The Plasticity dialog window serves to set parameters driving the stress update procedure.
The parameter Return to yield surface tolerance suggests the tolerance for satisfying the selected yield condition. Assuming nonlinear hardening/softening as in case of modified cam clay model the stress return mapping requires an iteration process.
The maximum number of iterations allowed is then given by the Max. No. of iterations for a single plastic step parameter. When employing the rigid-plastic version of the Mohr-Coulomb, the Drucker-Prager or the modified Mohr-Coulomb model, these parameters will not apply.
The default setting, evident in the figure, is recommended.
Parameters driving the stress return mapping