Investigation of the Effect of Milli-Scale Dimples on Planar Contact Lubrication

It has been proven that surface texturing significantly improves load capacity, wear resistance, friction coefficient, etc. The understanding of the mechanisms involved in the tribology of textured surfaces is mainly derived from hydrodynamic lubrication. In hydrodynamic lubrication, the load is supported by a fluid film. Therefore, the friction force is also dominated by the lubrication induced by the fluid film. Dimpled surface is a typical artificial textured surface. When bubbles exist in the dimples between the pair of surfaces, they also support the load because of the surface tension between the gas in the bubbles and the lubricant. Consequently, the drag will be greatly reduced because the viscosity of the gas can be neglected compared with the lubricant. In this article, the effects of dimple depth, surface roughness, and dimple shape and distribution on the gas existence and drag are investigated. Calculation results from Navier-Stokes equations are given to explain the experiment results.