A Film Thickness Correction Formula for Double-Newtonian Shear-Thinning in Rolling EHL Circular Contacts

Habchi, Wassim; Bair, Scott; Qureshi, Farrukh; Covitch, Michael J.

doi:10.1007/s11249-012-0078-6

Cited by 41 publications

(18 citation statements)

References 25 publications

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“…So long as inlet shear thinning does not occur, the composite piezoviscous response over the inlet region can be measured using high pressure rheometry [3] or estimated directly from measurements of EHD film thickness [4] [5] and applied in regression-based film thickness equations [6]. For polymer solutions and some very high molecular weight base fluids, where inlet shear thinning does occur, its effect can also be taken into account [7] [8]. Unfortunately our understanding of EHD friction is much less complete.…”

Section: Introductionmentioning

confidence: 99%

History, Origins and Prediction of Elastohydrodynamic Friction

2014

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There is currently considerable debate concerning the most appropriate rheological model to describe the behaviour of lubricant films in rolling-sliding, elastohydrodynamic contacts. This is an important issue since an accurate model is required in to predict friction in such contacts. This paper reviews the origins of this debate, which primarily concerns a divergence of views between researchers using high pressure, high shear rate viscometry and those concerned with the measurement and analysis of elastohydrodynamic friction; the former advocate a Carreau-based shear stress/strain rate model while the latter generally favour an Eyring-based one. The crucial importance of accounting for shear heating effects in analysing both viscometric and friction data is discussed. The main criticisms levied by advocates of a Carreau-based model against Eyring's model are discussed in some detail. Finally the ability of both types of rheological model to fit elastohydrodynamic friction measurements for a quite simple, well-defined base fluid is tested, using previously-measured pressure-viscosity behaviour for the fluid. Both models appear to fit the experimental data over a wide temperature range quite well, though fit of the Eyring model appears slightly closer than that of the Carreau-Yasuda model. Friction data from a wider range of welldefined fluid types is needed to identify categorically the most appropriate model to describe elastohydrodynamic friction.

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Section: Introductionmentioning

confidence: 99%

History, Origins and Prediction of Elastohydrodynamic Friction

2014

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“…The recent rapid advance in understanding over the last 7 years has been the result of this new approach. [2][3][4][5][6][7][8][9][10][11][12] An essential part of quantitative elastohydrodynamics is the identification, characterisation and use of reference liquids, 13 both for calibrating high pressure instruments and for exploring contact response to liquids with known properties. Most support for the effort to define reference liquids has come from researchers with interests other than tribology.…”

Section: Introductionmentioning

confidence: 99%

The temperature and pressure dependence of viscosity and volume for two reference liquids

Bair

2015

Lubr. Sci.

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The new quantitative elastohydrodynamics has resulted in rapid advances in understanding concentrated contact lubrication behaviour by employing real transport properties. A key component of this revolution has been the use of reference liquids. In this paper, two liquids, a triester and a perfluoropolyether, which are under consideration as possible viscosity standards are characterised to 1 GPa for conditions relevant to tribology. Two correlations are provided for interpolation and data smoothing, and an explanation for difficulties encountered with free volume theory is offered. The perfluoropolyether is only appropriate as a reference liquid when an identical lot is available. Copyright © 2015 John Wiley & Sons, Ltd.

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“…(22) (25) Thus the film thickness increases quite strongly with entrainment speed and viscosity and less strongly with radius and pressure viscosity coefficient. It is only weakly dependent on applied load.…”

Section: Ehd Film Thickness Calculationmentioning

confidence: 99%

“…In this case, shear thinning in the inlet results in a thinner EHD film thickness than predicted from low shear rate viscosity of the formulated oil. Some inlet shear thinning can also occur with base fluids that are based on relatively . Bair has recently proposed an EHD film thickness correction for such lubricants, based on knowledge of how their viscosity varies with shear rate, their flow curves [25]. However this requires knowledge of the flow curves at elevated pressure which are rarely available.…”

Section: Inlet Shear Thinningmentioning

confidence: 99%

Basics of EHL for practical application

Spikes

2014

Lubrication Science

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SUMMARYElastohydrodynamic lubrication (EHL) is present in all lubricated components whose elements roll together, including gears, rolling bearing, cams and constant velocity joints. These are characterised by having very localised and thus very high pressure contact, of order 1 to 3 GPa, between the elements.Two important practical properties of EHL contacts are the lubricant film thickness and the friction, and lubricant and machine designers and users need to be able to predict both of these. In principle they can be determined from full numerical solution of the elastohydrodynamic problem. However this is quite difficult and time-consuming and requires detailed knowledge of the rheology of the lubricant film at high pressure and shear rate. This paper is aimed at practising engineers and describes alternative approaches, i.e. how EHL can be applied to predict film thickness and friction in practical applications.

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A Film Thickness Correction Formula for Double-Newtonian Shear-Thinning in Rolling EHL Circular Contacts

Cited by 41 publications

References 25 publications

History, Origins and Prediction of Elastohydrodynamic Friction

History, Origins and Prediction of Elastohydrodynamic Friction

The temperature and pressure dependence of viscosity and volume for two reference liquids

Basics of EHL for practical application

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