Computation of DefGrad in VUMAT when *orientation used

[totofr]

Hi everybody,

I'm new in this forum.

I am writing a VUMAT subroutine for ABAQUS in order to implement a consitutive law under large deformation. I used the command *ORIENTATION for the material directions.

But how could I get the initial cosines in the subroutine ? How is the deformation gradient computed in VUMAT when there is initial material orientation ? Is it purely F or is it multiplied by another matrix rotation accounting for the initial orientation ? Same for the stretch U ?

Thank you for your help.

[Jorgen]

In order to get the most accurate answer to you question I recommend that you create a simple test case and then add a few print statements to your VUMAT code. That way you can find out the true results for yourself.

Since I don't quite recall on top of my head how Abaqus does it, it would be great if you would report your findings here when you are done!

-Jorgen