Tribological Performance of Circular-Concave-and-Spherical-Convex Compound Texture Under Hydrodynamic Lubrication

A novel circular-concave-and-spherical-convex (CCSC) compound texture in which a spherical convex is created in a circular concave was proposed to further improve the tribological performance of the circular concave texture under hydrodynamic lubrication. A numerical model based on the Reynolds equation was established to explore the effect of the spherical convex on tribological performance. The numerical results indicate that the spherical convex can enhance the lubricant suction and generate second hydrodynamic lubrication in the inlet region and bring about divergent wedge in the outlet region, and the two competing mechanisms determine the load-bearing capacity of the compound texture. There exists an optimal spherical convex height that makes the load-bearing capacity maximum at a specified minimum lubricating film height, and the optimal value decreases with the minimum lubricating film height increasing. For the compound texture with the optimal spherical convex height, the load-bearing capacity rises with the spherical convex bottom diameter increasing. Tribological experiments were conducted to examine the numerical results using a pin-on-disc test machine, and the experimental results agree well with the numerical results. The maximum friction reduction for the compound texture is 44% in comparison with smooth surface, whereas it is 21% compared with the optimal circular concave texture under the same conditions.