Simulation and fracture prediction for sintered materials in upsetting by FEM

Experiments dealing with the upsetting of sintered materials have resulted in the determination of a forming limit in terms of the local compressive and tensile strains. As the specimen is compressed, a plot of tensile strain versus compressive strain can be made. Fracture occurs when the strain path intersects the forming limit. Once the fracture locus is defined by an experimental method, it is possible to use the Finite Element Method to determine if some upsetting operation will exhibit a free surface crack during a deformation process. In this study, a finite element program has been developed to analyze the deformation processes of sintered metals in upsetting. At the same time, the effects of lubrication, height to diameter ratio, initial relative density, die shaping and preform shape on the forming limit of PM products are investigated. The locus strains are then calculated and possible defects leading to material failure are checked. The calculated results agree well with the experimental results.