Hi to all,
I'm trying to calculate numerical material Jacobian for Neo Hookean material model in UMAT Abaqus.
At the first increment, comparing exactly solution of DDSDDE with numerical one, everything OK but when I check at increment n+1 I see that DDSDDE component became huge in comparison with exact solution.
My question is:
How software calculate DDSDDE component at increment n+1 and how update stress (if necessary) ?
I calculate DDSDDE(1,1) as follow:
eps=1E-8
FDSTRAIN(1)=eps*dabs(DFGRD1(1, 1))
DDSDDE(1,1)=(stress_perturbated-STRESS(1) )/FDSTRAIN(1)
Thanks in advance
Dario
Finally I have written subroutine umat for Neo Hooken and also for Eight Chain hyperelastic model using perturbation method of deformation gradient and calculate DDSDDE matrix using central difference methid.
- Badges
- Science topic
- Similar topics
- Filing