Local Reduction in Thickness of Point Contact EHL Films Caused by a Transversely Oriented Moving Groove and Its Recovery

1994 ◽  
Vol 116 (3) ◽  
pp. 635-639 ◽  
Author(s):  
M. Kaneta ◽  
H. Nishikawa
Keyword(s):  
Shear Flow ◽  
Film Thickness ◽  
Relative Size ◽  
Point Contact ◽  
Transient Behavior ◽  
Optical Interferometry ◽  
Steel Ball ◽  
Groove Surface ◽  
Glass Disk ◽  
Local Reduction

Transient behavior of elastohydrodynamic (EHL) films caused by a transversely oriented groove passing through the EHL conjunction is directly observed using the optical interferometry technique. A steel ball on which the groove is formed is run against a smooth glass disk under conditions of rolling with sliding. It is shown that a local reduction in film thickness caused by the groove and its recovery depend strongly on shear flow dominating the EHL conjunction and side leakage along the groove. Surface kinematic conditions and the relative size of the groove with respect to the overall film thickness have also profound effects on the above phenomena.

PTFE and MoS2 Additives for Mineral Oil Film Formation in EHL Point Contacts

2016 ◽  
Author(s):  
Glenn Kwabena Gyimah ◽  
Zhongning Guo ◽  
Ping Huang ◽  
Shuzhen Jiang ◽  
Gary C. Barber
Keyword(s):  
Film Thickness ◽  
Viscosity Index ◽  
Point Contact ◽  
Rolling Speed ◽  
Optical Interferometry ◽  
Lubricant Film ◽  
Steel Ball ◽  
Engine Oil ◽  
Lubricant Film Thickness ◽  
Viscosity Index Improvers

Lubricant film-forming viscosity index improvers blended with commercial engine oil have been developed and studied by using optical interferometry. The influence of the viscosity index improvers (PTFE and MoS2) mixed with oil were experimentally studied and compared with engine oil without the index improvers as the baseline. The effect of the viscosity index improvers on lubricant film thickness, contact pressure and rolling speed for the case of a steel ball loaded on a flat glass surface in point contact condition was investigated. An optical interferometry technique which utilized a monochromatic two-beam interferometry light source, a microscope and a high-speed video recording device was used for the investigation. Hamrock and Dawson calculations for EHL film thickness were also used for comparative analysis. The lubricants used were commercial SAE #30 engine oil and PTFE and MoS2 mixed with commercial SAE #30 engine oil. The oil viscosities ranged from 0.0109 Pa.s to 0.255 Pa.s. The rolling speed and the loads were varied between 0.189 m/s to 0.641 m/s and 1 N to 2.6 N respectively. The lubricant film thickness stability at the point of contact between the steel ball and the glass disc was investigated for both steady and rolling state conditions. The viscosity index improvers were found to have a significant effect on the film thickness behavior under pure rolling point contact conditions.

Influence of a Surface Bump or Groove on the Lubricating Performance and Dimple Phenomena in Simple Sliding Point EHL Contacts

2004 ◽  
Vol 126 (3) ◽  
pp. 466-472 ◽  
Author(s):  
Peiran Yang ◽  
Jinlei Cui ◽  
Motohiro Kaneta ◽  
Hiroshi Nishikawa
Keyword(s):  
Numerical Solution ◽  
Significant Influence ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Optical Interferometry ◽  
Steel Ball ◽  
Experimental Results ◽  
Oriented Surface ◽  
Glass Disk ◽  
Good Agreement

The influence of a transversely or longitudinally oriented surface bump or groove on the lubricating performance and dimple phenomena in the simple sliding point contact composed of a steel ball and a glass disk has been investigated theoretically with numerical solution of the thermal elastohydrodynamic lubrication (EHL) and experimentally with optical interferometry technique. Good agreement has been obtained between the theoretical and experimental results. It has also been discovered that the surface bump or groove is dangerously harmful to the lubricating performance and has a significant influence on the dimple phenomena.

scholarly journals The Effects of Artificially-Produced Defects on the Film Thickness Distribution in Sliding EHD Point Contacts

1982 ◽  
Vol 104 (3) ◽  
pp. 365-375 ◽  
Author(s):  
C. Cusano ◽  
L. D. Wedeven
Keyword(s):  
Film Thickness ◽  
Contact Region ◽  
Thickness Distribution ◽  
Point Contact ◽  
Optical Interferometry ◽  
Point Contacts ◽  
Thickness Profile ◽  
Inlet Region

The effects of artificially-produced dents and grooves on the elastohydrodynamic (EHD) film thickness profile in a sliding point contact are investigated by means of optical interferometry. The defects, formed on the surface of a highly polished ball, are held stationary at various locations within and in the vicinity of the contact region while the disk is rotating. It is shown that the defects, having a geometry similar to what can be expected in practice, can dramatically change the film thickness which exists when no defects are present in or near the contact. This change in film thickness is mainly a function of the position of the defects in the inlet region, the geometry of the defects, the orientation of the defects in the case of grooves, and the depth of the defect relative to the central film thickness.

Effects of Asperities in Elastohydrodynamic Lubrication

1980 ◽  
Vol 102 (3) ◽  
pp. 374-378 ◽  
Author(s):  
M. Kaneta ◽  
A. Cameron
Keyword(s):  
Film Thickness ◽  
Glass Plate ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Critical Value ◽  
Optical Interferometry ◽  
Asperity Height ◽  
Height Ratio ◽  
Pure Rolling

Optical interferometry was used to study rough surfaces under lubricated point contact. Three dimensional “asperities” of chromium were sputtered onto a steel ball which was run against a smooth glass plate under both rolling and sliding. The experimental results were compared with the various published theories. The film thicknesses found in sliding are different from those observed in pure rolling, which are nearly equal to the theoretical values. Film thickness collapse occurred when the central film thickness/half asperity height ratio (λ ratio) reached a critical value.

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.

scholarly journals Determination of Viscosity and Pressure in an Elastohydrodynamic Rolling Contact by using Optical Interferometry: A Theoretical Study

1996 ◽  
Vol 210 (4) ◽  
pp. 259-268 ◽  
Author(s):  
J O Östensen ◽  
R Larsson ◽  
C H Venner
Keyword(s):  
Film Thickness ◽  
Apparent Viscosity ◽  
Measurement Errors ◽  
Theoretical Study ◽  
Point Contact ◽  
Thickness Measurement ◽  
Optical Interferometry ◽  
Rolling Contact ◽  
Force Balance

Optical interferometry has been used during the last 30 years for film thickness measurements in elastohydrodynamic (EHD) contacts. In the work presented in this paper the possibility of using optical interferometry for determining pressure and apparent viscosity in a fully flooded EHD point contact has been theoretically investigated. The pressure in the contact is computed from elastic deformation theory and force balance. The apparent viscosity can be obtained from the Reynolds equation when the film thickness and the pressure are known. To theoretically examine the sensitivity to measurement errors, different errors have been implemented in a set of ‘exact’ numerical data. From the theoretical study it can be seen that a film thickness map obtained from optical interferometry can be used for determination of both pressure and apparent viscosity measurement in an EHD point contact. The simulated errors that have been used do not influence the pressure within the Herzian region by more than a few per cent. However, to obtain reliable results from the apparent viscosity calculations, the measurements of film thickness, load and elastic modulus must be very accurate. It is seen, for example, that the resolution of the film thickness measurement has to be less than 1 nm to achieve high accuracy.

Variation of zero entraining velocity dimple in grease-lubricated reciprocating motion

2019 ◽  
Vol 233 (11) ◽  
pp. 1661-1687 ◽  
Author(s):  
Shanshan Wang ◽  
Jing Wang ◽  
Yiming Han ◽  
Weimin Li
Keyword(s):  
Film Thickness ◽  
Significant Influence ◽  
Optical Interferometry ◽  
Steel Ball ◽  
Surface Velocity ◽  
Reciprocating Motion ◽  
Test Rig ◽  
Maximum Surface ◽  
Disk Test ◽  
Starvation Conditions

In this study, experiments were conducted on a ball-on-disk test rig using optical interferometry to explore the variation in grease film thickness under zero entraining velocity reciprocating motion. The steel ball and the sapphire disk move at equal speeds but in opposite directions within a triangle wave. Three types of commercially available bearing greases with different consistencies, Centoplex 2EP, Centoplex 3, and MP-3, were used in these experiments. The variations in the surface dimple phenomenon with decreasing maximum surface velocity, differing grease consistency, and grease starvation conditions were studied. Results showed that the grease consistency exerts a significant influence on the surface dimple and the starvation severity.

scholarly journals Optical Analysis of Ball Bearing Starvation

1971 ◽  
Vol 93 (3) ◽  
pp. 349-361 ◽  
Author(s):  
L. D. Wedeven ◽  
D. Evans ◽  
A. Cameron
Keyword(s):  
Film Thickness ◽  
Ball Bearing ◽  
Point Contact ◽  
Experimental Measurements ◽  
Line Contact ◽  
Optical Analysis ◽  
Grease Lubrication ◽  
Theoretical Predictions ◽  
Pressure Stress ◽  
Starvation Conditions

Elastohydrodynamic oil film measurements for rolling point contact under starvation conditions are obtained using optical interferometry. The experimental measurements present a reasonably clear picture of the starvation phenomenon and are shown to agree with theoretical predictions. Starvation inhibits the generation of pressure and, therefore, reduces film thickness. It also causes the overall pressure, stress, and elastic deformation to become more Hertzian. Additional experiments using interferometry illustrate: the cavitation pattern, lubricant entrapment, grease lubrication, ball spin, and edge effects in line contact.

scholarly journals A thermal resistances-based approach for thermal-elastohydrodynamic calculations in point contacts

2017 ◽  
Vol 232 (11) ◽  
pp. 2088-2102 ◽  
Author(s):  
Eduardo de la Guerra Ochoa ◽  
Javier Echávarri Otero ◽  
Enrique Chacón Tanarro ◽  
Benito del Río López
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Thermal Effects ◽  
Good Accuracy ◽  
Computational Cost ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
New Approach ◽  
Ball On Disc

This article presents a thermal resistances-based approach for solving the thermal-elastohydrodynamic lubrication problem in point contact, taking the lubricant rheology into account. The friction coefficient in the contact is estimated, along with the distribution of both film thickness and temperature. A commercial tribometer is used in order to measure the friction coefficient at a ball-on-disc point contact lubricated with a polyalphaolefin base. These data and other experimental results available in the bibliography are compared to those obtained by using the proposed methodology, and thermal effects are analysed. The new approach shows good accuracy for predicting the friction coefficient and requires less computational cost than full thermal-elastohydrodynamic simulations.

Scale Effects in Generalized Newtonian Elastohydrodynamic Films

2008 ◽  
Author(s):  
I. I. Kudish ◽  
P. Kumar ◽  
M. M. Khonsary ◽  
S. Bair
Keyword(s):  
Film Thickness ◽  
Scale Effects ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Viscosity Coefficient ◽  
Shear Thinning ◽  
Effective Pressure ◽  
Practical Advantage ◽  
Inlet Zone ◽  
Real Machine

The prediction of elastohydrodynamic lubrication (EHL) film thickness requires knowledge of the lubricant properties. Today, in many instances, the properties have been obtained from a measurement of the central film thickness in an optical EHL point contact simulator and the assumption of a classical Newtonian film thickness formula. This technique has the practical advantage of using an effective pressure-viscosity coefficient which compensates for shear-thinning. We have shown by a perturbation analysis and by a full EHL numerical solution that the practice of extrapolating from a laboratory scale measurement of film thickness to the film thickness of an operating contact within a real machine may substantially overestimate the film thickness in the real machine if the machine scale is smaller and the lubricant is shear-thinning in the inlet zone.

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