Abaqus Tutorials

# eXtended Finite Element Method (XFEM)

In this Abaqus tutorial, I have introduced the extended finite element method or XFEM Method in Abaqus. You may be wondering what is XFEM? or how to use XFEM in Abaqus?

Join us in this Abaqus tutorial to answer these questions. This Abaqus tutorial is very useful for Abaqus beginners and also its Abaqus files are available for download at the end of this tutorial.

## XFEM Method in ABAQUS?

XFEM is a method in ABAQUS that allows you to study crack growth along an arbitrary, solution-dependent path without needing to re-mesh your model.

Abaqus XFEM (Extended Finite Element Method) is an advanced numerical technique available in Abaqus software that is used to simulate problems involving complex crack propagation, discontinuities, and other phenomena where traditional finite element methods may struggle.

The XFEM extends the capabilities of standard finite element analysis by allowing for the representation of discontinuities (such as cracks) within the elements without the need for explicit meshing of the crack surfaces. This significantly reduces the computational effort required for modeling crack propagation and allows for more accurate representation of crack paths.

In Abaqus, XFEM is implemented by enriching the standard finite element approximation with additional enrichment functions that capture the behavior of the discontinuity. These enrichment functions are used to represent the displacement field near the crack tip and provide accurate stress and displacement solutions in the vicinity of the crack.

### Abaqus XFEM

Abaqus XFEM allows for the modeling of various types of cracks, including straight, curved, branching, and interacting cracks. It also provides capabilities to simulate crack initiation, propagation, and interaction with other features in the structure. XFEM can be used for both two-dimensional (2D) and three-dimensional (3D) problems.

To use Abaqus XFEM, you typically need to define the crack geometry, specify the enrichment functions, and assign XFEM properties to the appropriate elements. Abaqus provides a range of tools and options to facilitate XFEM modeling, including crack growth criteria, adaptive remeshing, and post-processing capabilities to analyze crack paths and evaluate fracture parameters.

It is worth noting that XFEM requires careful consideration and expertise in setting up and validating the model, as well as understanding the underlying fracture mechanics principles. The Abaqus documentation and technical support can provide more detailed information, tutorials, and examples to help you effectively utilize the XFEM capabilities in Abaqus for your specific analysis needs.

See the full definition of XFEM on Wikipedia

This Abaqus XFEM crack propagation example illustrates the use of the 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.

If you want to know more about Abaqus projects, check out Abaqus projects

### XFEM Abaqus Tutorial

Now, follow the XFEM Abaqus tutorial…

#### Part Module

Part Module

then create a rectangle with the following dimensions.

next, create a circle in 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 the BK (Benzeggagh-Kenan) formulation to calculate the effective energy release rate from energy illustrated 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 is not needed in this Abaqus XFEM example.

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.  for a better presentation of the crack opening, you can increase the scale of the formation. 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.

### Abaqus XFEM Crack Propagation Example

Now download the Abaqus XFEM crack propagation example files and see if you were able to get things done right step by step.

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10 months ago

How we obtain the factor of safety using XFEM for a concrete gravity dam to see the effect of crack propagation on the dam safety