Contact ratio of rough surfaces with multiple asperities in mixed lubrication at high pressures

• Published in: Applied surface science Vol. 258; no. 8; pp. 3888 - 3896
• Main Authors: Xiao, Huaping, Guo, Dan, Liu, Shuhai, Pan, Guoshun, Lu, Xinchun
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.02.2012; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Contact ratio; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; High pressure; Mixed lubrication; Multiple asperities; Physics; Multiple asperities; Contact ratio; Mixed lubrication; High pressure; Pressure effects; Lubrication; Rough surfaces
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2011.12.053

► We realize high experimental pressure up to 3GPa. ► We acquire the profile of contact region between two solid surfaces employing light interference method. ► We investigate the relationship between contact ratio and many impact factors. ► We summarize a formula to calculate contact ratio under different conditions. Relative optical intensity interference was used to measure the lubrication film thickness when four kinds of polyalphaolefin (PAO) were used as lubricants confined between a smooth sapphire disc surface and a rough steel ball surface. Maximum Hertz contact pressure up to 3GPa was applied in the central part of the contact region in mixed lubrication. It was found that the contact ratio (the ratio of real contact region to the whole nominal contact region) is related to the film thickness, the applied pressure, the surface roughness and the rolling speed, and so on. Contact ratio evidently reduces as lubrication film thickness or rolling speed increases. Quantitative relationship between the contact ratio and the influence factors was summarized based on the nonlinear fitting of experimental measurements. A formula was put forward to calculate the contact ratio at high pressure conditions according to the current experimental results.