One-time determination of 20 material parameters in a strain-compensated constitutive model and its application in extrusion for an Al-Zn-Mg thin-walled profile

Abstract

A reasonable constitutive model is the key for accurate numerical simulation of extrusion process of aluminum alloy profiles. In this work, 20 material parameters in a fourth-order strain-compensated constitutive model of an Al-Zn-Mg alloy were determined by the inverse analysis method. Firstly, taking the minimization of shape error of specimens under different compression extents (10–60%) at the temperature of 475 °C and the strain rate of 1 s−1 as the optimization objective, the friction coefficient in hot compression test was determined by inverse analysis. Results showed that the friction coefficient was 0.031 and the global error was merely 1.001%, which demonstrated the practical lubrication condition between specimen and tool head could be reflected by the acquired friction coefficient. Then, based on the obtained friction coefficient, the inverse analysis was also used to identify 20 unknown material parameters in the fourth-order strain-compensated constitutive model at once by minimizing the difference between predicted and experimental force-displacement data. The predicted force-displacement curves matched the experimental ones well with the global error of only 6.07%. Finally, the developed constitutive model was applied in simulating the porthole and piercing extrusion for a hollow thin-walled profile and corresponding verified experiments were also carried out.