Session Th1: Thursday, June 15, 10:30-12:30
Thursday Jun 15 2023
10:30 - 11:10
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.
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.
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.
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.
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.
Session Th2: Thursday, June 15, 14:00-16:00
Thursday Jun 15 2023
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.
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.
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.
15:00 - 15:20
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.
15:20 - 15:40
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.
15:40 - 16:00
AN FE-EXPERIMENTAL METHOD FOR DETERMINING QCT-BASED CORTICAL BONE FRACTURE TOUGHNESS AND ULTIMATE STRESS [Keynote]
Maxime LevyDogwood B
Cortical bone fracture prediction using Phase Field Models (PFMs) requires the data on the spatial distribution of bone fracture toughness and ultimate stress. However such correlations with qCT parameters or associated bone density are not yet available in the literature. Here, we proposed an FE-Experimental method to determine bone fracture toughness and ultimate stress for different densities and find out potential correlations. Digital Image Correlation (DIC) and diverse standards for KIc calculation show values ranging from 2 to 9 MPa√m. Although it is consistent with reported data in the literature, further work is being conducted using qCT-scans and micro-CT data as well as Finite Element Analysis (FEA) to estimate bone density and determine more accurately the associated fracture toughness and ultimate stress.
Session F1: Friday, June 16, 10:30-12:30
Friday Jun 16 2023
10:30 - 11:10
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.
11:10 - 11:30
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 models the physical mechanism that keeps the system out of unphysical regions of the energy landscape. When coupled to elastodynamics, the augmented model correctly describes both subsonic and supersonic interface motion. This augmented model was then used for fracture simulations.
11:30 - 12:10
TALK MOVED TO SESSION Th2
Maxime LevyDogwood B