Frictional behaviour of engineering surfaces in overall lubrication regimes of point contacts

Abstract

The aim of the present paper is to study experimentally and numerically the frictional behaviour of engineering surfaces within all lubrication regions of point contacts. For this reason, a numerical solution proposed elsewhere by the current authors, which can predict friction under the different lubrication modes of elastohydrodynamic, mixed, and boundary lubrications, is introduced. Based on a deterministic model of mixed lubrication, the solution was combined with the variation of the lubricating films' physical state during the transition of lubrication modes. Results show that roughness amplitude has a great effect on the transition of friction regimes. In addition, it is also observed that variation of the friction coefficient has nearly the same trend as the true contact area ratio in the mixed lubrication state. Meanwhile, it is concluded that transverse roughness has better film-forming capacity than longitudinal roughness and thus leads to a lower magnitude of friction coefficient if the operating conditions are the same. Analysis of the mechanism of friction behaviour suggests that the true contact area ratio determines the friction behaviour of engineering surfaces in mixed lubrication. In smooth contacts, the comparison of experiment tests and simulation results suggests that friction variation results from gradual change of the liquid lubricant to solid-like matter with diminishing film thickness.

Assessment of the Morphology, Microstructure, Stereometric and Tribological Properties of Al₂O₃ Surface Layers Produced Electrolytically with the Alternating Current Method in the Presence of Molybdenum Disulfide

“…15 d, the AMo1_5 layer was characterized by a small amount of PEEK/ BG sliding film, the lowest coefficient of friction µ = 0.136 ± 0.002 (Figs. 8 b and 9 a) and the lowest PEEK/BG wear value of 0.0009 g. Our observations are consistent with the statement that friction variability results from the gradual change of liquid lubricant into the solid matter with decreasing film thickness [24,25]. The highest S k parameter also characterizes this layer after friction test equal to 0.993 mm.…”

“…An important part of the experimental research related to the industrial application is the measurement and evaluation of the geometric structure of the surface of machine elements and tools [19][20][21][22]23]. The authors [24,25] showed a new strategy for predicting friction and possible applications in engineering. When examining carbon alloys and carbon titanium alloys, it was found that the initial surface roughness has a significant impact on friction, wear process and wear activation energy [26].…”

Comparison of tribological behaviors of one-process and two-process steel surfaces in ball-on-disc tests

“…However, in works 9,10 wear of specimens was not considered. The results obtained by Wang et al 11,12 using ball-on-disc contact showed that roughness amplitude had a great effect on the transition on friction regimes.…”

The Influence of Disc Surface Topography after Vapor Blasting on Wear of Sliding Pairs under Dry Sliding Conditions

“…The results obtained by the authors of papers [7,8] showed that the roughness amplitude had a significant impact on the transition between various friction regimes. The results of the ball-on-disc studies presented in papers [9,10] indicate the existence of a correlation between surface topography parameters (in particular Rsk and Rku) and the friction force.…”