Influence of Contact Pressure on Central and Minimum Film Thickness Within Ultrathin Film Lubricated Contacts

2005 ◽  
Vol 127 (4) ◽  
pp. 890-892 ◽  
Author(s):  
I. Křupka ◽  
M. Hartl ◽  
M. Liška
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Nonlinear Behavior ◽  
Test Rig ◽  
Lubricated Contacts ◽  
Optical Test ◽  
Minimum Film Thickness ◽  
Lubricant Films ◽  
The Relationship ◽  
Contact Pressures

Recent numerical results have indicated that the relationship between the film thickness and the speed may not always follow the simple power law, especially under severe conditions. This paper is aimed at obtaining experimental results at high contact stresses and low speeds to study the thin film behavior. Ultrathin lubricant films were observed at maximum Hertz pressures of 0.52, 1.01, and 1.54 GPa by using an optical test rig. Central and minimum film thickness values were obtained with thin film colorimetric interferometry from chromatic interferograms. The nonlinear behavior of both central and minimum film thicknesses in log-log coordinates was observed as rolling speed and thereby film thickness decreased. This tendency became more obvious at higher contact pressures.

Central and Minimum Elastohydrodynamic Film Thickness at High Contact Pressure

1997 ◽  
Vol 119 (2) ◽  
pp. 291-296 ◽  
Author(s):  
M. Smeeth ◽  
H. A. Spikes
Keyword(s):  
High Pressure ◽  
Film Thickness ◽  
Contact Pressure ◽  
Applied Load ◽  
Optical Technique ◽  
Test Rig ◽  
Minimum Film Thickness ◽  
Elastohydrodynamic Film Thickness ◽  
Contact Pressures ◽  
High Contact Pressure

A new optical technique has been developed which is able to obtain accurate film thickness profiles across elastohydrodynamic (EHD) contacts. This has been used in conjunction with a high pressure EHD test rig to obtain both central and minimum EHD film thicknesses at high contact pressures up to 3.5 GPa. The results have been compared with the classical film thickness equations of Hamrock and Dowson and also with recent high pressure computations due to Venner. It is found that minimum film thickness falls more rapidly with applied load at high than at low contact pressures, with a film thickness/load exponent of −0.3. This confirms the findings of recent high pressure computational EHD modeling.

Rheology of Lubricants in Real Bearing Contacts

1975 ◽  
Vol 97 (2) ◽  
pp. 228-235 ◽  
Author(s):  
J. W. Kannel ◽  
S. S. Bupara
Keyword(s):  
Experimental Data ◽  
Film Thickness ◽  
Dynamic Pressure ◽  
Analytical Treatment ◽  
Experimental Conditions ◽  
X Ray ◽  
Lubricated Contacts ◽  
Fundamental Understanding ◽  
Machine Elements ◽  
Contact Pressures

Experimental traction-slip and lubricant film-thickness data have been determined for selected lubricants to provide information for use in conjunction with the design of lubricated machine elements. The traction-slip experiments were performed using a rolling-disk rheometer which closely simulates those conditions existent in real lubricated contacts; the film-thickness data were obtained using an X-ray technique. The range of experimental conditions included two rolling speeds (5000 and 10,000 rpm), several contact pressures [(690 – 2400 MN/m2) (100 to 350 ksi)], and three temperatures [(338, 366 and 423 K) (150, 200, and 300 F)]. The slip conditions imposed on the lubricants ranged as high as 6 m/s (1200 fpm) which is equivalent to a shear rate of approximately 0.5 × 108 sec−1. Interpretative analyses have been developed to infer basic lubricant properties from the experimental data. These analyses include time delay parameters and “dynamic” pressure-viscosity parameters. The analytical treatment of the data provides: (1) a generalization of the experimental data to apply over a wider range of conditions than those actually covered, and (2) a basis for comparing lubricants and obtaining a more fundamental understanding of lubricant behavior.

The development and application of the spacer layer imaging method for measuring lubricant film thickness

2001 ◽  
Vol 215 (3) ◽  
pp. 261-277 ◽  
Author(s):  
H. A. Spikes ◽  
P. M. Cann
Keyword(s):  
Film Thickness ◽  
Boundary Lubrication ◽  
Three Dimensional ◽  
Spectrometric Analysis ◽  
Imaging Method ◽  
Lubricated Contacts ◽  
Film Distribution ◽  
Spacer Layer ◽  
Lubricant Films ◽  
The 1960S

This paper reviews the historical development of optical interferometry as applied to the study of lubricant films. The technique was first applied to lubricated contacts in the 1960s, when it played an important role in the validation of the elastohydrodynamic theory of lubrication. Initially the method was not suited to the study of mixed and boundary lubrication because it could not measure film thicknesses of less than about 50 nm. In the 1970s, however, this limitation was partially overcome by the use of a spacer layer and this, coupled in the early 1990s with spectrometric analysis of the interfered light, enabled films down to just 1 nm thick to be measured in lubricated contacts, well within the boundary lubrication regime. Recently a number of workers have applied colorimetric image analysis to optical interference images to enable accurate three-dimensional maps of film distribution in lubricated contacts to be determined. This approach, coupled with the use of a spacer layer, has led to the spacer layer imaging method, which can map film thickness in boundary and mixed lubricated contact. Some recent applications of this technique are described.

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.

Study on the Crystallization Kinetics of Polymer Thin Films

2012 ◽  
Vol 466-467 ◽  
pp. 102-105
Author(s):  
Yi Jin Ren
Keyword(s):  
Thin Film ◽  
Growth Rate ◽  
Film Thickness ◽  
Crystallization Kinetics ◽  
Crystallization Time ◽  
Crystal Thickness ◽  
Polymer Thin Film ◽  
Crystal Growth Mechanism ◽  
The Relationship ◽  
Kinetics Of

The crystallization kinetics of polymer thin film has a great difference from that in the bulk. Generally, the growth rate of the crystal confined in thin film reduces with decreasing film thickness, which is believed that the interaction between chains and substrate is responsible for the decrease of the growth rate. In addition, the ratio of film thickness over crystal thickness is also a key parameter in determining the growth rate. The relationship between the crystal lateral size and the crystallization time also dominates the crystal growth mechanism in polymer thin film.

Elastohydrodynamie Lubrication of Big-End Bearings Part 2: Ratification

1991 ◽  
Vol 205 (2) ◽  
pp. 107-119 ◽  
Author(s):  
M B Aitken ◽  
H McCallion
Keyword(s):  
Film Thickness ◽  
Close Correlation ◽  
Connecting Rod ◽  
Test Rig ◽  
Collapse Mechanisms ◽  
Minimum Film Thickness ◽  
Inertial Loading ◽  
Film Collapse ◽  
Thickness Measurements

The elastohydrodynamic analysis developed in Part 1 of this work is ratified against previous Ruston and Hornsby big-end studies. Sufficiently close correlation with published in situ film-thickness measurements allows big-end bearing performance to be determined with some confidence; significant new insight was obtained. Elasticity body forces from connecting-rod motion were found to be an integral component of the big-end representation; it is a prevalent misconception that these forces can be neglected from theoretical as well as experimental test-rig works. Film collapse mechanisms, likened to vapour cavitation, were observed in the dynamically loaded elastic bearing; these were not detected in equivalent rigid bearing simulations. Cyclic minimum film thickness was observed during inertial loading, irrespective of gas force loading. Two separate minimum-film conditions were identified: one in the connecting-rod's neck and a second, at higher load, in the rod's cap. The second condition is critical from a design standpoint; significantly thinner films are predicted than by rigid bearing theory.

The Effects of Non-Flatness on the Performance of Slippers in Axial Piston Pumps

1983 ◽  
Vol 197 (4) ◽  
pp. 239-247 ◽  
Author(s):  
C J Hooke ◽  
Y P Kakoullis
Keyword(s):  
Film Thickness ◽  
Operating Conditions ◽  
Successful Operation ◽  
Small Deviations ◽  
Axial Piston Pumps ◽  
Satisfactory Performance ◽  
Wide Range ◽  
Minimum Film Thickness ◽  
Axial Piston ◽  
The Relationship

All previous analyses of slippers in axial piston pumps have assumed that the slipper running surface was perfectly flat and have all failed to explain the satisfactory performance of these bearings. It has been suggested, however, that slippers in axial piston pumps may depend, for their successful operation, on the small deviations from a perfect flat of the slipper surface. This paper examines the relationship between such a non-flatness and the minimum film thickness produced under steady operating conditions. It is shown that a very wide range of slipper non-flatnesses can lead to satisfactory slipper performance and that the minimum film thickness predicted is remarkably insensitive to the actual amount of deviation from flat.

Revisiting film thickness in slender elasto-hydrodynamically lubricated contacts

2010 ◽  
Vol 224 (12) ◽  
pp. 2549-2558 ◽  
Author(s):  
C H Venner ◽  
A A Lubrecht
Keyword(s):  
Film Thickness ◽  
Linear Function ◽  
Physical Meaning ◽  
Inlet Pressure ◽  
Relative Width ◽  
Time Varying ◽  
Surface Waviness ◽  
Lubricated Contacts ◽  
Minimum Film Thickness ◽  
Load Conditions

In this article, the problem of predicting the film thickness in so-called narrow or slender elliptic contacts is revisited. In particular, the variation of the minimum film and central film thickness and their ratio with load and ellipticity are studied. It is shown that the minimum film tends to decrease linearly with increasing ellipticity. The central film thickness, until a certain threshold, decreases very slowly, and then decreases linearly too, with a slope independent of the Hertzian pressure. The ratio central to minimum film thickness is not a constant and varies strongly with ellipticity and load conditions. In this article, it is shown that the ratio of central to minimum film thickness is a linear function of a single nondimensional parameter which has the physical meaning of the ratio of the length of the inlet pressure sweep to the relative width of the contact. Results for narrow contacts published in the engineering literature when represented as a function of this parameter exhibit the same trend. The behaviour is the consequence of the same unifying mechanism that, in the last decade, was discovered to determine aspects of behaviour in elasto-hydrodynamically lubricated (EHL) contacts under time varying conditions, such as surface waviness deformation. For these problems, the single parameter dependence facilitated the development of simple engineering tools (e.g. to predict the roughness deformation). The observation in this article that the ratio central to minimum film thickness is also governed by this parameter opens new perspectives to develop a simple computational engineering tool to predict central and minimum film thickness in EHL contacts.

CRITICAL SURFACE TENSION, CRITICAL SURFACE ENERGY AND PARACHOR OF MnSO3 THIN FILM

2016 ◽  
Vol 23 (03) ◽  
pp. 1650009 ◽  
Author(s):  
İ. A. KARIPER
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Surface Tension ◽  
Grain Size ◽  
Surface Energy ◽  
Film Thickness ◽  
Critical Surface ◽  
Critical Surface Tension ◽  
Average Grain Size ◽  
The Relationship

This study examines the critical surface energy of manganese sulfite (MnSO[Formula: see text] crystalline thin film, produced via chemical bath deposition (CBD) on substrates. In addition, parachor, which is an important parameter of chemical physics, and its relationship with grain size, film thickness, etc., has been investigated for thin films. For this purpose, MnSO3 thin films were deposited at room temperature using different deposition times. Structural properties of the films, such as film thickness and average grain size, were examined using X-ray diffraction; film thickness and surface properties were measured by and atomic force microscope; and critical surface tension of MnSO3 thin films was measured with Optical Tensiometer and calculated using Zisman method. The results showed that critical surface tension and parachor of the films have varied with average grain size and film thickness. Critical surface tension was calculated as 32.97, 24.55, 21.03 and 12.76[Formula: see text]mN/m for 14.66, 30.84, 37.07 and 44.56[Formula: see text]nm grain sizes, respectively. Film thickness and average grain size have been increased with the deposition time and they were found to be negatively correlated with surface tension and parachor. The relationship between film thickness and parachor was found as [Formula: see text] whereas the relationship between average grain size and parachor was found as [Formula: see text] We also showed the relationships between parachor and some thin films parameters.

Some Observations of the Relationship Between Film Thickness and Load in High Hertz Pressure Sliding Elastohydrodynamic Contacts

1973 ◽  
Vol 95 (3) ◽  
pp. 386-390 ◽  
Author(s):  
D. Lee ◽  
D. M. Sanborn ◽  
W. O. Winer
Keyword(s):  
Film Thickness ◽  
Measurement Technique ◽  
Thickness Measurement ◽  
Independent Study ◽  
Center Line ◽  
X Ray ◽  
Transmission Technique ◽  
Minimum Film Thickness ◽  
Film Thickness Measurement ◽  
The Relationship

The dependence of film thickness on Hertz pressure at pressure levels typical of design applications has been investigated. The data presented by investigators at NASA and Battelle using an X-ray transmission technique showing a dependence much greater than that indicated by commonly accepted theories are substantiated by an independent study using an optical interference film thickness measurement technique. It is also shown that the minimum film thickness is influenced to a much greater extent by the Hertz pressure than the center line film thickness.

Sign in / Sign up

Export Citation Format

Share Document