pure deformation of linear elastic body

[tsmsngi]

Dear, Dr. Jorgen

I'm in trouble.
I have been trying to carry out simple calculation of pure shear deformation of liner hypoelastic body in finite strain.
However, in my FE analysis, the body deform very strangely and I have never been able to find what is the problem because the subroutine is too simple.
I attach the input and user material subroutine file I wrote.


I have a plan to calculate pure shear deformation of polymer using elasto-viscoplastic constitutive equation based on molecuar chain network theory proposed by Dr. Mary C. Boyce. However, without solution of this simple problem, I wouldn't be able to step forward.


If you can answer to this problem, please tell me what is wrong in these files.

Sincerely yours,

[Jorgen]

First, why are you starting with a hypoelastic material model if you are ultimately thinking about switching to a hyperelastic type model?

I would start with a hyperelastic model and then add the viscoplasticity.
I wrote a simple VUMAT (http://polymerfem.com/forums/showthread.php?t=42) for the Neo-Hookean model that you can use as a template.

-Jorgen

[tsmsngi]

Sorry for my unclear question. I really need your help. Since I
would like to let you understand my situation, I try to make detailed
explanations as follows.

First, I want to perform the FE simulation with ABAQUS/Explicit
based on a rate form of a constitutive model. So I understand this model
is a relationship between the objective stress rate and the stretching
tensor. Simply speaking, this model can be derived from the hypoelastic
material. I can not change the model.

I wrote a user material subroutine based on the model and perform
some simualtions. It works under a tension and a compression, BUT I have
a trouble on a pure shear. Even if I do not consider the plastic part,
i.e. the model is for a pure elastic, I still have the trouble under the
pure shear. I attached the subroutine.

I read the subroutine again and again and for many times. I could
not still found my mistake.

I'm so happy if you will help me.

[Jorgen]

Oh, I see. Your modeling framework sounds just fine. My suspicion is probably the same as your, that there is likely some bug in the model implementation. Unfortunately, debugging a VUMAT is a very time consuming activity, and I simply don't have the time for that work as part of my free support.

Send me a private message if you want to discuss professional (payed for) support.

- Jorgen