The Effect of Working Parameters upon Oil-Lubricated EHD Contacts Subjected to Load Variation

Abstract

The technique of optical interferometry incorporated within a ball-on-disc apparatus has been widely used in the field of the experimental research in thin-film lubrication for approximately the past five decades. This paper presents the theoretical analysis of the dynamic response of an optical interferometry based experimental rig adapted for non-steady work. The dynamic response of the rig was analytically modelled as a three-degree of freedom, forced harmonic vibrating system with damping. Quantitative evaluation of damping of EHD contact was not one of the objectives of this paper, but the results obtained showed the opportunity to try a rather qualitative analysis. The aims of this experimental study are to investigate the effect of entrainment speed and overall film thickness on the oil film thickness of an EHD contact subjected to load cyclic variation. Experimental tests were carried out using different type of base oils with various viscosity. The behaviour of the EHD films was studied and analysed under forced harmonic load vibrations with frequency up to 100 Hz. The tests performed with lubricants of lower viscosity have shown that deviations from steady state film thickness become less and less pronounced as the viscosity of the lubricant decreases. When the amplitude of the oscillatory motion is significantly larger than the deformations of the surfaces under loading, it was observed that fluid entrainment is less important and film squeeze plays the dominant role in the film behaviour.