Simulation of rebound, flattening, and surface penetration regimes in high-velocity microparticle impacts using smoothed particle hydrodynamics

High-velocity microparticle impacts involving ductile metals underpin destructive events and solid-state deposition processes, such as cold spray. Simulating these dynamic events enables detailed evaluation of complex, rapidly evolving phenomena such as adiabatic shear instability. However, the rapid upturn in dynamic flow strength at extreme strain rates (> 10 ⁶ /s) associated with high-velocity impacts is often neglected, and validation exercises are scarce. This study presents meshfree simulations of microparticle impacts involving oxygen-free high-conductivity copper (Cu) and commercially pure aluminum (Al), using an axisymmetric smoothed particle hydrodynamics (SPH) approach coupled with a modified Johnson-Cook constitutive model with Cowper-Symonds rate sensitivity. The simulations were validated against recently published experimental data involving low-velocity particle rebound, critical profile dimensions, the onset of material jetting, deposition, and hydrodynamic penetration. Matched Al-Al and Cu-Cu, and mismatched Al/Cu particle-substrate pairs were considered, with particle diameters between 10 and 30 µm and impact velocities between 50 and 1300 m/s. The coefficients of restitution for low-velocity impacts and the critical velocity for bonding were predicted with average errors of 20.6% and 6.3%, respectively, across the parametric scope. The onset of hydrodynamic penetration (no net deposition), and critical post-impact profile features such as surface morphology, particle rim curling, and ejecta release (jetting) were also predicted with similar accuracy. Simulations of elliptical microparticle impacts quantified the influence of particle shape and orientation effects on the onset of bonding and post-impact flattened surface morphology. These findings highlight opportunities to simulate shock-induced phenomena in more realistic physical domains efficiently, thereby enabling more informed selection of materials and process parameters, as well as the design of solid-state-deposited surfaces.