| Stamping is a simple and efficient metal plastic forming method,which is widely used in sheet metal forming field.In recent years,with the deepening of automotive lightweight research and application of intelligent control technology,new materials and intelligent production equipment are also applied.The representative ones are high strength steel with higher strength and toughness and servo press with servo control technology as the core.However,the emergence of high strength steel also brings new challenges to the stamping forming process.Because of the high strength steel has high toughness,the stamping parts will produce great springback under the action of residual stress after unloading,which will directly affect the forming accuracy and practical application of the stamping parts.Therefore,this paper will take Vshaped bending parts as an example,based on the servo press to explore the springback prediction and control method of QP980 high-strength steel,the main research work and results are as follows:Existing studies show that the prediction results of mechanical deformation behavior of materials with different yield criteria and hardening models will be very different.In order to explore the appropriate finite element material model of QP980 high strength steel,four material models are established on the basis of unidirectional tensile test.Are the material model based on Hill anisotropic yield criterion,Barlat anisotropic yield criterion,Hill+Yoshida-Uemori and Barlat+Yoshida-Uemori,respectively.Then the finite element model of corrugated plate is established in Dynaform software and the forming and springback simulation of QP980 high strength corrugated plate is carried out.The simulation results show that the Barlat+Yoshida-Uemori material model can better predict the stress and deformation behavior of QP980.On the basis of the finite element simulation results,two kinds of corrugated plate dies of wedge type and lever type were designed through the calculation of related parameters,and the structure size of the dies was compared and corrected through the stamping test of servo press.The test results show that the wedge structure will cause uneven force on both ends of the plate and produce stress concentration,and the corrugated plate after forming is not sufficiently deformed and has large rebound,while the lever structure can form the corrugated plate better.In addition,the manufacturing accuracy of the die of the lever structure has certain errors.In order to explore the influence of sheet width and bending Angle on the springback of single Vshaped bending parts,this paper designed a comparison test of 25mm and 50mm sheet width at 60°,90°,120° bending forming.The test results show that the springback of the bending part decreases with the increase of the bending Angle,and increases with the decrease of the width of the sheet,and all the springback is positive.In addition,with the increase of bending Angle,the decline trend of sheet metal rebound in width direction is gradually gentle.In order to investigate the impact of stamping process parameters such as stamping speed,friction factor,punch fillet radius,die fillet radius and die structural parameters on springback of multiple continuous V-shaped bending parts(corrugated plates),orthogonal experiments were designed and GABP neural network prediction and optimization model was established.The orthogonal test results show that under certain factor levels,the springback Angle of corrugated plate firstly increases and then decreases with the increase of stamping speed,firstly increases and then decreases with the increase of friction factor,firstly increases and then decreases with the increase of punch fillet radius,and continuously increases with the increase of die fillet radius.The results show that the springback of corrugated plate after forming is reduced by 1.31%compared with that before optimization,which proves that the GA-BP neural network prediction and optimization model is reliable. |
