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Communication Dans Un Congrès Année : 2013

A Proper Pathway Towards A Quantitative Physics-Based Elastohydrodynamic Lubrication

Résumé

An efficient lubrication of machine elements like rolling element bearings or gears is essential everywhere, in our personal everyday life activity as well as in manufactures, transportation systems, energy plants ... New demands emerged from the society related to energetic issues, saving natural resources, environmental considerations and from the worldwide economic competition. Combined with the continuous evolution of technologies, the room for safety in the operation of highly loaded lubricated mechanisms has drastically been reduced. As an illustration, at the earlier stage of elastohydrodynamic lubrication (EHL), the typical film thicknesses reported were of the order of one micrometer or a little less: nowadays they can be as low as some nanometers. This made the EHD contacts operation much more sensitive to many influencing factors, like surface roughness, additives, contaminants, or to changes due to thermal effects, shear-thinning behavior of the lubricant, inlet starvation, etc. In this context, predicting film thickness or friction within very good confidence became much more relevant and important. However, in spite of the progress achieved in the field of modelling and simulation, and in the improvement of the experimental techniques, it must be stated that EHL has not been a quantitative, physics-based science. The literature clearly shows that properties of liquids have been used to validate assumptions without regard to sound theory or measurement, among them the pressure dependence of viscosity. Thermal effects and non-Newtonian response are often interchanged. We are unable to name the properties necessary for friction calculation and finally, who cares about density that has a direct influence on films thickness? In this presentation a methodology is proposed to succeed in this challenge. It breaks with the practices of the field and is based on three fundamental ideas, in line with a first initiative [1]: - Consider the actual properties of the lubricant, obtained through independent characterizations carried out over representative conditions, alternatively find them in the thermo-physics and rheology literature, - Take into account the multi-physics aspects of the EHL problem by using physics-based models to describe the lubricant behavior, - Validate the numerical models experimentally with representative operating conditions. In other words, this is an attempt for showing how one can achieve a quantitative prediction of EHL parameters based on the actual rheological behavior of the lubricant. For this purpose it is absolutely necessary - more than ever - to conduct both analytical experiments and multi physics simulations.

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Dates et versions

hal-00863104 , version 1 (18-09-2013)

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  • HAL Id : hal-00863104 , version 1

Citer

Philippe Vergne. A Proper Pathway Towards A Quantitative Physics-Based Elastohydrodynamic Lubrication. 3rd International Tribology Symposium of IFToMM, Mar 2013, Luela, Sweden. ⟨hal-00863104⟩
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