A review of starved EHL point contacts

This paper reviews some of the effects of inlet supply starvation on the film thickness in EHL point contacts. The insufficient supply of lubricant results in much lower film thicknesses, compared to the fully flooded situation. However, it is not this lack of thickness which is most important, but the lack of mobility associated with these thin layers that results in a behaviour dramatically different from the fully flooded contact. First an outline of the basic mechanisms of starved lubrication is presented. The problem is presented from two angles: what would the film thickness be if an oil lag;er of x mu m were present on the surface, and secondly: how much oil on the surface is required to obtain a central film thickness of y I-Lm Next the evolution of a starved film thickness with the number of overrollings is analysed, and finally two examples are discussed which highlight the reduced sideways mobility of these thin lubricant films. The first one shows the way the oil film thickness can vary significantly inside a single starved contact and the second one studies the evolution of local lubricant defects. This last analysis is closely linked to a specific type of surface damage encountered in grease lubricated bearings.