Correlation between Contact Angle Hysteresis and Hydrodynamic Lubrication

Theoretical studies have proved that different solid-liquid affinity surfaces have significant effects on hydrodynamic lubrication film. In general, contact angle (CA) is used to characterize the wettability of solid-liquid interface. However a theoretical model derived based on thermodynamic principles shows that the potential energy barrier of a surface is not only a function of contact angle, but also of another interfacial parameter, contact angle hysteresis (CAH). By modifying the surface of the slider, different affinity interfaces were obtained. The lubricating film thickness and the continuity of flow velocity were measured by a fixed-inclined slider bearing system using optical interference method and fluorescence method respectively. This study thus evaluated the two, CA and CAH, by conducting thin film hydrodynamic lubrication experiments with surfaces of hydrophilic and hydrophobic. Fundamental relation between the potential energy barrier and CAH was discussed. The results show that the correlation between CA and hydrodynamic lubrication oil film thickness was unsatisfactory. But CAH can better characterize the influence of interface effect on the hydrodynamic lubrication film thickness.