Energy partitioning within a micro-particle cluster due to impact with a rigid planar wall

Abstract

A combined finite and discrete element method is used to examine the energetics of a two-dimensional micro-particle cluster that impacts a rigid planar wall. The method combines conservation principles with an elastic-viscoplastic and friction constitutive theory to predict thermomechanical fields within particles resulting from both particle-wall and particle-particle contact. Emphasis is placed on characterizing the temporal and spatial partitioning of cluster energy with impact angle (0^◦ ≤ ${\phi}$ ≤ 80^◦, where ${\phi}$ = 0^◦ corresponds to normal impact). Predictions for a close-packed cluster of well-resolved particles having an average initial radius and uniform speed of 50μm and 300 m/s indicate that particles adjacent to the wall experience the largest plastic and friction work. Friction significantly affects cluster kinetic energy, but minimally affects its elastic strain energy and plastic work. Local temperature rises in excess of 900K are predicted for ${\phi}$ = 0^◦, increasing to 4,400K for approximately ${\phi}$ > 60^◦, with most of the cluster mass (≈98%) experiencing temperature rises less than 200K due to plastic work. These predictions highlight the importance of friction work as a heating mechanism that may induce combustion of energetic clusters. Sensitivity of the cluster response to its initial packing configuration is demonstrated.