Analysis of Humidity Effects on Early Stage of Sliding

The influences caused by difference in relative humidity (RH) on the early stage of dry sliding were studied using a horizontal ball-on-disc tribotester equipped with air-humidity controller. The ball displacement perpendicular to sliding surface and friction force during the initial stage resulted in different consequences with different percentage of RH. The middle rate of RH 49% showed a contradictory behavior with the common sense known that friction force of sliding decreases with increment of RH. Friction force of sliding can be dominated by water meniscus and water viscosity as well as local solid-solid contact in atmosphere at certain rate of RH.