Determination of material parameters for 7475 Al alloy from bulge forming tests at constant stress

This study describes a method of determining rheological parameters of 7475 Al alloy from a superplastic bulge forming test at constant stress. Two material models, based on power law, are chosen to fit the true stress, true strain and true strain rate obtained from experimental data. The finite-element simulation of bulge forming is used to examine the validity of the method suggested and the material models with the associated parameters obtained experimentally. The simulation results are compared successfully to the experimental ones. The influence of m and K variation with strain rate, on the deformed shape has been proved. The prediction of thickness at dome apex is improved when this variation was considered.