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How to define Strain gradient in VUMAT

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Posts: 25
 bb
Topic starter
(@bb)
Eminent Member
Joined: 17 years ago

Dear all,

I am wondering is there any way to define STRAIN GRADIENT from DEFGRAD of the material points?

Actually, since the strain of each material point is known, the strain gradient is known too, but it seems hard to define in VUMAT.

Many thanks.

Best,

yaning

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

You are right, there is no direct way to determine the strain gradient from within a VUMAT. I would think however, that you might be able to determine the strain gradient field from the previous time increment by storing strain and the corresponding locations in global variables, which you can then use to approximate the strain gradient.

- Jorgen

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Posts: 25
 bb
Topic starter
(@bb)
Eminent Member
Joined: 17 years ago

Dr. Bergstorm,

What the difference between material point and integration point? In VUMAT, nblock=number of the elements or nblock=number of the elements*number of integration points per element?

How can I get the coordinate and strain at integration points at each step in VUMAT?

It seems in UMAT I can use utility subroutine GETVRM to get these variables, right? But GETVRM only can be used for standard.

Many thanks.

Yaning

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

I think that most people mean the same thing when they say material point and integration point. I suppose that nblock = (nr elems) * (nr int points/elem).

You can get the coordinates through the coordMP parameter in the VUMAT.

- Jorgen

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