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Modeling of large strain deformation in Abaqus
Wed, 2008-10-29 13:43 - hadi
Hi everybody,
I'm trying to model large strain deformations in Abaqus by writing a user defined material code in order to implement the governing constitutive equations of the material. As far as I know, Cauchy stress tensor should be used in the model to presume non-linear finite elements, but I don't know how one can implement Cauchy stress tensor in a UMAT used by Abaqus.
Thanks,
Hadi
Forums:
Re: Cauchy stress tensor in a UMAT used by Abaqus
According to the Abaqus manual
"
STRESS(NTENS)
This
array is passed in as the stress tensor at the beginning of the
increment and must be updated in this routine to be the stress tensor
at the end of the increment. If you specified initial stresses (“Initial conditions,” Section 27.2.1 of the Abaqus Analysis User's Manual), this array will contain the initial stresses at the start of the analysis. The size of this array depends on the value of NTENS
as defined below. In finite-strain problems the stress tensor has
already been rotated to account for rigid body motion in the increment
before UMAT is called, so that only the corotational part of the stress integration should be done in UMAT. The measure of stress used is “true” (Cauchy) stress."
-- Biswajit