scholarly journals Discussion: “Isothermal Elastohydrodynamic Lubrication of Point Contacts: Part III—Fully Flooded Results” (Hamrock, B. J., and Dowson, D., 1977, ASME J. Lubr. Technol., 99, pp. 264–275)

1977 ◽  
Vol 99 (2) ◽  
pp. 275-276 ◽  
Author(s):  
R. K. Kunz ◽  
W. O. Winer
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Point Contacts

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.

Effects of out-of-contact lubricant channeling on friction and film thickness in starved elastohydrodynamic lubrication point contacts

2016 ◽  
Vol 231 (4) ◽  
pp. 432-440 ◽  
Author(s):  
Fadi Ali ◽  
Ivan Křupka ◽  
Martin Hartl
Keyword(s):  
Film Thickness ◽  
Digital Camera ◽  
Elastohydrodynamic Lubrication ◽  
Contact Condition ◽  
Friction Reduction ◽  
Rolling Element Bearings ◽  
Point Contacts ◽  
Practical Applications ◽  
Rolling Element ◽  
Ball On Disc

This study presents experimental results on the effect of out-of-contact lubricant channeling on the tribological performance of nonconformal contacts under starved lubrication. Channeling of lubricant was carried out by adding a slider with a limited slot for scraping the displaced lubricant on one of mating surfaces (ball). Thus, the scraped lubricant is forced to flow back into the depleted track through the limited slot resulting in robust replenishment. The measurements have been conducted using optical tribometer (ball-on-disc) equipped with a digital camera and torque sensor. The effect of lubricant channeling was compared to the original contact condition by means of measuring friction and film thickness. The results show that the out-of-contact lubricant channeling leads to a significant enhancement of film thickness and friction reduction under starved conditions. Indeed, the starved elastohydrodynamic lubrication contacts transformed to the fully flooded regime after introducing the flow reconditioning. Moreover, the film thickness decay over time, which is common with starved elastohydrodynamic lubrication contacts, has not been observed in the case of lubricant channeling. However, the beneficial effect of lubricant channeling diminishes as the original contact condition tends to the fully flooded regime. The results of this study can be easily implemented in practical applications such as radial and thrust rolling-element bearings.

Theoretical and experimental studies of the oil film in lubricated point contact

1966 ◽  
Vol 291 (1427) ◽  
pp. 520-536 ◽  
Keyword(s):  
Surface Layer ◽  
Film Thickness ◽  
Strong Evidence ◽  
Experimental Studies ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Experimental Results ◽  
Point Contacts ◽  
Previous Theory ◽  
Oil Film

A technique using Newton’s rings for mapping the oil film of lubricated point contacts is described. A theoretical value for the film thickness of such contacts in elastohydrodynamic lubrication is derived. The experimental results give the exit constriction predicted by previous theory but never shown in detail. The comparison of theoretical and experimental oil film thicknesses, which is satisfactorily accurate, gives strong evidence for a viscous surface layer some 1000Å thick. This film agrees with the known ‘lubricating power’ of the various oils tested.

Roughness Amplitude Reduction Under Non-Newtonian EHL Conditions

2005 ◽  
Author(s):  
A. D. Chapkov ◽  
C. H. Venner ◽  
A. A. Lubrecht
Keyword(s):  
Film Thickness ◽  
Pressure Fluctuations ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Quantitative Prediction ◽  
Point Contacts ◽  
Minimum Film Thickness ◽  
Roughness Amplitude ◽  
Average Film Thickness ◽  
Ehl Contact

The influence of surface roughness on the performance of bearings and gears operating under ElastoHydrodynamic Lubrication (EHL) conditions has become increasingly important over the last decade, as the average film thickness decreased due to various influences. Surface features can reduce the minimum film thickness and thus increase the wear. They can also increase the temperature and the pressure fluctuations, which directly affects the component life. In order to describe the roughness geometry inside an EHL contact, the amplitude reduction of harmonic waviness has been studied over the last ten years. This theory currently allows a quantitative prediction of the waviness amplitude and includes the influence of wavelength and contact operating conditions. However, the model assumes a Newtonian behaviour of the lubricant. The current paper makes a first contribution to the extension of the roughness amplitude reduction for EHL point contacts including non-Newtonian effects.

Thermal Elastohydrodynamic Lubrication of Point Contacts Using a Newtonian/Generalized Newtonian Lubricant

2008 ◽  
Vol 30 (1) ◽  
pp. 41-52 ◽  
Author(s):  
W. Habchi ◽  
D. Eyheramendy ◽  
S. Bair ◽  
P. Vergne ◽  
G. Morales-Espejel
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Point Contacts

Effect of changing geometrical characteristics for different shapes of a single ridge passing through elastohydrodynamic of point contacts

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mohamed Abd Alsamieh
Keyword(s):  
Film Thickness ◽  
Pressure Distribution ◽  
Reynolds Equation ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
Time Step ◽  
Content Type ◽  
Geometrical Characteristics ◽  
Different Shapes

Purpose The purpose of this paper is to study the behavior of a single ridge passing through elastohydrodynamic lubrication of point contacts problem for different ridge shapes and sizes, including flat-top, triangular and cosine wave pattern to get an optimal ridge profile. Design/methodology/approach The time-dependent Reynolds’ equation is solved using Newton–Raphson technique. Several shapes of surface feature are simulated and the film thickness and pressure distribution are obtained at every time step by simultaneous solution of the Reynolds’ equation and film thickness equation, including elastic deformation. Film thickness and pressure distribution are chosen to be the criteria in the comparisons. Findings The geometrical characteristics of the ridge play an important role in the formation of lubricant film thickness profile and the pressure distribution through the contact zone. To minimize wear, friction and fatigue life, an optimal ridge profile should have smooth shape with small ridge size. Obtained results are compared with other published numerical results and show a good agreement. Originality/value The study evaluates the performance of different surface features of a single ridge with different shapes and sizes passing through elastohydrodynamic of point contact problem in relation to film thickness and pressure profile.

A Parametric Study on Fatigue Life for Mixed Elastohydrodynamic Lubrication Point Contacts

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Xiao-Liang Yan ◽  
Xiao-Li Wang ◽  
Yu-Yan Zhang
Keyword(s):  
Shear Stress ◽  
Fatigue Life ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
Newtonian Flow ◽  
Lubrication Regimes ◽  
Close Relationship ◽  
Lubrication Characteristics ◽  
Effect Of Surface

The lubrication characteristics and fatigue life are numerically analyzed under full film and mixed lubrication regimes, in which the three-dimensional sinusoidal surfaces with changeable wavelengths in x and y directions are used, the geometry changes of the contact areas are described by the various ellipticity, and the non-Newtonian flow of lubricant is described by the sinh-law rheology model. The results show that the influences of characteristic shear stress, wavelength ratio, and ellipticity on lubrication characteristics and fatigue life are remarkable. The effect of surface topography on lubrication characteristics has a close relationship with speed. Increasing the ellipticity and decreasing wavelength ratio and characteristic shear stress can prolong the fatigue life.

Effects of Differential Scheme and Mesh Density on EHL Film Thickness in Point Contacts

2006 ◽  
Vol 128 (3) ◽  
pp. 641-653 ◽  
Author(s):  
Yuchuan Liu ◽  
Q. Jane Wang ◽  
Wenzhong Wang ◽  
Yuanzhong Hu ◽  
Dong Zhu
Keyword(s):  
Film Thickness ◽  
Numerical Solution ◽  
System Approach ◽  
Elastohydrodynamic Lubrication ◽  
Mesh Size ◽  
Point Contacts ◽  
Wide Range ◽  
Mesh Density ◽  
Differential Scheme

This paper investigates the effects of differential scheme and mesh density on elastohydrodynamic lubrication (EHL) film thickness based on a full numerical solution with a semi-system approach. The solution variation with different schemes and mesh sizes is revealed based on a set of numerical cases in a wide range of central film thickness from several hundred nanometers down to a few nanometers. It is observed that when the film is thick, the effects of differential schemes and mesh density are not significant. However, if the film becomes ultra-thin, e.g., below 10–20 nanometers, the influence of mesh density and differential schemes becomes more significant, and a proper dense mesh and differential scheme may be highly desirable. The present study also indicates that the solutions from the 1st-order backward scheme give the largest film thickness among all the solutions from different schemes at the same mesh size.

Analytical model for predicting the friction coefficient in point contacts with thermal elastohydrodynamic lubrication

2011 ◽  
Vol 225 (4) ◽  
pp. 181-191 ◽  
Author(s):  
J Echávarri Otero ◽  
P Lafont Morgado ◽  
E Chacón Tanarro ◽  
E de la Guerra Ochoa ◽  
A Díaz Lantada ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Analytical Model ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts

The Elastohydrodynamic Lubrication of Heavily Loaded Point Contacts

1980 ◽  
Vol 22 (4) ◽  
pp. 183-187 ◽  
Author(s):  
C. J. Hooke
Keyword(s):  
Exact Solution ◽  
Film Thickness ◽  
Close Agreement ◽  
Numerical Solutions ◽  
Elastohydrodynamic Lubrication ◽  
Substantial Part ◽  
Line Contact ◽  
Point Contacts ◽  
Contact Width ◽  
Inlet Zone

It is shown that the film thickness in heavily loaded point contacts can be accurately calculated by comparing the inlet and exit zones of the contact with those of an equivalent line contact. The results become increasingly accurate as the extent of the inlet and exit regions is reduced and in the limit yields an exact solution. Even for moderately loaded contacts in which the inlet zone occupies a substantial part of the contact width the results are in close agreement with existing numerical solutions.

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