# How to evaluate pure Mode-II SIF using Abaqus?

• Sagar Thakre
In summary: I've gone back to the problem and have found that I need to use a 3D element in order to properly model the crack.
Sagar Thakre
I am trying to evaluate pure Mode-II SIF using Abaqus for edge normal crack in the plate. The solution i am getting using Abaqus is not matching with the theoretical SIF.
The boundary condition i have used is shown in fig attached.
suggest me proper boundary condition to evaluate the SIF.

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• Boundary condition.JPG
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The last time I used Abaqus, it came with a thick book of example problems. I'm sure that at least one of those problems analyzed a crack.

The boundary conditions that you show are quite simple. The crack itself is not so simple. It is likely that your solution not matching is related to your selection of element and/or how you meshed your model.

As a master's student, your task is to figure out how to properly model this problem. You need to select the element, and justify your selection. Then you need to mesh your model properly, and justify that also. And you will need to convince your advisor.

jrmichler said:
The last time I used Abaqus, it came with a thick book of example problems. I'm sure that at least one of those problems analyzed a crack.

The boundary conditions that you show are quite simple. The crack itself is not so simple. It is likely that your solution not matching is related to your selection of element and/or how you meshed your model.

As a master's student, your task is to figure out how to properly model this problem. You need to select the element, and justify your selection. Then you need to mesh your model properly, and justify that also. And you will need to convince your advisor.
I have solved problem for Pure Mode-I on same plate and there is close agreement between theoretical and Abaqus results. I have used 2D CPS8R element in solving this problem.
but it is not working in case of Mode-II SIF.

Time to hit the fracture mechanics books. I did a quick search with search terms fracture mode 2 fea, and this popped up: http://www.mate.tue.nl/~piet/edu/frm/pdf/frmsyl1213.pdf. It discusses some of the challenges in modelling near a crack tip, and provides some references that appear to apply to your specific problem. Search forward from those sources, and you should find answers to your case.

jrmichler said:
Time to hit the fracture mechanics books. I did a quick search with search terms fracture mode 2 fea, and this popped up: http://www.mate.tue.nl/~piet/edu/frm/pdf/frmsyl1213.pdf. It discusses some of the challenges in modelling near a crack tip, and provides some references that appear to apply to your specific problem. Search forward from those sources, and you should find answers to your case.
Thanks.

## 1. How do I define a pure Mode-II loading in Abaqus?

In Abaqus, a pure Mode-II loading can be defined by applying a displacement boundary condition in the X direction and a rotation boundary condition in the Y direction on the crack surface.

## 2. What is the recommended element type for evaluating pure Mode-II SIF in Abaqus?

The recommended element type for evaluating pure Mode-II SIF in Abaqus is the cohesive element type, such as COH2D4 or COH3D8. These elements are specifically designed for modeling crack propagation and are capable of accurately capturing the Mode-II stress intensity factor.

## 3. How do I specify the crack geometry in Abaqus for evaluating pure Mode-II SIF?

The crack geometry can be specified in Abaqus by defining a crack path and inserting a crack element along the path. The crack element should have a defined orientation that corresponds to the Mode-II loading direction.

## 4. Can I directly obtain the Mode-II SIF from Abaqus output?

No, Abaqus does not directly output the Mode-II SIF. However, the Mode-II SIF can be calculated using the nodal displacements and the stress values from the cohesive elements using an external post-processing tool.

## 5. How do I ensure accurate results when evaluating pure Mode-II SIF in Abaqus?

To ensure accurate results, it is important to use a fine mesh around the crack tip and to make sure that the cohesive elements are aligned with the crack path. It is also recommended to perform a convergence study to determine the appropriate mesh size for obtaining accurate results.

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