Micromechanical analysis on the compaction of tetrahedral particles

Abstract

Understanding the roles of particle properties in powder compaction is important to many industrial products, such as tablets in pharmaceutics, briquettes in iron ore handling and green compacts in powder metallurgy. However, the role of particle shape in bulk compression and how it is related to the properties of the final compact are not well understood. In this study, we investigated the structural evolution, force distribution and compact strength of tetrahedral particles using discrete element method, with a focus on the effect of particle interlocking due to non-spherical particle shape. Tetrahedral particles were constructed using clumped sphere approach, which allows multiple contacts being set up between two contacted particles. Die compaction followed by unconfined compression were conducted on the assemblies of both spherical and tetrahedral particles. The results showed that the tetrahedral particle shape reduces the degree of particle rearrangement at the early stage of bulk compression but enhances the resistance to bulk deformation at the later stage due to enhanced shear resistance at interparticle contacts. The compact of tetrahedral particles presents a higher compressive strength due to increased number of interparticle bonding. Compared to the spherical particles, the macroscopic failure mode tends to be more ductile for the tetrahedral particles. The tetrahedral particle shape has no effect on the dominant bond failure mode but leads to a wider shear banding, more dispersed bond breakage and a slower bond breakage process. This work highlights the role of particle shape in densification mechanism and mechanical response of the formed powder compact.