Abstract
The main purpose of this study is to investigate the forgability of sintered powder compacts, including the void evolution and fracture prediction in the forming process. A new ductile fracture criterion for porous media is developed based on the maximum principal strain energy per unit of volume. It demonstrates that the strain energy density is governed by the maximum principal stress in material. Fracture will occur as the accumulation of strain energy density reaches the critical value at that point.
Experiments and Finite element analysis were conducted to establish the models. The material properties of sintered porous preforms were obtained from both the uni-axial tension and compression tests. The finite element models were verified with experiments of upsetting under different frictional conditions. Studies show that the results by the new criterion are more compatible with the experimental data than other previous forms. In addition, voids lead to the degradation of the strength and workability of materials. Friction contributes to the non-uniformity of deformation and density variation that causes the workpiece to fracture.
