abaqus user subroutine for membrane element

[tome]

Hi,

I'm trying to wirte a user subroutine for membrane element (m3d4). The consitutive model I used is neo-Hookean for test. Basically, the Jacobian I used for the subroutine is the same as that for a plane stress element. It's now based on the local coordniate system for membrane elements. But I got no convergence at all. I'm wondering if the Jacobian for membrane element is totally different from the other continuum element. I haven't figured it out. I beleive that the formulations I used for calculating stresses is correct because the vumat I wrote for membrame element works well.

Thanks,

Tom

[Jorgen]

I just checked my UMAT implementation of the neo-Hookean model and it works equally well for shell and membrane element type M3D4. I use the same Jacobian in both cases and it works just fine.

What type test case did you try to run?

- Jorgen