Hi Dipaloke, 'NLGEOM' should be turned to consider large deformation.

at every increment strain tensor is passed to umat. So if you just turn on nlgeom, then large strain tensor will go. However if your materail calculation is based on small strain, then it's not going to do anything (or might even corrupt the solution)...check out abaqus analysis manula->introduction->syntax and convention->convention

Hi Dipaloke,

in step definition nlgeom should be named yes or just mentioned in step definition to consider large deformation:

*Step, nlgeom = yes, inc=90000

But I think that this will influence your UMAT definition only if you have your stress-strain and other variables defined based on deformation gradient(s). Deformation gradients for previous and current increments are provided in DFGRD0 and DFGRD1, respectively.

Dear Soud, Abhimanyu and Vukašin,

I'd like to thank all of you for answering my question and help.

Regards,

Dipaloke