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3D fractional viscoelastic springpot

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New Member
Joined: 3 years ago

Hello everyone, 

I am trying to develop a model for soft tissue using fractional viscoelasticity in abaqus. I am using a springpot model defined using a VUMAT subroutine. 

I am testing with a single solid element (C3D8) in a displacement controlled simulation. I am currently running a tension test with displacement control along x varying linearly from 0 to 0.1 at the end of the dynamic step. With VUMAT, the strain at the end of the time increment is already known and the corresponding stress has to be evaluated and updated.

However, when I run the model, within a few increments my simulation errors out with excessive element distortion. Upon printing the strains, I notice that the strains in the y and z directions (lateral strains) quickly blow up causing excessive distortion.

Has anyone encountered similar issues? if so, can you please suggest how to debug the problem.




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Posts: 3998
Joined: 4 years ago

Unfortunately, it can be many things causing that. I recommendation is to carefully review all calculations steps performed by the VUMAT using print statements.


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Joined: 3 years ago

New Member
Posts: 2

Hi @jorgen, Thanks for responding. I could not figure out what was causing excessive element distortion. I had initially written the VUMAT in terms of bulk and shear modulus but when I rewrote the code in terms of lame's parameters, the error resolved itself.