Newbie qustions on abaqus' user subroutine

[ricewjx]

Dear all,

I'm trying to use the function of user subroutine of Abaqus but I'm new to it. Could anyone tell me the procedure to run the example provided by Abaqus? Say if I want to test the UMAT subroutine and do uniform tension test. Do I need to use CAE to create a geometry model first and then assign boundary conditions, element and material property to it or not? At what stage do I need to implement the .inp and fortran files and how? Thank you very much for your help!

Sincerely,

Jianxin Wang

[Jorgen]

Writing a user material subroutine is a serious undertaking that will require extensive experience about continuum mechanics, finite element theory, and computer programing. I suggest that you spend more time with ABAQUS learning how to use the software. Once you feel confident in your ABAQUS skills you can start thinking about writing your user subroutines. Also, I suggest that you carefully study the ABAQUS manuals, they contain a lot of information!

- Jorgen

[ricewjx]

Dr. Bergstrom:

Thank you for your reply. I was writing and using the finite element code developed by ourself. The reason I want to use Abaqus is because I developed a nonlinear constitutive model for ferroelectric materials and was trying to implement it into our FEM code. However, the consistent tangent stiffness matrix turns out to be nonsymmetric and our finite element code only solves symmetric matrix. Another reason is I would like to use the powerful pre- and post-processing function Abaqus has. Since this is my final project and I'm running out of time (I'll graduate next year), I really want to speed up and learning Abaqus from scratch will take a long time. That's why I'm here to ask for help. Could you kindly give me a simple example of how to run the UMAT example, from preprocessing to postprocessing? I really appreciate your help.

Best regards,

Jianxin

[Jorgen]

As you probably know, you can often get away using only the symmetric part of the tangent stiffness matrix (even when it is non symmetric). You can always try that first.

The pre- and post-processing with ABAQUS does not really change if you are using a UMAT or not. In the pre-processing you need to specify your material and you can simply select a "user material" and fill in the material parameters and the number of required state variables. In the post-processing you use ABAQUS/Viewer as you would with any other material. If you have state variables that you want to visualize you need to save them to the odb-file with the "*Output, Field" command.

Best of luck,
Jorgen

[mikejwg]

Hi, I am skillful in Umat for mechanical behavior. now i am just interest in piezoelectrici material constitutive modelling. I doubt that umat is deal with mechanical or thermomechanical, no eletric-mechanical-thermo coupling.
maybe we can help each other.

please contact with me:
wyjwg_niat@hotmail.com

Dear all,

I'm trying to use the function of user subroutine of Abaqus but I'm new to it. Could anyone tell me the procedure to run the example provided by Abaqus? Say if I want to test the UMAT subroutine and do uniform tension test. Do I need to use CAE to create a geometry model first and then assign boundary conditions, element and material property to it or not? At what stage do I need to implement the .inp and fortran files and how? Thank you very much for your help!

Sincerely,

Jianxin Wang