Physically based interaction model of cold spray particle bonding via smoothed particle hydrodynamics

Numerical simulation has become a crucial tool for investigating the deformation behavior and bonding mechanisms of cold spray (CS) particles. Some existing models can effectively predict the onset velocity for CS particle adhesion, but most neglect the physical process whereby unoxidized clean metal breaks through the barrier formed by surface oxide films, becomes exposed, and establishes metal-to-metal bonding under interfacial pressure. Consequently, these models fail to characterize the occurrence of localized metallurgical bonding. To achieve this goal, this study proposes a physically based interaction model implemented through Smoothed Particle Hydrodynamics (SPH) method, which separates the entire process of particle-substrate interaction into two phases. In the phase prior to clean metal exposure, contact model f₁ in form of a repulsive force simulates the interfacial contact inducing by large plastic deformation. In the phase following exposure, bonding model f₂ in form of Lennard-Jones potential simulates metal-to-metal connection established by localized metallurgical bonding. The clean metal exposure that controls the transition from f₁ to f₂ is critical, which is determined by a threshold ε_th of equivalent plastic strain. Through numerical testing of the proposed interaction model, the effects of parameters in this interaction model are thoroughly discussed, and suggestions for the values of these parameters are provided. Furthermore, the model is applied to simulations at varying impact velocities, and the calculated rebound velocity, deformation, and local bonding strength all exhibit agreement with experimental data, validating the efficacy and accuracy of the proposed model.