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.

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.

Lubricant Film Thickness and Wear in Rolling Point Contact

1965 ◽  
Vol 8 (4) ◽  
pp. 411-424 ◽  
Author(s):  
T. E. Tallian ◽  
E. F. Brady ◽  
J. I. McCool ◽  
L. B. Sibley
Keyword(s):  
Film Thickness ◽  
Point Contact ◽  
Lubricant Film ◽  
Lubricant Film Thickness

Pressure Calculation From Experimentally Evaluated Lubricant Thickness Within EHL Contacts

2007 ◽  
Author(s):  
M. Vrbka ◽  
M. Vaverka ◽  
R. Poliscuk ◽  
I. Krupka ◽  
M. Hartl
Keyword(s):  
Film Thickness ◽  
Contact Pressure ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Solution Technique ◽  
Lubricant Film Thickness ◽  
Smooth Contact ◽  
Friction Surfaces

This paper is concerned with elastohydrodynamic lubrication, especially determination of lubricant film thickness and contact pressure within a point contact of friction surfaces of machine parts. A new solution technique for numerical determination of contact pressure is introduced. Direct measurement of contact pressure is very difficult. Hence, input data of lubricant film thickness obtained from the experiment based on colorimetric interferometry are used for calculation of pressure using the inverse elasticity theory. The algorithm is enhanced by convolution in order to increase calculation speed. The approach gives credible results on smooth contact and it is currently extended to enable the study of contact of friction surfaces with dents.

Lubricant Film Thickness in Rough Surface, Mixed Elastohydrodynamic Contact

1999 ◽  
Vol 122 (1) ◽  
pp. 65-76 ◽  
Author(s):  
G. Guangteng ◽  
P. M. Cann ◽  
A. V. Olver ◽  
H. A. Spikes
Keyword(s):  
Film Thickness ◽  
Rough Surface ◽  
Smooth Surface ◽  
Rolling Speed ◽  
Lubricant Film ◽  
Operating Conditions ◽  
Mapping Technique ◽  
Lubricant Film Thickness ◽  
Model Surface ◽  
Surface Features

A spacer layer imaging method has been employed to map lubricant film thickness in very thin film, rough surface, rolling elastohydrodynamic (EHD) contacts. A series of model roughnesses have been produced by depositing tiny ridges and bumps on a steel ball surface and the influence of these features on film thickness has been investigated at a range of rolling speeds. It has been shown that all the model surface features studied form speed-dependent, micro-EHD lubricating films, but the detailed shape and thickness of these films depends upon the geometry of the feature and the rolling speed. All model surface features also produce a net increase in mean film thickness, compared to the smooth surface, under operating conditions where the film thickness is less than the out-of-contact height of the surface feature studied. For a real, random, rough surface, however, mean film thickness is less than the smooth surface case. The film thickness mapping technique has also been used to measure the effective roughness of surfaces in lubricated contact. This shows that surfaces based on 2-D array of tiny circular bumps become rougher as the rolling speed and thus film thickness increases. However, real, rough surfaces appear to show a decrease of in-contact roughness with increasing rolling speed. [S0742-4787(00)01001-8]

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.

Study of Direct Measuring of Lubricant Condition in Rolling Element Bearings With Microcomputer Technique

1990 ◽  
Vol 112 (1) ◽  
pp. 92-97 ◽  
Author(s):  
Dongchu Zhao
Keyword(s):  
Film Thickness ◽  
Strain Gage ◽  
Lubricant Film ◽  
Rolling Element Bearings ◽  
Main Program ◽  
Test Apparatus ◽  
Lubricant Film Thickness ◽  
Rolling Element ◽  
Lubricant Films ◽  
Flow Charts

A method for measuring the lubricant condition with strain gage in rolling element bearings and the instrument used are introduced. In order to illustrate the method and the instrument, the theory of measuring lubricant films in rolling element bearings using strain technique, test apparatus, microcomputer hardware as well as software, flow charts for the main program and subprograms, are first described in detail. In addition, the lubricant film thickness is measured for several different lubricants and results are compared with theoretical ones. It is demonstrated that using the method and the instrument introduced in this paper, one can measure the lubricant condition inside bearings very accurately.

Optimized Mapping of Pressure in Lubricated Point Contacts Based on Measured Film Thickness

2007 ◽  
Author(s):  
Radek Polisˇcˇuk ◽  
Michal Vaverka ◽  
Martin Vrbka ◽  
Ivan Krˇupka ◽  
Martin Hartl
Keyword(s):  
Film Thickness ◽  
Numerical Solution ◽  
Point Contact ◽  
Contact Fatigue ◽  
Lubricant Film ◽  
Rolling Contact ◽  
Experimental Film ◽  
Lubricated Contacts ◽  
Practical Performance ◽  
Traction Drives

The surface topography plays significant role in lifetime of highly loaded machine parts with lubricated contacts. Many elements like gears, rolling bearings, cams and traction drives operate in mixed lubrication conditions, where the lubricant film behavior closely implies the main practical performance parameters such as friction wear, contact fatigue and scuffing. For prediction of wear and especially contact fatigue, the values and distribution of the pressure in rolling contact are often required. The usual theoretical approach based on numerical solution of physical-mathematical models built around the Reynolds equation can be extremely time consuming, especially when lubricant films are very thin, and contact load and required resolution very high. This study presents a further refined approach to our previously published experimental method, based on on inverse elasticity theory and fast convolution transformation between the lubricant film thickness map and the pressure distribution within the point contact. The experimental film thickness maps of EHD lubricated contacts with smooth and dented surfaces were processed using colorimetric interferometry and validated using numerical solution, in order to calibrate numerical parameters and to find limits of the new approach.

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