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Converting Umat to Vumat

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Posts: 2
Topic starter
(@azerty)
New Member
Joined: 12 years ago

Dear All,

I am working on Morph model(Method of rubber phenomenology), I have the model written in Umat and want to convert to Vumat, since I am beginner in writing subroutine, help will be appreciated. I have attached a Umat code in the mail, which is to be converted to Vumat.

Thanking you,

Harsha

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6 Replies
Posts: 83
(@zhaiys)
Trusted Member
Joined: 17 years ago

There are a few things to consider, beside the numerical effectiveness required by a material routine for implicit vs explicit time integration:

1. You do not provide a tangent stiffness matrix (Jacobian) to the solver in a VUMAT.
2. Stresses and state variables are fed into the VUMAT as blocks of a certain length. the UMAT considers one integration point at a time, while the VUMAT gets info about a bunch of them. You can loop over the collection of integration points in a VUMAT.
3. Shear strain components are defined differently (13 and 23 components are reversed).

Topic Tags
6 Replies
Posts: 2
Topic starter
(@azerty)
New Member
Joined: 12 years ago

Dear matsgd,
Thank you for your help, now I solved problem

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Posts: 17
(@thegiving21)
Active Member
Joined: 8 years ago

Hi Harsha,
I have a same problem, I want to convert UMAT to VUMAT, could you please tell how did you do it ?
Thanks.

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Posts: 80
(@FrankMonkey)
Trusted Member
Joined: 15 years ago

Try
[url] https://soilmodels.com/umat-vumat/ [/url]
I do not know if this interface is mature.

Regarding this interface, and your query in general:

Subscribe to and seek assistance from the
ABAQUS mailing list
[url] https://groups.yahoo.com/group/r [/url]
or
[url] http://www.eng-tips.com/threadminder.cfm?pid=799 [/url]
or from the ResearchGate discussion forum.

Search the archive of the list before posting in it.
The list does not accept attachments.

For an intro to subroutines get the file
[url] http://imechanica.org/files/Writing [/url] User Subroutines with ABAQUS.pdf

Good luck

Frank

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Posts: 17
(@thegiving21)
Active Member
Joined: 8 years ago

Thank you Frank,
Can you please explain to me how to use this interface ? should I copy the UMAT subroutine into the interface VUMAT or what to do exactly ?
I appreciate your feedback

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Posts: 80
(@FrankMonkey)
Trusted Member
Joined: 15 years ago

No idea, I never used it.
Inquire on that site or in the mailing list

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