Failure prediction of AZ31B magnesium alloy sheet based on a micro-mechanical void model incorporating the asymmetric plasticity constitutive law

In this paper, a fracture criterion based on a micro-mechanics void model was applied to ductile fracture model of AZ31B magnesium alloy sheet. In particular, the fracture model was coupled with an advanced plasticity model in which the asymmetric cyclic response of magnesium alloy due to combined slip and twin deformation can be reproduced accurately. The extended McClintock fracture model adopted in this study as a fracture criterion for the magnesium alloy sheet takes into account the effect of shear deformation by adding Lode parameter dependency to the original model. Both the fracture model and the plasticity model were implemented in the explicit finite element code, LS-DYNA, via a user-defined material subroutine. The parameters of the proposed fracture model were identified using multi-directional mechanical tests, such as uniaxial tension, simple shear, and notched tension tests. As validation, the proposed model was compared with existing models for predicting the fracture patterns in test specimens and limit dome heights.