ABAQUS, subroutine USDFLD and plastic model

[hmousad]

Hello,
I'm modeling a material which its stress strain can be approximately bilinear so it has an certain Emodulus at the begining and then in the plastic region it has another E value.

I've tried to model it as classic metal plasticity. I then added the subroutine USDFLD to give those two values of E.

I feel confused now. When I'm modeling such a material am I supposed to use that subroutine to change the E or use a plasticity model? Actually I don't get the difference between the function of both. (Plastic material model and subroutine USDFLD)

Thanks a lot in advance,
Regards,

[sony020244]

to me, i think you'd better read more on user manual and books. fot your case, i think it is more suitable to write a UMAT other than USDFLD which is giving field variable. the general idea of UMat is to include the material model. for your specific case, you can define a critiario when the plasticity begins, before which E=E_elastic,and after which E=E(stress). I guess you can find this code in Abaqus user subroutine publication. it is very typical.

[Jorgen]

I agree with sony020244, in addition, can you not simply use the standard elastic-plastic material model?

Simple metal plasticity will have an initial elastic response followed by a plastic response that can be linear during monotonically increasing strain.

-Jorgen