Hi All,

I am trying to simulate tooth deformation. It involves that the density of tooth changes with deformation. I want to know is it possible to define density as a solution dependent variable in VUMAT?

 Thank you in advance!

 Shunlai

Hi, I’m trying to implement a mixed hardening J2 plasticity model. The idea is to use the Ludwik law to represent the isotropic hardening and the Amstrong-Frederick law for the kinematic hardening, both combine in a J2 classic von Mises model.

I need some advice for the return mapping algorithm.

Hi, i am trying to test a bulk metallc glass VUMAT with a simple compression test simulation. But since VUMAT is a Abaqus Explicit subroutine, that means I must set my compression simulation with setting of Abaqus Explicit right? So far I only have the experience in conducting compression test simualtion using ABAQUS Standard setting like static general step and surface-to-surface contact (standard). I don't know how to set up a simple compression test simulation with Abaqus Explicit settings, can anyone help me please?

Thanks and regards.

Hi, i am trying to test a bulk metallc glass VUMAT with a simple compression test simulation. But since VUMAT is a Abaqus Explicit subroutine, that means I must set my compression simulation with setting of Abaqus Explicit right? So far I only have the experience in conducting compression test simualtion using ABAQUS Standard setting like static general step and surface-to-surface contact (standard). I don't know how to set up a simple compression test simulation with Abaqus Explicit settings, can anyone help me please?

Thanks and regards. 

Hi there,

 Has anyone ever used a vumat subroutine with Eulerian elements? it seems that the stress update formulation is different from the way it is in Lagrangian approach! If you have any experience in this regard I'd highly appreciate if you share it with me.

 thanks

Hello everyone,

  I am using a VUMAT with isotropic hardening in my three dimensional model. Can someone tell me how is plasticity data passed into this subroutine? In VUMAT for kinematic hardening we define the yield stress and hardening modulus along with E and poisson's ratio in *User Material. I did not find any isotropic hardening VUMAT examples in manual. Do we define the hardening modulus or the yield stress-plastic strain data in isotropic hardening VUMAT? I will be really thankful if anyone can help me.

Thank you

Swapnil

hi,

    recently,i want to write a delamination law using vumat,but coh3d8 element with  a traction-separation has s33,s13,s23.in vumat,stressold(nblock,ndir+nshr),i don't kown if s33 is  correspond to stressold(nblock,3),and if s23 is  correspond to stressold(nblock,5),

   i hope someone can help me.

Dear All,

 I think that many students are looking for some tutorials about writing a UMAT in ABAQUS.

You can find a comprehensive tutorial for elastic problems.

This file contains: 

• Motivation

• Steps Required in Writing a UMAT or VUMAT

Closing date for receipt of applications: 30 January 2010You will join a research project “Optimise blast resistance of novel composites made with fibre metal laminates (FMLs)” sponsored by

Dear all,

I' m trying to make a model in VUMAT for shape memory alloy based on Lagoudas 's thermomechanical constitutive model. It seems that It's necessary an iteration to evaluate the thermoelastic prediction.

My questions are : is it possible to use an iterative loop in the VUMAT or it's better to avoid it??Could someone suggest me a different way so that I can avoid the iterative loop?

Many thanks,

Cece

Dear all,

 I'm new in imechanica. I need some informations about VUMAT for Nitinol. I would like to implement in fortran a subroutine for the behaviour of shape memory alloy.I looked for some subroutines already implemented but they have been developed in the implicit way.

It's true that with the VUMAT(explicit) I could have some problems of stability and convergence.Could someone suggest me any reason to make this model in the VUMAT?I know that in VUMAT I can't redifine the time increment so before running the analysis It's important to pay attention on Dt.

Is it better for dynamics analysis or for coupling with CFD software like FLUENT?

Hi,
Here is the issue:
I am working with a x64 version of
Abaqus/Explicit (6.8-2), and a 32bits version (6.7-1). MS VS2005 is
installed with the x64 compiler tools, Intel Fortran is correctly
installed (IA-32 and Intel64 versions). My OS is Windows Vista Enterprise (64 bits).
The routine is compiled and linked correctly by lauching the appropriate ifortvars.bat file prior to executing abaqus.

Everything works perfectly with the 32 bits version of Abaqus+Compiler, with one or more processors (I have 8 of them).

Hi all,

     Here I encoutered a error in ABAQUS when I include ALE with VUMAT. When ALE was not included with VUMAT, my job can work well while with the combination of VUMAT and ALE, the job cann't work any more due to a "Signal 8" error. And if I use a built-in material model and at the same time ALE, a job can work. Furthermore, element failure is considered in all of the cases.

    Anyone can give some suggetion? Thanks in advance!

Xinke

Hi everyone,

    I have a question about the objectivity tensor in ABAQUS software. Below is my question.   

Dear All,

     In ABAQUS manual, it is said for hyperelastic material, it is better to define it by stretch tensor U. But if I need to use deformation gradient F in the material model directly, I need to rotate the stress back to corotational frame. How should I do that?  Should I make a polar decomposition of F=R*U first, and then apply Rt*S*R? or I can use the relative spin increment already provided to do that? If so, how?

     Also, an alternative method I think is that I can rotate the deformation gradient to corotational frame  first, and then calculate the stress based on tranformed deformation gradient. Is that right?

Hi

I’m trying to develop a VUMat routine so I’ve already
started to learn its features. I recently got this problem that what exactly
the variable stepTime means! I created a model with 3 steps including the initial
step and I coded my routine somehow that when the stepTime is equal to 0 it
prints something into a file. Surprisingly only once in whole analysis the
stepTime would be 0 and that’s exactly at the beginning of the analysis when
totalTime is in fact 0. Could anyone please explain why this happens?

Thanks

I have noticed that a lot of people are using UMAT and VUMAT material model
subroutines for their researches. However, most of these subroutines do not
find their way to free code market and remain in the hands of the developers.
Therefore, a lot of wheel re-inventing has to be done by other people. Since
development and testing of a material subroutine takes a damn long time, I
think it is a good idea if each of us can share the subroutines she has
developed with the others. I know that a couple of subroutines are publicly
available and many other people also know that. Please comment about less-known
freely available subroutines.

I have noticed that a lot of people are using UMAT and VUMAT material model
subroutines for their researches. However, most of these subroutines do not
find their way to free code market and remain in the hands of the developers.
Therefore, a lot of wheel re-inventing has to be done by other people. Since
development and testing of a material subroutine takes a damn long time, I
think it is a good idea if each of us can share the subroutines she has
developed with the others. I know that a couple of subroutines are publicly
available and many other people also know that. Please comment about less-known
freely available subroutines.