Roughness attenuation and pressure rippling in EHL contacts

Surface roughness tends to reduce the life of EHL contacts and from the early work of Tallian onwards it has been recognized that the mechanism is via the production of pressure fluctuations in the conjunction. Long wavelength components of the roughness are flattened as they pass through the contact, shorter components are largely unmodified. The transition occurs, approximately, where the roughness wavelength is equal to the length of the inlet pressure sweep and it is possible to produce a single master curve relating the attenuation of the roughness to this ratio. This paper examines pressure rippling in EHL contacts and shows that the maximum amplitude occurs at the transition from short to long wavelength behaviour and that, for both short and long wavelengths, the amplitude tends to zero.