The effect of dimensional parameters of multi-asperity surfaces on friction at the nanoscale

Abstract

Experiments have shown thatnanoscale surface texture can effectively reduce the coefficient of friction (COF) between contact surfaces compared to a smooth surface. However, not all textured surfaces would have lower COF than smooth surfaces, as COF also depends on the counter surface radius that encounters the textured surface. In the current study, we use molecular dynamics on an aluminum surface to investigate a relationship between the spherical counter surface radius (R) and the surface texture variables such as radius of the asperity (r), and pitch length (L) that would effectively reduce the COF when compared to a smooth surface. A relationship is obtained, and it predicts that textured surfaces have lower COF than a smooth surface when R/(2 L − r) is greater than 1, otherwise textured surfaces have higher COF than the smooth surface. The relationship obtained is verified by using different surface texture variables and other material surfaces such as silver-nanodot spherical textured surface, and the core-shell spherical textured surface. Further, the trend predicted by the computational model agrees with experiments performed on core-shell spherical textured and smooth surfaces.