Session W1: Wednesday, June 14, 10:30-12:30
Wednesday Jun 14 2023
10:30 - 10:50
A PERIDYNAMIC FATIGUE MODEL BASED ON TWO-PARAMETER REMAINING-LIFE FORMULATION
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.
10:50 - 11:10
FAST INFERENCE OF CRACK TIP POSITION AND STRESS INTENSITY FACTORS FROM DISPLACEMENT DATA
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.
11:10 - 11:30
SIMULATING CRACK CLOSURE WITH COHESIVE ZONE ELEMENTS DURING CRACK GROWTH
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.
Session W2: Wednesday, June 14, 14:00-16:00
Wednesday Jun 14 2023
14:00 - 14:20
APPLICATION OF CONCURRENT ATOMISTIC-CONTINUUM COUPLING TO STUDY FRACTURE IN POLYMER NANOCOMPOSITES
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.
14:20 - 14:40
FRACTURE OF HIGHLY ELASTIC AND COMPOSITE MATERIALS AT COMPRESSION ALONG NEAR-SURFACE CRACK IN CASE OF SMALL DISTANCE BETWEEN FREE SURFACE AND CRACK
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.
14:40 - 15:00
RECENT ADVANCEMENTS AND APPLICATIONS IN DEVELOPMENT OF SMART CRACK GROWTH SIMULATION
SMART (Separating, Morphing, Adaptive and Remeshing Technology) is a finite element based crack growth simulation framework 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.
Session W3: Wednesday, June 14, 16:30-18:00
Wednesday Jun 14 2023
16:30 - 17:00
ADVANCED CRACK TIP FIELD QUANTIFICATION USING DIGITAL IMAGE CORRELATION, MACHINE LEARNING, AND INTEGRAL EVALUATION [Keynote]
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
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.
17:20 - 17:40
SINGULAR INTEGRAL EQUATION FOR SOLVING COHESIVE CRACK PROBLEM FOR INITIALLY RIGID TRACTION-SEPARATION RELATION
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.
Session Th1: Thursday, June 15, 10:30-12:30
Thursday Jun 15 2023
10:30 - 11:00
REDEFINED J-INTEGRAL AND J-INTEGRAL RANGE DELTA-J AS FINITE STRAIN ELASTIC-PLASTIC CRACK PARAMETERS [Keynote]
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.
11:00 - 11:20
THE VIRTUAL ELEMENT METHOD FOR EFFICIENT CRACK TIP LOADING ANALYSIS AND CRACK GROWTH SIMULATION
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.
11:20 - 11:40
3D FRACTURE MECHANICS ANALYSIS OF THERMOMAGNETOELECTROELASTIC ANISOTROPIC SOLIDS ACCOUNTING FOR CRACK FACE CONTACT WITH FRICTION
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.
11:40 - 12:00
CYCLIC EFFECTIVE NEAR-FIELD LOADING BASED ON THE DOMAIN INTEGRAL METHOD
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.
12:00 - 12:30
Session Th2: Thursday, June 15, 14:00-16:00
Thursday Jun 15 2023
14:00 - 14:30
DEVELOPMENT AND APPLICATION OF THE HYPERCOMPLEX FINITE ELEMENT METHOD FOR LINEAR AND NONLINEAR ENERGY RELEASE RATE CALCULATIONS [Keynote]
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.
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
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.
14:50 - 15:10
MECHANICAL MODEL OF SLIDING FRICTION AND THE STUDY OF THE ONSET OF SLIDING FRICTION
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.
15:10 - 15:30
ROLE OF LOCALIZATION LIMITERS AND LENGTH-SCALES IN MESH OBJECTIVE DYNAMIC FRACTURE MODELING
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