A new mechanism of hydrodynamic lubrication termed “inlet suction,” applicable to low convergence, micropocketed bearings, has been identified. In this, sliding of one of the bearing surfaces generates a subambient pressure in pockets close to the bearing inlet. Because this pressure is less than the external atmospheric pressure, lubricant is “sucked” into the bearing through the inlet land. This is quite a different mechanism from classical entrainment due to shear. In the current paper flow, hydrodynamic load support and friction are calculated using analytical solutions for simple pocketed bearings having a wide range of convergence ratios, including parallel surfaces. It is found that for the parallel case, inlet suction provides the only mechanism of hydrodynamic load support, and that inlet suction continues to play a major role in load support and friction reduction up to quite high convergence ratios. This mechanism of lubrication is believed to be responsible for the enhanced lubricant film formation and reduced friction of textured bearings, previously reported by a number of authors.

A new mass-conserving formulation of the Reynolds equation is developed using the concept of complementarity. This new method overcomes the drawbacks previously associated with the use of such complementarity formulations for the solution of cavitation problems in which reformation of the liquid film occurs. Validation against a number of analytical and semi-analytical formulations, for a variety of problems including textured bearings and squeeze film dampers, is performed. The current formulation is shown to be in very good agreement with existing analytical and numerical mass-conserving solutions

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It is shown that a simple parallel pad bearing containing a closed pocket can support load if it operates in an ambient pressure that is appreciably in excess of the cavitation pressure of the lubricating fluid. This arises due to fluid flow driven by subambient pressures in the inlet region of the pad (‘inlet suction’). Maximum load capacity occurs when the pocket is located near the inlet to the bearing and under conditions such that cavitation is just provoked.

An optical interferometric technique has been used to investigate fluid film thickness in sliding, isoviscous elastohydrodynamic contacts (I-EHL). Monochromatic 'twobeam' interferometry has been employed to map lubricant film thickness across a range of applied loads and entrainment speeds. The contact was formed between an elastomer sphere and plain glass disc, illuminated under red light, λ = 630 nm.Experimental work has employed sunflower oil and glycerol/water solutions as the test lubricants, due to their similar refractive indices and varying viscosity. A black and white image intensified camera has been employed to capture interference images and a computer processing technique used to analyse these images, pixel by pixel, and create film thickness maps based on their grey scale intensity representations.Comparison of film thickness results to theoretical models show reasonable qualitative agreement. Experimental results show both a reduced horseshoe, which is limited to the rear of the contact, and 'wedge' shaped film thickness profile within the Hertzian contact region. This is unlike conventional 'hard' EHL contacts where the horseshoe shaped pressure constriction extends around the contact towards the inlet.Experimental results suggest film thickness profiles take on a 'convergent wedge' shape similar to that used in many hydrodynamic bearings. It is likely that this 'wedge' is largely responsible for generating fluid pressure and therefore the loadcarrying capacity of the contact.

The onset of smearing damage was studied under controlled conditions in a custom test rig that simulates the passage of a rolling element through loaded and unloaded zones of a rolling bearing. The set-up comprises a spherical roller which is intermittently loaded between two bearing raceways driven at a prescribed speed. The roller is free to accelerate during the loading phase. Contact load, roller speed and acceleration and electrical contact resistance are recorded during the test. Contact shear stress, friction coefficient, frictional power intensity and elastohydrodynamic film thickness are calculated from the recorded kinematics data. Results suggest that the first onset of smearing occurs early in the loading phase where the roller is nearstationary and the frictional power intensity is high. The raceway speed at the onset of damage decreases with increasing load and increasing lubricant supply temperature. The maximum frictional power intensity is found to be relatively constant at all contact conditions that led to 2 smearing. An existing thermo-mechanical contact model is used to estimate the contact temperature distribution under smearing conditions and the potential for EHL film thickness reduction due to forward heat conduction.

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