The frictional energy dissipation and interfacial heat conduction in the sliding interface

The energy dissipation rate and interfacial thermal conductance between two sliding surfaces are important to accurately predict the interface temperature rise, while their physical mechanism is not well understood. In this study the energy dissipation and interfacial thermal transport between a sliding silicon film and a fixed silicon substrate are investigated by molecular dynamics simulations. The results show that the mean friction force first increases with increasing normal load. However, when the normal load exceeds the critical value of about 60 eV/Å, the interface atoms begin to collapse, causing the mean friction force to drop with the further increase of the normal load. Our study also shows that the energy dissipated during the friction process is quantitatively equal to the conducted heat. By extracting the interfacial temperature difference, it is found that the interfacial thermal conductance in sliding state is 2∼4 times higher than that in static state with the same normal load from 10 to 60 eV/Å. This is because the interfacial atoms suffer great dynamic impacts during the friction process, which excites more non-equilibrium phonons and helps to enhance the phonon interfacial transmission coefficient. The present investigation demonstrates that the dynamic excitation induced by the friction process can modify the interfacial thermal conductance, which would be of great significance to accurately predict the temperature rise of the sliding interface.