Closure to “Discussions of ‘Oil Film Thickness and Rolling Friction in Elastohydrodynamic Point Contact’” (1971, ASME J. Lubr. Technol., 93, pp. 379–381)

1971 ◽  
Vol 93 (3) ◽  
pp. 381-382
Author(s):  
R. Gohar
Keyword(s):  
Film Thickness ◽  
Point Contact ◽  
Rolling Friction ◽  
Oil Film

Oil Film Thickness and Rolling Friction in Elastohydrodynamic Point Contact

1971 ◽  
Vol 93 (3) ◽  
pp. 371-379 ◽  
Author(s):  
R. Gohar
Keyword(s):  
Film Thickness ◽  
Tungsten Carbide ◽  
Material Properties ◽  
High Pressures ◽  
Glass Plate ◽  
Point Contact ◽  
Rolling Friction ◽  
Significant Alteration ◽  
Oil Film ◽  
Rolling Ball

The effect of material properties upon the film thickness in elastohydrodynamic point contact is demonstrated with a rolling ball and plate machine. A 220 fold range of Young’s modulus is employed and a maximum Hertzian pressure of 5 × 105 lb f/in2 is reached. The oil film, which is measured by interferometry, shows no significant alteration at such high pressures, and is also fairly insensitive to the choice of bounding materials. Using a technique similar to that employed by Crook, the rolling friction between a tungsten carbide and a glass plate is found and compared with theory. The effect of spin is investigated and found to be slight.

Theoretical and experimental studies of the oil film in lubricated point contact

1966 ◽  
Vol 291 (1427) ◽  
pp. 520-536 ◽  
Keyword(s):  
Surface Layer ◽  
Film Thickness ◽  
Strong Evidence ◽  
Experimental Studies ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Experimental Results ◽  
Point Contacts ◽  
Previous Theory ◽  
Oil Film

A technique using Newton’s rings for mapping the oil film of lubricated point contacts is described. A theoretical value for the film thickness of such contacts in elastohydrodynamic lubrication is derived. The experimental results give the exit constriction predicted by previous theory but never shown in detail. The comparison of theoretical and experimental oil film thicknesses, which is satisfactorily accurate, gives strong evidence for a viscous surface layer some 1000Å thick. This film agrees with the known ‘lubricating power’ of the various oils tested.

Oil Film Thickness and Pressure Distribution in Elastohydrodynamic Point Contacts

1982 ◽  
Vol 24 (4) ◽  
pp. 173-182 ◽  
Author(s):  
A. Mostofi ◽  
R. Gohar
Keyword(s):  
Contact Problem ◽  
Film Thickness ◽  
Numerical Solutions ◽  
Point Contact ◽  
Point Contacts ◽  
Rolling Velocity ◽  
Oil Film ◽  
Static Contact ◽  
Theoretical Predictions ◽  
Interferometry Method

In this paper, a general numerical solution to the elastohydrodynamic point contact problem is presented for moderate loads and material parameters. Isobars, contours and regression formulae describe how pressure and oil film thickness vary with geometry, material properties, load, and squeeze velocity, when the rolling velocity vector is at various angles to the static contact ellipse long axis. In addition, the EHL behaviour under spin is examined. The theoretical predictions of film thickness compare favourably with other numerical solutions to the point contact problem, as well as with experimental results which use the optical interferometry method to find film thickness and

MEASUREMENT OF THIN OIL FILM THICKNESS USING ULTRASONIC TECHNIQUE

2008 ◽  
Vol 22 (11) ◽  
pp. 1081-1085 ◽  
Author(s):  
AKITOSHI TAKEUCHI ◽  
SEIICHI TERADA ◽  
SO TODA
Keyword(s):  
Film Thickness ◽  
Ultrasonic Wave ◽  
Quantitative Measurement ◽  
Piston Ring ◽  
Point Contact ◽  
Ultrasonic Technique ◽  
Thin Film Thickness ◽  
Ultrasonic Probe ◽  
Oil Film ◽  
High Frequency Probe

An application of ultrasonic technique is attempted for the purpose of measuring thin oil film thickness between two surfaces. The amplitude of the wave reflected from the boundary is vary depending on film thickness, because the ultrasonic wave emitted to the interface between two surfaces does multiple reflection and interference in oil film. Quantitative measurement of oil film thickness then can be possible. For instance, it is possible to measure the submicron film thickness which exists near the point contact formed by convex glass and plate with high frequency probe. And it is confirmed that the oil film thickness estimated from the echo height agrees with the film thickness decided by the curvature of the lens or obtained by the optical interference method, even if it is 100 nm. On the other hand, the thickness of oil film between cylinder and piston ring can be easily measured by setting the small ultrasonic probe on the back of piston ring. For example, the influence of the second ring and oil ring for the behavior of an oil film formed on a top ring is able to evaluate quantitatively. As mentioned above, it is cleared that quantitative evaluation of thin film thickness is possible with investigating the echo height obtained by ultrasonic wave pulse reflection method.

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