Hello,
While debuggin my UMAT code for Fung material for Simple shear mode I saw that UMAT is receiving a DROT matrix as input that is not identity. Since I have specified *orientation as show below, I was expecting that I should see DROT to be a n identity matrix. ( ref. abaqus user subroutine manual 1-1-40-9). As this UMAT code agrees with abaqus built-in Fung model for tension tests but not for simple shear, I was wondering if it has to do with the finite rotation aspect. 'DROT' not being identity hints that my material fiber directions are not being specified correctly. Is that right?
Has anyone faced situation like this?
Are possible other scenarios when DROT can be non-identity for simulation with local fiber directions specified ?
Or is there anything wrong in the way I specify material directions in the excerpt from .inp file given below:
---------------------------
*Element, type=C3D20RH
1, 5, 6, 8, 7, 1, 2, 4, 3, 12, 11, 10, 9, 13, 14, 15,
16, 18, 17, 19, 20
*Elset, elset=SET-2
1,
*Orientation, name=Ori-1,local directions=3
1., 0., 0., 0.,1.,0., 0., 0., 0.
3, 0.0
1.,0.0,0.0
0.0, 1.0, 0.0
0.0,0.0,1.0
** Section: Section-1-SET-2
*Solid Section, elset=SET-2, orientation=Ori-1, material=UMAT_MTRL
1.0,
*End Part
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Thanks,