Abstract:An important concern in forging of metal material is whether the desired deformation can be accomplished without failure of the work materials. In this paper, based on the plastic theory of porous metal materials, the compressible rigid plastic finite element method(FEM) was used to simulate the deformation processes of cylindrical upsetting of porous metal materials with full account of contact friction boundary conditions(m), the height to diameter ratio(H/D) and the initial relative density(R₀). Furthermore, combining the simulation results with the ductile fracture criterion, which is a strain-based criterion obtained by Lee and Kuhn, the critical technological parameters were predicted. This study revealed that larger height to diameter ratio and less friction factor can delay the local strain locus to intersect with the Lee-Kuhn’s fracture line, delaying the occurence of the surface crack. Meanwhile, it revealed that the initial relative density affects little on the forming of the crack. And the results of the finite element method agreed well with the experiment results of Lee and Kuhn.

Key words: porous metal materials　the critical technological parameters　defects