Oil-Film Starvation in Elastohydrodynamic Circular Contacts

1977 ◽  
Vol 19 (1) ◽  
pp. 22-29 ◽  
Author(s):  
A. Vakilzadeh ◽  
R. Gohar
Keyword(s):  
Film Thickness ◽  
Contact Region ◽  
Oil Droplet ◽  
Oil Film ◽  
Circular Contact

A formula for the oil-film thickness in a starved, elastohydrodynamic, circular contact is presented in terms of external parameters. Experiments are described which confirm the theory. Also examined are the oil droplet around the contact region, and the track shape made by the passage of the balls on the races.

Instrumentation of a Rolling Bearing With a Thin Film Piezo Coating for Oil Film Measurement

2007 ◽  
Author(s):  
R. S. Dwyer-Joyce ◽  
J. Zhang ◽  
B. W. Drinkwater ◽  
J. Elgoyen ◽  
K. J. Kirk
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Contact Region ◽  
Elastohydrodynamic Lubrication ◽  
Rolling Bearing ◽  
Oil Film ◽  
Deep Groove ◽  
Data Points ◽  
Bearing Loads ◽  
Piezoelectric Thin Film

This paper describes a novel design of oil-film monitoring sensor capable of measuring oil-film thickness in concentrated contacts. The approach is to use a thin (approx. 4 μm) sputtered coating of piezoelectric material, such as Aluminium Nitride. When correctly electroded this acts as an ultrasonic sensor with a usable bandwidth from 20–350 MHz. This sensor allows the interrogation of the small lubricated region between the ball and raceway without any special focusing requirements. Typically the dimensions of the contact region is less than a millimeter wide. This sensor system is then demonstrated experimentally on a deep groove ball bearing with the piezoelectric thin film on the external surface of the bearing outer raceway. The interaction of ultrasound with the oil-film is modeled using a quasi-static spring model and this allows properties such as film thickness to be extracted. The measured thicknesses are shown to agree well those obtained from classical elastohydrodynamic lubrication theory for the high bearing loads and low speeds where several data points can be collected from the contact during a ball passage. Measurement of oil film thickness in the region of 0.1–1 μm is demonstrated.

Ultrasonic measurement of oil film thickness between the roller and the inner raceway in a roller bearing

2015 ◽  
Vol 67 (6) ◽  
pp. 531-537 ◽  
Author(s):  
Kai Zhang ◽  
Qingfeng Meng ◽  
Wei Chen ◽  
Junning Li ◽  
Phil Harper
Keyword(s):  
Reflection Coefficient ◽  
Film Thickness ◽  
Contact Region ◽  
Ultrasonic Method ◽  
Roller Bearing ◽  
Piezoelectric Element ◽  
Content Type ◽  
Oil Film ◽  
Roller Bearings ◽  
Contact Width

Purpose – This paper aims to measure the oil film thickness between the roller and the inner ring in roller bearings by the ultrasonic method. The oil film thickness between the roller and the inner ring in roller bearings is a key performance indicator of the bearing lubrication condition. As the oil film is very thin and the contact region is very narrow, measurement of this film thickness is very challenging. A promising ultrasonic method was used to measure this film thickness, and this method was expected to overcome some drawbacks in other methods. Design/methodology/approach – A simplified roller bearing only configured one roller, and an inner ring was built up to investigate this measurement. A miniature piezoelectric element is bonded on the inner surface of the inner ring to measure the reflection coefficient from the layer of oil between the roller and the inner raceway. As the width of the line contact region is smaller than the width of the piezoelectric element, a ray model is used to calibrate the reflection coefficient measured. The quasi-static spring model is then used to calculate oil film thickness from the corrected reflection coefficient data. Findings – The results measured by this method agree reasonably well with predictions from elastohydrodynamic lubrication (EHL) theory. Also, a dynamic displacement of the rig caused by the skid of the roller versus the inner ring was found under light-load and high-speed conditions. Originality/value – This work shows that the oil film between the roller and the inner raceway in roller bearings can be measured accurately by ultrasound and shows a deal method when the contact width is smaller than the piezoelectric element width.

Rough Air-Soft Elastohydrodynamic Lubrication

2013 ◽  
Vol 420 ◽  
pp. 30-35
Author(s):  
Khanittha Wongseedakaew ◽  
Jesda Panichakorn
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Modulus Of Elasticity ◽  
Contact Region ◽  
Elastohydrodynamic Lubrication ◽  
Multilevel Methods ◽  
Inlet Temperature ◽  
Film Pressure ◽  
Air Inlet ◽  
Air Film

This paper presents the effects of rough surface air-soft elastohydrodynamic lubrication (EHL) of rollers for soft material under the effect of air molecular slip. The time independent modified Reynolds equation and elasticity equation were solved numerically using finite different method, Newton-Raphson method and multigrid multilevel methods were used to obtain the film pressure profiles and film thickness in the contact region. The effects of amplitude of surface roughness, modulus of elasticity and air inlet temperature are examined. The simulation results showed surface roughness has effect on film thickness but it little effect to air film pressure. When the amplitude of surface roughness and modulus of elasticity increased, the air film thickness decreased but air film pressure increased. However, the air inlet temperature increased when the air film thickness increased.

The Surface-Roughness of Bearing-Surfaces and its Relation to Oil Film Thickness at Breakdown

1949 ◽  
Vol 161 (1) ◽  
pp. 73-79 ◽  
Author(s):  
A. Cameron
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Hydrodynamic Theory ◽  
Quantitative Relation ◽  
Metal Contact ◽  
Initial Contact ◽  
Frictional Drag ◽  
Average Roughness ◽  
Finished Steel ◽  
Oil Film

In this paper the relation of surface roughness of bearing surfaces to allowable film thickness is studied quantitatively with a simple Michell pad apparatus. The pads used were faced with white metal and ran against mild steel collars. The lubricants studied were water, soap solution, paraffin, and light oil. There was little difference in the frictional behaviour of any of the lubricants, except that the aqueous lubricants would not run with very finely finished steel surfaces. The onset of metal to metal contact was detected by an increase in the frictional drag, and also by the change in electrical conductivity between the pad and collar—an extremely sensitive method. The paper shows that there is, at any rate for this system, a quantitative relation between the total surface roughness of the rubbing surfaces and the calculated oil film thickness both at the initial metal to metal contact and seizure. Initial contact occurs when the outlet film thickness, calculated from normal hydrodynamic theory, falls to three times the maximum surface roughness and seizure occurs when it is double the average roughness.

Influence of Surface Waviness on the Thermal Elastohydrodynamic Lubrication of an Eccentric-Tappet Pair

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
J. Wang ◽  
C. H. Venner ◽  
A. A. Lubrecht
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Surface Waviness ◽  
Film Pressure ◽  
Oil Film ◽  
Working Cycle ◽  
Temperature Oscillations ◽  
Minimum Film Thickness ◽  
Traction Coefficient ◽  
Oil Film Pressure

The effect of single-sided and double-sided harmonic surface waviness on the film thickness, pressure, and temperature oscillations in an elastohydrodynamically lubricated eccentric-tappet pair has been investigated in relation to the eccentricity and the waviness wavelength. The results show that, during one working cycle, the waviness causes significant fluctuations of the oil film, pressure, and temperature, as well as a reduction in minimum film thickness. Smaller wavelength causes more dramatic variations in oil film. The fluctuations of the pressure, film thickness, temperature, and traction coefficient caused by double-sided waviness are nearly the same compared with the single-sided waviness, but the variations are less intense.

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