Vibration Induced Reciprocating Sliding Contacts between Nanoscale Multi-Asperity Tips and a Textured Surface

Microgravity and vacuum are two main environments in outer space. In the microgravity environment, vibration is a typical phenomenon, and it will induce a reciprocating sliding contact between a journal and a bearing in a clearance joint. In vacuum environment, the adhesion effects are severe, and the friction forces are much higher than the ground environment. Nanoscale textures can reduce the contact area and trap the wear particles, which are beneficial to the friction reduction. Most of the current studies focus on the single-pass sliding contact. Actually, considering the roughness of the contact surfaces, a multi-asperity tip should be more reasonable. In this paper, vibration induced reciprocating sliding contacts between nanoscale multi-asperity tips and a textured surface are investigated using a multiscale method, and the material is FCC copper. Six rigid tips are modelled with different cylindrical asperities and slid on the textured surface. Corresponding to the tips, the average friction forces are compared, and the effects of the tip radii are analyzed. The total average friction forces of the textured surface are compared with the case of a smooth surface, and the mechanism of the friction reduction is discussed. The results showed that the total average friction forces decrease as the increase of the asperity radii, and the textured surface can reduce friction forces effectively compared with the smooth surface. This work could contribute to reducing friction by designing the tip and the textured surface in vibration induced reciprocating sliding contacts under microgravity, which will be beneficial to prolong the life of components on the spacecraft.