A bulge-test based viscoplastic model for superplastic deformation behaviour of a magnesium alloy

In this work, a new approach is proposed for modelling the superplastic deformation of AZ31B magnesium alloy sheets. Gas bulge tests were performed at 450 ℃ under three constant gas pressure levels of 0.4, 0.7, and 1.0 MPa. The dome height evolutions according to time were recorded in experiments and then translated into stress–strain curves using a new analytical approach. In order to predict the superplastic behaviour of the material, the Variable m-value Viscoplastic (VmV) model was considered in this study, whose constants were directly assessed from the bulge test results. The bulge forming of the magnesium alloy sheet was simulated with ABAQUS/Standard using the VmV model. The predicted dome height-time profiles and thickness distributions along the specimens were compared with the experimental results. Finally, a real case study (a resorbable cheekbone prosthesis) was simulated implementing the VmV model for validation purposes. The results from the simulation of both the bulge tests and the case study manufacturing revealed that the proposed model is able to effectively reproduce the superplastic behaviour of the AZ31B magnesium alloy.