No abstract

No abstract

In recent years it has been shown experimentally by a number of workers that simple, Newtonian liquids can slip against solid surfaces when the latter are both very smooth and lyophobic. It has also been shown theoretically how, based on a half-wetted bearing principle, this phenomenon may be used to significantly reduce friction in lubricated sliding contacts and thus make possible the hydrodynamic lubrication of very low load contacts. This paper describes the experimental validation of this concept. A low load bearing is constructed and the influence of surface roughness and the wetting properties of the surfaces on friction are investigated over a wide range of sliding speeds. It is shown that liquid slip can be used to considerably reduce friction in full film, hydrodynamic conditions.

The elastohydrodynamic (EHD) lubrication regime occurs in many machine elements where a combination of hydrodynamic effect, elastic deformation of the loaded surfaces and increase in the viscosity of the lubricant with pressure ensures the formation of a very thin, but continuous film of lubricant separating the contacting surfaces. Electrical methods to determine this film's thickness have preceded optical methods, which are widely used today. Although they generally give more qualitative thickness information, electrical methods have the main advantage that they can be applied to metallic contacts in machines, which makes them useful tools in the study of elastohydrodynamically lubricated contacts. This paper is part of a larger study on the application of electrical capacitance for the evaluation of film formation in EHD contacts. The main focus is on the quantitative measurements of film thickness using electrical capacitance. A new approach allowing the lubricant film thickness to be extracted from the measured capacitance is developed using a chromium-coated glass disc and subsequently applied to a steel-on-steel contact. The results show good agreement with optical measurements and theoretical models over a range of film thickness.

No abstract