Glass Transitions in Lubricants: Its Relation to Elastohydrodynamic Lubrication (EHD)

Al-Saad, Mohammed; Bair, Scott; Sanborn, D. M.; Winer, W. O.

doi:10.1115/1.3453197

Cited by 82 publications

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“…Equations (2) and (3) are valid below the solidification pressure only and over the temperature range 295±380 K. Alsaad et al [14] used dilatometry in order to measure the solidification pressure. Their isothermal results can be compared with the results obtained from the present investigation (Fig.…”

Section: Resultsmentioning

confidence: 99%

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Lubricant thermal conductivity and heat capacity under high pressure

Larsson

Andersson

2000

Proceedings of the Institution of Mechanical Engineers, Part J:

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The thermal conductivity ë and the heat capacity per unit volume, rc p , have been measured for a number of common lubricating oils. The oils tested were paraffinic and naphthenic mineral oils and a 50=50 blend of these. Poly-á-olefin, polyglycol, Santotrac, ester and rapeseed oils have also been tested. The measurements, using the transient hot-wire method, were carried out under isothermal conditions over a pressure range from atmospheric to 1.1 GPa and at two temperatures, 295 and 380 K (22 and 107 8C respectively).The temperature had only a marginal effect on thermal conductivity; however, the thermal conductivity was doubled as the pressure was increased to 1 GPa. The heat capacity per unit volume was influenced by both the pressure and the temperature. Some of the lubricants solidified as the pressure increased and the transition from a fluid to a solid state could be detected in the measurements of rc p .The relationship between the thermodynamic properties and the pressure and temperature are described by two empirical equations. These equations can be used in thermal elastohydrodynamic analyses.

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Section: Resultsmentioning

confidence: 99%

“…Transition regions under isothermal conditions: À À ÀÀ, beginning of the transition and end of the transition for Santotrac 50 presented in reference[14]; ÐÐÐ, transition for Santotrac in the present investigation…”

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confidence: 98%

Lubricant thermal conductivity and heat capacity under high pressure

Larsson

Andersson

2000

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…The glass transition pressure of all samples was investigated using the dilatometric technique described in Ref. (16) using the isothermal compression history. A modified version of the dilatometer of (16) was used to extend the pressure and temperature capability of the technique to 2 GPa and 400°C, respectively.…”

Section: Other High Pressure Resultsmentioning

confidence: 99%

An Experimental Verification of the Significance of the Reciprocal Asymptotic Isoviscous Pressure for EHD Lubricants

Bair

1993

Tribology Transactions

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The classical elastohydrodynamic film thickness solution which assumes a purely exponential variation of viscosity with pressure requires a pressure-viscosity coefficient. In general, liquid lubricant viscosity varies with pressure such that the local pressure-viscosity coefficient is a function of pressure, making the determination of the pertinent parameter for film thickness dqficult. Blok proposed a reciprocal asymptotic isoviscous pressure a* as a replacement for the initial pressure viscosity coefficient ao, based on the Weibull pressure transformation. The pressure-viscosity characteristics of seven liquid lubricants were measured with a falling body viscometer to pressure of 0.76 GPa and a0 and a* were calculated. Viscosity and glass transition results were applied to a model in current usage. The EHD film thickness was measured using interferometry supported by the measurement of the refractive index at elevated pressure. The reciprocal asymptotic isoviscous pressure was found to be more correct as a film thickness parameter than was the initial pressure viscosity coefficient.

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“…4 Therefore, it is diffi cult to form a relation between the traction coeffi cients and average spatial hole inside the fl uid. 30 We need to discuss the relation between the molecular structure and the momentum transfer mechanism in the fl uid layer.…”

Section: Molecular Mechanism Of Traction Focusing On Intra-and Interamentioning

confidence: 99%

Molecular dynamics simulations of elastohydrodynamic lubrication oil film

Washizu

Ohmori

2010

Lubrication Science

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Highlights • A mechanism for the limited shear-stress transition of an elastohydrody-namic lubrication (EHL) oil film is proposed. • The spatial structure and velocity profile showed gradual changes. • Suppression of the fluctuation is found in the EHL regime. Abstract All-atom molecular dynamics simulations of an elastohydrodynamic lubrication oil film are performed to study the effect of pressure. Fluid molecules of n-hexane are confined between two solid plates under a constant normal force of 0.1-8.0 GPa. Traction simulations are performed by applying relative sliding motion to the solid plates. A transition in the traction behavior is observed around 0.5-2.0 GPa, which corresponds to the viscoelastic region to the plastic-elastic region, which are experimentally observed. This phase transition is related to the suppression of the fluctuation in molecular motion.

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Glass Transitions in Lubricants: Its Relation to Elastohydrodynamic Lubrication (EHD)

Cited by 82 publications

References 0 publications

Lubricant thermal conductivity and heat capacity under high pressure

Lubricant thermal conductivity and heat capacity under high pressure

An Experimental Verification of the Significance of the Reciprocal Asymptotic Isoviscous Pressure for EHD Lubricants

Molecular dynamics simulations of elastohydrodynamic lubrication oil film

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