Point Contact EHL Based on Optically Measured Three-Dimensional Rough Surfaces

Abstract

This paper presents a numerical solution for the elastohydrodynamic lubrication in point contacts, using optically measured three-dimensional rough surface profiles as input data. The multi-grid computer program originally developed by Ai and Cheng (1993, 1994) is modified, so that both contacting surfaces can be three-dimensional measured rough surfaces moving at different velocities. Many different engineering surfaces are measured and analyzed in the present study, demonstrating that the numerical analysis is practical for real surfaces of bearings, cams, gears and other components, as long as a significant EHL film still exists. In addition, discussions are given in this paper for the effects of three-dimensional rough surface topography, which is related to machining process. It appears that, for the circular contact cases analyzed, surface roughness texture and orientation do not have a significant effect on the average film thickness, but they do affect the maximum pressure peak height and asperity deformation in the contact zone considerably.

Mixed lubrication analysis of modified cycloidal gear used in the RV reducer

“…For more details about how the surface roughness of honed gears is incorporated in the EHL model, please refer to Zhu and Ai, 28 Zhu et al, 29 etc. The initial estimate of elastic deformation is obtained with the original distributed pressure.…”

Solution agreement between dry contacts and lubrication system at ultra-low speed

“…The amplitude, A, is 0.4 µm for the transversal and longitudinal waves, but 0.2 µm for the isotropic one, while the wavelengths ω x and ω y in the following expressions are all 0.5a. The operating conditions used are summarized in Table 3 δ(x, y) A cos(2πx/ω x ) (12) δ(x, y) A cos(2πy/ω y )…”

“…Many full numerical solutions to line and point contact elastohydrodynamic lubrication (EHL) problems have been developed in the past, which include those by Dowson and Higginson [1], Ranger et al [2], Hamrock and Dowson [3], Oh and Rohde [4], Evans and Snidle [5], Okamura [6], Zhu and Wen [7], Lubrecht [8], Venner [9], Ai [10], Xu and Sadeghi [11], Zhu and Ai [12], and others. Great efforts have been made to significantly improve the solution convergence speed and accuracy.…”

Some aspects of gear tribology

“…Chang and Zhao [13] continued to study the differences between Newtonian and non-Newtonian lubricant models in transient micro-EHL and showed that the non-Newtonian effect was significant, particularly with roughness of relatively short wavelength. A study of micro-EHL under point contact conditions using measured roughness was carried out by Xu and Sadeghi [14] and Zhu and Ai [15]. In these studies, however, the amplitude of the roughness was relatively small compared to the thickness of the films generated.…”