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UMAT for mooney-rivlin model

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Posts: 6
Topic starter
(@jeffly)
Active Member
Joined: 15 years ago

Dear All

I am trying to model hyperelastic material with ABAQUS (UMAT)

I developed UMAT for mooney-rivlin model. However, there is an error, Too many attempts made for this increment.

I tried to change the increment size, fix the boundary and loading condition, mesh size. But, it didnt work.

And weird thing is that my umat was working properly with 3D solid homogeneous element (which is a unit cube at ABAQUS example input). But, when I chose the element as membrane or shell, it didnt work. Anyone has suggestion to fix the error?

Thanks.

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5 Replies
Posts: 3998
(@jorgen)
Member
Joined: 5 years ago

Did you code your UMAT differently depending on the element type?

Note that an Abaqus UMAT specifies the element type through NDI and NSHR, and that you need to specifically code the response for the elemetn types that you are interested in.

-Jorgen

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Posts: 31
(@jdhayanidhi)
Eminent Member
Joined: 15 years ago

May be I can give some advise if you post the UMAT file.

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Posts: 6
Topic starter
(@jeffly)
Active Member
Joined: 15 years ago

Thanks for your help.
I understand what is wrong with my umat and model.
I have another quick question. When I reduce the thickness of the 3D solid element (very thin) and run the model with uniaxial test, I have the same error, Too many attempts made for this increment.
Do you have any idea to fix it?I tried to change boundary condition, mesh size and increment size.
Again thanks for your help.

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Posts: 6
Topic starter
(@jeffly)
Active Member
Joined: 15 years ago

Thanks for your help

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Posts: 4
(@frankkevin)
New Member
Joined: 14 years ago

Hi,

I am also having similar problem which you were facing in this post. Please can you let me know that how you have changed your umat code for shell element in order to be compatible with that of brick. How you made compatible your stress and jacobian term for shells. Any help will be highly appreciated.

Thanks,

Ashwani.

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