Table of Contents
eXtended Finite Element Method (XFEM)
In this tutorial, we have introduced the extended finite element method or XFEM Metod in Abaqus. You may be wondering what XFEM is?
XFEM Method in ABAQUS?
XFEM is a method in ABAQUS that allowsĀ you to study crack growth along an arbitrary, solution-dependent pathĀ without needing to re-mesh your model.
See the full definition of XFEM on Wikipedia
this example illustrates the use of XFEM Method in the Abaqus standard solver to predict both crack initiation and propagation due to stress concentration in a plate with a hole that is subjected to tension.
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Now, follow the tutorialā¦
Part Module
Part Module
start with creating the part which is two-dimensional and deformable.
then create a rectangle with the following dimension.
next, create a circle at the middle of the left side with a radius of 0.5. after that, it needs to trim redundant curves.
Hint: partitioning of this space can help you to control measuring the part.
Property Module
in the property module, create a material with linear elastic behavior.
then we define the traction-separation behavior of the material using maximum principle stress criteria.
as you can see in this criterion if the maximum principal stress is positive and more than a critical value the crack initiates and propagates. if the value of this function is between 1 and 1 + tolerance the crack initiation will be considered in the next increments. but if the value is more than one plus tolerance this increment will be solved one more time by cutback.
then define the damage evolution rule based on energy and linear softening. also, use BK (Benzeggagh-Kenan) formulation to calculate effective energy release rate from energy illustrate in various models.
as it is shown in this formula it needs to enter the power.
then enter critical values of G1, G2, and G3. also use a stabilization option to simplify the convergence of the standard solver.
next, create a section and assign it to the part.
Assembly Module
then insert the part in the assembly module.
Step Module
in the step module, create a static general step.
as the convergence of the problem is not easy due to the propagation of the crack. so reduce the initial minimum and maximum size of increments. also, it needs to increase the maximum number of increments.
also, request two field outputs related to the enriched elements. the first one is the sign distance function to describe the correct surface. the second one is a state of XFEM elements.
Interaction module
in the interaction module, we create an XFEM crack and then select the domain. here we can also define the initial crack or specify contact properties. But it does not need in this example.
Load Module
in the load module, we apply x symmetry to the left side due to the symmetry of the problem.
the bottom face is fixed in y-direction and displacement is applied to the upper edge in this direction.
Mesh Module XFEM Method in ABAQUS
in the mesh module at first, using the seed edge option. apply a small mesh size in the region with stress concentration. we choose the quadrilateral and structured elements and then assign element types to the part.
elements are standard linear and plain strain finally.
next, generate the mesh.
Job Module XFEM Method in ABAQUS
in the Job module create the job and submit it.
Visualization Module
you can see the initiation and propagation of the crack beside the hole.Ā for a better presentation of crack opening, you can increase the scale of the formation. Ł ŁŁŲ¹ Ł Ų±Ų§ŁŁŲ§ŲŖ Ų¹Ų±ŲØŁ you can pull out the contour of PHILSM which shows the distance of points from the crack surface.
the status of an enriched element lies between 0 and 1 for correct elements.
Now download the files and see if you were able to get things done right step by step.
https://drive.google.com/file/d/1Lla7rkQL2ymiyoP_1XxQESep-2LxWkqk/view?usp=sharing
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