Optimization Of Surface Friction Characteristics Of Automotive Panel Dies And Preliminary Engineering Application Research

As an important basic process equipment,mold is one of the important indicators to measure the manufacturing level of a country.A large number of studies have shown that the friction characteristics of the mold/workpiece interface are the key factors affecting the plastic forming of the sheet,the friction characteristics of different regions have different effects on the forming properties,that is,the so-called favorable and harmful friction regions.In theory,there is an optimal distribution of friction characteristics at the mold/workpiece interface and an optimal micro-structure on the mold surface.In this paper,the automobile front panel and clamp are taken as the research objects,and the influence of friction on the uniformity and springback of forming parts is studied by combining theoretical analysis,numerical simulation and experiment.On this basis,the self-developed laser composite texture processing equipment was used to process convex and concave composite textures to optimize the distribution of friction characteristics at the mold/workpiece interface and improve the forming performance of the workpiece.Firstly,the stamping process and springback process of automobile panel mold are analyzed theoretically,and the typical characteristic structure of automobile panel mold is summarized by"decomposition-synthesis"analysis method.The automobile panel is decomposed into several feature structure units,and the stress-strain and tribological behavior of different regions of each feature structure unit are analyzed.The change of bending stress and unloading springback stress of the forming parts are analyzed to determine the friction sensitive area on the surface of the feature structure unit.Then the structural units are combined to determine the key friction sensitive areas on the mold surface of automobile panel.Secondly,on the basis of theoretical analysis,ABAQUS is used to simulate the stamping process of the front panel,revealing the influence of friction characteristics in different areas of the mold surface on the thickness and springback of the front panel,and determining the main influence areas of the mold surface.Using uniform design method,the friction coefficient of the mold surface was optimized with the former thickness of the front panel as the optimization objective,so as to obtain the optimal distribution of friction characteristics on the mold surface of the front panel.The simulation results after optimization show that the thickness distribution of front panel is more uniform,the probability of rupture at the thinnest part is reduced by 21%,and the variation range of sheet thickness after optimization is reduced by 7.4%.Due to the limitation of processing equipment,it is impossible to realize the mold processing of large automobile panel.Therefore,this paper carries out experimental research on the small clamp mold,and optimizes the friction coefficient of the clamp mold surface with the springback of the clamp as the optimization objective.The simulation results show that the residual stress of the clamp is improved,the mold fillet angle₁ increases by 0.669°,the₂ between the two sides decreases by 0.37°,the maximum springback(9 decreases by 0.442 mm,the curvature radiusdecreases by0.161 mm,and the springback is significantly improved.The feasibility of laser composite texture on the surface of the mold to control the uniformity and springback of the part was verified by numerical simulation of the forming process of the mold.Finally,according to the springback optimization results of the clamp,laser composite texture processing was carried out on the clamp mold to verify the actual effect of the laser composite texture mold.Firstly,the process parameters of laser texturing and laser micro-pits of SKD11 die steel were studied to determine the process parameters of laser composite modeling on the mold surface.Based on this,the clamp mold is taken as the research object,Based on this,the clamp mold is taken as the research object,and the textured shape of the clamp die 5,6,7,9,10 is processed,and the micro-pit morphology is processed in the convex f region of punch.In order to verify the technical effect of laser composite texture,the stamping experiments of clamp mold before and after optimization were carried out.The test results is similar to that of simulation results.₁ increases by 1.068°and₂ decreases by 1.122°.The final result shows that laser composite texture on the mold surface can effectively improve the forming quality of the formed part.