Crack Propagation of Metal Powder Compact

Simulation of crack propagation in metal powder during the cold compaction process is presented in this paper. Based on a fracture criterion of granular materials in compression, a displacement based finite element model has been developed to simulate the fracture process in a multi level component made of iron powder. Estimation of fracture toughness variation with relative density is established in order to provide the fracture parameters as compaction proceeds. A finite element model with adaptive remeshing technique is used to accomodate changes in geometry during the compaction and fracture process, while friction between crack faces is modelled using the six nodes isoparametric interface elements. Two widely used yield criteria for powder compact, namely Mohr-Coulomb and Elliptical cap are used in the models. Different crack growth patterns obtained by using these two yield criteria are presented and compared in terms of the influence of shear stress and relative density distributions. Even though the crack starts at different compaction step and different crack patterns are obtained when different yield criteria is used, shear crack is predicted to starts in the region with lower relative density and higher shear stress in both models.