THE ASYMMETRY OF THE TANGENT STIFFNESS MATRIX IN FINITE ELASTOPLASTICITY

It will be shown that for consistently formulated and thermodynamicall y based models of finite elastoplasticity with plastic anisotropies th e tangent stiffness matrix in finite element programs is non-symmetric in general. This will be considered for both, the model using the cor otational rate proposed by Schieck and Stumpf [1] and for models with Lie-derivatives. Only in the limit case of small elastic strains the s kew-symmetric contribution vanishes.