Theoretical Study On Properties Of Mixed Lubrication Of Inclined-micro-dimpled Surfaces

Proper surface texture produces significant hydrodynamic effect and reduces surface wear. In order to obtain better understand of the friction and wear mechanism of surface texture, theoretical study on properties of mixed lubrication of inclined-micro-dimpled surfaces was conducted here.First, a mathematical model of mixed lubrication of textured surface was established based on fluid lubrication theory and elastic deformation theory. The relationship of standard deviation of the surface roughness σ, asperity density η, and asperity radius of curvature β, was derived. Numerical solution method for the present mixed lubrication model was studied.Then, friction performance and wear regularity of inclined-micro-dimpled surfaces were analyzed. Results showed that when normal load, inclination angle or standard deviation of the surface roughness σ is small, the critical rotation speed for the transition from mixed lubrication to hydrodynamic lubrication is low. When film thickness ratio λ<1.5, the raise induced by elastic deformation on the non-textured surface embedded into the micro-dimple on the counterpart, which led to severe surface wear by the cutting action; when 1.5<λ<2.5, the embedment of the raise induced by elastic deformation was not obvious and the wear was mainly caused by the asperities contact on the non-dimple area; when λ>2.5, the non-textured surface possessed depression deformation and the gap between two surfaces increased, which made the wear caused by contact harder. When normal load or standard deviation of the surface roughness σ is large, wear of textured surface is severe.Finally, the elastic deformation of textured surface with multiple micro-dimples along radical direction was discussed. The wear position of textured surface was predicted through the elastic deformation. Results showed that surface near the inside radius of the friction pair suffered contact wear induced by deformation. When textured radius is large, wear of surface near the inside radius is severe. The experimental results verified the rationality of the theoretical predictions.Through the above research, working principles of surface inclined-micro-dimple under mixed lubrication was presented, which may provide theoretical guidance for controlling wear with surface texture technology in engineering practice.