Numerical Simulation of 3D Powder Compaction Processes Using Cap Plasticity Model

摘要

In this paper, recent activities to develop a simulation code for 3D finite element modeling of powder forming processes are presented. The compaction forming of metal powder is a process involving large deformations, large strain, non-linear material behavior and friction. Consequently, the numerical analysis of such a highly non-linear process is a formidable computational problem. For the successful modeling of powder compaction process several requirements have to be met [1-3]. Firstly, as the compaction process involves a very large reduction in volume, the formulation adopted must be capable of representing this physical process. Secondly, since powder is a factional and compressible material, the densification is dependent on the compaction stage and the material model needs to reflect the frictional and yielding characteristics of the powder. Thirdly, the involvement of two different materials, which have contact and relative movement in relation to each other, must be considered.In reference [1-3], the 2D FE model was developed for describing the isothermal deformation behavior of metal powder. The purpose of the present study is to extend the simulation of powder forming processes to 3D finite element analysis. As the forming process in powder compaction problems is a large deformation process, an elasto-plastic analysis often utilizes a large strain model. A large displacement formulation, based on a total and updated Lagrangian formulation is utilized. In order to describe the constitutive model of the highly non-linear behavior of powder materials, a cone-cap plasticity model is applied based on a hardening rule to define the dependence of the yield surface on the degree of plastic straining. This model reflects the yielding, frictional and densification characteristics of powder along with strain and geometrical hardening, which occur during the compaction process. Finally, the powder behavior during the compaction of a 3D multi-level component is numerically simulated. The predictive compaction forces at different displacements are computed and compared with the available experimental details reported in the literature. The simulation of the deformation is shown as well as the distribution of relative density and stress contours at different time stages. It is shown that the proposed 3D model using cap plasticity theory is capable of simulating the metal powder during compaction.