Calling third deviatoric invariant in VUSDFLD subroutine

[Manuel Costa]

So, I came up with a brick wall when creating a field variable with third deviatoric stress tensor invariant , J3, dependency.

The closest approach should be calling this invariant with subroutine SINV (Abaqus subroutine reference guide), but I don't understand why this invariant is not avaliable through this utility.

So I though of computing this invariant by means of the three stress invariants I₁, I₂ and I₃. but bad results have been produced.

It also seems wierd that they didn't introduce this invariant as a readily callable variable for this version.

Any ideas on how to properly introduce this invariant, through some utility subroutine or with a proper computation in ABAQUS 2019?

 

[FEA way]

I'm afraid that the only way is to calculate the third deviatoric stress invariant from stress tensor components. Just make sure that all your formulas are correct.