Experimental Research And Numerical Simulation On Bending For 1060 Aluminum Alloy Variable Thickness Plates In Multi-point Forming

Multi-point forming of variable thickness plates adopts a series of basic bodies with height-adjustable arrangement rules instead of press-formed mould surfaces,replacing padding with polyurethane mats to solve the problems of high production cost,long design and manufacturing cycle,and repeated utilization rate of traditional in press-bending forming.In this paper,the combination of theoretical analysis,finite element simulation and forming experiments are used to investigate the force deformation and rebound of multi-point bending and the effect of various process parameters on the formation of variable thickness plates.The bending experiments provides theory and data accumulation for the new process of forming.Based on the combination of finite element simulation and experimental results,the law of force deformation of the thick plate during the forming process was studied,and the experimental mold was designed according to its stress deformation characteristics;the compression of the polyurethane pad and the engineering stress were deduced.Relations,the formula of repeated bending springback analysis of the causes of reverse springback.The results show:The thick plate has the characteristics of uneven force and discontinuous deformation.The simulation results of the compressive engineering stress deduced from the Mooney-Rivlin constitutive relation are basically consistent with the theoretical calculation rules,which verifies the rationality of the theoretical calculation based on the compression-engineering stress relationship.During the forming process,the surface pressure in the thick zone should be greater than the thin zone by adjusting the adjustment compensation amount and the polyurethane pad parameter so that the thick zone is fully formed and the thick zone is uniformly deformed.There are repeated bending phenomena during the bending process of differential thick plates.Different springback amounts in different regions will lead to uneven rebound of the entire thick plate,and the curvature radius is not continuous.In order to investigate the law of forming deformation of thick plate,a single variable experiment was carried out for the process parameters affecting the bending of the thick plate.Combined with the finite element simulation results,the influence laws of various factors were explored,and the sectional bending test was completed.The results showed that: As the forming force increases,the trend of the radius of curvature of the thick plate decreases,and the springback displacement decreases.The forming force continues to increase until it is fully formed,and the changing trend of the curvature radius and rebound displacement slows down;the thick plate is thin,intermediate,and thick The radius of curvature and springback of the zone are basically close to each other,with a slight offset.The deformation and rebound of the thin zone ofthick and thick zone thick plate are more affected by the thick zone,and the step length of the thick thick plate in the small thick zone is longer.Thick areas are less constrained by thin areas.When the polyurethane pad has a high hardness,it can provide a more uniform surface pressure for the thick plate.As the thickness of the polyurethane mat increases,the corresponding surface pressure in the thick zone decreases,the surface pressure in the thin zone increases,and the forming effect changes with the plate parameters;the shape compensation amount should always be smaller than the step thickness,so that the thick plate in the thick zone is greater in surface pressure than in the thin zone.The smaller the step thickness in the force state is,the thicker the thin zone thickness is,and the higher the bending stiffness is,the larger the first bending R1 is,the smaller the reverse bending moment is,and the area of the reverse rebound zone is smaller.As the step thickness increases,the area of influence of reverse springback increases.The larger the proportion of thick zones,the shorter the length of the steps,and the weaker the effect of reverse springback caused by repeated bending in the forming process.For the segmented bending forming,the more the number of bending and bending,the larger the area of repeated bending and bending,the greater the maximum number of repetitions,but the smaller the deformation of each bending bending.Overall rebound amount: S60<S40<S80<S100.The amount of bending at the same time affects the number of bending and the amount of deformation at each bending.