Experimental Study on Lubrication Film Thickness Under Different Interface Wettabilities

Ultrathin liquid lubrication film thicknesses at the molecular scale are measured by a new apparatus developed by the authors. Mica is used as the solid specimen and octamethylcyclotetrasiloxane (OMCTS), cyclohexane and n-hexadecane are used as liquid specimens. From experimental measurements, discretization of the lubrication film thickness is observed when the thickness is less than about 10 times the molecular diameter of the intervening liquid. Analysis of experimental data shows that the discretization of the lubrication film thickness is due to the solvation force. Dynamic measurements show that the solvation force is almost the same as the non-sliding case and is independent of the sliding speed of the solid surface.

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Experimental Study of Lubrication Film Formation in Multiple Contacts Device Under Starved Conditions

ASME/STLE 2012 International Joint Tribology Conference ◽

10.1115/ijtc2012-61123 ◽

2012 ◽

Author(s):

Petr Svoboda ◽

David Kostal ◽

Ivan Krupka ◽

Martin Hartl

Keyword(s):

Experimental Study ◽

Film Thickness ◽

Numerical Models ◽

Film Formation ◽

Lubrication Film ◽

Multiple Contacts ◽

Optical Test ◽

Starved Lubrication ◽

Traction Drives ◽

Lubrication Conditions

Some machine elements such as gears, rolling bearings, cams and traction drives operate under starved lubrication conditions where the average lubricant film thickness is considerably less than under fully flooded conditions. These parts must operate correctly, often over prolonged periods with sufficient performance. One of the most important parameters determining the performance and life of machine parts is a lubrication film thickness, which is generated within elastohydrodynamic lubricated (EHL) non-conformal contacts. The film thickness in this regime is often time dependent and its value is governed by lubricant supply. If loss outstrips supply this leads to very thin films, which can no longer fulfill their role of separating the surfaces, and thus component failure can result. To achieve optimum bearing performance and component life, it is obviously desirable to be able to predict when starvation will occur. Today the film thickness and pressure in EHL can be predicted using numerical models also in the case of starvation. Although it is very essential to solve the starved EHL problems very little work aimed at comparing experiment and theory has been done. Especially in the case where the starved lubrication model requires as input the inlet layer thickness. This is crucial if the validity of numerical models is to be properly established. This paper is focused on the study of starved lubrication conditions on lubrication film formation. A new optical test rig with multiple EHL contacts was developed for experimental study of lubrication film formation.

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Experimental Study on Discretization of Ultrathin Liquid Lubrication Film Thickness.

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series C ◽

10.1299/kikaic.63.537 ◽

1997 ◽

Vol 63 (606) ◽

pp. 537-542

Author(s):

Hiroshige MATSUOKA ◽

Takahisa KATO

Keyword(s):

Experimental Study ◽

Film Thickness ◽

Lubrication Film

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A Simplified Model for Calculating Hydrodynamic Lubrication Film Thickness in Elastoplastic Line Contacts

Flow Turbulence and Combustion ◽

10.1007/s10494-011-9352-1 ◽

2011 ◽

Vol 87 (4) ◽

pp. 707-723

Author(s):

Yongbin Zhang

Keyword(s):

Film Thickness ◽

Hydrodynamic Lubrication ◽

Simplified Model ◽

Lubrication Film ◽

Line Contacts

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A New Postulation of Viscosity and Its Application in Computation of Film Thickness in TFL1

Journal of Tribology ◽

10.1115/1.1456090 ◽

2002 ◽

Vol 124 (4) ◽

pp. 811-814 ◽

Cited By ~ 16

Author(s):

Chaohui Zhang ◽

Jianbin Luo ◽

Shizhu Wen

Keyword(s):

Thin Film ◽

Experimental Data ◽

Film Thickness ◽

Solid Surface ◽

Contact Area ◽

Elastohydrodynamic Lubrication ◽

Thin Film Lubrication ◽

Lubrication Film ◽

Viscosity Modification ◽

Film Lubrication

In this paper, a viscosity modification model is developed which can be applied to describe the thin film lubrication problems. The viscosity distribution along the direction normal to solid surface is approached by a function proposed in this paper. Based on the formula, lubricating problem of thin film lubrication (TFL) in isothermal and incompressible condition is solved and the outcome is compared to the experimental data. In thin film lubrication, according to the computation outcomes, the lubrication film thickness is much greater than that in elastohydrodynamic lubrication (EHL). When the velocity is adequately low (i.e., film thickness is thin enough), the pressure distribution in the contact area is close to Hertzian distribution in which the second ridge of pressure is not obvious enough. The film shape demonstrates the earlobe-like form in thin film lubrication, which is similar to EHL while the film is comparatively thicker. The transformation relationships between film thickness and loads, velocities or atmosphere viscosity in thin film lubrication differ from those in EHL so that the transition from thin film lubrication to EHL can be clearly seen.

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