EHL line contact central and minimum film thickness equations for lubricants with linear piezoviscous behavior

Anuradha, Parinam; Kumar, Parveen

doi:10.1016/j.triboint.2011.05.009

Cited by 16 publications

(11 citation statements)

References 6 publications

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“…Figure 1 illustrates the comparison between the values predicted from the Yasutomi free-volume model and measured from viscometer showing a good agreement. Furthermore, a better agreement with the measured data of the Yasutomi results compared to the Roelands law is observed [4,24]. Since the Roelands model was not intended to be accurate at high pressures [10], comparisons at EHL pressures are not really sensible.…”

Section: Theoretical Modelmentioning

confidence: 88%

“…It is characterized by concentrated forces, high contact pressures (1-3 GPa), thin lubricant films (1-2000 nm), and short durations. Due to the high pressure and the limited contact area, elastic deformation of the surfaces will occur and it is not negligible, and the pressure dependence of viscosity plays a crucial role in EHL simulation because the viscosity at the inlet has crucial influence on film formation [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%

“…This effect is more pronounced for fragile liquids than for strong liquids. The Roelands model underestimates the viscosity at both low and high pressures [4]. For this reason the most significant step in EHL simulations is to include the realistic pressure-viscosity response of the lubricant used in corresponding experiments.…”

Section: Introductionmentioning

confidence: 99%

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Effect of an Improved Yasutomi Pressure-Viscosity Relationship on the Elastohydrodynamic Line Contact Problem

2013

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This paper presents the application of an improved Yasutomi correlation for lubricant viscosity at high pressure in a Newtonian elastohydrodynamic line contact simulation. According to recent experimental studies using high pressure viscometers, the Yasutomi pressure-viscosity relationship derived from the free-volume model closely represents the real lubricant piezoviscous behavior for the high pressure typically encountered in elastohydrodynamic applications. However, the original Yasutomi correlation suffers from the appearance of a zero in the function describing the pressure dependence of the relative free volume thermal expansivity. In order to overcome this drawback, a new formulation of the Yasutomi relation was recently developed by Bair et al. This new function removes these concerns and provides improved precision without the need for an equation of state. Numerical simulations have been performed using the improved Yasutomi model to predict the lubricant pressure-viscosity, the pressure distribution, and the film thickness behavior in a Newtonian EHL simulation of a squalane-lubricated line contact. This work also shows that this model yields a higher viscosity at the low-pressure area, which results in a larger central film thickness compared with the previous piezoviscous relations.

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Section: Theoretical Modelmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

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Effect of an Improved Yasutomi Pressure-Viscosity Relationship on the Elastohydrodynamic Line Contact Problem

2013

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“…Формально режим трения в диапазоне контактных давлений P 2 …P 3 может быть назван граничным или переходным режимом. Трение в режиме граничной смазки исследовано в большом количестве работ [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. В большинстве случаев граничная смазка рассматривается применительно к контактам поршневых колец с гильзой цилиндра.…”

Section: Discussionunclassified

Anti-wear additives influence upon hydrodynamic friction mode parameters in bearings of internal-combustion engines

Задорожная¹,

Zadorozhnaya²,

Mukhortov³

et al. 2016

Bulletin of Bryansk State Technical University

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An essential condition to ensure an engine life having 300,000 – 1 000,000 km according to race consists in assurance of a minimum wear rate of crankshaft bearings. For such units as connectingrod bearings a maximum allowable value of bearing brass wear makes 100 mkm which corresponds to an integral linear wear intensity of 10-14 …10-13 that is possible only at a hydrodynamic mode of friction actually at all modes of engines operations. Ensuring liquid friction in all range of contact pressures is achieved both through design methods, and technological ones. To the latter belongs first of all the application of lubricants with high wearresistant properties. In this connection arises a problem to reveal a mechanism and degree of the effect of lubricant components upon a range of contact pressure where liquid friction is realized. This paper reports the experimental evidences of the increase of contact pressures at which is achieved a minimum value of a constant of friction at the introduction in lubricant a standard wear-resistant additive – dialkyldithiophosphate of zinc (ZDDP). So, at the introduction in coal oil without additives I-20A (viscosity type ISO 32) 1.25 and 2.5% ZGGP maxi-mum contact pressure at which is realized a hydrody-namic mode of friction increases by 1.8 and 2 times accordingly. Because of impossibility to explain experimental data by a chemical interaction of ZDDP with surface material of tribo-coupling there is offered and substantiated a mechanism of ZDDP influence upon rheological parameters of lubricant in a separation layer. A rheological model allowing the computation of the wearresistant additives influence upon a value of hydrodynamic pressures in a lubrication layer is of-fered. The idea of the initiation by a wearresistant additive of multimolecular adsorption of lubricant on the surface of tribocoupling may be used for the optimization of ZDDP structure and also for the prognostication of changes in pressure coefficient of viscosity in a lubrication layer.

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“…Recently, EHL film thickness formulas have been developed for shear-thinning oils 15,16 and lubricants with linear piezo-viscous response. 17 Typically, the ambient pressure in EHL analyses is assumed to be atmospheric and the aforesaid film thickness formulas are also based upon this assumption. However, in many practical situations, the ambient pressure is significantly above the atmospheric value.…”

Section: Introductionmentioning

confidence: 99%

New equations for enhanced film thickness in line contacts under pressurized ambient conditions

Kumar

2016

Proceedings of the Institution of Mechanical Engineers, Part J:

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An elastohydrodynamic lubrication model is proposed for line contacts under pressurized ambient conditions often encountered in hydraulic pumps, submarine machinery and many other submerged systems. It has been demonstrated that the film forming behavior under such conditions is essentially different from that in conventional elastohydrodynamic lubrication contacts. The numerical simulation results are regressed to develop new central and minimum film thickness equations for Newtonian fluids as functions of ambient pressure, speed, load, and material parameters. An alternative approach is also discussed which involves the use of existing film thickness formulas with ambient viscosity and pressure–viscosity coefficient pertaining to the desired pressure range. A film thickness enhancement of more than 100% over conventional elastohydrodynamic lubrication case is observed. This enhancement is shown to be highly sensitive to the pressure–viscosity coefficient. Besides, the effect of shear-thinning behavior is also investigated and it is found to lower the film thickness enhancement, especially at high ambient pressures.

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EHL line contact central and minimum film thickness equations for lubricants with linear piezoviscous behavior

Cited by 16 publications

References 6 publications

Effect of an Improved Yasutomi Pressure-Viscosity Relationship on the Elastohydrodynamic Line Contact Problem

Effect of an Improved Yasutomi Pressure-Viscosity Relationship on the Elastohydrodynamic Line Contact Problem

Anti-wear additives influence upon hydrodynamic friction mode parameters in bearings of internal-combustion engines

New equations for enhanced film thickness in line contacts under pressurized ambient conditions

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