In this paper a computational fluid dynamics (CFD) approach for solving elastohydrodynamic lubrication using the freely available package OPENFOAM is introduced. The full Navier–Stokes equations are solved, which enables the entire flow domain to be modeled and all gradients inside the lubricated contact to be resolved. The phenomenon of cavitation is taken into account by employing a homogenous equilibrium cavitation model, which maintains a specified cavitation pressure inside the cavitating region. The energy equation used considers the effects of heat conduction and convection, viscous heating, and the heat of evaporation. The developed method has been applied to a series of cases of lubricated metal-on-metal line contact with an entrainment velocity of uent=2.5m∕s, viscosities η0=[0.01,1]Pas, and slide-to-roll ratios SRR=[0,1,2] under both thermal and isothermal conditions. The isothermal results are compared to the Reynolds theory and most results agree very well. Only the high-viscosity pure rolling case shows small differences. The combined effects of temperature, pressure, and shear-thinning are studied for the thermal cases. A temperature-induced shear band occurs in the case of sliding combined with very large viscosity compared to the isothermal case, which results in significant pressure variations across the thickness of the film. The impact of temperature on the friction force is discussed, showing differences of up to −88.5% compared to the isothermal case. The developed method is capable of giving new insights into the physics of elastohydrodynamic lubrication, especially in cases where the usual assumptions of the Reynolds theory break down.

Tests have been performed on a two-disk machine in order to evaluate the role of inclusions, surface roughness and operating conditions on rolling contact fatigue of AISI 52100 and M50 bearing steels. Important parameters-such as nature and location of inclusions, small and large wavelengths of surface roughness, normal loading or sliding conditions-on crack initiation and propagation stages have been identified. The operating conditions have been selected to encompass typical jet engine applications. Tests have been carried out up to 4.2 GPa, for two different surface finishes. Surface distress and sub-surface damage which could result in catastrophic failure have been observed. Indeed, surface initiated deep spalling (observed at 3.5 GPa for unpolished surfaces and under rolling plus sliding conditions) as well as sub-surface initiated deep spalling (at 4.2 GPa for polished specimens) have been observed. Sub-surface micro-cracks were detected early and followed during some interrupted tests by the means of an ultrasonic echographic device. Results of our experiments are analyzed and discussed in relation to the rolling contact fatigue theories.

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Computation of the EHL film thickness of micro-pitted surfaces for starved elastohydrodynamic conjunctions has been performed. Transient calculations have shown that pits filled with lubricant release part of their content in the inlet zone as they enter the EHL contact. Initially, a fraction of this released oil remains in the inlet region and produces an upstream shift of the meniscus. The remainder of the oil is entrained and builds up the film thickness at the trailing edge of the pit. With time, the fraction of oil in the inlet also becomes entrained and the meniscus slowly returns to its equilibrium position. The time interval during which the film thickness is enhanced thus becomes prolonged and may persist even after the pit has left the contact. Computations carried out with several pits have shown that this process is not disturbed. The beneficial increase of film thickness is lost if the contact becomes fully flooded. Experimentally, the advantage of making small recesses in bearing surfaces has been shown before. This paper now reveals the lubrication mechanisms involved, allowing improvements in the design of surface features in EHL contacts.