Study on Influencing Factors of U-bending Springback Prediction of DP780 Dual-phase Steel
Springback is a key factor affecting the dimensional and shape accuracy of cold-formed high-strength steel parts,and the accuracy of high-strength steel springback prediction depends on the accurate material model,it is important to study the influence of the material model on springback prediction accuracy.Based on tension-compression tests with two different strain levels and multi-cycle tension-compression tests,the parameters of the DP780 dual-phase steel Yoshida-Uemori(Y-U)kinematic hardening model were determined.The influence of different hardening models and yield criteria on the U-bending springback prediction was analyzed by LS-DYNA finite element simulation software,and compared with the springback tests.The results show that the Y-U model parameters obtained by different tensile-compression test strategies have great differences,and the Y-U model obtained by the multi-cycle tensile-compression tests has higher prediction accuracy and the U-bending springback error can be controlled within 5％.With the increase of pre-strain,the elastic modulus of DP780 dual-phase steel decreases sharply and gradually becomes flat.The Y-U model considering elastic modulus degradation can improve the prediction accuracy of U-bending springback.Compared with the Swift isotropic hardening model,the Y-U kinematic hardening model combined with the Hi1148 yield criterion can obtain higher springback prediction accuracy.The yield criterion has a certain influence on the springback prediction of DP780 dual-phase steel,but its influence on the springback accuracy is significantly lower than that of the hardening model.The research results provide a theoretical basis for the selection of advanced high-strength steel material models and the improvement of springback prediction accuracy.
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