A distorted yield surface model for Bauschinger behaviourWednesday (06.11.2019) 09:15 - 09:35 Part of:
A new continuum plasticity model is suggested for Bauschinger type of reverse stress reductions. The model combines the best parts of the classical non-linear kinematic hardening models and of the more recent homogeneous yield function-based anisotropic hardening (HAH) model. A new mathematical yield surface formulation is proposed, where the yield surface is flattened and softened in the reverse of a prescribed direction, e.g. the loading direction during proportional loading. The flattening of two directions is controlled by a pair of second order back-stress tensors, which evolves in a similar manner as the back-stress tensor in classical kinematic hardening models. Unlike the HAH model, the origin doesn't have to be located inside the elastic region of the proposed yield surface. Furthermore, the roundness of the new yield-surface corners, being introduced along the border of the flattened part, is controlled by a yield surface exponent rather than by the magnitude of the Bauschinger effect, which is the case in the HAH model. Hence the model is better suited for numerically stable finite-element implementations. More complex Bauschinger behaviour, with permanent softening, can also be modelled by the new model, an example is given for an AA1200 alloy.