Research On Analytical Model For Bending Springback Of Wide Heavy Plates

In recent years,the rapid development of automobile industry has put forward higher requirements for automobile lightweight,which also makes the development of high-strength steel plate,aluminum alloy plate and sandwich sheet.However,these materials in the manufacturing process have a common problem,springback is difficult to predict.The springback mechanism of different plates is also different.They have different stress-strain states,which increases the complexity of the springback problem.Based on this background,the analytical model of sheet metal bending springback is studied,in order to improve the efficiency and accuracy of springback prediction of simple bending parts.Firstly,the beam-plate theory and the springback mechanism are analyzed,especially the basic hypothesis of beam-plate theory and the cause of springback.Secondly,for the bending springback prediction of wide heavy plates,the strain characteristics in the bending process are analyzed based on the Timoshenko beam theory and plane strain hypothesises.An analytical model for bending springback is proposed based on Hill's quadratic anisotropic yield criterion and exponential hardening model,and the inward movement of neutral layer and thickness thinning of plates are considered.The springback angle of the thick Invar alloy plate are calculated under three-point bending test,and the results are compared with the experimental values and calculated ones by another analytical model,the accuracy of the analytical model is verified by experiments.Finally,for the bending springback of aluminum alloy-polymer sandwich sheets and hot formed high strength steel plate with continuous gradient hardness in thickness direction,the stress distribution characteristics of these two kinds of sheet metal thickness direction are analyzed,and an analytical model for bending springback is proposed based on the Timoshenko beam theory assumption and the Hill yield criterion.The numerical simulation of bending springback of sandwich sheets based on ABAQUS is carried out.The simulation results are compared with the analytical results as well as the experimental results.The effect of central layer thickness on bending springback of aluminum alloy-polymer sandwich sheets and the accuracy of analytical results and numerical simulation results were investigated.