Experimental study of elastohydrodynamic lubrication films under cyclic intermittent entrainment

Elastohydrodynamic lubrication(EHL) films were measured by interferometry under conditions of cyclic intermittent lubricant entrainment,and three types of local film dimples were indentified.The first dimple is generated from intermittent stops of the bounding surfaces,and the pure rolling produces larger oil entrapment than pure sliding.The second film dimple is generated by the velocity oscillation in the start-up process,and the resultant crescent-shaped dimple moves through the Hertzian contact region at the entrainment speed.When pure disc sliding is employed,the boundary slippage may lead to the third dimple,which is near the inlet region and related to the speeds and the time interval between two stops.The observed phenomena can be explained by the squeeze effect,the entrainment effect and the wall slippage.