The Elastohydrodynamic Friction and Film Forming Properties of Lubricant Base Oils

Günsel, Selda; Korček, Š.; Smeeth, Matthew; Spikes, H. A.

doi:10.1080/10402009908982255

Cited by 71 publications

(65 citation statements)

References 20 publications

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“…Such behaviour is expected at high speeds, where grease friction is determined by its base oil properties as discussed above. Indeed, EHL friction with oil is known to be strongly dependant on the molecular structure of the oil, including molecular shape and flexibility, since these characteristics determine the 'fluid' friction arising from shearing the film molecular layers at high pressure [35][36][37]. Low shear strength, and thus low friction, is favoured by oils containing linear, aligned and flexible molecules.…”

Section: Effect Of Base Oil Typementioning

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: Effect Of Base Oil Typementioning

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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“…For example, at 398 K, the COF is about 0.04 at the nearly zero film thickness, dropping rapidly to about 0.01 at roughly 30-nm film thickness, which is about at the same order of magnitude as the composite roughness of the balldisk interface. This is the film thickness below which the contacting asperities bear a significant portion of the load [22]. For the cases of the same film thickness in the full-film lubrication regime, operation at a higher temperature results in a lower viscosity, and hence a lower COF, as observed.…”

Section: Coefficient Of Friction (Cof)mentioning

confidence: 58%

“…The system uses a polished AISI 52100 steel ball of 19.050 mm diameter, which is pressed, under 20 N load, against an optically transparent glass disk coated with a 500 nm thick silica spacer layer. The respective Young's moduli of the glass disk and steel ball are 75 and 210 GPa, giving a maximum Hertzian pressure of 0.54 GPa [5,22]. The root mean square (RMS) roughness values of the glass disks and steel balls are about 5 and 14 nm, respectively, giving a composite roughness of about 15 nm.…”

Section: Film Thickness Testsmentioning

confidence: 85%

Elastohydrodynamic lubrication properties and friction behaviors of several ester base stocks

Zolper

Liu

et al. 2015

Friction

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This paper reports a series of studies on the lubricant properties, elastohydrodynamic film thickness, and coefficients of friction of several commercially available ester base stocks, i.e., diisooctyl phthalate (DIOP), diisodecyl phthalate (DIDP), diisotridecyl phthalate (DITDP), diisooctyl sebacate (DOS), diisotridecyl sebacate (DTDS), trihydroxymethylpropyl trioleate (TMPTO), and pentaerythritol tetraoleate (PETO). The results include densities and viscosities from 303 to 398 K, and elastohydrodynamic lubricant film thicknesses and friction in the boundary, mixed and full-film lubrication regimes measured at several temperatures, loads, and speeds. These ester base stocks have different lubrication abilities owing to their chain lengths, geometric configurations, and molecular rigidity. This study provides quantitative insight into the use of ester-based lubricants for low friction through the entire lubrication regime (boundary to full film) by utilization of suitable type and size of the ester base stocks.

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“…In applying equations (4,5) for determining the pvc of the estolides, we used PAO as the reference fluid since its pvc has already been reported [24]. The dynamic viscosities of PAO and the test fluids used in these calculations are summarized in table 2.…”

Section: Pressure-viscosity Coefficient Of Estolidesmentioning

confidence: 99%

“…Pressure-viscosity coefficient (pvc) of a test fluid can be determined from film thickness data using equation (3) [24]. The procedure for pvc determination using this method requires film thickness data for a fluid with known pvc data, which will be referred to as the reference fluid, under identical conditions as that of the test fluids.…”

Section: Pressure-viscosity Coefficient Of Estolidesmentioning

confidence: 99%

Film-forming properties of estolides

2007

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Estolides are biobased materials obtained from the synthesis of ingredients derived from agricultural products. They are oligoesters obtained by the reaction of fatty acids and/or methyl esters with a double bond. By varying the chemistries of the starting materials and the reaction conditions, estolides of varying chemical structures (e.g., branching), and physical properties (e.g., mol wt, viscosity, pour point, cloud point) are obtained. Estolides have been found to have suitable properties for some lubrication applications. In this work, the effect of estolide physical/chemical variability on film thickness and pressure-viscosity coefficient (pvc) were examined. The results showed that estolides have lower pvc than the non-polar hydrocarbon PAO, but much higher than seed oils (e.g., soybean, jojoba, canola), which are used as feedstock in estolide synthesis. The film thickness and pvc properties of estolides were also found to be dependent on the structure (e.g., homo-versus co-oligomer) and purity of the estolide oils.

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The Elastohydrodynamic Friction and Film Forming Properties of Lubricant Base Oils

Cited by 71 publications

References 20 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

Elastohydrodynamic lubrication properties and friction behaviors of several ester base stocks

Film-forming properties of estolides

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