Simulation and analysis of the impact of micron-scale particles onto a rough surface

Normal impact of micron-scale copper particles onto a rough copper surface is investigated in the 25–150 m/s impact velocity range, by the finite element method. Surface roughness is generated numerically and incorporated into the finite element model. Particle size is varied in a range comparable to the magnitude of the standard deviation of the surface roughness. Isotropic hardening with strain rate effects and thermal softening due to plastic heat dissipation are included in the model. Analysis is carried out in plane strain mode and impact of single and multiple particles are modeled. The effects of surface roughness on the mechanics of impact, energy exchange, rebound characteristics of the particle and the residual stresses in the substrate are investigated. Impacts on peaks and valleys cause response similar to oblique impact, affecting the rebound behavior of the particle by changing the rebound direction and increasing the rebound energy of the particle. Impacts also cause surface smoothening by crushing the surface peaks; however, collapse of adjacent peaks can provoke stress concentrations and initiate crack formation. Influence of surface roughness on the aftermath of particle impacts decreases with increasing particle size and impact velocity. For impact velocities higher than 50 m/s, no significant difference is observed between impact on smooth and rough surfaces in terms of residual stress generation in the substrate. In general, it is concluded that the effect of surface roughness should be taken into account for low velocity impacts where only the surface peaks deform, or for small particles with size comparable to the standard deviation of the surface roughness.