U-Bending Analysis with an Emphasis on Influence of Hardening Models

In this paper the effect of different hardening models in simulating the U-bending process for AA5754-O and DP-Steel, taking a benchmark of NUMISHEET 93 2-D draw bending, has been discussed. The hardening models considered in simulations are: isotropic hardening, pure (linear) kinematic hardening and combined (nonlinear kinematic) hardening. The influence of hardening models on predicting springback and final state variables such as equivalent plastic strain, sheet thickness and punch force has been studied. The combined hardening model predicted the springback parameters well and the isotropic hardening over predicted the springback. The results of springback prediction have been compared with the results reported in the literature. A relation between the level of the final equivalent plastic strain and the amount of springback has been found. The obtained results show that attaining higher amount of equivalent plastic strain in the sheet leads to the less springback after unloading. Comparison between the two materials demonstrates that the aluminum alloy requires lower punch force which means superior formability and exhibits smaller springback.