Entrance process and interface distribution of nanoparticles in point contact

Nanoparticles have proven to be effective in reducing friction and wear in tribological systems. Previous research mainly focused on the behavior of nanoparticles within the contact region, often overlooking the dynamics of particle's ingress into the interface. This study introduces an innovative model to elucidate the entry process of particles in point contact, grounded in mechanical analysis. The model is employed to investigate the distribution and load-bearing capacity of nanoparticles within the interface, considering variables such as velocity, applied load, particle concentration, particle size, and friction coefficient. Relative ball-on-disk experiments were conducted to verify the model's prediction, with particular attention to the elemental distribution of particles along the wear tracks. Both theoretical and experimental results indicate that the distribution of particles shifts from covering the whole contact interface to concentrating at the edge in the movement direction as the external load increases and the velocity decreases. Additionally, while the spatial distribution of particles remains constant, the particle concentration within the interface significantly increases with higher nanoparticle concentrations. The enhanced tribological performance of nanofluid is attributed to a greater number of particles entering the contact region.