Experimental Study On The EHL Oil Film In Point Contacts Under Oil Starvation

This thesis studies the variation of the EHL oil film under oil starvation.The work is divided into three parts: experimental study on the dimple variation in starved EHL for simple sliding condition,the effect of starvation on surface dimple under opposite sliding condition and the performance of greasefilm thicknessunder reciprocation motion.In the present thesis,a ball-on-disk testing rigwas used to capture optical interference images and the experimental images were processed with a multi-beam intensity-based(MBI)lubricating film measuring technique to reconstruct the film shape.The oil supplied conditions in the experiments were divided from fully supply,middle starvation to heavy starvation,to investigate theEHL films under different starvationdegrees.Thesteel ball and the glass disk/sapphire disk weredriven by two servo motors which were controlled by PLC program.In the study of starved oil dimple under simple sliding condition,the oil dimple variation from fully supplied to severe starvation was revealed.The effect of viscosity on starved oil dimple was considered,and the comparisons of experimental results between lubricant PB680 and lubricant PB950 were given.The influence of sliding velocity,the applied load on the depth,the positionand the number of dimple were analyzed.It should be noted that the severity of the oil starvation played a role like the reduction of the velocity.The study of starved oil dimple under simple sliding and steel-glass contact conditionswas extended into opposite sliding in steel-sapphire contactsubsequently.The film thickness and shape of starved EHL under different entrainment velocity,loads and slide-to-roll ratios wereanalyzed.Under opposite sliding condition,the effects of the bilateral oil starvation,left oil starvation and right oil starvation on the variation of oil film were investigated.It was also found that oil starvation can generate a starved constriction.At last,the lubricating property of greasewas investigated when the glass did reciprocating motion and the ball stationary.The glass disk moved in triangular wave and rectangular wave,respectively.The influences of glass disk sliding velocity,stroke and cycle number on film thickness was analyzed,and the results showed thatno matter what kind of movement form,the center film thickness fell to a constant value after long periods of movement.