Film thickness interrelationship of base oil and grease lubricated compliant and hard non-conformal contacts

2021 ◽  
pp. 135065012110535
Author(s):  
Josef Fryza ◽  
Petr Sperka ◽  
Ivan Krupka ◽  
Martin Hartl
Keyword(s):  
Experimental Study ◽  
Film Thickness ◽  
Point Contacts ◽  
Oil And Grease ◽  
Base Oil ◽  
Oil Film ◽  
Lubrication Regime ◽  
Plastic Components ◽  
Insight Into

The interfaces of plastic components are often operated as self-lubricating or lubricated with greases close to the piezoviscous-elastic lubrication regime. However, current basic tribological knowledge about grease-lubricated compliant contacts is still very limited. This experimental study provides insight into relations between film thicknesses of grease and its base oil in compliant polymethylmethacrylate–steel and stiff glass–steel point contacts at different speeds and loads. The results are compared with predictions. The ratio between grease and its base oil film thickness was found to be significantly influenced by the interplay of load and the non-Newtonian response of grease, especially for the compliant contact, while the effect of speed and the slide-to-roll ratio was considerably lower. The role of viscoelasticity and grease thickener concentration is discussed.

scholarly journals Thermoelastohydrodynamics of grease-lubricated concentrated point contacts

2009 ◽  
Vol 224 (3) ◽  
pp. 683-695 ◽  
Author(s):  
B K Karthikeyan ◽  
M Teodorescu ◽  
H Rahnejat ◽  
S J Rothberg
Keyword(s):  
Film Thickness ◽  
High Pressures ◽  
Plug Flow ◽  
Elastohydrodynamic Lubrication ◽  
Solid Surfaces ◽  
Point Contacts ◽  
Base Oil ◽  
Oil Film ◽  
Lubricated Contacts ◽  
Pressure Spike

Isothermal and thermoelastohydrodynamic lubrication (TEHL) analyses of grease lubricated bearings are presented. A grease plug flow is formed in the conjunction that, with no shear at the boundaries with the solid surfaces, adheres to them in the region of high pressures under isothermal conditions. The elastohydrodynamic lubrication grease pressure distribution conforms fairly closely to that of its base oil alone, with the exception of inlet trail and pressure spike regions. The dependency of film thickness on speed (rolling viscosity) and load parameters for the base oil agrees with previously reported findings of the research community. For grease there are subtle differences with the base oil film thickness load and speed dependencies. However, it is clear that extrapolated oil film thickness formulae for oils can be used reasonably for the prediction of grease films, at least as a first approximation. The results presented agree well with optical interferometric measurements reported in the literature for grease-lubricated contacts at low temperatures and low surface velocities. TEHL analysis shows breakdown of the plug flow and significant reduction in film thickness, which can lead to changes in the regime of lubrication to mixed or boundary conditions.

Synergistic Antiwear Effects of Zinc Dialkyl Dithiophosphate and Different Detergents

2008 ◽  
Author(s):  
G. Pennecot ◽  
K. Komvopoulos ◽  
E. S. Yamaguchi
Keyword(s):  
Wear Rate ◽  
Boundary Lubrication ◽  
Base Oil ◽  
Temperature Range ◽  
Zinc Dialkyl Dithiophosphate ◽  
Contact Voltage ◽  
Lubrication Regime ◽  
Steel Surfaces ◽  
Dialkyl Dithiophosphate ◽  
Insight Into

The effectiveness of blends consisting of base oil, some secondary zinc dialkyl dithiophosphate (ZDDP), and different detergents to form antiwear tribofilms on steel surfaces sliding in the boundary lubrication regime was investigated in the temperature range of 105–125°C. The efficacy of the tribofilms formed from these blends was evaluated in terms of contact voltage and wear rate measurements. The best antiwear performance was demonstrated by the tribofilm formed from the blend containing sulphonate detergent. The results of this study provide insight into competing effects between ZDDP and different detergents that affect significantly the antiwear performance of the formed tribofilms.

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.

A new insight into catalytic role of copper sulfate on elemental mercury oxidation: DFT and experimental study

Fuel ◽  
2019 ◽  
Vol 252 ◽  
pp. 10-18 ◽  
Author(s):  
Shu Yang ◽  
Kang Liu ◽  
Min Liu ◽  
Xu Yan ◽  
Cao Liu ◽  
...  
Keyword(s):  
Experimental Study ◽  
Copper Sulfate ◽  
Elemental Mercury ◽  
Mercury Oxidation ◽  
Catalytic Role ◽  
Insight Into

Oil Film Thickness and Pressure Distribution in Elastohydrodynamic Point Contacts

1982 ◽  
Vol 24 (4) ◽  
pp. 173-182 ◽  
Author(s):  
A. Mostofi ◽  
R. Gohar
Keyword(s):  
Contact Problem ◽  
Film Thickness ◽  
Numerical Solutions ◽  
Point Contact ◽  
Point Contacts ◽  
Rolling Velocity ◽  
Oil Film ◽  
Static Contact ◽  
Theoretical Predictions ◽  
Interferometry Method

In this paper, a general numerical solution to the elastohydrodynamic point contact problem is presented for moderate loads and material parameters. Isobars, contours and regression formulae describe how pressure and oil film thickness vary with geometry, material properties, load, and squeeze velocity, when the rolling velocity vector is at various angles to the static contact ellipse long axis. In addition, the EHL behaviour under spin is examined. The theoretical predictions of film thickness compare favourably with other numerical solutions to the point contact problem, as well as with experimental results which use the optical interferometry method to find film thickness and

Experimental study on lubrication regime variation in point contacts

2008 ◽  
Vol 41 (6) ◽  
pp. 451-460 ◽  
Author(s):  
F. Guo ◽  
Z. Fu ◽  
P.L. Wong ◽  
P. Yang
Keyword(s):  
Experimental Study ◽  
Point Contacts ◽  
Lubrication Regime

On the crucial role of ellipticity on elastohydrodynamic film thickness and friction

2016 ◽  
Vol 230 (12) ◽  
pp. 1503-1515 ◽  
Author(s):  
J-D Wheeler ◽  
N Fillot ◽  
P Vergne ◽  
D Philippon ◽  
GE Morales Espejel
Keyword(s):  
Film Thickness ◽  
Maximum Pressure ◽  
Fluid Viscosity ◽  
Point Contacts ◽  
Entrainment Velocity ◽  
Minimum Film Thickness ◽  
Elliptical Contact ◽  
Thickness Variations ◽  
Poiseuille Flows

The study reported here deals with elastohydrodynamic point contacts and it is focused on the influence of contact ellipticity. In five velocity–load reference cases, ellipticity was varied from slender to wide configurations, including the circular contact. For each case, Hertzian pressure, Hertzian area, load, and entrainment velocity were kept constant while the ellipticity was varied by changing the curvature radii. In this context, the maximum central film thickness did not occur for the infinitely wide contact, but for a slender configuration close to the circular case. Moreover, the minimum film thickness reached its optimum for a wide but finite elliptical contact. For low ellipticity ratios, specific film thickness features were obtained. In particular, very high central/minimum film thickness ratios are found. The cause of these behaviors was found in the change of the convergent shape. When the ellipticity was varied, the Poiseuille flows parallel and transverse to the entrainment direction were significantly modified and these modifications were quantitatively analyzed for the different cases. The competition between the Couette and the Poiseuille flows was totally different between the narrow and the wide elliptical contact, and this change was responsible for the film thickness variations with ellipticity. Ellipticity also had an effect on friction as it influenced the maximum pressure which in turn impacts the fluid viscosity.

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