In ANSYS 11.0 and prior, for penalty-based methods (i.e., pure penalty algorithm, augmented Lagrange formulation ‐ see KEYOPT(2)), if the underlying solid elements had a nonlinear material model (e.g., TB,MISO), the contact stiffness was reduced by a factor of 100.  This was to aid in convergence, anticipating the reduction in the material stiffness beyond yielding, for example.

In ANSYS 12.0.1, the automatic reduction factor of 100 is no longer used.  Instead, whether the underlying solid has linear or nonlinear material properties, the automatically-calculated contact stiffness is used as-is.  This will improve accuracy of results for contact models at 12.0.  However, note that convergence may become slightly more difficult, in which case the use of automatic contact stiffness update (KEYOPT(10)) will help. Note that while the contact stiffness update algorithm itself hasn’t changed, the difference due in the automatically-calculated contact stiffness for nonlinear materials will influence the update algorithm behavior and may show differences between 11.0 and 12.0.1.