The unusual behaviour of a lubricant boundary layer

Rozeanu, L.; Snarsky, L.

doi:10.1016/0043-1648(77)90047-3

Cited by 15 publications

(4 citation statements)

References 2 publications

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“…for heavy loads, high rolling speeds, large slide-roll ratios and high bulk fluid temperatures. This has been well proved by both the experiments of Rozeanu (1977Rozeanu ( , 1978Rozeanu ( , 1980 on hydrodynamic lubrication in sliding bearings and the researches of Zhang et al (2001aZhang et al ( , b, 2002aZhang et al ( , b, 2003aZhang et al ( , b, 2004aZhang et al ( , 2000 on EHL.…”

Section: Discussionmentioning

confidence: 64%

“…They showed by experiments that the contact-fluid In experiments, the observation of the contact-fluid interfacial shear strength and contact-fluid interfacial slippage effects in EHL is much more difficult than in a plain hydrodynamic bearing due to the small contact width, extremely thin fluid film and very short transit time of an EHL contact. Zhang et al (2001aZhang et al ( , 2002aZhang et al ( , b, 2000 observed by numerical simulation the similar phenomena in isothermal EHL of ideally smooth line contacts due to the contact-fluid interfacial shear strength and contact-fluid interfacial slippage effects as Rozeanu et al (1977Rozeanu et al ( , 1978Rozeanu et al ( , 1980 observed in a sliding hydrodynamic bearing. Zhang et al (2002a) analytically showed that in EHL, the contact-fluid interfacial shear strength and contact-fluid interfacial slippage effects cause the difference of the velocity of the fluid film at the contact surface from the speed of that contact surface and the changes of the pressure distribution and especially the pressure gradients within the fluid film.…”

Section: Contact-fluid Interfacial Shear Strength and Contact-fluid Interfacial Slippage Effects In Ehlmentioning

confidence: 71%

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Contact‐fluid interfacial shear strength and its critical importance in elastohydrodynamic lubrication

Zhang¹

2006

Industrial Lubrication and Tribology

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Purpose -To review, analyze and present the effects of the contact-fluid interfacial shear strength and contact-fluid interfacial slippage and the critical importance of these effects in elastohydrodynamic lubrication (EHL). Design/methodology/approach -The experimental and theoretical research results of the contact-fluid interfacial shear strength and its caused contact-fluid interfacial slippage in hydrodynamic lubrication and especially in EHL obtained in the past decades and progressed in recent years by the present author and by others are reviewed. Analysis and presentation are made on both the contact-fluid interfacial shear strength versus fluid pressure curve for a given bulk fluid temperature in an isothermal EHL and the influence of the bulk fluid temperature on this curve. Findings -It is very clearly and well understood from the present paper that the value of the contact-fluid interfacial shear strength in the inlet zone in an EHL contact, i.e. at low EHL fluid film pressures is usually low and usually has rather a weak dependence on the EHL fluid film pressure. This proves the correctness of the EHL theories previously developed by the author based on the assumption of this low value and dependence on the EHL fluid film pressure of the contact-fluid interfacial shear strength. It is also very clearly understood that the bulk fluid temperature usually has a strong influence on the value of the contact-fluid interfacial shear strength in EHL and the increase of this temperature usually significantly reduces the value of the contactfluid interfacial shear strength in EHL. Practical implications -A very useful material for the engineers who are engaged in the design of EHL on gears, cams and roller bearings, and for the tribology scientists who thrust efforts in studying EHL and mixed EHL both by theoretical modeling and by experiments. Originality/value -A new and generalized mode of mixed EHL is originally proposed by incorporating the finding of a more realistic mode of the contact regimes in a practical mixed EHL based on the contact-fluid interfacial shear strength and contact-fluid interfacial slippage effects. This mode of mixed EHL should become the direction of the theoretical research of mixed EHL in the future.

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Section: Discussionmentioning

confidence: 64%

Section: Contact-fluid Interfacial Shear Strength and Contact-fluid Interfacial Slippage Effects In Ehlmentioning

confidence: 71%

Contact‐fluid interfacial shear strength and its critical importance in elastohydrodynamic lubrication

Zhang¹

2006

Industrial Lubrication and Tribology

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“…The flow in Figure 1(a) can be equivalently treated as Figure 1(b) shows. The interfacial slippage on the adhering layer-fluid interface is assumed, but that on the adhering layer-wall surface interface is ignored, as in a normal channel flow the adhering layer-fluid interfacial slippage would more easily occur because of the adhering layer-fluid interface considerably weaker than the adhering layer-wall surface interface (Rozeanu and Snarsky, 1977). The adsorbed layers respectively on the coupled channel walls are taken as completely the same.…”

Section: Frontiers In Heat and Mass Transfermentioning

confidence: 99%

Influence of the Fluid-Wall Interaction on the Multiscale Flow Through a Micro Slit Pore Considering the Adsorbed Layer-Fluid Interfacial Slippage

Zhang¹

2020

Frontiers in Heat and Mass Transfer

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A multiscale analysis is carried out for the pressure driven flow rate through a micro/nano slit pore when the adsorbed layer-fluid interfacial slippage is considered. The flow of the adsorbed layer on the channel wall is described by the flow factor approach model for nanoscale flow, and the flow of the continuum fluid intermediate between the two adsorbed layers is described by a continuum fluid model. The adsorbed layer-fluid interfacial slippage is considered, while the adsorbed layer-wall surface interfacial slippage is ignored. The weak, medium-level and strong fluid-wall interactions and the solid adsorbed layer assumption are respectively taken. It is shown that when the thickness of the adsorbed layer is far lower than the continuum fluid film thickness, the adsorbed layer can be treated as a solid layer in spite of the fluid-wall interaction, otherwise the fluid-wall interaction has a significant influence on the critical power loss on the channel for motivating the interfacial slippage and on the total volume flow rate through the channel before the occurrence of the interfacial slippage; However, when the adsorbed layer-fluid interfacial slippage occurs, the fluid-wall interaction has a negligible influence on the normalized total volume flow rate through the channel vs. power loss on the channel curve and when using this curve for calculating the dimensionless volume flow rate through the channel the adsorbed layer can be taken as a solid layer. In general, only when the fluid-wall interaction is strong, the adsorbed layer can be taken as a solid layer in simulating the channel flow.

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“…The wall slippage was found to occur in a hydrodynamic journal bearing long time ago [29,30]. It was interpreted as the result of the shear stress exceeding the capacity of the adhering layer-fluid interface in a normal hydrodynamic journal bearing and found to pronouncedly reduce the load-carrying capacity of the bearing [29][30][31]. On the other hand, the friction coefficient of the bearing is significantly increased [31,32].…”

Section: Introductionmentioning

confidence: 99%

Energy-Conserved Hydrodynamic Lubricated Components with Wall Slippage

Huang

Zhang

2023

International Journal of Rotating Machinery

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The hydrodynamic thrust slider and journal bearings as well as hydrodynamic lubricated gears with the merit of energy conservation by the wall slippage are reviewed. The principle for designing these hydrodynamic contacts is to artificially set the wall slippage on the stationary surface in the hydrodynamic inlet zone. To design the wall slippage on the moving surface in the hydrodynamic outlet zone can also give additional benefits. The technical merits of these mechanical components are the improved load-carrying capacity and the lowed friction coefficient, i.e., the energy conservation due to the wall slippage. Owing to the designed wall slippage, the carried load of the hydrodynamic step bearing can be increased by 200%~400% while its friction coefficient can be reduced by 50%~85%, and the load-carrying capacity of the hydrodynamic journal bearing can be increased by nearly 100% while at the same time, its friction coefficient can be reduced by more than 60%. For hydrodynamic lubricated gear contacts, by covering ultrahydrophobic or oilphobic coatings on the slower moving surface, the friction coefficient can be approaching to vanishing and the contact load-carrying capacity can be increased very significantly for large slide-roll ratios under medium or heavy loads.

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The unusual behaviour of a lubricant boundary layer

Cited by 15 publications

References 2 publications

Contact‐fluid interfacial shear strength and its critical importance in elastohydrodynamic lubrication

Contact‐fluid interfacial shear strength and its critical importance in elastohydrodynamic lubrication

Influence of the Fluid-Wall Interaction on the Multiscale Flow Through a Micro Slit Pore Considering the Adsorbed Layer-Fluid Interfacial Slippage

Energy-Conserved Hydrodynamic Lubricated Components with Wall Slippage

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