Research On Design And Optimization Of Die-face For High Strength Steel Complex Auto Panel

High-strength steel has a high cost performance and is the material of choice for lightweight of auto.However,high-strength steel panels are prone to cracking,wrinkling,springback and other defects during the stamping process,which seriously restricts the development cycle of the die,and the development of dies for complex panels is more difficult.In this paper,the rear floor skin part is taken as the research object,mainly to solve the defects of cracking,wrinkling,springback and other defects to improve the forming quality.The design and optimization of the die-face are carried out.The main research contents are as follows:(1)First,the panel is subjected to process analysis to determine the content of the process involved in the stamping.Then according to the stamping process design specification,the process design and the preliminary design of the die-face were carried out in each process in Autoform,and the simulation was carried out.The simulation results show that the part has defects such as cracking and wrinkling during the drawing process,and the die-face optimization is needed.(2)Optimize the drawing die-face.First,design and optimize the drawbeads.Taking the height of the drawbead as a variable,the orthogonal simulation experiment was carried out,and the multi-objective evaluation function was designed.The range analysis method was used to analyze the calculation result of the functional formula,and the optimal drawbead height combination was obtained.Then,the interim drawing radius for the cracking risk area and the interim drawing radius for the maximum thickening area of the edge fillet were optimized respectively.By analyzing the maximum thinning rate after shaping,the maximum thickening rate,with FLD etc.,the two optimal radii are 11 mm.Finally,the die-face generated in AutoForm was reconstructed in UG,and the stamping simulation was carried out.The simulation results were the same as before,and the formability of the workpiece was good.The drawbeads were re-optimized and the optimal combination of drawbead heights was obtained: 3.2,1.4,1.3,1.0 mm.(3)Optimize the springback compensation of the die-face.Firstly,according to the rebound characteristics of the part,four kinds of springback compensation strategies are formulated,and the optimal compensation strategy is selected by the method of springback compensation and simulation comparison: the final springback measurement results are used to compensate the various processes.Then,using this strategy for springback compensation and optimization,the optimization method of springback compensation is: select different compensation coefficients for each iteration,and use the obtained optimal iteration result as the basis of the next iteration.The compensation coefficients obtained at each stage are: first stage 0.8,0.6,0.4,second stage 0.8,0.6,0.8,and third stage 1.0,1.0,1.0.Finally,the springback measurement error is controlled within ±0.5mm.(4)The whole process stamping test was carried out.The sample was formed with good quality and no forming defects,thus verifying the effect of drawing die-face optimization.After a round of debugging and repairing,the pass rate of the free-springback detection of the sample by the three-coordinate measuring instrument is 91%,achieved a pass rate of 85% or more,thus verifying the effect of springback compensation optimization.