Identifying the optimal interfacial parameter correlated with hydrodynamic lubrication

The effects of boundary (liquid/solid) slip on hydrodynamics are well recognized. However, it is extremely difficult to quantify in-situ boundary slip in a lubrication contact. Therefore, an effective interfacial parameter that is well correlated with the lubrication effect is of practical significance. This paper presents an examination of common interfacial parameters, including surface tension, contact angle, contact angle hysteresis, and a recently proposed spreading parameter. Specimen surfaces of different hydro/oleophobicity were prepared and characterized using the aforementioned interfacial parameters. These samples were further used as bearing surfaces in hydrodynamic lubrication tests. The correlations of these parameters with the measured lubricating film thickness were examined and compared. The key parameter closely related to the hydrodynamic effect was identified.