Research On The Models For The Springback Prediction Of QP Steel Stamping

Sheet metal forming is a common kind of metal forming procedure which is widely applied in automobile manufacturing.AHSS has a relatively high strength and good plastic ductility.It can meet the safety and lightweight demand of automobile.However,AHSS has a relatively high yielding limit and the Bauschinger effect occurs during the reverse loading,thus leading to serious springback during AHSS sheet stamping and it’s difficult to give a precise prediction of the springback value.Springback can influence the dimensional accuracy and shape of the final product.Precise prediction is needed to control and solve the problem of springback.QP steel is a new kind of AHSS.Relatively serious springback can impose restrictions on the application of QP steel in automobile manufacturing.Research on the springback of AHSS is insufficient by now,and especially poor for QP steel.The springback of QP steel cannot be predicted precisely.Therefore,the springback prediction of QP steel using several hardening models is studied and the choice of springback prediction models for QP steel is analyzed in this paper.The main research content is as follows,(1)The modeling theory of Swift isotropic hardening model,Chaboche model,Y-U model and NSK model is analyzed,and the solution of the material parameters of the five hardening models is summarized based on the theory.(2)The material parameters of the five models of the four types of QP steel are solved from the strain-stress data of uniaxial tension,cyclic tension,loading-unloading experiments of QP980CR-1.0,QP980GI-1.0,QP1180CR-1.2,QP1180GI-1.2.Analysis of the description of the material deformation characters using the five hardening models is done through comparison of simulating curves using the models and experimental curves of cyclic tension.(3)The model description precision of the properties of the material is introduced.The comparison of the description precision of several important stages of the cyclic tension test is used for the quantitative analysis of the model.(4)The stamping springback of typical U shape part is simulated using five hardening models with the help of FEM simulation software LS-DYNA.The predicting results are compared with the experimental result.Analysis of the comparison shows that in general Y-U model has the best springback prediction precision for QP steel stamping and is followed by NSK model.