DEM investigation of the role of friction in mechanical response of powder compact


The discrete element method (DEM) based simulations were conducted to study the effects of particle-particle and particle-wall frictions on the compaction behaviour of wet particles. The results showed that in the die compaction the particle-wall friction had a minimum effect on the initial particle re-arrangement stage and mainly affected the particle deformation stage. The inter-particle friction, on the other hand, reduced the particle re-arrangement in the initial stage but had no significant effect on the deformation stage. This was attributed to their different roles in force transmission: while the particle-wall friction reduces the force transmission resulting in increased density/stress gradients in the compaction direction, the inter-particle friction enhances the vertical pressure transmission. Their different roles were also reflected in the unconfined axial compression: the compressive strength of compacts decreased with increasing particle-wall friction but increased with increasing inter-particle friction. It was also observed that the compact stiffness increased with inter-particle friction but showed no dependence on particle-wall friction. While the dominant failure mode did not vary with the frictional condition, larger particle-wall frictions caused smaller failure areas which were mainly localized at the bottom of the compacts.