Effects of a thickener structure on grease elastohydrodynamic lubrication films

2000 ◽  
Vol 214 (4) ◽  
pp. 327-336 ◽  
Author(s):  
M Kaneta ◽  
T Ogata ◽  
Y Takubo ◽  
M Naka
Keyword(s):  
Film Thickness ◽  
Direct Observation ◽  
Film Formation ◽  
Elastohydrodynamic Lubrication ◽  
Rolling Speed ◽  
Molecular Structures ◽  
Optimum Temperature ◽  
Oil Viscosity ◽  
Base Oil ◽  
Different Types

The effects of the thickener structure and base oil viscosity on the grease film formation in rolling point elastohydrodynamic contacts have been discussed on the basis of direct observation using the optical interferometry technique. Three different types of diurea greases without additives have been used as test greases. As the base oils three kinds of ether-type synthetic oils having similar molecular structures but different viscosities were used. The film behaviour of fresh greases has also been compared with that of the degraded greases. It has been found that the behaviour of grease elastohydrodynamic lubrication films is basically influenced by the thickener structure and base oil viscosity. The adhesion or deposition of the thickener on the contacting surfaces and oil starvation which affect film formation depend on the thickener structure, base oil viscosity and rolling speed. Furthermore, it has been suggested that there is an optimum temperature which gives a maximum film thickness according to the consistency of the grease.

The lubrication of rollers II. Film thickness with relation to viscosity and speed

1961 ◽  
Vol 254 (1040) ◽  
pp. 223-236 ◽  
Keyword(s):  
Film Thickness ◽  
Surface Temperature ◽  
Frictional Heating ◽  
Specific Effect ◽  
Elastohydrodynamic Lubrication ◽  
Rolling Speed ◽  
Frictional Heat ◽  
Oil Viscosity ◽  
The Mean ◽  
The Difference

Systematic measurements with a disk machine of the thickness of the hydrodynamic oil film between loaded rollers have been made with respect to load, rolling speed, sliding speed and oil viscosity. It has been found that the viscosity of greatest im portance with respect to film thickness is the viscosity of the oil at the surface temperature of the disks (tjs) ; the viscosity of the oil supplied by the lubricating jet and the viscosity attained by the oil on its passage through the pressure zone are unim portant. It has been shown that film thickness is independent of load at loads exceeding 7 x 10 7 dyn cm -1 , but is dependent upon the rolling speed u (the mean peripheral speed of the disks) as well as upon rjs. To within +15 % all the results are expressed by h* = 0-8[(m^ ) /100] 0.5 where h% is the film thickness in microns when utjs is expressed in dyncm -1 . Particularly is it noteworthy that this same expression remained true even when sliding was introduced. (The ranges of conditions covered by the experiments were loads from 7 x 10 7 to 2 x 10 8 dyncm -1 , rolling speeds from 32 to 1000 cm s -1 , sliding speeds up to 480 cm s -1 and values of rjs from 0.14 to 1.19P.) It is also shown that an implication of the insensitivity to sliding is that on the entry side there is little frictional heating of the oil due to the sliding up to a point where the pressure approaches 1 x 10 9 dyncm -2 . The experimental results, have been compared with the theory of the elastohydrodynamic lubrication at the conjunction of the disks. The theory disregards frictional heating and predicts a film thickness proportional to (zb/s) 0.7 in contrast with the exponent of 0.5 given by experiment. Evidence is cited that the difference is not due to frictional heat but it is suggested that the discrepancy is due to a specific effect of speed upon the increase in viscosity which oils exhibit under pressure.

Effects of transversely oriented defects and thickener lumps on grease elastohydrodynamic lubrication films

2001 ◽  
Vol 215 (3) ◽  
pp. 279-288 ◽  
Author(s):  
M Kaneta ◽  
H Nishikawa ◽  
M Naka
Keyword(s):  
Film Thickness ◽  
Contact Area ◽  
Surface Defects ◽  
Film Formation ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Optical Interferometry ◽  
Transient Behaviour ◽  
Different Types

Using the optical interferometry technique, transient behaviour of grease films at an elastrohydrodynamic lubrication (EHL) point contact caused by a transversely oriented groove and long bump passing through the contact area is directly observed with three different types of diurea grease without additives. The effects of the thickener content on the grease film formation are also examined. It has been found that the behaviour of EHL films depends strongly on the thickener structure, and the effects of surface defects on EHL films become pronounced as the film thickness decreases. It has also been found that the thickener lumps move through the EHL conjunction while repeating attachment to the surfaces and detachment from them, and the thickener lumps deposited on the surfaces affect the film behaviour as a kind of solid bump.

The Shear-Thinning Elastohydrodynamic Film Thickness of a Two-Component Mixture

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Yuchuan Liu ◽  
Q. Jane Wang ◽  
Ivan Krupka ◽  
Martin Hartl ◽  
Scott Bair
Keyword(s):  
Film Thickness ◽  
Ambient Pressure ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Shear Thinning ◽  
Component Mixture ◽  
Base Oil ◽  
Viscosity Models ◽  
Viscosity Behavior ◽  
Pure Rolling

Lubricant base oils are often blends of different molecular weight cuts to arrive at a specified ambient pressure viscosity and, to improve the temperature-viscosity behavior or to simply increase the viscosity, viscosity-modifying polymer additives are often added to the base oil. This paper investigates the effect of mixture rheology on elastohydrodynamic lubrication (EHL) film thickness using EHL contact measurements and a full numerical analysis for three synthetic lubricants including two single-component lubricants PAO650 and PAO100 and a mixture of these. The pressure and shear dependences of the viscosity of these lubricants were measured with high-pressure viscometers; viscosities were not adjusted to fit experiment. The point contact film thicknesses for these lubricants in pure rolling were measured using a thin-film colorimetric interferometry apparatus. Numerical simulations based on the measured rheology show very good agreement with the measurements of film thickness while the Newtonian prediction is up to twice the measurement. These results validate the use of realistic shear-thinning and pressure-viscosity models, which originate from viscosity measurements. It is conceivable that simulation may provide a means to “engineer” lubricants with the optimum balance of film thickness and friction through intelligent mixing of components.

The Effect of Kinematic Conditions on Film Thickness in Compliant Lubricated Contact

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
David Nečas ◽  
Tomáš Jaroš ◽  
Kryštof Dočkal ◽  
Petr Šperka ◽  
Martin Vrbka ◽  
...  
Keyword(s):  
Film Thickness ◽  
Optical Glass ◽  
Film Formation ◽  
Fluorescent Microscopy ◽  
Elastohydrodynamic Lubrication ◽  
Constant Load ◽  
Fluid Viscosity ◽  
Lubricating Film ◽  
Theoretical Predictions ◽  
Lubricated Contact

The present paper deals with an investigation of film formation in compliant lubricated contact. Despite these contacts can be found in many applications of daily life including both biological and technical fields, so far little is known about the lubrication mechanisms inside the contacts. The main attention is paid to the effect of kinematic conditions on central film thickness. For this purpose, fluorescent microscopy method was employed. Experiments were realized in ball-on-disk configuration, while the ball was made from rubber and the disk was from optical glass. The contact was lubricated by glycerol and polyglycol to examine the effect of fluid viscosity. The measurements were conducted under pure rolling and rolling/sliding conditions. The entrainment speed varied from 10 to 400 mm/s and constant load of 0.2 N was applied. Experimental results were compared with two theoretical predictions derived for isoviscous-elastohydrodynamic lubrication (I-EHL) regime. It was found that the thickness of lubricating film gradually increases with increasing entrainment speed, which corresponds to theoretical assumptions. Against expectations, evident influence of slide-to-roll ratio (SRR) on film formation was observed. In the last part of the paper, some limitations of this study are discussed and several recommendations for further methodology improvement are suggested.

Experimental study of starvation in grease-lubricated finite line contacts

2017 ◽  
Vol 69 (6) ◽  
pp. 963-969 ◽  
Author(s):  
Zhijian Wang ◽  
Xuejin Shen ◽  
Xiaoyang Chen ◽  
Qiang Han ◽  
Lei Shi
Keyword(s):  
Film Thickness ◽  
High Viscosity ◽  
Operating Conditions ◽  
Test Rig ◽  
Oil Viscosity ◽  
Content Type ◽  
Base Oil ◽  
Optical Test ◽  
Line Contacts ◽  
Finite Line

Purpose The purpose of this paper is to study starvation in grease-lubricated finite line contacts and to understand film-forming mechanisms of grease-lubricated finite line contacts. Design/methodology/approach A multiple-contact optical elastohydrodynamic (EHL) test rig is constructed to investigate the influences of lubricant properties on film thickness and lubrication conditions at different working conditions. The film thickness is calculated according to the relative light intensity principle. The degree of starvation is evaluated by the air–oil meniscus distance and the corresponding film thickness. Findings The experimental results show that for greases with high-viscosity base oil, the high-frequency fluctuation of film thickness is observed in low-speed operating conditions. Reducing the viscosity of the base oil and improving running speed can weaken the fluctuation of film thickness. The degree of starvation increases with increasing base oil viscosity, rolling speed and the crown drop. In addition, reducing the replenishment time by reducing the gap between the rollers also can increase the degree of starvation. Originality/value Starvation is often to occur in finite line contacts, such as roller bearings and gears; there are still limited finite line contact EHL test rigs, much less multiple-contact optical test rigs. Therefore, the present work is undertaken to construct the multiple-contact test rig and to evaluate the mechanism of starvation in finite line contacts.

Numerical analysis for the influence of water film on adhesion between rail and wheel

1998 ◽  
Vol 212 (5) ◽  
pp. 359-368 ◽  
Author(s):  
H Chen ◽  
A Yoshimura ◽  
T Ohyama
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Material Parameter ◽  
Numerical Solutions ◽  
Adhesion Force ◽  
Elastohydrodynamic Lubrication ◽  
Water Film ◽  
Rolling Speed ◽  
Linear Regression Method ◽  
Water Film Thickness

The adhesion force between rail and wheel is one of the important factors for proceeding towards the realization of high-speed railway. On the other hand, it is supposed that the water film formed between the rail and wheel has a remarkable influence on the adhesion force under rainy condition at higher speeds. In this paper, taking Bett and Cappi's viscosity values of water, which show quite a different behaviour from the viscosity of oil, the influence has been investigated of important factors such as rolling speed, contact pressure and temperature on water film thickness for a smooth surface by applying elastohydrodynamic lubrication theory. Based on the numerical solutions, an empirical equation has been developed for water film thickness relating to rolling speed, load and material parameter by using a linear regression method and comparing it with other authors' works on a lower material parameter or elastic-isoviscous contact. Furthermore, in order to understand the influence of the above factors and the surface roughness on the adhesion force, adhesion coefficients have been calculated on a trial basis in the case of rough surface contact under limited conditions, and the theoretical results have been compared with the measured values of the tests on Japanese Shinkansen vehicles in the field.

scholarly journals Elastohydrodynamic Performance of Unexcited Electro-Rheological Fluids

1996 ◽  
Vol 10 (23n24) ◽  
pp. 3181-3189 ◽  
Author(s):  
R.S. Dwyer-Joyce ◽  
W.A. Bullough ◽  
S. Lingard
Keyword(s):  
Film Thickness ◽  
Base Fluid ◽  
Film Formation ◽  
Contact Region ◽  
Elastohydrodynamic Lubrication ◽  
Solid Particles ◽  
Fluid Film ◽  
Test Results ◽  
Er Fluids ◽  
Er Fluid

Exploratory test results are presented for a series of mixtures of unexcited electrorheological (ER) fluids under elastohydrodynamic lubrication (ehl) conditions. These were obtained from direct observation of film formation in an optical interferometric apparatus. Results are presented as photographs of the fluid film and plots of film thickness versus speed for a range of ER fluid solid fractions. Adequate film formation is limited by the tendency of the solid particles to evade the contact region. At very low contact speeds particles enter the chl contact and generate a fluid film. At higher speeds the particulates do not become entrained in the contact; the film formation is then determined by the viscosity of the base fluid.

Paper 3: Lubrication of Rollers with Oils Containing Polymers

1966 ◽  
Vol 181 (15) ◽  
pp. 192-199
Author(s):  
G. M. Hamilton ◽  
W. G. Robertson
Keyword(s):  
Film Thickness ◽  
Polymer Solutions ◽  
Shear Stresses ◽  
Oil Viscosity ◽  
Base Oil ◽  
Oil Film ◽  
Mineral Oils ◽  
Inlet Region ◽  
Thickness Measurements

The shear stresses in an elastohydrodynamic oil film have been calculated. In the inlet region they are of the order of 107 and in the outlet 109 dyn/cm2. While such stresses do not affect mineral oils they are liable to cause breakdown of polymers in multigrade oils. To test this film thickness measurements were carried out in a four-disc machine with a range of polymer solutions. It was found that the degree of viscosity loss varied greatly; some polymer solutions showed no loss whilst others merely exhibited their base oil viscosity. By measuring the viscosity of samples scraped from the disc surfaces it was possible to divide the observed viscosity loss into permanent and temporary components.

scholarly journals EHL oil film thickness under rolling-sliding contact

1970 ◽  
Vol 38 ◽  
pp. 58-60 ◽  
Author(s):  
DM Nuruzzaman ◽  
MAA Sheikh
Keyword(s):  
Film Thickness ◽  
Contact Pressure ◽  
Mechanical Engineering ◽  
Elastohydrodynamic Lubrication ◽  
Rolling Speed ◽  
Sliding Contact ◽  
Slip Ratio ◽  
Oil Film

The Elastohydrodynamic lubrication (EHL) minimum oil film thickness is theoretically investigated under rolling with sliding contact. The effects of contact pressure, rolling speed and slip ratio on the EHL minimum oil film thickness are calculated numerically. It is found that for a range of contact pressure from 0.5 to 3.5 GPa, the minimum oil film thickness gradually decreases with the increase in contact pressure. As the rolling speed increases from 3500 to 4500 rpm, oil film thickness is increased. It is also found that the oil film thickness is not much influenced by the slip ratio. Keywords: EHL oil film thickness, Contact pressure, Rolling speed, Slip ratio. DOI: 10.3329/jme.v38i0.902 Journal of Mechanical Engineering Vol.38 Dec. 2007 pp.58-60

Correlation of base oil viscosity in grease with vibration severity of damaged rolling bearings

2018 ◽  
Vol 70 (2) ◽  
pp. 264-272 ◽  
Author(s):  
Imran Moulaalli Jamadar ◽  
Dipakkumar Vakharia
Keyword(s):  
Theoretical Model ◽  
Design Methodology ◽  
Oil Viscosity ◽  
Rolling Bearings ◽  
Content Type ◽  
Base Oil ◽  
Lubricant Oil ◽  
Bearing Failures ◽  
Different Types ◽  
Lubrication Condition

Purpose The main objective of the paper is to explore the theoretical correlation of base oil viscosity in grease and to study the effect of grease grade on mechanical vibrations associated with the damaged rolling bearings. Design/methodology/approach For theoretical purposes, formulation theory of dimensional analysis was implemented. Experiments were then performed on the test bearings lubricated with three different types of greases, namely, SKF LGHP2, SKF LGMT3 and SKF LGWA2. Findings The numerical results obtained from the theoretical model along with the results of experiments show that the vibration amplitudes of the defective bearings come down to a lower level when it is lubricated with the grease of a higher base oil viscosity. Research limitations/implications The promising results from the theoretical model make it usable for the practical rotating machineries applying a variety of the rolling bearings. Consequently, if the bearing is not severely damaged, its performance can be increased by lubricating it with thicker grease. Originality/value Despite many significant contributions in the field to detect the presence of defects, not many studies have been performed that relate the lubrication condition of the rolling bearings with the vibration response, because around 50-75% of the bearing failures are attributed to be lubrication related. Hence, there is need to develop a mathematical model that can correlate the vibration severity of the bearings with viscosity of the lubricant oil in the greases along with other design and operating parameters.

Sign in / Sign up

Export Citation Format

Share Document