The Generalized Newtonian Fluid Model and Elastohydrodynamic Film Thickness

Bair, Scott; Qureshi, Farrukh

doi:10.1115/1.1504086

Cited by 72 publications

(36 citation statements)

References 28 publications

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“…For the case of a power-law exponent, n [ 0.6, the two models roughly yield the same results by writing k = l/G [5]. Replacing the two occurrences of 2 on the RHS of Eq.…”

Section: Modelsmentioning

confidence: 60%

“…Shear-thinning was assumed to be responsible for films being thinner than predicted by the Newtonian theory. Recent inlet Grubin-style calculations based upon the measured shear response of lubricants [2][3][4][5] have reinforced the earlier finding by Dyson and Wilson [6] that film thinning is the result of ordinary shear-thinning of the power-law type. The solution of the coupled Reynolds and elasticity equations to predict film thickness for realistic shear dependent viscosity has eluded researchers, until very recently [7].…”

Section: Introductionmentioning

confidence: 72%

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A Quantitative Solution for the Full Shear-Thinning EHL Point Contact Problem Including Traction

et al. 2007

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We present a realistic elastohydrodynamic lubrication (EHL) simulation in point contact using a Carreau-like model for the shear-thinning response and the Doolittle-Tait free-volume viscosity model for the piezoviscous response. The liquid lubricant modeled is a highviscosity polyalphaolefin which has been shown by highpressure viscometry to possess a relatively low threshold for shear-thinning as a single-component liquid lubricant. As a result, the measured EHL film thickness is about onehalf of the Newtonian prediction. We derived and numerically solved the two-dimensional generalized Reynolds equation for the modified Carreau model based on Greenwood. In this simulation, viscosity was not treated as an adjustable parameter; the models used for the pressure and shear dependence of viscosity were obtained entirely from viscometer measurements. Truly remarkable agreement is found in the comparisons of simulation and experiment for traction coefficient and for film thickness in both pure rolling and sliding cases.

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“…For the case of a power-law exponent, n [ 0.6, the two models roughly yield the same results by writing k = l/G [5]. Replacing the two occurrences of 2 on the RHS of Eq.…”

Section: Modelsmentioning

confidence: 60%

Section: Introductionmentioning

confidence: 72%

A Quantitative Solution for the Full Shear-Thinning EHL Point Contact Problem Including Traction

et al. 2007

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“…This is again a Grubin style line contact inlet zone analysis. The pressure variation of low shear viscosity was represented by equations (8) and (9). The shear dependent viscosity was represented by equation (4).…”

Section: Film Thickness Calculationsmentioning

confidence: 99%

“…The purpose of this paper is to conclusively demonstrate that the nature of the shear-thinning within a lubricating film in a concentrated contact follows the ordinary power-law form that has been described by empirical models [9] that bear the names Carreau, Carreau-Yasuda, Ellis, Cross, Spriggs, Ferry, Rabinowitsch, and Ree-Eyring [9]. This will be accomplished by calculating both film thickness and traction from the measured nonlinear shear response of a liquid with a low critical shear stress for shearthinning.…”

Section: Introductionmentioning

confidence: 97%

A unified shear-thinning treatment of both film thickness and traction in EHD

2005

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A conclusive demonstration has been provided that the nature of the shear-thinning, that affects both film thickness and traction in EHL contacts, follows the ordinary power-law rule that has been described by many empirical models of which Carreau is but one example. This was accomplished by accurate measurements in viscometers of the shear response of a PAO that possesses a very low critical stress for shear-thinning and accurate measurements in-contact of film thickness and traction under conditions which accentuate the shear-thinning effect. The in-contact central film thickness and traction were entirely predictable from the rheological properties obtained from viscometers using simple calculations. These data should be invaluable to researchers endeavoring to accurately simulate Hertz zone behavior since the shear-thinning rheology is extensively characterized and accurate in-contact data are available to test. In addition, a new model has been introduced that may be useful for the rheological characterization of mixtures.

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“…[64][73] [100][101][102][103]. This is based on a paper in 1958 [71] in which Ree, Ree and Eyring state that Eyring's original equation did not adequately describe the shear thinning of complex fluids to which other researchers were applying it, and provided an extended model based on multiple flow units to apply to such materials.…”

Section: Eyring Versus Carreau-yasudamentioning

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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The Generalized Newtonian Fluid Model and Elastohydrodynamic Film Thickness

Cited by 72 publications

References 28 publications

A Quantitative Solution for the Full Shear-Thinning EHL Point Contact Problem Including Traction

A Quantitative Solution for the Full Shear-Thinning EHL Point Contact Problem Including Traction

A unified shear-thinning treatment of both film thickness and traction in EHD

History, Origins and Prediction of Elastohydrodynamic Friction

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