I have a question about the feasibility concerning the co-utilization of XFEM and cohesive elements in Abaqus. In fact, in the documentation, they did mention that XFEM could be simultaneously used with the surface-based cohesive behavior approach. But they didn't mention if the cohesive elements could be used simultaneously.
Hello Zhao,
Using cohesive elements in conjunction with XFEM doesn't make sense in my point of view. The concept of XFEM is useful when the crack path is not known a priori, when it is the case we use the cohesive elements. However, if you want to use a cohesive law to drive the crack growth which is modeled using XFEM you can do that. In this case the cohesive law plays the role of the crack growth criterion.
Hello, dear Bouhala and Chen,
Thank you very much for your replies.
In fact, I want to use these two approachs in two different places. Concretely, I'm modelling a multicrystalline plate with big grains. And I want to simulate the intergranular and transgranular fracture at the same time. So I take the XFEM method for the elements in the grains and insert some cohesive elements at the grain boundaries. I don't know if such a model is correct or not in Abaqus.
Best regards,
ZHAO Lv
The use of the cohesive elements at the grain boundary makes sense since you are expecting dislocations to accumulate there and eventually cause crack initiation. On the other hand, since the location and path of the intergranular damage is not known a priori, it makes more sense to use the XFEM approach there.
Hello Mr. Zhao,
You are absolutely correct. I meant to say "transgranular" damage, which corresponds to the damage that goes through the grain, rather than along its edges. Therefore, I would use a method such as XFEM or some type of continuum based damage model to predict the path of damage within the grain. And, the cohesive elements to detect damage occurring along the edges of the grains (intergranular).
Hello Mr. Pourboghrat,
But I have a worry about the co-utilization of XFEM and cohesive elements. Because the cohesive elements at the grain boundaries share the nodes with the solid elements in the grains who introduce some enrichement functions in the fomulation (XFEM). So in your opinion, it will be correct or not to co-utilize these two approachs in my modelling? Thank you.
ZHAO Lv
Dear Zhao,
I haven't tried XFEM personally, but used cohesive elements. I'm guessing it will be okay to mix the two models, since XFEM must be based on some type of continuum damage model, which operates based on some limit strains to decide whether final damage occurs or not. Similarly, cohesive elements use some limit displacement at the interface to decide whether progressive damage turns into final separation. Given that at the grain boundary one of the two damage criterion will prevail first (probably not simultaneously) the final damage will be decided based on XFEM or Cohesive criterion. The validity of your prediction can only be decided if you have experimental proof. I suggest mixing XFEM and cohesive element in your model, and based on the results that you get assess if it's appropriate or not. I wish I could have been of more help.
Good luck,
Farhang
Hi Zhao,
May I ask how's the progress of your issue? Recently I've tried to combine XFEM with cohesive surface method. I've assigned XFEM for the one bulk material and the cohesive for the interface connecting the other material. It turned out that once the crack propagated to the interface and then later the job will abort due to convergence issue.
I'm facing the similar problem Qingqing Zhao . Did you find any solutions?
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