NaN in UMAT

[Shahrzad1989]

Hi
I am working with a UMAT. It works fine with coarse meshes but when I refine the mesh, dstran and consequently statevariables get NaN. Does anybody have experience with this problem. I will be grateful to have your comments

 

[FEA way]

It is always recommended to check UMAT with single element test. If it works fine and gives correct results in this test but fails in case of more complex model then carefully examine message and data files generated by the software. Find all errors and warning messages in these files. Also try running the analysis with different type of elements and refined mesh.