Numerical Analysis of the Cavitation Effect of Asymmetric Micro-Texture in Sliding Friction Pair Surface

Surface micro-texture technology has become a new and effective means to improve the surface tribological performance of friction pairs. Unlike traditional symmetric textures, asymmetric textures are more conducive to improving the tribological characteristics of friction pairs. The flow of lubricating oil in microtexture pits is often influenced by inertial effects and accompanied by cavitation phenomenon, and the occurrence of cavitation effect is closely related to the shape and position of microtextures. In order to investigate the cavitation effect and its influence factors of the asymmetric micro-texture in sliding friction pair surface, the numerical calculation model of sliding friction pair with surface texture was established and solved based on N-S equation in this paper. The effects of the structural parameters of asymmetric groove micro-texture, the motion speed of the surface of the friction pair and the lubricant viscosity on cavitation phenomenon (gas-phase distribution, area rate of cavitation) and the tribological performances (oil film bearing capacity, friction coefficient) in the asymmetric groove micro-texture were investigated. The results showed that, asymmetric groove micro-texture had a greater bearing capacity than symmetric micro-texture, while its friction coefficient was less than that of symmetric micro-texture. When considering the cavitation effect, the asymmetric groove micro-texture improved the friction properties more significantly than the symmetric groove micro-texture, and the cavitation effect was more significant with larger cavitation area ratio and maximum gas-phase volume fraction when groove of asymmetric micro-texture was further away from the entrance. When the cavitation effect was considered, the asymmetric groove micro-texture increased the bearing capacity by 7% to 13% and reduced the friction coefficient by 10% to 38% compared with the symmetric groove micro-texture. Motion speed of sliding friction pair and lubricant viscosity had important influence on the cavitation effect. The higher motion speed, the more obvious the cavitation effect of the asymmetric micro-texture, and the asymmetric micro-texture was more effective in enhancing the bearing capacity whether the cavitation effect was considered or not. When the speed was greater than 10 m/s, the friction coefficient was smaller than that without the consideration of the cavitation effect, and the friction coefficient of the asymmetric micro-texture was smaller than that of the symmetric micro-texture. The higher the lubricant viscosity, the more significant asymmetric micro-texture cavitation on the contact pair surface, and the ability to improve the bearing capacity was significantly better than that of symmetric micro-texture. When the lubricant viscosity was 0.18 Pa∙s, it could be seen that the asymmetric micro-texture pre-groove had been almost completely cavitated. This study had some significance for the design and analysis of surface micro-tructure of sliding friction pair.