The Effect of Stearic Acid Adsorption on Lubricating Oil Film in Slider-on-disc Contact under Limited Lubricant Supply

doi:10.3901/JME.2023.21.321

Abstract

Abstract: Under conditions of limited oil supply, the effect of stearic acid oiliness additive is studied on the relationship between oil film thickness of PAO10 (polyα-olefin) and inclination angle of the slider with an optical test rig for measuring the film lubrication in the slider-on-disc contact. The influence of lubricating oil accumulation at slider inlet on the bearing capacity of lubricating oil film was analyzed theoretically, and the adsorption of stearic acid on solid surface is characterized. The results show that the film thickness presented an overall decrease with the increase of the inclination angle of the slider. The "dewetting" effect induced by the adsorption of stearic acid changes the lubricant distribution in term of the classical bi-side-ridge to discrete strip/droplet on the lubricating track, which improves the oil supply at the inlet of the contact and increases the thickness of the oil film. Particularly, the experiment found that the lower oil supply at low sliding speed actually induces abnormal higher oil film thickness. The adsorption of stearic acid makes non-wetting droplet-like oil accumulation in the inlet area, and the additional Laplace pressure formed increases the bearing capacity of the oil film; when the oil supply quantity is lower, the radius of curvature of the inlet lubricant accumulation is smaller, and the additional pressure is higher and so the film thickness increases.

Key words: stearic acid, limited lubricant supply, inclination, film thickness, slider-on-disc contact

CLC Number:

TH117

JIAN Yusheng, JING Zhaogang, GUO Feng, WONG Pat Lam, HAN Suli, LI Xinming. The Effect of Stearic Acid Adsorption on Lubricating Oil Film in Slider-on-disc Contact under Limited Lubricant Supply[J]. Journal of Mechanical Engineering, 2023, 59(21): 321-329.

References

[1] 温诗铸, 黄平,田煜,等. 摩擦学原理[M]. 北京:清华大学出版社, 2018. WEN Shizhu, HUANG Ping, TIAN Yu, et al. Principles of tribology[M]. Beijing:Tsinghua University Press, 2018.
[2] LI X M, GUO F, WONG P L, et al. Regulation of lubricant supply by wettability gradient in rolling EHL contacts[J]. Tribology International, 2018, 120:565-574.
[3] GE L, WANG C, YAN K, et al. Design of groove structures for bearing lubrication enhancement based on the flow mechanism analysis[J]. Tribology International, 2021, 158(2):106950.
[4] MOON J H, LEE H D, KIM S I. Lubrication characteristics analysis of an air-oil lubrication system using an experimental design method[J]. International Journal of Precision Engineering and Manufacturing, 2013, 14(2):289-297.
[5] XU M, JIN G, DAI Q, et al. Ferrofluid lubrication for ball bearings to avoid starvation[J]. Industrial Lubrication ang Tribology, 2020, 72(10):1227-1232.
[6] SPIKES H. Friction modifier additives[J]. Tribology Letters, 2015, 60(1):1-26.
[7] REDDYHOFF T, KU I, HOLMES A S, et al. Friction modifier behavior in lubricated MEMS devices[J]. Tribology Letters, 2011, 41(1):239-246.
[8] SIMIC R, KALIN M. Adsorption mechanisms for fatty acids on DLC and steel studied by AFM and tribological experiments[J]. Applied Surface Science, 2013, 283(15):460-470.
[9] FRY B M, CHUI M Y, MOODY G, et al. Interactions between organic friction modifier additives[J]. Tribology International, 2020, 151(1):106438.
[10] 韩露娟. 硬脂酸吸附对限量供油面接触油膜润滑影响的实验研究[D]. 青岛:青岛理工大学, 2021. HAN Lujuan. Experimental study on the influence of stearic acid adsorption on lubrication in conformal contact under limited lubricant supply[D]. Qingdao:Qingdao University of Technology, 2021.
[11] GUO F, WONG P L, FU Z, et al. Interferometry measurement of lubricating films in slider-on-disc contacts[J]. Tribology Letters, 2010, 39(1):71-79.
[12] 马冲,郭峰,付忠学,等. 微型滑块面接触润滑油膜测量系统[J]. 摩擦学学报, 2010, 30(4):419-424. MA Chong, GUO Feng, FU Zhongxue, et al. Measurement of lubricating oil film thickness in conformal contacts[J]. Tribology, 2010, 30(4):419-424.
[13] 韩素立,郭峰,邵晶,等. 基于荧光漂白成像的润滑油膜剪切流速测量[J]. 摩擦学学报, 2017, 37(4):442-448. HAN Suli, GUO Feng, SHAO Jing, et al. Velocity profile measurements of oil film under pure shear based on fluorescence photobleaching imaging method[J]. Tribology, 2017, 37(4):442-448.
[14] 王茜. 面接触副表面润湿性对液体膜润滑影响的实验研究[D]. 青岛:青岛理工大学, 2018. WANG Qian. Experimental study of the wettability of conformal contact surfaces on liquid film lubrication[D]. Qingdao:Qingdao University of Technology, 2018.
[15] 胡福增. 材料表面与界面[M]. 上海:华东理工大学出版社, 2007. HU Fuzeng. Material surface and interface[M]. Shanghai:East China University of Science and Technology Press, 2007.
[16] 杨沛然. 流体润滑数值分析[M]. 北京:国防工业出版社, 1998. YANG Peiran. Numerical analysis of fluid lubrication[M]. Beijing:National Defense Industry Press, 1998.
[17] KALIN M, KUS M. New strategy for reducing the EHL friction in steel contacts using additive-formed oleophobic boundary films[J]. Friction, 2021, 9(6):1346-1360.