Study On Deformation And Densification Law Of Powder Forging And Numerical Simulation Of Forging Process

Powder forging (P/F) is a new-style and high-performance plastic forming technology which combines conventional powder metallurgy (P/M) with precision forging techniques. The paper has systemically studied the deformation law and the densification mechanism during powder forging process (especially cold forging) based on the combined methods of theoretical study, experimental testing and numerical simulation.In theoretical study field of plastic forming for porous metal materials, the yield cfiterions for compressible P/M materials are systemically studied and those for compressible P/M materials based on cold-forging are analyzed and compared especially. Then the calculation formulae of deforming force, the density of workpiece and sizes for upsetting, repressing, and closed die forging are deduced. They are analyzed and discussed quantificationally at the same time.Based on the study of the deformation law and densification mechanism of powder forging, the experimental research method is adopted in this paper. According to experimental results of upsetting and closed die forging of deoxidize Fe porous materials, the local strain limit criterion for the cracking on surface has been achieved. The effect of different initial relative density( 0), the relative height(H/D) and the factional factor(m) on cracking strain limit of upsetting deformation is farther discussed. Meanwhile, based on the experimental results, the limit process parameters have been confirmed for the cracking limitation. After that, the sizes design of mould and that of sintered porous materials green can be optimized. And according to microcosmic analysis of experimental workpieces, the law of density distribution of powder forging is researched, too.At the same time, the yield criterion and constitutive equations for the compressible rigid plastic finite element method have been deduced and the formula representing relationship between g, the coefficient of materialvolume compressibility method of rigid plastic finite method, and , the relative density of powder materials, has been established and researched. The MARC finite element method is used to simulate the deformation process of a cylindrical upsetting and closed die forging of porous metal materials, and influence on its deformation law and densification mechanism brought by different initial relative density, the relative height and the frictional factor is analyzed then. The numerical results are compared with those of experiments at last.Therefore, the results obtained in this paper may enrich the precision plastic forming theory, promote the applications of P/F technology and improve the development of numerical simulation for powder metallurgy. This is of significant.