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ABAQUS UMAT

Can someone post an example of UMAT and VUMAT for the same elasto-plastic problem?

Submitted by rctron on
ABAQUS UMAT
Abaqus VUMAT
#ABAQUS
abaqus subroutine

I want to understand how the stress update algorithm is modified for the different definitions of stress rate in ABAQUS/Standard and ABAQUS/Explicit formulations. I know the relationships, I just want to see how it's coded in a subroutine.

Also, the Hughes-Winget algorithm is used to update the stress defined by the Green-Naghdi stress rate by using the Jaumann rate. How to implement that in VUMAT? Can someone please post an example to clarify these aspects?

How to include temperature effects on the shear rates in Dr. Huang's crystal plasticity code

Submitted by rctron on
research
Crystal plasticity
CPFEM UMAT Dr Huang
ABAQUS UMAT

I am using Dr. Huang's crystal plasticity code for an adiabatic process where temperature increase due to deformation need to be calculated. Dr. Huang's CP UMAT code does not consider the temperature effect of shear rate or hardening. Is there a way to include temperature effects in the current UMAT code?

http://www.columbia.edu/~jk2079/Kysar_Research_Laboratory/Single_Crysta…

Question about implicit creep subroutine in Abaqus

Submitted by Oskar Xavier on
research
ABAQUS
ABAQUS UMAT
creep
Implicit
Jacobian
Constitutive law

The implicit implementation of creep in abaqus requires dh/d(\delta \epsilon_c ) as Jacobian in Newton-Raphson's iteration. The derivative can be expanded as shown in the figure attached. The term dh/dq, the one underlined by a green stroke, is expected to be provided by users through specifying DECRA, whereas the term dq/d(\delta \epsilon), underlined by a red one, is confusing me. It seems that that term is computed by Abaqus but I have no idea how it is done. The same question applies to the last derivative on the right hand side.

Thank you very much !

Calculating material jacobian matrix for ABAQUS UMAT subroutine

Submitted by fantasmaamin on
ABAQUS
ABAQUS UMAT
abaqus subroutine
Material Jacobian
finite element

Hello everyone, 

 

I found that there is no comprehensive topic about how to calculate material jacobian matrix for UMAT while it's one of the most complicated and important parts of writing a subroutine and a lot of the researchers deal with it. 

I think it would be great if experts share their sources and experiences here for all. I personally, try to provide the basics and essential materials as well. 

Here is an essential available PDF on Imechanica:

Assigning crystal plasticity material constants for one crystal with more than one element (default of Dr Huangs model)

Submitted by Hidroxid on
research
Crystal plasticity
CPFEM UMAT Dr Huang
ABAQUS UMAT

Hi!

 

I am just a beginner in Abaqus UMAT and I have started working with Dr Huang's crystal plasticity UMAT in Abaqus.

When I am assigning one material constants for one element crystal it works but when I try to assign it to more than one element for one crystal (for example group of elements with same grain orientation) it give me error code 144.

Can anybody explain me the reason?

 

 

Thanks in advance,

Kind regards,

Omid

 

UMAT subroutine for 3d solid elements

Submitted by hermatician on
ABAQUS UMAT
Abaqus/Fortran

Dear All,
I am okay in ABAQUS although trying subroutines for the first time.
I am trying to modify some codes available online, but the primary UMAT which I am posting here, is not working.
It shows no error in .log file but the job monitor says "Problem during compilation - D:\Abaqus Work Directory\Trial_user_subroutine\try\Umat_mine.for"

Please help me this, its very urgent.
Thanking you all,
P.S. The code is attached in .txt format
Here is the code


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