Study On Friction And Springback For Sheet Metal Forming

Sheet metal forming is one of the important manufacturing methods in vehicle and engineering industry. In sheet metal forming,contact and friction ,springback ,are correlative a question for discussion.Friction and statejield condition,stress condition of sheet metal are sticking point.Friction and springback are key of making process planning and process parameter and die design.And the question are difficult problem in making process planning.In the dissertation, contact and friction,springback were studied detailedly.In the paper, mechanics model of contact and friction based on fractal mathematics is set up according to the theory of contact and friction. Then the model is applied to calculate the forming load.And studing object were tested by HOMMELWERKE model roughness profiler, fractal character of sheet metal was proved.It is foundation for building correctness contact and friction mechanics model. Besides , the method using neural network to predict friction coefficient is proposed,based on friction coefficient testing by universal material tester.Then start with the spring theory of pure bend in the sheet metal forming, under contact and friction is set up, springback equation on bending and drawing was derived or analysed .As a result of many unknown parameter appeared in theory solution method, writer adopted research method of combining theory solution and simulation solution with test solution, a method based on cubic spline and neural network to predict springback is also put forward in the paper, that is, suppose the forming part is composed of a good many section, and each section is predigested to be a curve, the surface which is constituted of all curves is exactly part surface. Each section curve is regarded as a spline curve, then make use of springback simulation result after unloading of the spline and some modified value such as friction , clearance, press margin power and round radius of punch to predict each section springback . In the light of the method , each section's spline curve structure part's shape after springback.And yield condition of material were analysed under contact and friction, punch, applicable yield condition was confirmed. At last,writer carry out finite element simulation research and put forward the solving scheme to finite simulation of thicker sheet metal forming.By experiment validating, can obtain conclusion:(1) Fractal character of sheet metal was proved. Mechanics model of contact and friction based on fractal mathematics is set up, then the model is applied to calculate the forming load. Experiment prove the calculating result using the model is right and the precision is higher than experience formula.(2) The method using neural network to predict friction coefficient is feasible, predict friction coefficient can been used to engineering.(3) Simulation result based on cubic spline and neural network to predict springback can been used to engineering, and the simulation calculation is faster.