Impact Mechanics of Porous Particles

The impact and bonding mechanism(s) of micron-scale particle deposition in cold spray has attracted extensive studies in the recent years. This work extends these studies to investigate the influence of particle porosity on impact, rebound and bonding behaviors of single particles. The finite element method was used to simulate the impact process. The performance difference between hexahedral and tetrahedral meshing, as well as the difference between pure Lagrangian method and Coupled-Eulerian-Lagrangian (CEL) method were compared. Effects of high-strain-rate, heat generation due to plasticity, material damage and failure, interfacial friction, and heat transfer were taken into account. While the main focus of the study was WC-17Co, Al-6061 was also simulated as a reference material. The volumetric porosity of the particle was varied in the 0 - 35%, by subtracting uniformly distributed spherical voids of diameter 1 micrometer from a solid spherical particle. The effects of porosity on the kinetic energy absorption during the impact, as well as bonding were investigated, and internal energy dissipation mechanisms were studied. It was found that the influence of porosity increases with the impact velocity and the pores channel the stress waves in unique ways not observed for solid particles.