Elastohydrodynamic Film Collapse During Rapid Deceleration. Part I—Experimental Results

Abstract

This paper describes a study of the behavior of elastohydrodynamic lubricated contacts subjected to rapid halting. Experiments have been carried out using ultrathin interferometry coupled to a high-speed camera to measure the change in lubricant film thickness and shape during fast, controlled deceleration, both in pure sliding and pure rolling conditions. Film collapse is seen to occur in two stages. The first persists throughout the deceleration period and, during this stage the film geometry remains almost constant across the contact. In this stage of film collapse, the film thickness lags behind the value predicted from steady-state theory, which means that when motion ceases, a thicker than expected film is present. The second stage of film collapse ensues when the entrainment speed falls below a critical value of approximately 0.002 m/s and is characterized by the formation of a central entrapment and classical, normal approach, squeeze behavior.