Hi all,

I'm interested in the user subroutine UDMGINI to define a user specified initiation criterion for an XFem crack using cohesive response. I want to define a sort of "enhanced version" of the built-in QUADS criterion

According to the documentation, in subroutine UDMGINI the stress tensor can be called  through the array STRESS(NTENS). However I'm not sure of what this stress tensor is supposed to represent. Is it the "nominal traction stress tensor" with 3 components  (tn, ts and tt), or is it the full stress tensor with, let say, the 6 stress components for a symmetric tensor?

So far and from some elementary tests I've been doing, it seems that  STRESS(NTENS) is actually the full stress tensor at integration points... Then I find it confusing to understand how to use it as it should be a singular stress tensor. And also using the full stress tensor to define the initiation criterion would not make sense in the framework the surface traction-separation cohesive behavior.

Any input/comments would be greatly appreciated!