Description
This is a plasticity model where kinematical hardening and Lankford parameters can be defined as constants or as functions of
the effective plastic strain.
A J2 (von Mises) yield criterion is combined with a non-assiciated flow rule. The non-associated flow rule is defined to satisfy the
given Lankford parameters.
The effective plastic flow stress is defined as:
$\displaystyle{ \sigma_y = f(\epsilon_{eff}^p) \cdot g(D)}$
where $f(\epsilon_{eff}^p)$ is a user defined CURVE or FUNCTION and $g(D)$ is an optional damage softening.
$g(D)$, where $D$ is the damage level, is defined as:
$g(D) = \left\{
\begin{array}{cc}
1 & D \leq s_0 \\
\displaystyle{ 1 + \frac{D-s_0}{1-s_0} \cdot (s_1-1)} & D \gt s_0
\end{array}
\right. $
That is, $g(D)$ drops linearly from 1 at $D=s_0$ to $s_1$ at $D=1$ (full damage).
Initial material orientation is defined using either INITIAL_MATERIAL_DIRECTION, INITIAL_MATERIAL_DIRECTION_VECTOR or INITIAL_MATERIAL_DIRECTION_WRAP.
