Experimental Investigations Into the Behavior of Elastohydrodynamic Lubricating Films

1982 ◽  
Vol 104 (1) ◽  
pp. 91-98 ◽  
Author(s):  
G. S. A. Shawki ◽  
M. O. A. Mokhtar ◽  
A. A. Abdel-Ghany
Keyword(s):  
Temperature Distribution ◽  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Contact Temperature ◽  
Experimental Investigations ◽  
Capacitive Transducer ◽  
Full Contact ◽  
The Subject ◽  
Critical Reduction ◽  
Lubrication Conditions

This paper presents the results of experimental investigations conducted on a disk machine specially designed and constructed to determine film behavior under elastohydrodynamic lubrication conditions. Oil film thickness is measured by a novel electronic technique utilizing a capacitive transducer. Besides film geometry, measurements include temperature distribution and frictional traction in the film, all taken under pure sliding conditions. Recordings of full contact profile confirm by way of example the development of a critical reduction in film thickness towards the exit end of the Hertzian zone, this being accompanied by a critical increase in contact temperature. Further work on the subject is proceeding.

Your EHD Rig May Not Be As Elastohydrodynamic As You Think

2021 ◽  
Vol 143 (8) ◽  
Author(s):  
Scott Bair ◽  
Wassim Habchi
Keyword(s):  
Film Thickness ◽  
Short Note ◽  
Elastohydrodynamic Lubrication ◽  
Viscosity Coefficient ◽  
Experimental Investigations ◽  
Poor Agreement ◽  
Elastic Regime ◽  
The Poor ◽  
The Subject ◽  
Primary Instrument

Abstract The concentrated contact formed between a steel ball and a glass disc—the optical elastohydrodynamic lubrication (EHD) rig—has been the primary instrument for experimental investigations of elastohydrodynamic film thickness. It has been a source for values of pressure-viscosity coefficient, a difficult-to-define property of liquids. However, comparisons with the pressure dependence of the viscosity obtained in viscometers show little agreement. There are multiple reasons for this failure including shear-thinning and compressibility of the oil. Another reason for the poor agreement is the subject of this short note. The optical EHD rig using glass as one surface will only be in the piezoviscous-elastic (EHD) regime when the pressure-viscosity coefficient is large. For low values, it would be operating in the isoviscous-elastic regime (soft EHD).

Three-Dimensional Temperature Distribution in EHD Lubrication: Part II—Point Contact and Numerical Formulation

1993 ◽  
Vol 115 (1) ◽  
pp. 36-45 ◽  
Author(s):  
Kyung-Hoon Kim ◽  
Farshid Sadeghi
Keyword(s):  
Temperature Distribution ◽  
Film Thickness ◽  
Numerical Study ◽  
Control Volume ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Numerical Formulation ◽  
Energy Equations

A numerical study of Newtonian thermal elastohydrodynamic lubrication (EHD) of rolling/sliding point contacts has been conducted. The two-dimensional Reynolds, elasticity and the three-dimensional energy equations were solved simultaneously to obtain the pressure, film thickness and temperature distribution within the lubricant film. The control volume approach was employed to discretize the differential equations and the multi-level multi-grid technique was used to simultaneously solve them. The discretized equations, as well as the nonorthogonal coordinate transformation used for the solution of the energy equation, are described. The pressure, film thickness and the temperature distributions, within the lubricant film at different loads, slip conditions and ellipticity parameters are presented.

Relationship Between Temperature Distribution in EHL Film and Dimple Formation

2004 ◽  
Author(s):  
Kazuyuki Yagi ◽  
Keiji Kyogoku ◽  
Tsunamitsu Nakahara
Keyword(s):  
Phase Transition ◽  
Experimental Study ◽  
Temperature Distribution ◽  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Infrared Emission ◽  
Maximum Temperature ◽  
Oil Film ◽  
Oil Flow ◽  
Ball Surface

This paper describes an experimental study on dimple formations under elastohydrodynamic lubrication (EHL) conditions. The oil film thickness between a ball surface and a sapphire disk was measured using optical interferometry and the temperatures of both the surfaces and of the oil film averaged across it were measured by an improved infrared emission technique. It was found that temperature profile across the oil film varies abruptly along the direction of the oil film thickness and the Couette flow decreases due to the viscosity wedge action as the oil flow is close to the dimple zone. The maximum temperature rise in the dimple zone sometimes reached above 400 K and thus the phase transition of the oil from liquid to glass may not occur.

Investigation of the Discharge-Voltage Method of Measuring the Thickness of Oil Films Formed in a Disc Machine under Conditions of Elastohydrodynamic Lubrication

1966 ◽  
Vol 181 (1) ◽  
pp. 633-652 ◽  
Author(s):  
A. Dyson
Keyword(s):  
Film Thickness ◽  
Metal Surfaces ◽  
Thick Films ◽  
Elastohydrodynamic Lubrication ◽  
Discharge Voltage ◽  
Suitable Alternative ◽  
Electrical Capacity ◽  
Non Linear ◽  
Oil Films ◽  
Lubrication Conditions

It is reported in the literature that the ‘discharge-voltage’ method offers a simple means of measuring the thickness of oil films between moving metal surfaces. To confirm this report it is necessary to compare discharge-voltage measurements with film thickness measured by an alternative method. So far as the author is aware no such comparison of measured film thicknesses in elastohydrodynamic lubrication conditions has been published. Under these conditions, a suitable alternative way of estimating the thicknesses of oil films between moving metal surfaces is to measure the electrical capacity between them. This method has been applied to a disc machine and a short programme of work undertaken to compare film thickness estimated in this way with the results of discharge-voltage determinations. It was found that there was some relation between discharge voltage and film thickness but that, in general, this relation was non-linear and depended on the slide/roll ratio and on the temperature. It is therefore concluded that the discharge voltage does not measure the thickness of oil films in the simple way suggested; there were some indications that it may be possible to use it to measure relatively thick films, of the order of 40 μin (1 μm) or thicker, at high slide/roll ratios.

Grease thermal elastohydrodynamic lubrication properties of tripod sliding universal couplings

2018 ◽  
Vol 70 (1) ◽  
pp. 133-139
Author(s):  
Ye Zhou ◽  
Degong Chang ◽  
Songmei Li
Keyword(s):  
Temperature Distribution ◽  
Film Thickness ◽  
Pressure Distribution ◽  
Geometric Model ◽  
Elastohydrodynamic Lubrication ◽  
Effective Radius ◽  
Grease Lubrication ◽  
Content Type ◽  
Lubricating Film ◽  
Lubrication Properties

Purpose This paper aims to improve the grease thermal elastohydrodynamic lubrication (TEHL) properties of the tripod sliding universal coupling (TSUC) under automotive practical conditions. For this purpose, the effect of effective radius was theoretically investigated. Design/methodology/approach Based on the simplified geometric model, the effect of effective radius on the pressure distribution, film thickness and temperature distribution of the TSUC was theoretically investigated using the multigrid and stepping methods. The TEHL properties were compared with the results obtained using the isothermal calculation method. Findings The results show that the thermal effect has a great impact on the film thickness and the pressure distribution of grease lubrication properties. Moreover, larger effective radius results in a wider but lower pressure distribution, a wider and thicker lubricating film and a lower temperature distribution. Originality/value The TSUC can be widely used in the front drive automotive transmission because it can transmit larger torque than before. The effect of effective radius on the thermal grease lubrication properties under automotive practical conditions provides a new direction for designing it.

Elastohydrodynamic Lubrication of Elliptical Contacts for Materials of Low Elastic Modulus: II—Starved Conjunction

1979 ◽  
Vol 101 (1) ◽  
pp. 92-98 ◽  
Author(s):  
B. J. Hamrock ◽  
D. Dowson
Keyword(s):  
Elastic Modulus ◽  
Film Thickness ◽  
Rolling Direction ◽  
Numerical Procedure ◽  
Elastohydrodynamic Lubrication ◽  
Radius Of Curvature ◽  
Low Elastic Modulus ◽  
Minimum Film Thickness ◽  
Contour Plots ◽  
Lubrication Conditions

By using the theory and numerical procedure developed by the authors in earlier publications, the influence of lubricant starvation upon minimum film thickness in starved elliptical elastohydrodynamic conjunctions for low-elastic-modulus materials has been investigated. Lubricant starvation was studied simply by moving the inlet boundary closer to the center of the conjunction. The results show that the location of the dimensionless inlet boundary m* between the fully flooded and starved conditions can be expressed simply as m* = 1 + 1.07 [(Rx/b)2Hmin,F]0.16, where Rx is the effective radius of curvature in the rolling direction, b is the semiminor axis of the contact ellipse, and Hmin,F is the dimensionless mimimum film thickness for the fully flooded condition. That is, for a dimension-less inlet distance m less than m*, starvation occurs; and for m ≥ m*, a fully flooded condition exists. Furthermore, it has been possible to express the minimum film thickness for a starved condition as Hmin,S = Hmin,F [(m − 1)/(m* − 1)]0.22. Contour plots of the pressure and film thickness in and around the contact are presented for both the fully flooded and starved lubrication conditions. It is evident from the contour plots that the inlet pressure contours become less circular and that the film thickness decreases substantially as the severity of starvation increases. The results presented in this report, when combined with the findings previously reported, enable the essential features of starved, elliptical, elastohydrodynamic conjunctions for materials of low elastic modulus to be ascertained.

Some important aspects of thermal elastohydrodynamic lubrication

2010 ◽  
Vol 224 (12) ◽  
pp. 2588-2598 ◽  
Author(s):  
P Kumar ◽  
P Anuradha ◽  
M M Khonsari
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Thermal Expansivity ◽  
Viscous Heating ◽  
Line Contact ◽  
Rheological Equation ◽  
Transient Conditions ◽  
The Subject ◽  
Thermal Ehl

Thermal effect in elastohydrodynamic lubrication (EHL) has been the subject of study for the last four decades; however, some important aspects related to the physical behaviour of the lubricant in response to pressure, temperature, and shear rate remain largely neglected. This paper presents a brief review of the thermal EHL literature and sheds light on the importance of accurate characterization of the lubricant properties such as viscosity, density, rheology, and thermal conductivity. Full thermal EHL line contact simulations under steady-state and transient conditions show that using the ambient value of thermal expansivity, which has been the usual trend, may overestimate the central film thickness and introduce unrealistic features in transient EHL characteristics. Also, it is demonstrated that the most extensively used rheological equation – the sinh law – for characterizing the behaviour of shear-thinning lubricants underestimates the effect of viscous heating on EHL traction and film thickness.

Three-Dimensional Temperature Distribution in EHD Lubrication: Part I—Circular Contact

1992 ◽  
Vol 114 (1) ◽  
pp. 32-41 ◽  
Author(s):  
Kyung Hoon Kim ◽  
Farshid Sadeghi
Keyword(s):  
Temperature Distribution ◽  
Film Thickness ◽  
Temperature Rise ◽  
Thermal Effects ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Simultaneous System ◽  
Ehd Lubrication ◽  
Energy Equations ◽  
Circular Contact

A complete numerical solution of Newtonian thermal compressible elastohydrodynamic lubrication of rolling/sliding point (circular) contact has been obtained. The multilevel multigrid technique was used to solve the simultaneous system of thermal Reynolds, elasticity and the energy equations with their boundary conditions. The effects of various loads, speeds, and slip conditions on the lubricant temperature, film thickness, and friction force have been investigated. The results indicate that the temperature rise in the contact is significant and thermal effects cannot be neglected.

On the Surface Dimple Phenomena in Elliptical TEHL Contacts With Arbitrary Entrainment

2002 ◽  
Vol 125 (1) ◽  
pp. 102-109 ◽  
Author(s):  
Jing Wang ◽  
Peiran Yang ◽  
Motohiro Kaneta ◽  
Hiroshi Nishikawa
Keyword(s):  
Temperature Distribution ◽  
Theoretical Analysis ◽  
Film Thickness ◽  
Frictional Coefficient ◽  
Elastohydrodynamic Lubrication ◽  
Minor Axis ◽  
Hertzian Contact ◽  
Intermediate Angle ◽  
Minimum Film Thickness ◽  
Good Agreement

Theoretical analysis and optical interferometry experiments are performed to investigate the dimple phenomena in thermal elastohydrodynamic lubrication (TEHL) of elliptical contacts under pure sliding conditions. The lubricant entrainment is along the major and minor axes of the Hertzian contact ellipse or at some intermediate angle. Good agreement is achieved between theoretical and experimental results and the surface dimple phenomena occurring in glass-steel conjunctions are explained by the temperature-viscosity wedge mechanism. The influence of the angle between the minor axis and the entrainment vector on the position and shape of the dimple, the central and minimum film thickness, the temperature distribution and the frictional coefficient is discussed.

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.

Sign in / Sign up

Export Citation Format

Share Document