Regulating particle rebound through rough surfaces

High-velocity particle impact on solid surfaces is a fundamental issue in contact mechanics, tribology, and impact dynamics, prevalent in cold spraying, shot peening, and erosive wear. In these processes, particle rebound is governed by coupled normal contact and tangential friction associated with impact velocity, surface morphology, and impact angle. However, a systematic understanding of how surface roughness and impact angle regulate particle rebound and energy dissipation remains lacking, as these coupled effects induce heterogeneous stress localization and multiple dissipation mechanisms. Here, molecular dynamics simulations are used to investigate the rebound behavior of particles impacting rough surfaces. A semi-analytical model is developed for the normal restitution coefficient under head-on impact, revealing an inverse scaling with dimensionless velocity. Furthermore, the effect of surface roughness on coefficient of restitution is velocity dependent: it reduces restitution at low velocities by enhancing local plastic dissipation, but slightly increases restitution at high velocities by suppressing overall particle deformation. Under oblique impact, the deformation mode transitions from normal compression to plowing wear with increasing impact angle. These findings deepen the understanding of energy dissipation and particle deformation modes during impact and provide guidance for surface pretreatment and process optimization in surface modification technologies.