An improved Yasutomi correlation for viscosity at high pressure

Bair, Scott; Mary, Charlotte; Bouscharain, Nathalie; Vergne, Philippe

doi:10.1177/1350650112474394

Cited by 66 publications

(47 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The curves fitted to the data in Fig. 10 represent the improved Yasutomi model [37] below. An equation of state is not necessary to apply this correlation.…”

Section: Linear Dependence Of Shear Stress On Pressurementioning

confidence: 99%

Classical EHL Versus Quantitative EHL: A Perspective Part II—Super-Arrhenius Piezoviscosity, an Essential Component of Elastohydrodynamic Friction Missing from Classical EHL

2016

Self Cite

View full text Add to dashboard Cite

Ninety years of high-pressure measurements with many different types of viscometers have shown that faster-than-exponential (super-Arrhenius) pressure dependence of viscosity is universal for glass-forming liquids and, therefore, all typical liquid lubricants. Dielectric spectroscopy at elevated pressure also yields super-Arrhenius response in the dependence on pressure of the primary relaxation time. In contrast, classical elastohydrodynamic lubrication (EHL) has gone to great lengths to ignore this phenomenon, including fictional accounts of the results of viscometry. As a result of this, classical EHL is unable to quantitatively account for one of the most important properties affecting friction at low sliding velocity, the low-shear viscosity. Differences in friction between similar liquids at low sliding velocity can be explained by their different inflection pressures. Some observed liquid response to shear stress at high pressure can be explained with the measured super-Arrhenius pressure dependence. It should be clear that, had classical EHL employed realistic pressure dependence of viscosity from its beginning, the field would have been in a better position today to solve engineering problems which involve the differences among molecular structures.

show abstract

“…The curves fitted to the data in Fig. 10 represent the improved Yasutomi model [37] below. An equation of state is not necessary to apply this correlation.…”

Section: Linear Dependence Of Shear Stress On Pressurementioning

confidence: 99%

Classical EHL Versus Quantitative EHL: A Perspective Part II—Super-Arrhenius Piezoviscosity, an Essential Component of Elastohydrodynamic Friction Missing from Classical EHL

2016

Self Cite

View full text Add to dashboard Cite

show abstract

“…Based on the finite element method, the numerical model solves simultaneously the Reynolds, the solids deformation and the load balance equations. Typically, the Reynolds equation was solved using 2×10 4 degrees of freedom and the convergence was achieved when a relative deviation lower than 10 the Newtonian viscosity follows a modified WilliamsLandel-Ferry (WLF) correlation [16] and the density varies according to the Murnaghan [17] equation. Both constitutive equations were fitted to independent characterizations carried out with high pressure devices, see Ref.…”

Section: Models and Conditionsmentioning

confidence: 99%

On the relevance of analytical film thickness EHD equations for isothermal point contacts: Qualitative or quantitative predictions?

et al. 2016

Self Cite

View full text Add to dashboard Cite

Thin film and elastohydrodynamic lubrication regimes are rather young domains of tribology and they are still facing unresolved issues. As they rely upon a full separation of the moving surfaces by a thin (or very thin) fluid film, the knowledge of its thickness is of paramount importance, as for instance to developing lubricated mechanisms with long lasting and efficient designs. As a consequence, a large collection of formulae for point contacts have been proposed in the last 40 years. However, their accuracy and validity have rarely been investigated. The purpose of this paper is to offer an evaluation of the most widespread analytical formulae and to define whether they can be used as qualitative or quantitative predictions. The methodology is based on comparisons with a numerical model for two configurations, circular and elliptical, considering both central and minimum film thicknesses.

show abstract

“…(1). A brief summary of the authors' experience in the matter shows that this dependence can be successfully described with one of two equations of state, namely the Tait [21,22] or the Murnaghan [23] expressions for the density variations, and one of the three viscosity-pressure-temperature relationships, the extended Doolittle [24], the Bair and Casalini [25] or the modified WLF equations [3,26]. Comparisons quantitatively consistent with experiments conducted under various EHD operating conditions and lubricants proved the combinations of these equations to be relevant for accurately predicting film thickness and traction.…”

Section: Viscosity-pressure Dependence and Viscositypressure Coefficimentioning

confidence: 99%

Classical EHL Versus Quantitative EHL: A Perspective Part I—Real Viscosity-Pressure Dependence and the Viscosity-Pressure Coefficient for Predicting Film Thickness

Vergne

Bair

2014

Tribol Lett

Self Cite

View full text Add to dashboard Cite

That classical elastohydrodynamic lubrication (EHL) is not a quantitative field can be illustrated by its failure to provide a consistent and rigorous definition of the viscosity-pressure coefficient. Indeed, if the pressure dependence of viscosity cannot be accurately described, then the viscosity-pressure coefficient cannot be defined. Classical EHL has employed fictional narratives to justify the pressure dependences that have been utilized. In this context, the purpose of this perspective article is to review specific and real needs from EHL and to show that data and models describing the viscosity-pressure dependence are already available and how they can properly be used. The final aim is to encourage researchers to change their philosophy of classical EHL to a quantitative approach, in which every hypothesis and every result, whether experimental or numerical, would be justified on the basis of acceptable physics.

show abstract

An improved Yasutomi correlation for viscosity at high pressure

Cited by 66 publications

References 19 publications

Classical EHL Versus Quantitative EHL: A Perspective Part II—Super-Arrhenius Piezoviscosity, an Essential Component of Elastohydrodynamic Friction Missing from Classical EHL

Classical EHL Versus Quantitative EHL: A Perspective Part II—Super-Arrhenius Piezoviscosity, an Essential Component of Elastohydrodynamic Friction Missing from Classical EHL

On the relevance of analytical film thickness EHD equations for isothermal point contacts: Qualitative or quantitative predictions?

Classical EHL Versus Quantitative EHL: A Perspective Part I—Real Viscosity-Pressure Dependence and the Viscosity-Pressure Coefficient for Predicting Film Thickness

Contact Info

Product

Resources

About