Numerical investigations on springback characteristics of aluminum sheet metal alloys in warm forming conditions

In this study, we investigated the effect of temperature gradients on the final part quality (i.e., springback) in warm forming of lightweight materials. Thermo-mechanically coupled finite element analysis (FEA) models encompassing the heating of the sheet blank and tooling, forming, part ejection, and cooling were developed for simple channel drawing process. A comparison was made between the 2D rigid and 3D elastic tooling FEA models to evaluate the effect of non-uniform temperature distribution and tooling distortion on the forming performance and part quality. The accuracy and reliability of the rigid FEA model were successfully validated through the comparison with the experiments reported in the literature. By accurately measuring the springback amount in three distinct tooling regions (i.e., die corner, punch corner, and side wall), the effect of forming temperature distribution on the part quality were explained in detail under a wide range of operating conditions. In addition, the dependence of springback on blank holder force (BHF), friction condition, and forming rate was also analyzed. The detailed stress distribution of the blank elements was compared to gain a fundamental understanding of the springback mechanism in warm forming process.