The Stamping Springback Mechanism Of Advanced High Strength Steel Under The Influence Of Residual Stress

With the increasing number of cars,the problem of energy consumption and air pollution is becoming more and more serious.The use of advanced high strength steel sheet to produce automobile structural parts has become the main measure to realize energy saving and emission reduction in the automobile industry.Advanced high strength steel has the characteristics of high strength and low plasticity,so it is more likely to cause springback,crack and other defects in stamping forming than ordinary steel.At the same time,the uneven plastic deformation of metal leads to the residual stress in the strip steel during the process of rolling production.When the residual stress is too large,it will have a great influence on the subsequent stamping process of the steel sheet.The influence of initial residual stress on the springback results was not considered in the previous study of the advanced high strength steel sheet stamping and springback.So this research has some significance.Based on the plane strain assumption and the Mises yield criterion,the traditional springback mechanical model in sheet metal bending whose material was elastoplastic hardening was established.Based on the traditional springback mechanical model,the theoretical model for bending springback of AHSS plate with the influence of initial residual stress was built,and the relationship between the initial residual stress and the bending moment and the springback angle was obtained.The calculation results of two kinds of springback mechanical models were compared by an example,and the influence rule of the initial residual stress on the offset of the stress neutral layer and the springing angle was analyzed.Based on the ABAQUS finite element software,the finite element model of dvanced high strength steel sheet bending deformation and springback was established,which considered the influence of initial residual stress.Firstly,the effect of initial residual stress on the tangential stress-strain state during bending deformation was studied.The results show that when the initial residual stress is considered,the stress and strain of the sheet is not uniformly distributed along the width direction,and the value of stress and strain is related to the state of the residual stress in this position.The inhomogeneity of stress and strain distribution leads to the fluctuation of the rebound angle value along the width direction.Then the simulation results of the sheet springback angle were compared with the theoretical calculation results to verify the correctness of the theoretical model.Finally,in order to further study the influence rule of initial residual stress on the bending springback results,the change of sheet springback angle under five different bending forming processes(sheet thickness,bending angle,material strength,etc.)was analyzed.The conclusions and results of the study have certain reference value for the production and processing of the sheet strip with considering the influence of initial residual stress.