Abstract: With the improvement of automobile body requirements for lightweight, high efficiency and energy saving, the application of advanced high strength steel in automobile industry is on the rise because of its high specific strength, specific stiffness and other properties. Therefore, it is of great significance to study the springback behavior of advanced high strength steel and summarize its springback law for improving the forming accuracy. Current research is mainly based on U-bending test to study the influence of different material models on springback. The applicability of yield criterion and hardening model to Draw-bending springback prediction needs further study. Based on Drawing-bending test platform, the influence of roll radius and normalized back force on springback of DP780 is studied. Moreover, the influence of different hardening models (Hollomon model, Y-U model) and yield criteria (Mises, Hill48, Yld2000) on Drawing-bending springback prediction is studied by using PAM-STAMP finite element analysis software. The results show that increasing the bending radius and normalized back force can reduce the side wall crimp rebound. For the springback prediction, the accuracy of Draw-bending springback prediction can be improved when the material parameters of Y-U model are solved by a double-precision solver. Because of the particularity of DP780 anisotropy, the combination of Y-U hardening model and Mises yield criterion or Yld2000 yield criterion can obtain higher prediction accuracy. For the prediction of thickness and section radius, the combination of Y-U hardening model and Yld2000 yield criterion can obtain better prediction accuracy.

Key words: draw-bending, back force, bending radius, yield criteria, hardening model