Roughness in rolling-sliding EHL contacts

A simplified treatment of roughness effects in rolling-sliding elastohydrodynamic lubricated (EHL) contacts was developed by the author [4]. This analysis predicted that the original amplitude would be attenuated under the conjunction and that a decaying, complementary wave would be generated at the inlet. This complementary wave would be carried through the contact at the entrainment velocity and, for sinusoidal. roughness, its wavelength would be given by lambda u/v, where A is the wavelength of the original roughness, u the entrainment velocity, and v the velocity of the rough surface. This simplified analysis predicted the degree of attenuation of the original roughness and the decay rate of the complementary wave but did not determine the amplitude of the complementary wave. This paper presents a more detailed account of this analytical approach including compressibility effects together with a more accurate allowance for the coupling between the decay of the complementary wave and its wavelength. It also extends the work, using a perturbation analysis, determining accurate values for the pressures and clearance variations produced, under rolling-sliding conjunctions, by low-amplitude roughness. The perturbation results are compared with the predictions of the simplified analysis. It will be shown that the analysis is remarkably accurate. In addition, it appears to be relatively straightforward to determine the magnitude of the complementary wave for any given operating condition. The effect of low-amplitude, sinusoidal roughness on EHL contacts can then be expressed in terms of the operating conditions together with a single value for the amplitude of the complementary wave. This simplification suggests that it may be possible to produce a method for the rapid analysis of roughness effects in rolling-sliding conjunctions without the need for any detailed EHL calculations.