Session W1: Wednesday, June 14, 10:30-12:30
Wednesday Jun 14 2023
10:30 - 11:10
TOWARDS PRACTICAL SIMULATION OF STEEL FRACTURE IN STRUCTURAL AND EARTHQUAKE ENGINEERING APPLICAITONS [Keynote]
Gregory DeierleinDogwood A
Over twenty-five years ago, unexpected fractures occurred in dozens of welded steel frame buildings during the 1994 Northridge earthquake. This prompted major research programs to (1) develop more reliable connection details for new buildings, (2) develop strategies to repair and retrofit damaged buildings, and (3) to assess the seismic safety of buildings. Efforts to develop alternative designs for new and retrofitted steel connections primarily relied on large-scale laboratory testing of connection subassemblies. Since then, significant advancements have been made in nonlinear finite element techniques to simulate the inelastic behavior of structural components and systems, although challenges remain to reliably simulate fracture, particularly for seismic design, where structural components are designed to undergo large-scale yielding. This presentation will summarize research on continuum-based fracture mechanics, where cyclic void growth models are used to assess ductile fracture initiation and propagation under large scale cyclic yielding. The models are implemented through finite element analyses and validated through a series of tests on notched axial bars, compact tension specimens, and large scale steel subassembly tests of braces and column base connections. Applications to use detailed finite element models to calibrate macro-scale models for incorporating fracture limit states in overall structural system response are also described.
11:10 - 11:30
MICROVOID CHARACTERISTICS AT FRACTURE IN ASTM A992 STEEL UNDER MONOTONIC AND ULTRA-LOW CYCLE FATIGUE LOADING
Surajit DeyDogwood A
Ductile fracture is the fracture initiating mechanism in steel structures subjected to both overloading and ultra-low cycle fatigue (ULCF) loading. This paper aims to characterize the statistical distribution of microvoids on the fracture surface of structural steel specimens subjected to monotonic and ULCF loading by employing advanced microscopy techniques. Furthermore, the relationship between the experimentally inferred mean microvoid size and the state of stress and strain is investigated.
11:30 - 11:50
DUCTILE FRACTURE OF LOW-YIELD-POINT STEEL UNDER DIFFERENT STRESS STATED
Zucheng YaoDogwood A
Low-yield-point steel LYP225, distinguished from the ordinary carbon structural steels by lower yield strength, preferable strain-hardening and better ductility, is widely applied in metallic dampers. Ductile fracture of these dampers after severe earthquakes were commonly observed. This paper experimentally investigates the ductile fracture of LYP225 steel under different stress states, and predicts the fracture initiation with the Hosford-Coulomb fracture model.
11:50 - 12:10
MULTISCALE SIMULATION OF STRUCTURAL WELDMENTS
Amit KanvindeDogwood A
While sophisticated simulation techniques are regularly applied in natural hazards engineering, they are limited in ability to capture several important failure mechanisms. A significant limitation is the capability to reliably simulate fracture in structural steel weldments. Predicting fracture in weldments is inherently challenging due to various factors. Moreover, when weldments do not have a sharp, pre-existing flaw, or are subjected to large-scale yielding or earthquake-induced Ultra Low Cycle Fatigue (ULCF – characterized by few cycles of large strain) – all of which occur frequently in modern buildings, conventional fracture and fatigue mechanics are invalidated. Given that fracture often initiates in the weld region, this represents a major obstacle to effective structural performance assessment. This is addressed this through a coordinated program of (1) physical tests and fractography on thermomechanically generated samples of various weld microstructures for discovery of fracture micromechanisms, (2) formulation of new continuum-based fracture criteria for these different microstructures, (3) numerical implementation, and (4) calibration and validation of the developed framework using laboratory testing. A key research challenge is to effectively upscale local models, considering spatial variation of microstructure and interaction between mechanisms to predict fracture at the component/structure scale, while also characterizing the uncertainty in these predictions.
Session W2: Wednesday, June 14, 14:00-16:00
Wednesday Jun 14 2023
14:00 - 14:20
FATIGUE LIFE ASSESSMENT OF A TRUSS GIRDER BRIDGE USING LINEAR FRACTURE MECHANICS APPROACH
Sudip TalukdarDogwood A
In transportation system, bridges are continuously subjected to vehiclular loads that causes accumulation of stresses in different components. The weakest region are some times prone to the development of fatigue crack, that grows leading to collapse if proper maintenance and reparing are not carried out. In this paper, a method of estimation of fatigue life of a truss girder bridge has been outlined using linear fracture mechanics approach after synthesizing the vehicle induced stress history. Von-Mises stresses which accounts for all the principal stresses at a gusset plate of a critical joint was utilized to obtain stress-cycle histogram. Number of cycles required to grow an initially detected crack of very small dimension to a threshold value has been obtained to predict the fatigue failure. The effect of the length of the bridge, vehicle speed and compound traffic growth on remaining life of the bridge has been studied
14:20 - 14:40
ENHANCED REAL TIME FATIGUE CRACK MONITORING AND UPDATING IN WELDED STRUCTURAL COMPONENTS
Liuyang FengDogwood A
Cracks emerging from geometrically discontinuous locations under cyclic environmental loadings are critical concerns for the safety of the existing structural components. The crack-based fatigue assessment is essential for the evolving digital twin of sustainable infrastructures, including bridges, ships, and offshore platforms, to optimize the lifetime cost of these structures. This study presents an enhanced neural network-bootstrap particle filtering algorithm to construct the complex relationship between the normalized strain relaxation indicators and the crack profiles based on the numerical simulation and experimental validation. The high-cycle fatigue bending test of the welded plate connections confirms the robustness of the proposed approach in estimating the fatigue crack initiation and propagation through both strain measurement and nondestructive testing data. To overcome the uncertainties caused by the limited strain measurement, crack measurement, and different non-destructive techniques, this study combines a bootstrap particle filtering approach with an interpolation method to update the crack prediction algorithm. As validated by the experimental results, the intelligent crack sizing approach demonstrates a potential solution for crack size forecasting through affordable strain gauges in the broad framework of digitally twinning the next-generation infrastructure.
14:40 - 15:00
EFFECT OF NON-METALLIC INCLUSIONS ON THE FRACTURE TOUGHNESS OF 42CRMO4 STEEL IN THE DUCTILE-BRITTLE TRANSITION RANGE
Kevin KochDogwood A
In this article, the effect of the volume content and distribution of non-metallic inclusions on the fracture toughness of a quenched and tempered 42CrMo4 steel is investigated. The investigations focused on the material behavior in the ductile-brittle transition range. To this end, fracture toughness tests were performed on 42CrMo4 with different inclusion characteristics. These were achieved by metal melt treatment with functional filter materials. The results showed a significant effect of both volume content and distribution of the non-metallic inclusions. The transition to brittle material behavior was accompanied by a decreasing fracture toughness as well as low scatter of the test data.
15:00 - 15:20
LOW-CYCLE FATIGUE ANALYSIS OF ALUMINUM ALLOY GUSSET JOINTS AND LATTICED SHELL BASED ON CONTINUUM DAMAGE MECHANICS
Bohan LiDogwood A
Aluminum alloys have been widely used for structures in environments subject to corrosion. However, aluminum alloys have lower elastic modulus as compared to steels, and are more sensitive to low-cycle fatigue failure. This study performed low-cycle fatigue experiments of aluminum alloy gusset joints. A damage-coupled cyclic plastic constitutive model of 6061-T6 aluminum alloy was established based on continuum damage mechanics. Numerical simulations of the joints and a latticed shell were carried out incorporating the constitutive model. Low-cycle fatigue life of the joints and the latticed shell structure were estimated based on damage distribution calculated by the simulations.
15:20 - 15:40
MODELLING OF PLASTICITY AND DUCTILE FRACTURE FOR LOW TO MEDIUM INDIAN STRUCTURAL STEEL GRADES
Tamilselvan NambirajanDogwood A
The data points available for developing a Fracture Locus (FL) database for structural steel used in the Indian construction industry are extremely limited. The current study is conducted to determine the FL data points for three different grades of Indian structural steel, namely E250, E350, and E450. Uniaxial tests on notched dog bone specimens of three different specimen configurations are performed. The selected configuration is used to determine points for plotting FL corresponding to high-stress triaxiality (0.7 < T >1) and Lode angle (L) almost equal to 1. With the help of numerical simulation, the FL points are obtained and reported. The accuracy of numerical simulation is checked by precisely matching the load versus displacement obtained from the experiment. Six fracture prediction models are chosen for the present study. These six models are chosen using the following criteria, (1) only depends on stress triaxiality (b) depends on both stress triaxiality and Lode angle and (c) the number of coefficients used. The effectiveness of all the selected models in predicting fracture initiation across all three steel grades is compared, and the findings are reported.
Session W3: Wednesday, June 14, 16:30-18:00
Wednesday Jun 14 2023
16:30 - 16:50
THE TIP FIELDS OF SHARP V-NOTCH UNDER CREEPING CONDITION CONSIDERING OUT-OF-PLANE EFFECT
Weichen KongDogwood A
Notches in creeping solids at high temperatures have drawn considerable attention due to their importance in structural integrity assessment. Understanding the three-dimensional (3D) effect on the notch tip field is important for the fracture mechanics analysis of engineering materials and structures. This paper presents an asymptotic solution for 3D sharp V-notched structures subjected to mode Ⅰ creep loading condition.
16:50 - 17:10
CONSTANT CTOA DETERMINATION FOR STABLE DUCTILE CRACK GROWTH AND ITS APPLICATION TO RUNNING FRACTURE CONTROL FOR GAS TRANSMISSION PIPELINE
Xian-Kui ZhuDogwood A
The crack tip opening angle (CTOA) has been used as a reliable fracture toughness to characterize stable crack growth for thin-wall structures in low-constraint conditions. Recently, it has been found that CTOA can be also utilized as a robust fracture parameter to describe arrest fracture toughness for gas transmission pipelines in modern ductile steels. This is a great improvement of the traditional fracture control technology for gas pipelines, where a Charpy-vee notch (CVN) impact energy based two curve model developed at Battelle (BTCM) was used to determine the arrest toughness. While the CVN-based BCTM is not applicable to modern pipeline steels with grades X70 and above, the CTOA-based BTCM works well for these high grades, but requires constant CTOA. This work develops four methods to determine constant CTOA using the single edge notched bend (SENB) specimens, including a load-displacement linear fit method, a logarithmic load-displacement linear fit method, a stable tearing energy method, and a J-differentiation method. The test results for A285 carbon steel show that these CTOA methods can determine nearly identical critical CTOA values over stable ductile crack growth using the SENB specimens.
17:10 - 17:30
FAILURE ANALYSIS AND RESIDUAL LIFE ESTIMATION USING A MIXED METHOD OF X-RAY FRACTOGRAPHY AND SIMULATION
Francois ChurlaudDogwood A
In order to guarantee passengers safety while improving rolling stock maintenance, the French railroad company, SNCF, studies the evolution of cracks that can propagate in fatigue loading situations, particularly for locomotive axles. This research aims to determine the crack propagation history, which is a determining factor in maintenance, studying fracture surfaces while combining X-ray fractography analysis and numerical methods for variable amplitude loads
Session Th1: Thursday, June 15, 10:30-12:30
Thursday Jun 15 2023
10:30 - 11:10
WARP3D: OPEN SOURCE SOFTWARE FOR 3D NONLINEAR FRACTURE MECHANICS [Keynote]
Robert DoddsDogwood A
The WARP3D project (warp3d.net) provides all source code, extensive documentation and ready-to-run executables on Windows, Linux and macOS for researchers and practitioners worldwide. Developed by a group at the University of Illinois starting in the late 1990s to support academic research, WARP3D capabilities focus on modeling nonlinear fracture processes primarily in metals from the microscale to structural components. This presentation describes the origin and several key capabilities of the code.
11:10 - 11:30
ASSESSING UNCERTAINTY IN CREEP LIFE OF GRADE 91 STEEL USING CRYSTAL PLASTICITY AND GRAIN BOUNDARY MICROSTRUCTURAL MODELS
Timothy TrusterDogwood A
This paper examines time to minimum creep rate and its uncertainty with respect to a set of fourteen material parameters. The microstructural model of Grade 91 steel includes both dislocation creep and grain boundary opening/sliding within a finite element model, and hence the simulations are relatively expensive and have several sources of nonlinearity. We will propagate uncertainty in the input material parameters of these two mechanisms and determine the aggregate uncertainty in the predicted time to minimum creep rate as well as the sensitivities of the parameters. The cost, stability, accuracy of the polynomial chaos expansion as a means for stochastic dimensional reduction is assessed against the classical Monte Carlo method.
11:30 - 11:50
3-D CRACK MODELING CASE STUDIES FOR FITNESS-FOR-SERVICE ASSESSMENT USING WARP3D AND FEACRACK
Greg ThorwaldDogwood A
Two case studies are presented to investigate the use of 3-D crack meshes in Warp3D FEA for FFS assessments. A focused type crack mesh is used for ductile tearing analysis to determine if a cylinder model can be used as approximation for a pipe elbow. The limiting flaw curve results comparison shows an elbow model is needed to obtain more accurate results. A cell type crack mesh is used to examine pipeline hydrotest pressures to cause fatigue crack retardation by crack face closure. The test pressure giving the most benefit is determined by comparing crack closure results from several load cases.
11:50 - 12:10
CRACK-DEFECT INTERACTIONS IN ADDITIVELY MANUFACTURED TI-6AL-4V: DUAL SCALE POROSITY MODELLING USING WARP3D
Huck Beng ChewDogwood A
Localized microstructural defects that often lead to unpredictable fracture have limited the wider adoption of additively manufactured (AM) alloys in critical components. In addition to the background porosity responsible for ductile failure in conventional alloys, defects resulting from the AM process can include large pre-existing voids (~30 μm) resulting in a dual-scale porosity failure process in AM alloys. In the present work, we undertook a numerical approach to explore the dual-scale void and crack interaction processes in both two and three dimensions in AM Direct Metal Laser Melted (DMLM) Ti-6Al-4V. A small-scale yielding modified boundary layer model with monotonically increasing applied displacement was used. The Gurson ductile damage model was implemented to model typical background pores, while the larger AM defects were explicitly represented in a finite element mesh. Fracture resistance curves were numerically generated for random instantiations of AM void distributions with increasing levels of AM defects. Individual outliers of fracture resistance, both over and under perfroming, were analyzed in more detail. It was seen that AM defects may activate a larger fracture process zone ahead of the crack tip, promote crack tortuosity, and on occassion lead to increased local material toughness over the conventional alloy.
Session Th2: Thursday, June 15, 14:00-16:00
Thursday Jun 15 2023
14:00 - 14:20
A NODE RELEASE APPROACH TO CALIBRATE COHESIVE PROPERTIES FOR FRACTURE SPECIMENS AND WELDED PLATE CONNECTIONS
Xudong QianDogwood A
Calibration of the cohesive zone models reqires determination of a number of critical parameters in the traction-separateion law. This paper introduces an approach to determine the traction-separation law, namely the Park-Paulino-Roesler model, through the node-release analysis implemented in the finite element research code WARP3D. The validation of the proposed approach utilizes results from the single-edge-notched bend, SE(B), specimens with varying levels of crack-front constraints and welded plate specimens.
14:20 - 14:40
3-D CONSTRAINT EFFECTS IN SUBSIZE SE(B) SPECIMENS OF NFA-14YWT WITH TRANSVERSE DELAMINATION
Claudio RuggieriDogwood A
This investigation addresses a numerical investigation of the crack front fields and effects of crack-tip constraint in subsized SE(B) specimens with transverse delamination. Nonlinear numerical analyses of very detailed 3-D finite element models of SE(B) fracture specimens for nanostructured ferritic alloy (NFA) material enable assessing the effects of prescribed delamination cracks on the crack front fields with increased deformation levels as characterized by the J-integral. Overall, the present analyses reveal important features of 3-D crack front fields in fracture specimens with transverse delamination that have a direct bearing on the often observed toughness increase in fracture testing of materials with through-thickness anisotropy in mechanical properties.
14:40 - 15:00
15:00 - 15:20
PIPE RUPTURE SIMULATIONS FOR TWO-PHASE CO2-MIXTURE
Bruce WilliamsDogwood A
Control of ductile fracture propagation to ensure arrest is an essential element of design of pipelines transporting natural gas and other fluids such as dense-phase CO2. Full-scale pipe rupture simulations have been carried out using Finite Element Analysis (FEA). The simulations captured an accurate pressure loading profile behind the crack tip resultant from the escaping fluid. Results for loading profiles representative of both natural gas and a CO2 mixture are compared, the difference being that the CO2 mixture can exist as a two-phase fluid (liquid and gas) compared to the single-phase natural gas.
15:20 - 15:40
VFT COMPUTATIONAL WELD MODELING CODE ADAPTED TO WARP3D: PROBLEMS OF CRACK GROWTH AND FRACTURE IN RESIDUAL STRESS FIELDS
Frederick (Bud) BrustDogwood A
Residual stresses caused by the welding process 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. The Virtual Fabrication Technology (VFTTM) computational weld modeling code, which can be used to predict the weld residual stresses (WRS) caused by the welding process, was adapted to the WARP3D open-source code recently. This effort describes the weld modeling process using VFT/WARP3D, provides predictions of WRS fields in several welded components, and provides crack growth predictions and fracture response in several example problems.
15:40 - 16:00
DEVELOPMENT AND VALIDATION OF A COMPUTATIONAL FRAMEWORK TO SIMULATE DUCTILE CRACK PROPAGATION IN STEEL STRUCTURES DUE TO ULTRA-LOW CYCLE FATIGUE USING WARP3D
Andy ZiccarelliDogwood A
Ductile cracks which form in steel components of civil structures due to ultra-low cycle fatigue may display significant growth prior to component failure. A computational framework was developed to simulate the growth of ductile cracks in structural steel utilizing the WARP3D platform. The basic model formulation is presented, followed by selected results from a small-scale experimental testing program. Results of simulations utilizing the proposed framework demonstrate good agreement with the experimental results.
Session Th3: Thursday, June 15, 16:30-18:00
Thursday Jun 15 2023
16:30 - 16:50
MIXED MODE FATIGUE CRACK GROWTH BEHAVIOUR UNDER MICROSTRUCTURAL VARIATION IN FLASH-BUTT WELDS
Yiping WuDogwood A
The strength loss due to welding process poses a high risk of catastrophic rolling contact fatigue failure in the heat affected zones of flash-butt rail welds. Accurate characterisation of fatigue crack growth behaviour in such regions can provide a database for developing safer and more efficient maintenance strategies. This extended abstract details an experimental study on fatigue crack growth behaviour in flash-butt welds in a hypereutectoid rail steel with a hardness level of over 400 HV. Groups of mixed mode fatigue crack growth tests were carried out at parent rail region, partially spheroidised region, fully spheroidised region, re-austenitised region and bond line region. Fractographic analysis was performed to aid the application of the marker band method as well as to analyse the morphology of fracture surfaces. Once all experiments are finished, an equivalent stress intensity factor formula will be fitted to quantify the mixed mode crack driving force in different regions, and modifications of crack growth direction prediction criteria will be proposed for crack growth under the influence of microstructural variation. The current work will provide a reliable database for predicting rolling contact fatigue crack growth at different regions in flash-butt rail welds.
16:50 - 17:10
FRACTURE TOUGHNESS CHARACTERIZATION OF 316L STAINLESS STEEL WELDED PLATES AT LIQUID NITROGEN (77 K) AND LIQUID HELIUM (4 K) TEMPERATURES
Enrico LuconDogwood A
In the framework of a collaborative project between ASME, NASA, and NIST, quasi-static fracture toughness tests were performed at liquid nitrogen temperature (77 K, or 196 °C) and liquid helium temperature (4 K, or -269 °C) on precracked SEN(B) specimens extracted from the centers of four separate lots of welded 316L stainless steel plates. Although the plates were produced in accordance with the same specifications from the same material (316L), large differences in fracture toughness have been observed, with the toughest weld exhibiting almost twice the critical toughness of the least tough at 77 K (219 kJ/m2 vs. 113 kJ/m2), and about seven times the critical toughness of the least tough at 4 K (146 kJ/m2 as compared to 21 kJ/m2). Charpy absorbed energies previously obtained at 77 K for three of the four welds were found to be strongly linearly correlated with fracture toughness at both test temperatures, with an exception represented by the fourth weld, which provided the highest impact toughness and the second lowest quasi-static fracture toughness. Dynamic toughness measurements at impact loading rates were also performed on precracked SEN(B) specimens, in order to deconvolute the roles of strain rate and notch sensitivity on the fracture properties.
17:10 - 17:30
EFFECT OF BOLT PRELOAD ON FRETTING FATIGUE BEHAVIOUR OF DOUBLE LAP BOLTED JOINTS WITH CLASS B SURFACE FINISH IN HIGH-CYCLE FATIGUE: EXPERIMENTAL AND NUMERICAL INVESTIGATION.
Alireza ZangouieDogwood A
Slip-critical bolted connections are prone to developing fretting damage between the contacting surfaces. In this study, the effect of two different bolt preload values, 90 and 145 kN, on the fretting fatigue behaviour of steel double-lap bolted joints with a Class B (shot-blasted) surface under high-cycle fatigue conditions is investigated experimentally and numerically. The experimental results show that increasing the bolt preload decreased the total fretting fatigue life significantly. Moreover, the proposed numerical method was able to predict crack initiation and crack propagation behaviours successfully.