Experimental Study On Elastohydrodynamic Lubrication Behavior By Lubricant Supply Regulation

It is generally recognized that high-speed bearings will operate for much of the time in the starved regime of elastohydrodynamic lubrication(EHL).Thus,the supply of lubricant becomes important in determining bearing operation.Great efforts were taken in an attempt to ensure adequate lubricant supply for bearings,but the rolling elements running so fast that the lubricant does not have enough time to flow back to the rolling track,resulting in starvation.Moreover,most of previous studies were focused on the occurrence of starvation and the film reduction.It seems there are only few studies on lubricant supply regulation and starvation suppression.Therefore,it is necessary to explore regulation strategies of lubricant reflow.This thesis studied two approaches for lubricant supply regulation and their positive effects to EHL film building: 1)a novel cage design to improve the lubricant flow and its replenishment;2)enhancement of lubricant supply by adsorption of oiliness additive on the solid under limited lubricant supply.The main work includes:(1)Build-up of an optical multi-point-contact EHL test rig.The purpose of this apparatus is to observe the influence of cage structure and number of rolling elements on the lubricant flow and film formation.In this apparatus,one bearing race of a thrust bearing was replaced by a glass disc,thus the film evolutions in rolling element-disc contacts can be measured using multi-beam interference technique.(2)Test of lubrication behavior by the optical multi-point-contact test rig.To validate the reliability of the test rig,the transition trends of the lubrication state were observed under different running conditions.The film formations of a full bearing were further analyzed.(3)Effects of cage structure on lubricant supply and EHL films.The main purpose is to develop a regulation approach of lubricant supply through different cage structures.The variations of film evolutions with cage structures were observed.To clarify the role of the cage structure,the film thickness had been measured at different speeds,viscosities,loads,number of rolling elements and oil amount.Then thus the relationship between lubricant flow and cage structure was established.(4)Oiliness additive on thin EHL films under limited lubricant supply.The main purpose is to explore the effects of oiliness additive on surface modification and improvement of limited lubricant supply.The adsorption behavior of stearic acid was evaluated employing different apparatus.The film formations with lubricant amount,time speed and load were analyzed.