in nonhomogeneous MEE materials.
EXTENDED ABSTRACT
14:30 - 15:00
Keynote
EFFECT OF TEMPERATURE ON THE MODE I FRACTURE BEHAVIOR OF A ROLLED MAGNESIUM ALLOY
S Arjun SreedharGrand Ballroom A
The temperature dependence of the mode I fracture behavior of a rolled Mg AZ31 alloy having near basal texture is studied in this work through four-point bend fracture experiments in the temperature range from 25 to 100 deg Celsius. It is found that the operative fracture mechanism changes from twin-induced quasi-brittle cracking to one mediated by ductile void growth and coalescence as temperature is raised above 65 deg Celsius. A concomitant reduction in tensile twin development near the crack-tip is observed with enhancement in temperature, while at the specimen far-edge it increases, resulting in pronounced texture changes at higher temperature. The reduction in tensile twin evolution with energy release rate and enhancement in micro-void growth rate near the crack-tip over the above temperature range are rationalized through simplified analyses. The change in fracture mechanism from brittle to ductile and higher dissipation due to tensile twinning at the specimen far-edge as temperature increases results in significant enhancement in fracture toughness.
EXTENDED ABSTRACT
14:50 - 15:10
SMALL CRACK GROWTH BEHAVIORS AND CLOSURE EFFECTS IN A NICKEL-BASE POWDER METALLURGY SUPERALLOY AT HIGH TEMPERATURE
Xiaoguang YangGrand Ballroom A
Crack closure effects play an important role in dominating small crack propagation behaviors, which were rather less well investigated, especially at high temperature in the air. Based on photomicroscopy and digital image correlation, small crack growth behaviors and growth rates are investigated both at 600℃ and RT in air for a Powder Metallurgy superalloy, then the crack displacement fields are measured. Two max. stress levels and two stress ratios are considered in order to understand their effects on small crack growth behaviors. The experimental results reveal the crack growth behaviors ranged from 80 m to ~1000m. With the help of EBSD at the grains of the crack growth path, links of this particular growth behaviors with the microstructure features, such as the orientation, grain boundary, are discussed. Using DIC-measured crack opening displacement with the crack growth, the roles of oxides and roughness induced crack closure in early small crack propagation at high temperature are analyzed. Finally, a crack closure model is proposed including the combined effects of oxide-induced, roughness-induced and plasticity-induced crack closure (OICC, RICC and PICC).
EXTENDED ABSTRACT
15:10 - 15:30
20 KHZ CRACK GROWTH RATE TESTING IN ADVANCED HIGH STRENGTH TOOL STEELS
Mohamed SadekGrand Ballroom A
High nitrogen chromium alloyed PM tool steels display, among other attractive properties, high strength and improved corrosion resistance. Also, powder metallurgy is a manufacturing process that allows the fabrication of near net shape complex geometries and high-quality components in an economical way. Nitrogen acts in an effective way replacing the carbon by the formation of hard carbonitride phases and permits higher amounts of chromium in solid solution. The low carbon and high nitrogen contents, where most of the carbon is replaced by nitrogen, suppresses the formation of metal carbides is in favor of the formation of metal nitrides (MX) and carbonitrides (M2X) allowing a higher nominal amount of chromium in solid solution. As a result of the PM rout well dispersed and fine distribution of nitrides and carbonitrides is created in a martensitic matrix. The microstructure obtained controls the mechanical properties of the steel grade, and a balance of high strength and high toughness is required. In the present study the influence of the nitride and carbonitride distributions on the fatigue properties, and in particular the stress intensity threshold and the early crack growth, was investigated using a 20 kHz ultrasound test equipment.
EXTENDED ABSTRACT
14:00 - 16:00 Symp09-Th2: Fatigue and Fracture of Additively Manufactured Materials
Organizers: Bo Chen, Nagaraja Iyer, and Filippo Berto
14:00 - 14:20
MODELING OF MIXED-MODE CRACK GROWTH BEHAVIOR IN LB-PBF TI-6AL-4V USING A CRITICAL PLANE FRAMEWORK
Ali FatemiGrand Ballroom E
Many service loading conditions are multiaxial, and small cracks have been shown in many situations to grow in mode II or mixed-mode due to the orientation of defects and microstructural effects, particularly in additively manufactured metals. This paper uses fracture mechanics with a critical plane framework to predict crack growth rates using only mode I constants from the literature.
EXTENDED ABSTRACT
14:20 - 14:40
SIGNIFICANCE OF INTRA-BUILD DESIGN VARIABLES ON THE FRACTURE TOUGHNESS PROPERTIES OF ELECTRON BEAM MELTED TI6AL4V
Melody MojibGrand Ballroom E
Structurally reliable materials are essential for adopting additive manufacturing (AM) metals in safety-critical applications. Limited data on the damage-tolerance properties of metal AM materials exists, hindering the acceptance of AM metals in fracture-critical applications. A design of experiments (DOE) is used in this study to investigate the role of build space and part design parameters on the fracture toughness properties of Electron Beam Melted (EBM) Ti6Al4V. ASTM E399 tests were performed on over 100 compact tension (CT) samples in the as-built and machined conditions to obtain fracture toughness properties and evaluate the influence of part size and location within 80% of the build space. Results were comparable to wrought annealed titanium, with less than 10% variation in overall fracture toughness. Specimen location within the build envelope contributed to the observed variation, with an increase in properties with build height and specimens located in the center of the build envelope. The location-dependent properties result from changes in microstructure and porosity throughout the build space. While the experimental EBM Ti6Al4V fracture toughness properties are promising for future applications, it is crucial to consider the variation in properties due to build space location and design parameters when designing for consistency.
EXTENDED ABSTRACT
14:40 - 15:00
FACTORS GOVERNING THE FATIGUE PERFORMANCE OF AM TI-6AL-4V COMPONENTS
Derek WarnerGrand Ballroom E
Before an additively manufactured component can be safely used in a load bearing application, its mechanical performance must be qualified. Traditional qualification approaches, involving the fabrication and testing of many identical components, negate one of the greatest benefits of additive manufacturing, i.e. the ability to quickly and cheaply fabricate one-off components. Thus, qualification methods that rely less on mechanical testing and more on predictive modeling are of value. This is most true for high cycle fatigue performance, where mechanical testing requires significant resources and produces stochastic results.
High cycle fatigue failure is difficult to predict because it can depend nonlinearly on many parameters, e.g. part geometry, residual stresses, surface characteristics, material defect characteristics, grain and dislocation structures, mechanical and environmental loading characteristics and their history. This has motivated a succession of fatigue models with ever increasing mechanistic fidelity, with some now diving down to the atomic scale. This raises the question of: what level of mechanistic detail is required to sufficiently predict the performance of AM Ti-6Al-4V components? In this talk, I will give my perspective on this question, building from a decade of AM Ti-6Al-4V fatigue modeling and experimentation across scales.
EXTENDED ABSTRACT
15:00 - 15:20
FATIGUE LIFE PREDECTION OF THE AA2024-T351 ALUMINUM ALLOY
Naila HfaiedhGrand Ballroom E
The purpose of this styudy is to investigate the cyclic behaviour of the AA2024-T351 aluminum alloy widely used in the aircraft industry. This alloy shows a relatively low ductility at room temperature and is generally heat treated in various conditions to suit particular applications. Monotonic and cyclic tests have been conducted in order to characterize the fatigue behaviour and determine the fatigue life of aluminum alloy. Cyclic tests in the Low Cycle Fatigue (LCF) regime were performed under fully reversed total strain amplitudes ranging between 0.6% and 1.2%. The elastoplastic behaviour was analysed through the stress-strain hysteresis loops leading to evaluate kinematic and isotropic hardenings. The AA2024-T351 was also shown to be prone to cyclic strain hardening. Besides, symmetric High Cycle Fatigue (HCF) tests were also performed and the Stress-Number of cycles (S-N) curve until 107 cycles was plotted. A fatigue limit of about 150 MPa was found. Based on all LCF and HCF tests, the fatigue life could be represented in a strain approach by the Manson-Coffin-Basquin law. Moreover, observations of the fracture surfaces were carried out using a Scanning Electron Microscope (SEM) in order to detect the crack initiation and follow the propagation for the two fatigue regimes.
EXTENDED ABSTRACT
15:20 - 15:40
MECHANICAL RESISTANCE ASSESMENT OF 316L STAINLESS STEEL ADDITIVELY-REPAIRED STRUCTURES
Fabien SzmytkaGrand Ballroom E
To quickly characterize the static and cyclic mechanical strength of a structure repaired by additive manufacturing, a specific specimen is developed and then repaired using two processes (laser direct energy deposition and cold spray) with adjustable parameters. The fundamental role of the microstructure in the vicinity of the repaired area in the initiation and propagation of cracks under cyclic loading is highlighted and discussed
EXTENDED ABSTRACT
15:40 - 16:00
FRACTURE TOUGHNESS OF A DUPLEX STAINLESS STEEL BUILT BY DIRECTED ENERGY DEPOSITION : EFFECT OF THE DEPOSITION DIRECTION
David RoucouGrand Ballroom E
Additive manufacturing of duplex stainless steels (DSS) has recently seen some research interest. In particular, the use of directed energy deposition (DED) is still new and the fabricated materials remain to be fully characterized. In addition, materials produced by additive manufacturing can present anisotropic fracture properties. This study aims to characterize the fracture toughness of a DSS manufactured by DED, taking into account the orientation with regard to the printing strategy.
EXTENDED ABSTRACT
10:30 - 10:50
ACCELERATED DESIGN AND INTEGRITY ASSESSMENT OF ADDITIVELY MANUFACTURED METALLIC STENTS USING MACHINE-LEARNING MODELS
Yu QiaoGrand Ballroom E
In this work, we investigate the potential of laser powder bed fusion (L-PBF) to meet the stringent requirements imposed on metallic stents for the treatment of aortic dissection. Here, we use microstructure-based modeling to describe the mechanical properties of L-PBF 316L stainless steel. The derived structure-property relationships then serve as a database for training machine learning (ML) models, such as convolutional networks (CNN) and graphical neural networks (GNN). Based on the established modeling framework, we are able to predict the deformation and fracture behavior of 316L stents and identify the improved stent design in an efficient manner.
EXTENDED ABSTRACT
14:00 - 16:00 Symp10-Th2: Small Scale Specimen Testing
Organizers: V. Jayaram, Raghu V. Prakash, N Jaya Balila, Robert Lancaster, Bernd Gludovatz, and Dan Gianola
14:00 - 14:40
Keynote
IMPACT OF GRAIN BOUNDARY MODIFICATIONS ON FRACTURE TOUGHNESS OF TUNGSTEN BASED NANOMATERIALS [Keynote]
Daniel KienerGrand Ballroom B
Nanostructured materials commonly excel with respect to their strength, but their ductility and toughness remain limiting factors for deployment in safety related applications. In this work, using grain boundary engineering concepts in conjunction with severe plastic deformation for microstructural refinement, we aim to develop nanostructured and nanocomposite materials that overcome these limitations. Since material volumes are limited, we utilize small scale testing approaches to examine the respective material properties such as strength, ductility and fracture toughness. We detail on the one hand challenges and recent advancements in small scale fracture experiments, and on the other hand the effectiveness of the mentioned grain boundary engineering approaches to design outstanding nanomaterials overcoming strength-ductility-toughness limitations.
EXTENDED ABSTRACT
14:40 - 15:00
A NOVEL SMALL-SCALE BEND GEOMETRY CREEP TEST TO EVALUATE DEFORMATION AND CAVITATION DAMAGE IN POLYCRYSTALLINE AND BI CRYSTAL COPPER
Elsiddig ElmukashfiGrand Ballroom B
Understanding the mechanisms of creep deformation and damage (cavitation) in engineering components materials is important, but despite the significant research that has been conducted over the past 50 years, there is still a lack of understanding of the microstructural processes that influence and control the development of damage. To provide further insights into this, in the present work a novel small-scale constant load cantilever beam geometry test specimen is used. The materials selected for the tests are polycrystalline and bi-crystals of high purity copper. The copper provides a simple model material for exploring initiation and early growth of creep cavitation and allows comparison with crystal-based model predictions.
In this study, both creep deformation and creep cavitation were measured. For the latter, a range of higher spatial resolution techniques were adopted including scanning electron microscopy, electron backscattered diffraction and focused gallium ion beam serial section milling. Creep cavity number density and size measurements were made using advanced image analysis procedures. Polycrystalline and bi-crystal results are compared, with particular attention given to the role of Schmid factor and misorientation on the initiation and early growth of the creep cavities. These experimental results inform the development of microstructural based models of cavitation.
EXTENDED ABSTRACT
15:00 - 15:20
ANALYSIS OF FRACTURE BEHAVIOUR OF MULTILAYERS BY CANTILEVER AND CLAMPED BEAM BENDING GEOMETRY
Ashwini Kumar MishraGrand Ballroom B
Multilayering of metal/ceramic combinations can help to achieve better strength and toughness than the individual material constituents. The effect of elastic-plastic mismatch in multilayers on the crack driving force and eventually on fracture resistance has been analyzed in this work. The enhancement in fracture toughness by decreasing layer spacing has been predicted from finite element calculations and verified by micro-cantilever fracture tests. Further, calculations have been carried out for a more stable clamped beam bend geometry to determine R-curve behavior in such multilayers.
EXTENDED ABSTRACT
15:20 - 15:40
OPTIMIZATION AND USE OF HIGH-THROUGHPUT MICROMECHANICAL TESTING DESIGN FOR 3D-PRINTED POLYMERS
Stanislav ZakGrand Ballroom B
Modern materials behave differently on a micro-scale level than in bulk applications. Therefore, with ever present miniaturization, the materials’ testing on a micron-level is gaining importance. 3D printing with a sub micron precision, such as direct laser writing by two-photon lithography, allows for relatively fast manufacturing of miniaturized specimens for micromechanical testing. In combination with precise loading by a nanoindenter tip, high throughput micromechanical testing is enabled. Presented research shows design process of miniaturized cantilever and push to pull device specimens for fracture mechanics testing, aided finite element modelling, together with high throughput testing of polymeric materials with varied printing parameters and loading conditions. Such in situ and ex situ experimental setup allows for systematic fracture mechanics testing on the small scale for common materials used in small-scale 3D printing.
EXTENDED ABSTRACT
15:40 - 16:00
MICRO-BENDING FOR MULTI-SCALE FRACTURE CHARACTERIZATION OF CEMENT-BASED MATERIALS AND CERAMICS
Santiago El AwadGrand Ballroom B
The last few years have seen the development of several testing techniques at the micro-scale to characterize the mechanical properties of multi-scale materials. One such novel methods are micro-cantilever bending tests to assess mechanical properties of materials. Micro-cantilever tests allow for a variety of test configurations, including scaled chevron-notch geometry allowing controlled crack-growth prior to critical failure load. Chevron notches are convenient at such length scales since they allow for ex-situ measurements of crack length – avoiding the need to directly measure crack length, which could be a challenge at such scale. The test approach provides access to R-curve behavior for quasi-brittle materials on the micro-scale and opens the door to investigate more sophisticated topics, i.e., creep crack growth. Moreover, the technique complemented with visualization and scanning tools, such as Scanning Electron Microscopy and Microtomography, allows for a proper and extensive analysis of the crack growth phenomena.
The motivation of this work revolves around expanding currently available knowledge on multiscale characterization of cement-based materials with the focus on fracture testing at the micro- and mesoscale through the novel micro-bending technique. This test opens the door to understanding fracture, toughening mechanisms, and evolution of these properties regarding processing variables.
EXTENDED ABSTRACT
14:00 - 16:00 Symp12-Th2: Phase-Field Models of Fracture
Organizers: Israel Garcia, Fabian Welschinger, and Vladislav Mantic
14:00 - 14:20
NUCLEATION AND PROPAGATION OF FRACTURE IN ELASTOMERS DURING POKER-CHIP EXPERIMENTS
Aditya KumarDogwood B
The poker-chip experiments of Gent and Lindley (1959) – in which they bonded thin disks of elastomers to metal plates at two ends and applied tension – jump-started investigations into the phenomenon of cavitation. Despite their importance, these experiments and other similar experiments have yet to be fully explained. One likely reason for their elusiveness is that it had long been mistakenly presumed that cavitation in elastomers could be explained on the basis of an elastic instability. Another reason is that a unified nucleation and propagation fracture theory in large deformations to explain cavitation as a fracture phenomenon had not existed. Recently, Kumar, Francfort, and Lopez-Pamies (2018) have introduced a comprehensive macroscopic phase-field theory for the nucleation and propagation of fracture in elastomers undergoing arbitrarily large quasistatic deformations. In this work, we quantitatively analyze the poker-chip experiments using this theory and showcase the theory’s ability to model nucleation and propagation in a unified manner.
EXTENDED ABSTRACT
14:20 - 14:40
A FLEXIBLE COMPUTATIONAL FRAMEWORK FOR A HIGH-PERFORMANCE EXTENSION OF A QUASI-STATIC PHASE-FIELD MODELING TO A DYNAMIC REGIME
Lamia MerselDogwood B
The dynamic aspect of crack propagation is a topic of deep interest in material science. The phase field fracture modeling has shown encouraging results in a dynamic framework but remains challenging in terms of the time discretization resolution. Though the implicit time integration methods are mainly used in the literature, they become limiting in nonlinear problems due to the resolution of the system of equations required. Thus, explicit time integration schemes are an alternative to avoid these massive matrix operations. This paper presents the approaches set up to adapt the coupled formulation to a full explicit time integration for both equations.
EXTENDED ABSTRACT
14:40 - 15:00
SIMULATION OF OFF-AXIS FRACTURE OF THIN-PLY COMPOSITE LAMINATES USING PHASE FIELD
Anatoli MitrouDogwood B
Thin-ply laminates can offer significant advantages for aeronautical design, however, obtaining design allowables for such laminates requires efficient simulation tools. Previous simulation methods used for standard composites pose significant drawbacks when it comes to thin-ply composites, and therefore motivate the advent of new numerical techniques. The Phase Field method, a possible solution, is applied here, in an equivalent single layer approach, to simulate the fracture of multidirectional thin-ply laminates subjected to off-axis loading. The anisotropic nature of the fracture energy multidirectional laminates present is considered through an analytical formulation that feeds the inputs of the method. It is shown that accurate predictions can be obtained compared to experiments for off-axis open-hole tension (OHT) of a hard laminate. But this does not mean the same accuracy will be achieved regardless of the laminate type and lay-up. The issue is nicely illustrated considering a cross-ply laminate that presents the peculiarity of having the same translaminar fracture toughness in the two principal material axes. This creates some inaccuracies in the simulation due to the way the phase field model is formulated. A discussion on this issue and possible ways to circumvent it, under current development, will be presented.
EXTENDED ABSTRACT
15:00 - 15:20
PHASE FIELD MODELLING OF BRITTLE FRACTURE: AN EXTENSION TO FRACTURE SURFACE TOPOLOGY
Retam PaulDogwood B
In order to model inter-granular brittle fracture, a two-dimensional staggered phase field method has been implemented in the commercial finite element code ABAQUS/Standard. Rate independent variational principle has been used for the above diffused fracture modelling. Besides, an attempt to study fracture surface topology to gain an insight to fracture profiles and processes, has been made through calculation of a universal Hurst Exponent. Consequently, its universality has also been verified.
EXTENDED ABSTRACT
15:20 - 15:40
A SIMPLE ABAQUS PHASE FIELD IMPLEMENTATION FOR THE STUDY OF TRANSVERSE CRACKING IN COMPOSITE LAMINATES
Sindhu Bushpalli ShivareddyDogwood B
In the recent years, phase-field approach has gained remarkable attention in the field of Fracture Mechanics and has offered solutions to numerous problems involving crack onset and propagation. In the present paper, a Abaqus implementation of the phase-field approach using only a user material subroutine is extended to study intralaminar damage in CFRP composites. To this end, the capability of modeling orthotropic elastic behavior, transverse cracks and residual stresses has been introduced in the formulation. To validate the implementation, mechanical models with three different configurations were considered and Numerical results were compared with the analytical solution of benchmark problems.
EXTENDED ABSTRACT
15:40 - 16:00
MODELING FRACTURE IN FUNCTIONALLY GRADED MATERIALS WITH PHASE-FIELD METHOD
P.C. SidharthDogwood B
Phase field fracture predictions in functionally graded plates are carried out using exponential finite element shape functions. The rule of mixtures is employed to estimate the material properties according to the volume fractions of the constituent materials, which have been varied according to given grading profiles. Crack propagation paths and load deflection behaviors are investigated in paradigmatic examples of single-edge notched plate specimens to gain insight into the crack growth resistance of FGMs by conducting numerical experiments over a wide range of material gradation profiles and orientations.
EXTENDED ABSTRACT
14:00 - 16:00 Symp15-Th2: Advanced Computational Methods in Fracture
Organizers: P.R. Budarapu, M.K. Pandit, A.K. Pradhan, S. Natarajan, T. Rabczuk
14:00 - 14:30
Keynote
DEVELOPMENT AND APPLICATION OF THE HYPERCOMPLEX FINITE ELEMENT METHOD FOR LINEAR AND NONLINEAR ENERGY RELEASE RATE CALCULATIONS [Keynote]
Harry MillwaterHickory
The augmentation of existing finite element codes to use complex and hypercomplex variables and algebras provides an accurate and straightforward method to compute the energy release rate for linear and nonlinear solids. The basic concept is to introduce complex nodes defined by real and imaginary nodes. The real nodes define the geometry and the imaginary nodes define the perturbation to the real mesh. The crack is extended using imaginary coordinates surrounding the crack tip. The solution of the complex system of equations then yields a complex displacement with the imaginary displacement equal to the derivative of the displacement with respect to the crack length. Subsequently, the energy release rate (the derivative of the strain energy with respect to the crack length) can be determined using from the complex strains and stresses. The results indicate that the ERR results are as accurate as the J integral but the method has several advantages: there are no contours to interrogate – only one result is provided, the method works for both linear and nonlinear materials with loading and unloading, unlike the J integral, and no integral formulation must be developed and implemented. Numerical examples demonstrate the accuracy of the method.
EXTENDED ABSTRACT
14:30 - 14:50
FINITE ELEMENT MODELING FOR PREDICTING OPTIMAL HOLE PROFILE IN A FINITE SQUARE PLATE OF HETEROGENEOUS BRITTLE MATERIAL (WC+CO) UNDER UNIAXIAL COMPRESSION OR UNIAXIAL DISPLACEMENT
Yitzchak YifrachHickory
The objective of this paper is to develop numerical models to predict and optimize the ratio (D/W) of hole diameter D over plate width W of a square plate with a center hole. The plate is made from tungsten carbide. The geometry of the model was a square plate with a circular hole in the center. FEM simulation was performed for hole diameter to plate width ratio from 0 to 0.71 in terms of fracture strength (Sut or Suc) under uniaxial compression, or uniaxial displacement. SCF values in the simulations showed good fit with analytical values.It is shown that maximum normal tensile stress develops at the upper point along the free edge of vertical hole,and maximum compressive stresses at left and right horizontal points along the free edge of the hole.. The numerical solution of the normal tensile stress distrbution on the "future fracture plane in Mode I" guarantees a certain degree of stability in the crack propagation in heterogeneous brittle materials.This stability, caused the compliance of the plate to remain independent of crack length, and hence
the fracture toughness can be measured by the critical load itself. The results are relevant to the design of inserts cutting tools.
EXTENDED ABSTRACT
14:50 - 15:10
FINITE ELEMENT SIMULATION OF CRACK PROPAGATION IN BRITTLE PLATES
Igor GribanovHickory
A method for modeling fracture in stiff plates of uniform thickness is presented. The Mindlin-Reissner plate theory within the framework of the finite element method is utilized. The fracture criterion is based on the Rankine theory, in which a crack is initiated when normal traction at a node exceeds a given tensile strength. The traction is calculated as a path integral around a crack tip or a tentative split. The propagation direction is such that the normal traction at the crack tip is maximized. A time-based criterion for crack initiation and propagation is added to the model, which yields better correspondence with the experimentally observed fracture patterns. The proposed methodology was implemented in an in-house code. Initial validation shows excellent agreement between the proposed methodology’s predictions and the realistic fracture patterns of ice floes.
EXTENDED ABSTRACT
15:10 - 15:30
MECHANICAL MODEL OF SLIDING FRICTION AND THE STUDY OF THE ONSET OF SLIDING FRICTION
Yiran LiHickory
Friction widely exists in our daily life and nature, and the onset of sliding friction plays an important role. However, the underlying physical mechanism of this dynamic process is still unclear. This paper will further explore the physical nature of crack like defects. We reduce the experimental configuration to a slider-substrate model, where the slider can be described using thin long beams and the substrate is considered as an elastic half-space. In this way, the relevant displacement and stress field solutions can be obtained by solving Cauchy singular integral equations. The numerical results can well describe the experimental results. By introducing a critical criterion for static dislocation nucleation, the calculated critical forces are in good agreement with those of the sliding precursor. Based on the model, the dynamics of the sliding precursor is further considered. It is found that the strain field caused by the moving dislocation is in good agreement with the strain field caused by the defect in the experiment, and the transient emission process of the interface edge dislocation is similar to the spatio-temporal dynamic behavior observed in the experiment. These works may contribute to further understanding of the mechanism related to sliding friction processes.
EXTENDED ABSTRACT
15:30 - 15:50
ROLE OF LOCALIZATION LIMITERS AND LENGTH-SCALES IN MESH OBJECTIVE DYNAMIC FRACTURE MODELING
Kedar KiraneHickory
The objective of this work is to critically assess two commonly used localization limiters, viz. the crack band model (CBM) and rate dependent damage (RDD) for continuum scale dynamic fracture predictions. For this purpose, dynamic mode I fracture for an isotropic brittle material is considered under various loading rates and mesh sizes. A scalar damage model is employed, in conjunction with both localization limiters. The analyses reveal that neither of the localization limiters can successfully regularize the solution across all loading rates. Thus, with local damage models, mesh objective prediction of dynamic fracture can be completely ensured only if the mesh size is kept fixed.Role Of Localization Limiters And Lengthscales In Mesh Objective Dynamic Fracture Modeling
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14:00 - 16:00 Symp17-Th2: Damage, Fracture, and Fatigue of Composites
Organizers: Raj Das and Rhys Jones
14:00 - 14:20
FATIGUE CHARACTERIZATION OF ADHESIVELY-BONDED GFRP JOINTS VIA SELF-HEATING
Nithinkumar ManoharanChestnut
High cycle fatigue (HCF) of composite structures is known to exhibit self-heating coupled with stiffness degradation due to progressive damage accumulation. Recent advances have been made in correlating fatigue damage accumulation to full-field temperature fields during the HCF of composite structures. This work uses a thermal medium wave infrared camera to quantify self-heating in adhesively bonded unidirectional glass fiber reinforced polymer (UD-GFRPs) specimens under tension-tension fatigue loading.
EXTENDED ABSTRACT
14:20 - 14:40
FAILURE MECHANISMS OF STEEL FIBERS EMBEDDED IN HSFRSCC
Luiz Carlos De AlmeidaChestnut
The bond stress transfer between fibers and matrix is the basic resistant mechanism of fiber-reinforced composite materials. Interfacial bond properties and failure mechanisms of the composite are commonly evaluated through single pullout tests on unreinforced matrices. The small size of the molds used to cast the samples prevents the fibers from being randomly distributed in the matrix and makes it difficult to compact the mixture. Krahl et al. (2020) developed an innovative portable pullout machine that allows testing fibers embedded in fiber-reinforced matrices with larger sample sizes. This paper discusses the experimental results of single fiber pullout tests carried out with the portable machine on high-strength fiber-reinforced self-compacting concrete (HSFRSCC). The bond behavior of hooked-end steel fibers and their relationship with the failure mechanisms are analyzed for fiber contents of 0% and 0.75%. The results show that bond and failure mechanisms were influenced by the presence of fibers in the matrix.
EXTENDED ABSTRACT
14:40 - 15:00
AN ANALYTICAL APPROACH FOR THE FRACTURE CHARACTERIZATION IN CONCRETE UNDER CYCLIC LOADING CONDITION
Bineet KumarChestnut
Many civil engineering infrastructures frequently encounter repetitive loading during their service life. Due to the inherent complexity observed in concrete, like quasi-brittle materials, understanding the fatigue behavior in concrete still poses a challenge. Moreover, the fracture process zone characteristics ahead of the crack tip have been observed to be different in fatigue loading than in monotonic cases. Therefore, it is crucial to comprehend the energy dissipation associated with the fracture process zone (FPZ) due to repetitive loading. It is well known that stiffness degradation due to cyclic loading provides a better understanding of the fracture behavior of concrete. Under repetitive load cycles, concrete members exhibit a two-stage stiffness degradation process. Experimentally it has been observed that the stiffness decreases initially with an increase in crack length and subsequently increases. In this work, an attempt has been made to propose an analytical expression to predict energy dissipation and, later, the stiffness degradation as a function of crack length.
EXTENDED ABSTRACT
15:00 - 15:20
THE EFFECT OF FIBER ORIENTATION AND INFILL PATTERN ON FLEXURAL STRENGTH OF ADDITIVELY MANUFACTURED COMPOSITE SPECIMEN
D.G ThakurChestnut
Additive Manufacturing (AM), also known as 3D Printing, has been there for more than two decades and has recently gained importance for manufacturing functional products. AM has excellent developments in recent days with a huge number of applications in industry, automotive, aerospace, medical, architecture, food, fashion, etc. Composite materials are widely used in structures with weight as a critical factor especially in aerospace industry. In recent periods, AM has gained lot of importance in fabricating composite material. Fused Deposition Modelling (FDM) is one of the promising AM technology used for the fabrication of complex geometry product using continuous fiber reinforced composite material. There is lot of research on effect of fiber orientation on flexural strength of composite materials made using conventional manufacturing processes. It will be interesting and significant to study the effect of fiber orientation (0°, 0°/90°, +45°/-45°) and infill pattern (honeycomb, triangular & rectangular) on flexural strength of additively manufactured continuous fiber reinforced polymer composite. Now-a-days, continuous fiber reinforced thermoplastic composite materials are becoming more important in industrial applications due to inherit advantages such as excellent mechanical performance, recycling and potential lightweight structures. In present study, carbon was used as continuous fiber reinforced material which has high flexural
EXTENDED ABSTRACT
15:20 - 15:40
FRACTURE AND FATIGUE STUDIES ON META-SANDWICH AUXETIC CORE
Rohit MadkeChestnut
Inspired by the Parker solar probe's heat shield, a carbon-carbon semi-auxetic laminate sandwiching a lightweight carbon auxetic core has been designed in this work. The fracture and fatigue crack propagation in 2D and 3D auxetic core at ambient and extreme temperatures have been predicted and compared with conventional honeycomb cores and foams. Comparative studies have been performed between the results obtained by in-house codes of phase-field fracture (PFF) in FEniCS and the extended finite element method (XFEM) in ABAQUS™.
EXTENDED ABSTRACT
15:40 - 16:00
ON THE LIMIT EQUILIBRIUM OF SMALL-SCALE INTERFACIAL SHEAR CRACKS AT THE CORNER POINT OF THE INTERFACE OF A PIECEWISE HOMOGENEOUS COMPOSITE
Alexander KipnisChestnut
A plane static symmetric problem of elasticity theory for a piecewise homogeneous isotropic plane with an interface in the form of sides of angle, containing small-scale interfacial shear cracks at a corner point and a loaded internal semi-infinite crack, is considered. The exact solution to this problem is constructed by the Wiener – Hopf method in combination with the apparatus of the Mellin integral transform. The stress intensity factor at the tips of interfacial cracks was determined and the nature of the change in the breaking load was studied.
EXTENDED ABSTRACT
14:00 - 16:00 Symp18-Th2: Mechanical Behavior in Nuclear Materials
Organizers: Dong Liu, Filippo Berto, and Robert O. Ritchie
14:00 - 14:40
Keynote
MATERIALS PROPERTY CHANGES AFTER IRRADIATION EVLAUATED USING SMALL SCALE MECHANICAL TESTING. [Keynote]
Peter HosemannWalnut
Radiation damage can lead to significant property changes in structural materials. Radiation induced swelling, embrittlement or increase in yield strength are just a few. The dose, dose rate and temperature together determine the effect on the material which can have significant engineering impact. Therefore, it is key to understand how a material changes under radiation and being able to predict the property changes. Small scale mechanical testing offers a wide range of benefits especially when working with materials in nuclear application. The reduced size allows to handle highly radioactive materials while also enabling ion beam irradiations as a surrogate to quantify radiation damage. In this work we will provide examples on how small-scale mechanical testing provided deep insight into the mechanical deformation of materials after irradiation. We investigate how the properties change due the radiation induced dissolution of precipitates or due to the formation of new features such a cavities, dislocation loops or precipitates. We will highlight how the plasticity and associated mechanical property values change. Last but not least we will introduce scaling studies performed in order to extract bulk properties from small scale tests. Mesoscale mechanical tests enabled using laser fabrications are shown.
EXTENDED ABSTRACT
14:40 - 15:00
HIGH TEMPERATURE CREEP CAVITATION IMAGING AND ANALYSIS IN 9%CR 1%MO P91 STEELS
Eirini GalliopoulouWalnut
The creep lives of enhanced high-temperature strength and creep resistance of 9%Cr 1%Mo P91 steels in boiler and piping systems of high-temperature plants are limited by the formation of cavitation. P91 steels are characterised by various secondary phases and a complex grain boundary microstructure which leads to regions of increased stress accumulation resulting in the initiation of cavities. In order to predict and possibly extend the creep lives of P91 structure components in energy applications, it is important that the processes promoting the initiation and early growth of cavities are understood. This paper employs microscopy techniques as well as image segmentation tools in order to quantify and characterize the cavitation and the secondary phases present in ex-service and creep tested P91 samples.
EXTENDED ABSTRACT
15:00 - 15:20
PREDICTING THE MACROSCOPIC CYCLIC BEHAVIOUR OF POLYCRYSTALLINE STEELS BASED ON MATERIAL MICROSTRUCTURE VIA SURROGATE MODELLING
Hugh DorwardWalnut
Crystal plasticity finite element models can simulate the effect of microstructure on the cyclic behaviour of polycrystalline steels and can simulate the resulting local plastic strain. However, such models are computationally expensive and are therefore limited to simulation on small volume elements of material. In this work, a Gaussian process regression model is proposed as a surrogate model to predict macroscopic quantities of interest based on input parameters relating to the cyclic loading and material microstructure. The advantage with relation to computational expense of the surrogate can be leveraged for the purposes of undertaking uncertainty quantification and sensitivity analysis regarding the effect of the model inputs on the output prediction.
EXTENDED ABSTRACT
16:00 - 16:30 Coffee 4B
Coffee Break PM
16:30 - 18:00 Parallel Sessions Th3
Parallel sessions symposia Th3
16:30 - 18:00 Symp04-Th3: Brittle Fracture: 100 years After Publication of Griffith’s Theory
Organizers: Claudio Ruggieri, and Laszlo Toth
16:30 - 16:50
DUCTILE-BRITTLE TRANSITION FRACTURE MODE AND THE OCCURRENCE OF ABNORMAL FRACTURE APPEARANCE IN X65 Q & T SEAMLESS PIPELINE STEEL
Marcelo ParedesGrand Ballroom C
The new generation of advanced high strength steels for oil & gas transportation exhibit better mechanical response and fracture toughness not only in corrosive media, but also in arctic environments. In particular, under these latter conditions, X65 Q&T pipeline steels do not reveal a clear ductile-to-brittle transition (DBT) temperature and, in some cases, inverse fracture. It is still unclear the actual causes of this phenomenon typically observed in impact tests such as Charpy and drop-weight tear experiments. This study aims at the understanding of the underlying mechanisms controlling this abnormal behavior, which leads mostly to disqualifying a particular material for a certain engineering application. In general, thorough mechanical and material characterizations are intended to be conducted in order to unveil the relationship between microstructure characteristics and structural configurations. By means of a phenomenological fracture model, the statistical nature of the brittle fracture and the size effects will be deemed into a more general computational damage framework incorporating also ductile fracture from the upper shelf energy region.
EXTENDED ABSTRACT
16:50 - 17:10
ANALYTICAL SOLUTION OF CMOD COMPLIANCE FOR SINGLE EDGE NOTCHED TENSION SPECIMENS IN END-CLAMPED CONDITIONS
Xian-Kui ZhuGrand Ballroom C
The oil and gas industry favors to use less conservative fracture toughness measured from a single edge notched tension (SENT) specimen in the end-clamped conditions in terms of J-integral or crack-tip opening displacement (CTOD) or their resistance curves, where the elastic unloading compliance technique is usually utilized to monitor the incremental crack growth during the single specimen test. Several numerical solutions of crack mouth opening displacement (CMOD) compliance obtained from the finite element analysis (FEA) are available for the end-clamped SENT specimens. However, they have different accuracies and different applicable ranges of crack length ratio a/W, and they may be inconsistent with the existing solutions of their stress intensity factor (K) solutions for the same end-clamped SENT specimen because both the compliance and the K factor were determined separately by FEA. Based on a full-range analytical K solution, this work develops a more accurate, analytical solution of CMOD compliance equation for the end-clamped SENT specimens. Comparisons with various existing FEA results confirm the higher accuracy of the proposed analytical compliance solution. As a result, the proposed CMOD compliance solution can be used to determine more accurate crack length for the SENT testing.
EXTENDED ABSTRACT
17:10 - 17:30
PREDICTORS OF CRACK PROPAGATION
Barna SzaboGrand Ballroom C
Stress intensity factors are viewed as specializations of a family of drivers of crack propagation, defined on three-dimensional stress fields, to two-dimensional stress fields. The question of which driver is best suited for the prediction of crack propagation in three dimensions will have to be decided on the basis of evidence developed through the application of a model development process. The procedure for rational choice of a predictor of crack propagation in metals, caused by cyclic loading, is addressed.
EXTENDED ABSTRACT
17:30 - 17:50
NOVEL BENDING BASED METHODS FOR INTERFACE FRACTURE ENERGY MEASUREMENT OF THERMAL SPRAY COATINGS
Saim AbbasGrand Ballroom C
A novel modified cantilever beam method and modified clamped beam method with DIC (Digital Image Correlation) is developed to measure the interface fracture energy of ceramic/metal interface. The experimental execution for these geometries is demonstrated on an Air Plasma Sprayed (APS) YSZ coating on a steel substrate. For modified cantilever method, a pre-crack is first made along the interface, followed by the interface test. These methods use the same geometry for both pre-cracking and testing. The value of interface fracture energy is obtained as the critical energy release rate, Gc, using numerically computed values of J-integral. The results of both the geometries are compared.
EXTENDED ABSTRACT
16:30 - 18:00 Symp06-Th3: Microstructures and Fracture in Advanced Materials
Organizers: Tong-Yi Zhang, Chad Landis, Weiqiu Chen, Ralf Müller, and Jie Wang
16:30 - 17:00
Keynote
MIXED FINITE ELEMENT METHOD FOR FRACTURE MODELING OF PIEZO- AND FERROELECTRIC MATERIALS WITH STRAIN GRADIENTS (FLEXOELECTRICITY) [Keynote]
Sergey KozinovGrand Ballroom A
Following the continuous miniaturization of the microelectromechanical systems (MEMS), a size-dependent phenomenon of flexoelectricity starts to play an essential role at the micro- and nanoscale. Direct flexoelectricity is an electromechanical coupling of strain gradients, which are inversely proportional to the length scale, and electric field. Due to the application of strain gradients, the centrosymmetry of the unit cells is broken, allowing a wider choice of dielectrics to be used in applications. In the proposed research, the nonlinear ferroelectric material behavior is further enhanced with strain gradients and applied to fracture problems with naturally occurring gradients of electromechanical fields near the crack tip. Or in another way, it is the incorporation of the remanent strains and polarization into the flexoelectric formulation. Our solution demonstrates the strong influence of the gradients on the ferroelectric domain switching behavior, leading to modified electromechanical fields close to the crack tip compared to the well-known ferroelectric problems.
EXTENDED ABSTRACT
17:00 - 17:20
THE INFLUENCE OF FLEXOELECTRIC EFFECT ON THE DOMAIN STRUCTURE AND FRACTURE TOUGHNESS OF FERROELECTRIC MATERIALS
Yangqin GuoGrand Ballroom A
Due to the impressive electromechanical properties, ferroelectric materials are widely used in actuators, memory devices and other electronic devices. However, the instinct weak strength and brittleness of ferroelectrics make it easy to failure under external force and electric field. Furthermore, giant strain gradient will be generated near the crack tip with the action of external forces. As a consequence, flexoelectricity is expected to sharply affect the domain configuration and local electromechanical behavior. In this work, the time-dependent Ginzburg-Landau (TDGL) theory and phase field model are used to study the influence of flexoelectric effect on the domain structure and fracture toughness of PbTiO3 in the vicinity of the crack tip. The results show that flexoelectric effect reduces the fracture toughness near the crack tip and breaks the symmetry of the domain structure and fracture toughness. Fracture toughness of parallel to the polarization direction decreases more than that perpendicular to the polarization direction. Compared with anti-parallel to the polarization direction, the flexoelectric effect is more likely to weaken the fracture toughness of parallel to the polarization direction. As a conclusion, flexoelectric electric effect is vatal influence on the reliability design of ferroelectric materials and devices.
EXTENDED ABSTRACT
17:20 - 17:40
THE USE OF CHEVRON-NOTCH METHODOLOGY IN THE DETERMINATION OF FRACTURE TOUGHNESS OF HIGH STRENGTH TOOL STEELS
Helio GoldensteinGrand Ballroom A
The experimental determination of fracture toughness of ultra high strength tool steels often presents limitations due to difficulty in producing fatigue pre-cracked specimens. The alternative methodology using chevron-notched samples allows reliable and reproductive results of KICV. The improvement of these steel types toughness is a permanent challenger due the high amount of large, hard and brittle carbide particles. Control of solidification, conformation process and heat treatments can change the morphology, distribution, size and type of carbides. Surprisingly cast specimens with large dendrite arm spacing and decomposed and spheroidized carbides showed higher fracture toughness
EXTENDED ABSTRACT
17:40 - 18:00
CHARACTERIZATION OF ICE ADHESION: MODES OF LOADING AND MICROSTRUCTURE
Ashraf BastawrosGrand Ballroom A
We present fracture mechanics-based approaches to characterize interfacial fracture parameters for the tensile and shear behavior of a typical ice/aluminum interface. An experimental framework employing single cantilever beam, direct shear, and push-out shear tests were developed to achieve near mode-I and near mode-II fracture conditions at the interface. Both analytical (beam bending and shear-lag analysis), and numerical (finite element analysis incorporating cohesive zone method) models were used to extract mode-I and II interfacial fracture parameters. The combined experimental and numerical results, as well as surveying published results for the direct shear and push-out shear tests, showed that mode-II interfacial strength and toughness could be significantly affected by the test method due to geometrically induced interfacial residual stress. As a result, the apparent toughness of the zero-angle push-out test could reach an order of magnitude higher than those derived from direct shear tests. Moreover, it was found that the interfacial ice adhesion is fracture mode insensitive and roughness insensitive for tensile and shear modes, for the observed modes of failures in this study.
EXTENDED ABSTRACT
16:30 - 18:00 Symp10-Th3: Small Scale Specimen Testing
Organizers: V. Jayaram, Raghu V. Prakash, N Jaya Balila, Robert Lancaster, Bernd Gludovatz, and Dan Gianola
16:30 - 17:10
Keynote
HIGH-CYCLE FATIGUE IN THE TEM: NANOCRYSTALLINE METALS [Keynote]
Brad BoyceGrand Ballroom B
In-situ TEM high-cycle fatigue experiments on electron transparent thin films of nanocrystalline Pt and Cu have revealed not only microstructural-sensitive crack propagation, but also unexpected microstructural-scale crack healing. Based on the experimental observations, atomistic modeling, and continuum-scale microstructural modeling, the mechanism appears to be crack flank cold welding facilitated by local compressive microstructural stresses and/or grain boundary migration. While these observations are specific to pure nanocrystalline metal thin films under a high-vacuum environment, there are potentially much broader ramifications. The existing observations can be used to help rationalize suppressed fatigue crack propagation rates in vacuum, subsurface, or under contact-inducing mixed-mode stresses; and even the precipitous decline in propagation rates near the fatigue threshold.
EXTENDED ABSTRACT
17:10 - 17:30
17:30 - 17:50
16:30 - 18:00 Symp17-Th3: Damage, Fracture, and Fatigue of Composites
Organizers: Raj Das and Rhys Jones
16:30 - 16:50
ON THE DESIGN OF CRACK-ARRESTING LAYERS IN POLYPROPYLENE BASED MULTILAYER COMPOSITES
Johannes WienerChestnut
In natural materials, outstanding properties can be attained through an advantageous combination of different materials in intricate microstructures. Usually, a matrix material contributes high strength and stiffness (“hard phase”), while interlayer (IL) materials are often proteins with low strength and modulus (“soft phase”) but high strains at break. The combination of both phases leads to crack arresting properties, thus dramatically increasing the fracture toughness and damage tolerance of the composite. Renowned examples of such effects are nacre as well as deep-sea sponges. The same concepts shall be mimicked to increase the fracture toughness of talcum reinforced polypropylene (PP). The challenge lies in preserving specimen stiffness while also utililzing the crack arresting properties of soft ILs. In this contribution, two types of PP with different mechanical properties are used as ILs. Normalized parameters for fracture toughness and specimen stiffness are used in order to assess the overall properties of multilayer composites. The trade-offs between stiffness and toughness are illustrated, while optimized structures also demonstrate that both properties can be attained simultaneously.
EXTENDED ABSTRACT
16:50 - 17:10
TAGUCHI BASED – FUZZY METHOD OPTIMIZATION OF PROPOSED ULTRA-HIGH STRENGTH STEEL /UHMWPE HELMET UNDER VARIABLE IMPACTOR CONDITIONS.
Ignatius Ebo-QuansahChestnut
Ultra high strength steel (UHSS) is known for its high strength, high modulus and high energy absorption ability through plastic deformation. However, it is less appealing for lightweight applications due to it relatively high density despite their cheap price. Therefore, all advanced helmets are made from advanced lightweight polymeric materials which are very expensive. The advantages of these classes of material can be harnessed by combining the synergies between them. This study seeks to investigate the application of thin layers of high strength steel and ultra-high molecular weight polyethylene (UHMWPE) in designing cheap and low weight helmet under impact application. Optimization of the proposed helmet under variable impact conditions has been performed through a Taguchi-based fuzzy logic approach. The optimization study investigated the integrity of the proposed helmet considering variable helmet weights, impact velocities and impactor masses. Optimum combinations of these design parameters were obtained through the utilization of Taguchi orthogonal array matrix. Maximization of fracture energy and reaction forces between inner shell and cushion of helmet were considered as criteria for the optimization procedure. Input data for the optimization process were obtained through numerical simulation using the explicit finite element program - LS-PrePost.
EXTENDED ABSTRACT
17:10 - 17:40
Keynote
PROGRESSIVE DAMAGE IN CMC MINICOMPOSITES WITH THICK INTERPHASES UNDER TENSILE LOADING [Keynote]
Suhasini GururajaChestnut
In this work, a composite cylinder assemblage (CCA) model has been used to model the progressive damage behavior under tensile loading of a three-phase ceramic matrix single-tow mini-composite composed of carbon fiber, silicon carbide (SiC) matrix and boron nitride (BN) interphase. A 3-phase shear lag model has been used to capture the matrix crack-driven stress redistribution in the presence of a finite thickness interphase. A probabilistic progressive modeling approach has been proposed to predict the tensile response of ceramic matrix composite (CMC) minicomposites. Multiple matrix cracking, interfacial debonding, and fiber failure have been considered as the damage modes. The predicted tensile response of CMCs from the progressive damage modeling approach agrees with experimental results obtained with C/BN/SiC minicomposites. Finally, the influence of volume fractions, constituent properties, and interfacial properties on the mechanical behavior of CMC minicomposites has been presented.
EXTENDED ABSTRACT
17:40 - 18:00
NON-DESTRUCTIVE EVALUATION OF DEFECTS IN COMPOSITE BI-MATERIAL STRUCTURES AND ESTIMATION OF FRACTURE FRONT USING DATA DRIVEN TERAHERTZ TIME DOMAIN ANALYSIS
Sushrut KarmarkarChestnut
The high luminosity Large Hadron Collider (HL-LHC) will collide particles at unprecedented rates to search for new physics and make high precision measurements to challenge the standard model with emerging technologies that pose high demands for the materials of charged particle tracking detector support structures. Tracking detectors at current (and future) colliders are encounter high-radiation environment where polymeric and carbon fiber composite materials are used in the mechanical support structures of the detectors. The accumulated radiation dose for these materials and thermal loads lead to defects like voids and cracks due to de-gassing and thermal cycling. Terahertz time domain spectroscopy is used to map these strains in a bi-material strip and trace the locations of fractures in a thermal interface material (TIM) layer or an adhesive layer. Statistical data driven terahertz scan image processing analysis is used for predicting the fracture propogation behavior to validate the cohesive FEA model for the fracture observed.
EXTENDED ABSTRACT
16:30 - 18:00 Symp18-Th3: Mechanical Behavior in Nuclear Materials
Organizers: Dong Liu, Filippo Berto, and Robert O. Ritchie
16:30 - 17:00
Keynote
IN SITU X-RAY TOMOGRAPHY IMAGING OF CRACK INITATION AND PROPAGATION IN NUCLEAR GRAPHITE AT 1000°C [Keynote]
Dong LiuWalnut
Nuclear-grade graphite is a critically important high-temperature structural material for current and potentially next generation of fission reactors worldwide. It is imperative to understand its damage-tolerant behaviour and to discern the mechanisms of damage evolution under in-service conditions. Here we perform in situ mechanical testing with synchrotron X-ray computed micro-tomography at temperatures between ambient and 1,000 °C on a nuclear-grade Gilsocarbon graphite. We find that both the strength and fracture toughness of this graphite are improved at elevated temperature. Whereas this behaviour is consistent with observations of the closure of microcracks formed parallel to the covalent-sp2-bonded graphene layers at higher temperatures, which accommodate the more than tenfold larger thermal expansion perpendicular to these layers, we attribute the elevation in strength and toughness primarily to changes in the residual stress state at 800–1,000 °C, specifically to the reduction in significant levels of residual tensile stresses in the graphite that are ‘frozen-in’ following processing. A range of other nuclear grade graphite materials were tested and compared with Gilsocarbon graphite.
EXTENDED ABSTRACT
17:00 - 17:20
BRITTLE FRACTURE MECHANISMS OF THREE MODEL LOW ALLOY STEELS CHEMICALLY REPRESENTATIVE OF A MACROSEGREGATED FORGING
Cainã BemficaWalnut
The influence of the chemical composition on the brittle fracture behaviour of pressure vessel steels was investigated. Two model materials with chemical compositions simulating zones of moderate and severe positive macrosegregation were characterized and compared with the non-segregated material. Fractographic analysis suggests that brittle fracture mechanisms depend on the chemical composition through the induced microstructure.
EXTENDED ABSTRACT
17:20 - 17:40
TRANSIENT CREEP-FATIGUE CRACK GROWTH IN CREEP-DUCTILE AND CREEP-BRITTLE MATERIALS: APPLICATION TO ALLOY 617 AND ALLOY 718
Joshua PribeWalnut
Creep-fatigue crack growth is an important failure mechanism for materials operating at high temperatures. While crack growth laws have been developed for hold-time loads and constant-amplitude cyclic loads, load transients must also be considered for determining component lifetimes. In this study, computational fracture mechanics simulations are used to study crack growth in two nickel-base superalloys at elevated temperatures following overloads. The computations demonstrate that post-overload crack growth depends strongly on the magnitude of crack-tip viscoplastic deformation in the bulk material. In some cases, a classical retardation effect is absent. Dynamic recovery and hardening due to viscoplastic strain gradients are also shown to influence post-overload crack-tip fields and crack growth.
EXTENDED ABSTRACT
18:00 - 19:00 Exhibition
Exhibition
19:00 - 21:00 Banquet
Conference Banquet
Friday Jun 16 2023
07:30 - 08:30 Registration 5
Registration
08:30 - 10:00 Honor and Plenary Session P6
Plenary session P6
08:30 - 09:10
Plenary Lecture
MODELING FRETTING FATIGUE IN MULTIAXIAL AND VARIABLE LOADING CONDITIONS [Plenary Lecture]
Sylvie PommierGrand Ballroom E
Predicting fretting-fatigue life under multiaxial and variable loading conditions requires taking into account the effects of stress gradients and the fact that stress concentration areasn where cracks may intiate, are mobile and move, along with the contact front, when the normal load varies. This paper proposes a model, analogous to linear fracture mechanics approaches, to take into account the gradient effects around the contact front through intensity factors and to describe the displacement of the contact front and the non-linear behaviour of the contact partial slip region with an incremental model based on these intensity factors.
EXTENDED ABSTRACT
09:15 - 09:55
Plenary Lecture
TENSILE TWINNING: BANE OR BOON FOR FRACTURE OF MAGNESIUM ALLOYS [Plenary Lecture]
R. NarasimhanGrand Ballroom E
In this paper, an overview of recent experiments and some simulations aimed at understanding the
fracture behavior of magnesium is presented. The effects of crystallographic orientation, notch acuity,
temperature and strain rate are examined. The results show that tensile twins critically influence the
fracture mechanism operative near a crack or notch tip. On the other hand, they contribute significantly to
plastic dissipation and toughening. Also, they impart hardening which can retard micro-void growth.
EXTENDED ABSTRACT
10:00 - 10:30 Coffee 5A
Coffee Break AM
10:30 - 12:30 Parallel Sessions F1
Parallel sessions symposia F1
10:30 - 12:30 Symp04-F1: Brittle Fracture: 100 years After Publication of Griffith’s Theory
Organizers: Claudio Ruggieri, and Laszlo Toth
10:30 - 10:50
A GENERALIZED SOLUTION TO THE COMBO-CRACK PROBLEM
Haimin YaoGrand Ballroom C
A crack combo refers to a dual crack configuration containing an interior penny-shaped crack (PSC) and a coplanar concentric externally circular crack (ECC). Although the axisymmetric elasticity problem regarding crack combo has been attempted with different approaches in the literature, high-accuracy numerical solutions remain deficient not to mention analytical solutions, especially for general loading cases. To attain accurate solutions to the crack combo problem for typical loading cases, the axisymmetric elasticity problem of the crack combo was re-visited by solving a pair of simultaneous Fredholm integral equations based on the Gauss-Lobatto quadrature. Two typical loading cases are considered, including pressure load on the surface of PSC and remote force load. The high accuracy of the obtained solutions in the whole spectra of size of the PSC and ECC was obtained and verified by finite element simulations. Our results provide generalized and more accurate solutions to the combo crack problem or equivalently the annular contact problem, which are worthy of being included in the handbook of solutions to basic crack problems.
EXTENDED ABSTRACT
10:50 - 11:10
AN ANALOGY IN FRACTURE DYNAMICS: CRACKS AS OSCILLATORS
Yuri PetrovGrand Ballroom C
The incubation time fracture criterion (ITFC) is used to analytically investigate dynamic crack initiation under short pulse loads. Particular attention is paid to the phenomenon of delayed fracture – a fundamental fracture effect that can be observed in experiments with short pulse loads. The effect can be described in the following way: the material failure occurs after local stresses reached their maximum values, meaning that the fracture takes place at a drop stage of the local stress, and thus delay is present. It is shown that the fracture delay effect manifests itself when minimal required critical threshold loads are applied to the system. We believe that such loads are a key tool for experimental investigation of the dynamic fracture effects. The conditions for the fracture delay are found, threshold load parameters are evaluated and the corresponding analytical formulas are given. Additionally, a simple analogy based on a mass-spring model is discussed. Analytical formulas available for the oscillator model are used to find some non-obvious similarities between the crack instability under short pulse loads and the oscillator failure when analogous loads are applied: the dynamic fracture process in the crack vicinity appears to exhibit inertial behavior
EXTENDED ABSTRACT
11:10 - 11:30
THERMAL FRACTURE ANALYSIS OF FUNCTIONALLY GRADED COATINGS ON A HOMOGENEOUS SUBSTRATE
Vera PetrovaGrand Ballroom C
The paper deals with thermal fracture analysis of an functionally graded coating (FGC) on a homogeneous substrate (FGC/H) with the goal to find a direction for optimizing the material combination and gradation of FGCs to improve the thermal fracture resistance of FGCs.
EXTENDED ABSTRACT
11:30 - 11:50
OPERANDO EXPERIMENTS TO CHARACTERISE BRITTLE FRACTURE-LIKE EVENTS IN CERAMIC ELECTROLYTES VIA PHOTOELASTICITY
Christos AthanasiouGrand Ballroom C
Solid electrolytes at current densities that are relevant to real battery operating conditions are prove to the penetration of lithium metal protrusions, also known as “dendritic” events, that are formed during battery charging. In this work, we show via operando photoelasticity experiments that the dendritic events at high current densities can be understood by the classic Griffith - Irwin fracture theory.
EXTENDED ABSTRACT
10:30 - 12:30 Symp06-F1: Microstructures and Fracture in Advanced Materials
Organizers: Tong-Yi Zhang, Chad Landis, Weiqiu Chen, Ralf Müller, and Jie Wang
10:30 - 10:50
HOW DOES THE CRACK VELOCITY AFFECT THE CRACK FRONT DEFORMATION AND THE EFFECTIVE TOUGHNESS IN HETEROGENEOUS MATERIAL?
Bingbing HaoGrand Ballroom A
In brittle failure, the pinning of the crack by tough obstacles deforms the crack front and ultimately enhance the crack growth resistance of materials. In this study, we investigate the effect of the crack speed vm on this mechanism through a combined theoretical and experimental investigation of the pinning of a crack by triangular obstacles of various shapes. Our work reveals that crack pinning is hindered when the crack speed gets closer to an intrinsic velocity v0 that emerges from the rate sensitivity of the fracture energy. Our work suggests that the beneficial effect of collective pinning in disordered materials is optimized in the limit vm << v0 and vanishes when vm ≈ v0. EXTENDED ABSTRACT
10:50 - 11:10
GROWTH AND COALESCENCE OF MULTIPLE CRACKS - EXPERIMENTS AND FRACTURE MECHANICS BASED MODEL
Sophie SchackertGrand Ballroom A
Short crack growth tests are carried out on the coarse-grained nickel-based cast alloy Iconel 100 (IN100) and two microstructures of the austenitic stainless steel AISI 347 using the replica technique. IN100 is tested under TMF and AISI347 isothermally. For both materials, several cracks are found which grow together to form the final main crack. Atypically, the final main crack length does not develop exponentially. To describe the damage evolution of the final main crack, a model is developed based on inelastic fracture mechanics, which includes the different crack driving forces along the crack front, and applied to the test results.
EXTENDED ABSTRACT
11:10 - 11:30
CHARACTERIZATION OF THE DAMAGE TOLERANCE OF NANODESIGNED COATINGS BASED ON HIGH ENTROPY ALLOYS
Martina Prof. ZimmermannGrand Ballroom A
Coatings are primarily designed to offer excellent wear and corrosion resistance. However, these properties are adjusted at the expense of the damage tolerance of the materials applied. By introducing the concept of high entropy alloys new property combinations are expected. In this contribution coatings composed of purely refractory HEA nitride as well as coatings containing non-refractory elements such as Al or Si will be presented. The focus is on a comparison of different experimental strategies to evaluate the damage tolerance of these coatings.
EXTENDED ABSTRACT
11:30 - 11:50
A HYBRID EXPERIMENTAL AND NUMERICAL INVESTIGATION ON THE FRACTURE PROPERTIES OF ZIRCONIUM WITH MAX PHASE COATINGS COVERING A WIDE RANGE OF STRESS STATES
Boyu PanGrand Ballroom A
This work aims to carry out a hybrid experimental and numerical investigation on the fracture properties of the zirconium cladding tube coated with Cr2AlC, which belongs to the group of MAX phase materials. A macroscopic failure criterion is finally developed based on the experimental and numerical simulation results, thus contributing to the design of the accident-tolerant fuel system (ATFs) in nuclear power plants. A series of in-situ bending tests involving various sample geometries covering a wide range of stress states are carried out under a quasi-static condition. Oxidized samples and samples aged in hot water under high pressure are also involved to consider the aging and oxidation effect on material failure. The modified Bai-Wierzbicki (MBW) damage model and the analytical Yoon2014 model are coupled in the simulation so the damage and strength differential effect can be considered in modeling material failure. By transferring boundary conditions between the micro- and macroscopic model as a weak macro-micro coupling, homogenization is achieved so that a micromechanical sub-model can also be developed and the micromechanical simulation and macroscopic simulation can be cross-scale bridged.
EXTENDED ABSTRACT
10:30 - 12:30 Symp09-F1: Fatigue and Fracture of Additively Manufactured Materials
Organizers: Bo Chen, Nagaraja Iyer, and Filippo Berto
10:50 - 11:10
FATIGUE LIFE OF LASER POWDER BED FUSION (L-PBF) ALSI10MG ALLOY: EFFECTS OF SURFACE ROUGHNESS AND POROSITY
Raj DasGrand Ballroom E
The fatigue life of components manufactured by the laser powder bed fusion (L-PBF) process is dominated by the presence of defects, such as surface roughness and internal porosity. The present study focuses on the relative effect of surface roughness and porosity in determining the fatigue properties of AlSi10Mg alloy produced by L-PBF built in the Z direction for as-built (ASB), machined (M) and machined & polished (M&P) conditions. As-built L-PBF samples possess higher surface roughness (1.5-2 µm) compared to the machined (0.8-1.0 µm) or polished ones (0.3-0.75 µm). For ASB samples, surface roughness was found to be the dominant factor affecting fatigue life. However, for M or M&P samples with relatively low surface roughness, the subsurface porosity becomes the dominant factor affecting fatigue failure rather than variations in the surface roughness. The pore size and location effects are analysed using linear elastic fracture mechanics theory, and the critical stress intensity factors (SIF) for L-PBF AlSi10Mg alloy samples are estimated.
EXTENDED ABSTRACT
11:10 - 11:30
FATIGUE LIFETIME ESTIMATION OF ELECTRON BEAM MELTED MICRO-SIZED PARTS BASED ON SURFACES REGENERATED BY MACHINE LEARNING APPROACH
Reza TalemiGrand Ballroom E
The fatigue response of additive manufactured parts, using the electron beam melting technique, is detrimentally affected by their surface defects. These surface defects, produced by the multiple phenomena during the additive manufacturing (AM) process, are the main origins of premature crack initiation and lead to subsequent fatigue failure. This study focuses on estimating the fatigue lifetime of electron beam melting (EBM) manufactured Ti-6Al-4V micro-sized parts using a combination of machine learning and finite element modelling. A Generative Adversarial Network (GAN) is trained to generate 2D surface profiles of the EBM-manufactured Ti-6Al-4V micro-sized parts based on experimental data taken from the literature. Next, the regenerated 2D surface profiles are randomly used to construct 2D Finite Element (FE) models to find and calculate the stresses at critical defects. Finally, Continuous Damage Mechanics (CDM) and Theory of Critical Distance (TCD) are implemented to estimate the fatigue lifetime. This way, hundreds of simulations are performed using regenerated surface profiles. The obtained results show that using both GAN and finite element simulation makes it possible to numerically reproduce the observed fatigue scatter data which is an inherent characteristic of additively manufactured materials.
EXTENDED ABSTRACT
11:30 - 11:50
EFFECTS OF DEFECT, LOADING MODE AND MICROSTRUCTURE ON LPBF 316L FATIGUE BEHAVIOR
Franck MorelGrand Ballroom E
The present study aims to investigate the high cycle fatigue (HCF) performance of steel 316L fabricated by the laser powder bed fusion (LPBF) process. Bending and torsional fatigue test specimens built horizontally (0°), inclined (45°), and vertically (90°) have been prepared and tested in the as-built and polished states. The presence of multiple lack-of-fusion defects at the surface or subsurface is detrimental to the endurance under cyclic loading. A more pronounced defect sensitivity in bending compared to torsion is found. Microstructural features are seen to compete with inherent defects to affect fatigue performance in the condition that the effective defect sizes are close to the critical fatigue crack size.
EXTENDED ABSTRACT
11:50 - 12:10
CORRECTING FOR RESIDUAL STRESS EFFECTS ON FATIGUE CRACK GROWTH RATES OF ADDITIVELY MANUFACTURED TYPE 304L STAINLESS STEEL
Christine SmuddeGrand Ballroom E
Additively manufactured (AM) metal builds contain residual stress that can influence measured fatigue crack growth rates (FCGRs), which may then bias the interpretation of the performance of AM materials. In the present work, the on-line crack compliance (OLCC) method was used to determine the residual stress intensity factor, Kres, while simultaneously collecting fatigue crack growth rate data in edge crack compact (C(T)) specimens of both AM and wrought materials. Measured near-threshold FCGR data in AM 304L C(T) specimens appear elevated in comparison with data from wrought specimens over a range of applied ∆K. By quantitatively accounting for residual stress, the results for materials processed by the different methods are brought into good agreement, demonstrating the importance of accounting for residual stress when interpreting fatigue crack growth data in AM materials.
EXTENDED ABSTRACT
10:30 - 12:30 Symp10-F1: Small Scale Specimen Testing
Organizers: V. Jayaram, Raghu V. Prakash, N Jaya Balila, Robert Lancaster, Bernd Gludovatz, and Dan Gianola
10:30 - 11:10
Keynote
EFFECT OF ELECTRIC CURRENT ON PRE-CRACKED THIN METALLIC SHEETS: FROM CRACK PROPAGATION TO CRACK HEALING [Keynote]
Praveen KumarGrand Ballroom B
Both scientifically and technologically, it is important to study the effects of electric current pulses on the structural integrity of metallic components. As an electric current reverses its direction across a crack, massive current crowding occurs at the crack tip, thereby generating a non-uniform temperature field sourcing away from the crack tip, and considerable electromagnetic forces are generated on the crack faces that open the crack in Mode I. Recent studies have shown that due to the synergistic effects of the above two stimuli, a pre-existing flaw may grow as well as heal upon application of an electric current pulse of high density. While one is a bane for structural integrity, the other one is a boon to in-service components. Here, we will discuss the reasons behind crack propagation upon application of an electric current and then explore the attributes responsible for a transition from flaw propagation to flaw healing upon passage of an electric current pulse. Furthermore, the synergetic role of mechanical load and magnetic field in the propagation of a pre-existing flaw will be discussed. We will establish the complementary roles of electric current, magnetic field and mechanical load in the failure of pre-cracked metallic sheets.
EXTENDED ABSTRACT
11:10 - 11:30
FRACTURE AND FATIGUE BEHAVIOR OF ADDITIVELY MANUFACTURED MAR-M 509 CO-BASED SUPERALLOYS
Rohit Kumar YadavGrand Ballroom B
Mar-M 509 is a Cobalt-based superalloy suitable for elevated temperature applications like nozzle guide vanes and blades in aero engines and gas turbines. Short cycle aging heat treatment of laser powder-bed-fusion processed Mar-M 509 is a novel route explored in this study to enhance the mechanical properties of this alloy, especially tensile ductility and fracture toughness, while retaining room and elevated temperature strengths. A detailed microstructural analysis is carried out using advanced characterisation tools and correlated to miniature, small volume, room temperature tensile tests and fracture toughness and fatigue tests using clamped beam geometry combined with digital image correlation-based in-situ strain mapping across the longitudinal and transverse directions, before and after heat treatment. Mechanisms leading to corresponding changes in fracture and fatigue properties will be discussed.
EXTENDED ABSTRACT
11:30 - 11:50
INTEGRATING SIMULATION, MACHINE LEARNING, AND EXPERIMENTAL APPROACHES FOR HIGH-THOUGHPUT SMALL-SCALE FRACTURE INVESTIGATIONS
Xing LiuGrand Ballroom B
From Da Vinci to Galileo to modern experimentalists a variety of characterization methods have been introduced for investigating the fracture of materials. Determining fracture properties of materials at small length scales, with complex shapes, under extreme environmental conditions, is still extremely challenging. We will show how this gap is addressed by introducing two novel methods to investigate fracture. The first one involves light for contactless mechanical testing, while the second method integrates experiments with data-driven approaches to address issues related to complex shapes.
EXTENDED ABSTRACT
10:30 - 12:30 Symp12-F1: Phase-Field Models of Fracture
Organizers: Israel Garcia, Fabian Welschinger, and Vladislav Mantic
10:30 - 11:10
Keynote
A PHASE-FIELD MODEL FOR THE MULTISCALE ANALYSIS OF FRACTURE IN SHORT GLASS FIBER REINFORCED POLYMERS [Keynote]
Fabian WelschingerDogwood B
Understanding and modeling the fracture mechanical behavior of short glass fiber reinforced polymers (SFRPs) is challenging: the strong heterogeneity induced by the manufacturing process causes a tight coupling of the material microstructure to the effective response on the component scale. Aiming to account for this microstructural complexity, fracture is approached using a multiscale approach. To resolve the microstructure induced anisotropy and its relationship with the macroscopic material behaviour, an isotropic phase-field fracture model is extended via the fiber orientation interpolation concept. The approach is fed by micromechanical simulations calibrated by experimental data. A validation of the proposed approach is obtained by means of numerical investigations compared to experimental findings.
EXTENDED ABSTRACT
11:10 - 11:30
PHASE FIELD MODELING ON ELASTOMERS CONSIDERING THE NONLINEAR MATERIAL VISCOSITY
Heng FengDogwood B
With inevitable flaws, elastomers are susceptible to rupture leading to the reduction in stretchability and loss of functionallity. In the present work, a finite element (FE) framework is proposed with the incorporation of polymer dynamics into the phase field modeling (PFM). The driving force to the fracture of viscoelastic elastomers is identified and the micro-mechanism of material viscosity is further accommodated with the consideration of polymer chain breakage to capture the disentanglement before fracture. The FE model is validated with comparison with existing experimental data, and is expected to provide guidance for the design of elastomer based transducers.
EXTENDED ABSTRACT
11:30 - 11:50
AN AUGMENTED PHASE-FIELD MODEL WITH VISCOUS STRESSES FOR DEFECT DYNAMICS
Janel ChuaDogwood B
This work begins by applying phase-field modeling to predict 1-d interface motion with inertia in an elastic solid with a non-monotone stress-strain response. In classical nonlinear elasticity, it is known that subsonic interfaces require a kinetic law, in addition to momentum balance, to obtain unique solutions; in contrast, for supersonic interfaces, momentum balance alone is sufficient to provide unique solutions. However, conventional phase-field models coupled to elastodynamics are unable to model, even qualitatively, the supersonic motion of interfaces. This work identifies the shortcomings in the physics of standard phase-field models to be: (1) the absence of higher-order stress to balance unphysical stress singularities, and (2) the ability of the model to access unphysical regions of the energy landscape.
This work then proposes an augmented phase-field model to introduce the missing physics. The augmented model adds: (1) a viscous stress to the momentum balance, in addition to the dissipative phase-field evolution, to regularize singularities; and (2) an augmented driving force that