Study On The Effect Of Discrete Lubricant Supply On Slider-on-Disc Contact Film Thickness Under Limited Lubricant Supply Based On Surface Modification

With the increasing pressure on carbon emissions,energy saving and environmental protection have become a world-renowned theme.In order to ensure the safe operation of mechanical equipment,traditional lubrication methods usually use excessive lubricants.However,this sufficient oil supply lubrication method will cause increased friction power consumption and waste of resources.It can be seen that the traditional lubrication method has been unable to meet the requirements of energy saving and environmental protection in today’s society.It is extremely necessary to study a small and efficient oil supply method.Limited lubricant supply(LLS)can achieve the purpose of precise lubrication and ideal lubrication by using a very small amount of lubricating oil,which has gradually become a hot topic in tribology research.Therefore,in this paper,the distribution of lubricant on the surface of friction pair is regulated by surface modification to improve the lubriacnt supply on the surface of friction pair,so as to realize the enhancement of conformal contact lubrication under limited lubricant supply.The wettability of the solid surface is regulated by the in-situ adsorption of stearic acid additives and surface coating,and theses effects on slider-on-disk contact lubricating oil film was studied experimentally by using the slider-on-disc contact lubricating oil film measurement system under limited lubricant supply.At the same time,two different oil supply models are established according to the experimental results and numerical analysis is carried out to explore the influence of the two oil supply models of the bilateral ridge oil supply model and the discrete state oil supply model on the lubrication performance of the conformal contact.Firstly,the effect of stearic acid adsorption on the establishment of conformal contact lubricating oil film under limited lubricant supply was studied.When different mass fractions of stearic acid were added to the PAO10 lubricanting oil,the adsorption of stearic acid on the surface of the glass disk caused "dewetting" of the lubricant on the lubricating track,and the lubricating oil changed from the classical bilateral ridge distribution to a discrete strip or droplet distribution.With the increase of stearic acid content in lubricating oil,the dispersion of lubricating oil on the lubrication track is more obvious.The distribution width of lubricating oil on the lubrication track is less than the width of the slider.The height of discrete lubricant liquid strip/drop is greater than the thickness of the uniformly spread lubricating oil layer,which can be carried earlier at the entrance of the slider and promote the establishment of the lubricating oil film.At the same time,under the effect of "dewetting" induced by stearic acid adsorption,the lubricanting oil accumulates at the slider inlet and the surface tension of the liquid has a certain degree of influence on the establishment of the lubricanting oil film,and the film thickness of low oil supply is greater than that of high oil supply.Secondly,the effect of wettability gradient on the conformal contact lubricanting oil film was investigated when the surface of glass disc and the side of slider was coated with oleophobic AF anti-fingerprint oil.Under limited lubricant supply,when the sliding speed is low,with the rotation of the AF glass disc,the lubricating oil can adhere to the surrounding of the slider to participate in lubrication under the action of wettability gradient.With the increase of sliding speed,under the action of capillary force,the lubricating oil crawls on the side of the slider inlet and is fixed on the side of the slider inlet.It cannot enter the contact area to participate in lubrication,which reduces the utilization efficiency of the lubricating oil.The oleophobic AF coating on the side of the slider can effectively inhibit the creep of the lubricating oil during the conformal contact lubrication process and significantly improve the lubrication performance.At the same time,the Laplace additional pressure formed by the accumulation of lubricating oil in the inlet area of the slider can further improve the bearing capacity of the slider bearing.Finally,according to the above test results,the bilateral ridge oil supply model and the discrete oil supply model are established and numerically analyzed.Under limited lubricant supply,the influence of different working conditions(sliding speed,oil layer distribution,number of liquid strips,oil supply volume)on the film thickness,pressure and starved oil state of the slider-on-disk contact area was studied,and the lubrication characteristics under two oil supply models were compared.The results of theoretical calculation are consistent with the experimental results.