Study On Contact-impact Dynamic Response Of The Die In Sheet Metal Stamping

As it is well known, stamping is used widely in sheet metal manufacture. The processing is a complex nonlinear problem, in which elastoplastic deformation and shear fracture are included. Compared with other processing technology, stamping not only focuses on bringing sheet metal to elastoplastic deformation, but also making it separated. When the sheet metal is ruptured, it releases deformation energy instantaneously, which mostly will act on the upper-die. It is very similar to collision -impact processing. During the pressing motion, the upper-die always under such impact, its mechanical properties will be affected so much that it maybe fall into failure. The present thesis investigated the contact-impact dynamic response of the die in stamping using finite element method (FEM).First, three stages in collision processing was analysed, the methods and formulae in each stage were summarized, and then the two-object collision model was used as an example to explain the application of the method and formulae.Then the initial and boundary conditions of the model in stamping, constitutive equation of material nonlinearity, the effect of suppositional mass and velocity were discussed.Based on the analysis of the theories about the contact-crashworthiness and the nonlinear finite element method, this paper carried out a systematical study on the numerical simulation of impact of some upper-die with typical shapes, such as orbicular, foursquare and concave. A simple simulation model was based on nonlinear finite element method. By analysing the stress and the strain of the upper-die, the deformation of the structure and the position broken first during the impacting process were confirmed. The results of the structures impact were calculated and analyzed. And the effect of blanking clearance on the processing of sheet metal blanking was discussed, which was supposed to be directly relative to the selection of material and mechanical technology of stamping die in the real sheet metal forming.In addition, this paper tried to do some research about the impact response of the parts which are joined with the upper-die, which would do much good for the further study.