Powder Technology, Vol.345, 589-600, 2019
Prediction of the anisotropic mechanical properties of compacted powders
The multi-particle finite element method (MPFEM) was used to test the anisotropic elastic and plastic properties of compacted powders with cohesive contacts. A representative volume element (RVE) of monodisperse, spherical, deformable particles was used to investigate the powder properties after compaction. Efficient periodic boundary conditions and an RVE of only 50 particles allowed extensive parameter studies. During parameter studies the relative density after compaction, the contact cohesion strength and the strain path during compaction were varied. The strain paths were characterized by the ratios of the applied principal strains during compaction that results in different Dirichlet boundary conditions on the RVE. Seven different strain paths were considered including the practically important isostatic and closed die compaction. The outcome of the parameter study were the elastic constants of an orthotropic material model, the uniaxial yield strength for tension and compression, and the yield surfaces for general load cases. No anisotropy was observed for isostatic compaction but increasing anisotropy was observed with increasing ratio of the principal strains during compaction. Regression curves were generated to describe the mechanical properties as a function of the model parameters. In this way, continuous functions were obtained which were capable to describe the distribution of the mechanical material properties in a FEM model of a heterogeneous compacted powder part. (C) 2019 Published by Elsevier B.V.
Keywords:Powder compaction;Multi-particle finite element method;Cohesive particle contact;Anisotropy;Elasticity;Yield surface