Investigating silica interface rate-dependent friction behavior under dry and lubricated conditions with molecular dynamics

WQ Xu and ZY Yin and YY Zheng, ACTA GEOTECHNICA, 18, 3543-3554 (2023).

DOI: 10.1007/s11440-022-01792-2

The interfacial properties of silica determine the intrinsic behavior of sand and are of great importance due to its widespread application in geotechnical engineering. To investigate the sand behavior from a bottom-up perspective, the molecular dynamics approach is adopted for both dry and lubricated conditions. Friction simulations are performed using a virtual spring to pull the silica slider on the substrate at a wide range of velocities when different normal loads are applied. It has been found that the orientation of the silica surface influences dry friction. The friction force for the surface with normal vector along (001) direction is larger than that on (100) surface due to anisotropic energy corrugation, and the model with incommensurability has the smallest friction force. The Prandtl-Tomlinson model could explain the stick-slip phenomenon, and as the dominant friction mechanism shifts from thermal activation to phonon excitations and the delay effect of motion transmission, the velocity dependence of the friction crosses over from the logarithmic to the linear relationship at around 10 m/s. The Amontons law for adhering surface describes the silica interfacial friction behavior well. The friction force is linearly correlated with the external normal load and remains a finite value F-0 when the external load equals 0. The lubricated friction results indicate that the friction coefficient decreases against the water content, while there is a non-monotonic relationship between F-0 and water content. The friction coefficient and F-0 increase with the velocity in both dry and lubricated conditions in the studied velocity range (0.1-100 m/s). It should be pointed out that the obtained force-displacement relationship is fundamental and can be applied to enhance current inter-particle laws of silica sand in micromechanics-based modeling approaches.

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