Film Thickness of Grease in Rolling Contacts

Palacios, J.M.; Cameron, A.; Arizméndi, L.

doi:10.1080/05698198108983045

Cited by 37 publications

(24 citation statements)

References 6 publications

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“…For example, certain types of thickeners have been reported to be able to adhere on the surface and form a thin residual layer of deposited thickener particles [6][7][8], while other studies suggest that, during the lubrication process, grease is mechanically degraded and transforms into a Newtonian suspension of thickener particles in oil, with a higher viscosity than that of the base oil alone [9,10]. Therefore, thickener type [4,11], concentration [12] and thickener particle dimensions [13] appear to have a strong influence on film formation and consequently affect friction by determining the lubrication regime.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Base Oil Properties on the Friction Behaviour of Lithium Greases in Rolling/Sliding Concentrated Contacts

et al. 2017

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This study investigates the influence of base oil type and viscosity on the frictional behaviour of lithiumthickened bearing greases. A series of model lithium greases were manufactured by systematically varying viscosity and type of base oil, so that the influence of a single base oil property could be studied in isolation. In addition, selected greases were blended with oleic acid, with the purpose of evaluating its effectiveness in further reducing grease friction. Friction coefficient and film thickness were measured in laboratory ball-on-disc tribometers over a range of speeds and temperatures. For a specific oil type, the influence of base oil viscosity on friction was found to be closely related to its effect on film thickness: greases formulated with PAO oils covering a wide range of viscosities gave very similar friction at the same nominal film thickness. For a given base oil viscosity, base oil type was found to have a strong influence on grease friction under all test conditions. PAO-based greases generally produced lower friction than mineral-and ester-based greases. Addition of oleic acid to the test greases did not significantly affect friction within the range of test conditions employed in this study. The results provide new insight into the frictional behaviour of greases, which may be used to help inform new low-friction grease formulations for rolling bearing applications.

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Section: Introductionmentioning

confidence: 99%

The Influence of Base Oil Properties on the Friction Behaviour of Lithium Greases in Rolling/Sliding Concentrated Contacts

et al. 2017

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“…In the range of studied speeds, the central film thickness was found to increase with a slope of &0.62-0.71, which is in accordance with the film thickness equations from Hamrock and Dowson [12] for fully flooded conditions. In many cases, the grease films were found to be higher than their corresponding bled oils, which are ascribed to the presence of thickener material influencing the effective viscosity of the lubricant in the contact [3,13,14]. The fully flooded film thickness of water contaminated greases was found to be almost independent of water ( Fig.…”

Section: Fully Flooded Film Thicknessmentioning

confidence: 88%

Impact of Water on EHL Film Thickness of Lubricating Greases in Rolling Point Contacts

et al. 2016

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This paper investigates the influence of water on the EHL film thickness of six commercial lubricating greases under fully flooded and starved conditions. Although grease can absorb large quantities of water, separation occurs due to pressure and shear, leading to free water. This does not have an impact on the film thickness under fully flooded conditions. However, water does have an effect on the film thickness under starved conditions where the differences are related to the change in oil bleed. In the presence of water, an increase in oil bleed was found for lithium, lithium complex and polyurea grease. These greases showed a reduction in the levels of starvation and, therefore, thicker films. Water contamination led to lower oil bleed for calcium sulfonate complex greases, which led to an increase in starvation, and therefore, thinner films compared to their uncontaminated counterparts.

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“…For a point contact, the base oil power relation for minimum film thickness with speed suggested by Gohar [29] is 0.7 and by Palacios et al [30] is 0.74. The results obtained here are reasonably close to their findings.…”

Section: Effect Of Speed and Load On Film Thicknessmentioning

confidence: 88%

Thermoelastohydrodynamics of grease-lubricated concentrated point contacts

Karthikeyan

Teodorescu

Rahnejat

et al. 2009

Proceedings of the Institution of Mechanical Engineers, Part C:

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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.

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Film Thickness of Grease in Rolling Contacts

Cited by 37 publications

References 6 publications

The Influence of Base Oil Properties on the Friction Behaviour of Lithium Greases in Rolling/Sliding Concentrated Contacts

The Influence of Base Oil Properties on the Friction Behaviour of Lithium Greases in Rolling/Sliding Concentrated Contacts

Impact of Water on EHL Film Thickness of Lubricating Greases in Rolling Point Contacts

Thermoelastohydrodynamics of grease-lubricated concentrated point contacts

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