<CRITERION> unsym#
Description#
This criterion models the equivalent stress and deformation with deviatoric and hydrostatic terms. The criterion is written:
(371)#\[f_{cr} = (1-a)\sigma_{eq} + a\:\trace{\ten \sigma} - R\]
This criterion accepts a single coefficient a which must be input
on a separate line from the unsym token. This criterion is also
non-associated where the flow normal is written:
(372)#\[\ten n = \frac{3}{2} \frac{\ten \sigma ' - \ten X}{J_2(\ten \sigma-\ten X)}\]
with the \(\ten X\) term being the summation of back stresses. Often
this criterion is used in conjunction with the ziegler kinematic
hardening options [M9], but this is not
necessarily so.