Abaqus Umat for Shell elements

Hi everyone,

Im pretty new to implementation of Umats but i have coded some materials for a 3D case using solid elements, which have worked out fine. Now Im trying to do the same thing using shell elements (S4 and S4R) and I have some questionmarks here...

- What are the compeonets in the stress/stain tensor (STRESS and DSTRAIN) (S11,S22,S12,S33 ???) ?

- What is the size of the Jacobian?

- Do I need to convert my 3D implementaion to plane stress?, and if that is needed do I have to provide the out of plane strain (how is that done in this case)?

I would be very thankfull for some valuable hints 🙂

Mangan

1) Stress and dstrain are: [11, 22, 12]
2) Jacobian is 3x3
3) Yes, you will (likely) have to re-implement your code. Yes, you will need to return the out of plane strain (for a VUMAT).

-Jorgen