The mechanism of fluid film lubrication in ultra-thin conjunctions under counterformal concentrated circular point contacts is discussed in this paper. The significance of squeeze film action in increased load carrying capacity is highlighted. The numerical predictions made in acceleration-deceleration motion of a ball against a flat race is found to conform with the experimental findings of other research workers for polar branched lubricants down to a film thickness in the region of 20 nm. This conformance with the experimental findings has enabled a fundamental understanding of the multi-physics of film formation when conditions promoting the formation of ultra-thin films of the order of few nanometres have been employed, with the use of a non-polar lubricant. This paper provides the first ever solution of the combined effect of viscous, surface and molecular forces under transient conditions.

This paper investigates the phenomenon of lubricated impact dynamics of ellipsoidal bodies upon semi-infinite elastic solids, giving rise to Hertzian contact conditions. The analysis conforms to the numerical predictions and experimental findings of others, when the physics of motion of the lubricant can be described through Newtonian continuum mechanics, with the dominant viscous action embodied in the transient solution of Reynolds' equation. The equivalence of squeeze film action under impacting conditions with that of a converging gap in pure entraining motion is shown. This concept is extended to study the accelerative nature of the lubricant film surface, and its concordance with Reynolds' assumption through use of a relativistic frame of reference and hyperbolic geometry.When the investigation is extended to the case of ultra-thin film conjunctions of the order of a few to several molecular diameters of the intervening fluid layer, the physics of fluid film motion through impact involves more complex kinetic interactions. These include the effect of structural force of solvation, as well as that of a meniscus force, formed in such narrow conjunctions. The former, through active dispersion, tends to promote a structureless environment, whilst the latter through wetting action encourages the formation of a coherent film. This paper shows the interplay between these competing kinetics.

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This paper aims to show the characteristics of ultra-thin films for non-Newtonian fluid using Ree-Eyring model where intermolecular forces of solvation and Van der Waal's are considered in addition to the hydrodynamic action to fulfill an identified need for such a conjunction. In this case, the film thickness and pressure distribution are obtained by simultaneous solution of the modified Reynolds’ equation incorporating the effect of non-Newtonian fluid, film thickness equation including elastic deformation caused by all contributing pressures and the load balance equation using Newton-Raphson method with Gauss-Seidel iterations. Effect of changing the operating conditions of speed, load, Eyring shear stress and slide-roll ratio on the characteristic of the contact has been studied. The results show that, for the case where the hydrodynamic action is the only pressure acting to support the applied load capacity, the film thickness and the pressure gradient at the exit of the contact obtained using non-Newtonian model is different than that formed using the Newtonian model especially for the increased value of slide-roll ratio. The main results of this study are that for ultra-thin film, the film thickness formed using non-Newtonian model is smaller compared to that obtained using Newtonian case and the discretization of the film thickness as the gap is reduced occurs similar to the results obtained using Newtonian model. The pressure shape shows no difference compared to that formed using the Newtonian case in which an oscillation around the Hertizan contact pressure shape due to the solvation effect appears. The results also show that for ultra-thin film, changing the Eyring shear stress does not affect the film thickness formation.

The paper investigates the mechanisms that contribute to the formation of a lubricant film formed between contiguous bodies in concentrated contacts in conjunctions of order of few nanometers. It has been observed that in such vanishing gaps a lubricant film is formed due to the combined effects of Newtonian slow viscous action and molecular and structural forces in the intervening fluid and with surfaces in contact. The mechanism of solvation is not in accord with classical physics, but is little understood in the structureless environment that ensues beyond the continuum that is usually promoted by viscous action. The paper strives to explain the behaviour of this narrow conjunction, particularly the role of solvation effect under stop-start motion.