Constitutive equations of stress-strain responses of aluminum sheet under stress path changes

Aluminum sheet metals have been widely utilized for a light weight construction of automobile. However, these metals still remain one of the difficult materials to predict the accurate final shapes after press forming processes, because of several mechanical weak features such as strong plastic anisotropy of yield stress, large Lankford value, and so on. In order to solve the problems, the present author has developed a new constitutive model. The model can describe accurate non-proportional hardening behaviors of an aluminum sheet metal. In the present research, several experimental procedures were carried out to reveal the mechanical properties of an aluminum sheet under proportional and non-proportional loading. From the comparisons between experimental data and the corresponding calculated results by the proposed constitutive model, the performance of our model was evaluated. The evaluation of some springback analyses were also carried out. The calculated results show good agreements with the corresponding experimental data.