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Questions about Vumat

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Posts: 11
Topic starter
(@artiger)
Active Member
Joined: 15 years ago

Hello

I have some questions, I want to convert a umat subroutine into vumat subroutine, my umat subroutine includes some internal subroutines, I want to know if a vumat subroutine can have internal subroutines.
My second question is if DROT(3,3) (which is Rotation increment matrix) in umat is omitted in vumat framewok and if I should omit all DROT(3,3) in my subroutine, and where should I use relSpinInc(nblock,nshr) (which is Incremental relative rotation vector at each material point defined in the corotational system.)

I have attached the umat subroutine that I want to convert into vumat, and paper that explains the theory of constitutive model.

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

I did not have time read your attachement 🙁

Yes, a VUMAT can have internal subroutines!

The use of DROT and relSpinInc will depend on the specific formulation of your constitutive theory. In many simple cases you can simply ignore the DROT stuff when cnverting to a VUMAT.

-Jorgen

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3 Replies
Posts: 11
Topic starter
(@artiger)
Active Member
Joined: 15 years ago

Dear Dr Jorgen

Thank you very much for replying my post.

Is it possible for you to see the attachment and give me some guide to convert the umat in the attachment into vumat. the paper that explains the theory of constitutive law exists in the attachment. please guide me because I do not have enough expertise to convert umat into vumat.

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

The paper and the Fortran code are easy to read. It would take a few hours to convert the UMAT to a VUMAT, and I am afraid that I currently dont have time for that exercise.

I suggest that you either study the documentation carefully enough that you can perform the conversion, or that you find someone who can do the conversion for you, perhaps for a fee. I can do the conversion for you, but I would have to charge for my time. Send me a private message if you are interested.

-Jorgen

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