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 rearrangement 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. (C) 2017 Elsevier B.V. All rights reserved.