On ultrahigh velocity micro-particle impact on steels - A multiple impact study

A computational model is presented to investigate the ultrahigh-velocity multiple particle impact process on steels. It uses a Monte Carlo framework to model the stochastic nature of the particle flow and the finite element (FE) method to model the individual particle impact process, while considering the thermal diffusion process. The model predictions show a reasonably good agreement with the corresponding experimental data using a high-tensile steel specimen at various conditions. A simulation study using the model is then conducted and shows that it is essential to consider thermal diffusion which causes the temperature at the impact site to rapidly cool down in a multiple particle impact process. As a consequence, the impact result is impact-sequence and impact-time dependent. The study reveals that inertia-induced fracture is the primary material removal mechanism at the normal impacts, while the thermal instability-driven failure, or specifically the adiabatic shear banding (ASB) induced failure, as well as the elongation-induced fractures are the two major material removal mechanisms at oblique impact angles. These failures occur at the pile-up lips (at normal and oblique impact angles) and the crater bottom (at oblique impact angles). It is the thermal-instability-driven failure that contributes to the higher material removal rate at oblique impact angles.