Measurement of the Rheology of Lubricant Films Within Elastohydrodynamic Contacts

Spikes, H. A.; Anghel, Veronica; Glovnea, Romeo

doi:10.1023/b:tril.0000044509.82345.16

Cited by 33 publications

(45 citation statements)

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“…where T rise_oil is the temperature rise of oil film (note: in certain studies this refers to the maximum temperature through the thickness, and in others it refers to the average temperature), T oil is the temperature of oil film, T s is the average temperature of the two surfaces, ∆T i is the temperature rise at inlet region, h is the film thickness of the oil film, K oil is the conductivity of Santotrac 50 which is assumed to be 0.104 W/mK at 40 °C [27], τ is the mean shear stress of the oil film, and b is a constant which is suggested to vary broadly in the range between 4 and 24 [27], although other values have also been considered [48]. The differing choice of constant, b, should depend on two factors (1) whether T rise_oil refers to the maximum or average film temperature, and (2) whether heat is assumed to be generated evenly throughout the thickness of the film (Couette flow) or just in the median plane.…”

Section: Resultsmentioning

confidence: 99%

“…7a can also be used to test equations, based on theory originally developed by Carslaw and Jeagar [26] and Archard [46] that are commonly used in studies to calculate the oil film temperature, (e.g. see [27,47,48]…”

Section: Resultsmentioning

confidence: 99%

“…Following this, Spikes [27] further improved the technique by applying thin film coatings of chromium and aluminium onto transparent disc specimens in order to separate the radiations from both bounding surfaces.…”

Section: Introductionmentioning

confidence: 99%

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3D Measurements of Lubricant and Surface Temperatures Within an Elastohydrodynamic Contact

Reddyhoff

Dini

2017

Tribol Lett

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We present an infrared microscopy technique, capable of measuring the temperature of both the bounding surfaces and the oil film in an elastohydrodynamic contact. This technique can, for the first time, spatially resolve the oil film temperature in three dimensions. The contact is produced by loading a steel ball against a sapphire disc, and the film is viewed using an infrared microscope focussing through the disc. Two band pass filters are used to isolate the radiation from the oil film, and Planck's law is applied to data obtained at a known temperature as part of the calibration procedure. The proposed technique requires the emissivity of the oil film to be measured, which is acquired in situ and is shown to vary strongly as a function of thickness and temperature. The technique is validated under pure rolling conditions, when the temperature of the oil film is equal to the controlled lubricant reservoir temperature, and also compared to an equation commonly used to predict average film temperatures, confirming the value of the unknown constant. The technique is then used to gain insights into the thermal/rheological behaviour within a contact. This is important since the temperature of elastohydrodynamic contacts is critical in determining friction and hence the efficiency of machine components and this technique enables much needed validation and provides input data for CFD and numerical simulations.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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3D Measurements of Lubricant and Surface Temperatures Within an Elastohydrodynamic Contact

Reddyhoff

Dini

2017

Tribol Lett

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“…[2][3][4][5], whereas less attention has been paid to cases (ii) and (iii), which can occur under pure rolling conditions. The effect of shear heating from rolling (case ii) can be shown under EHL conditions, to be effectively zero (see Sect.…”

Section: List Of Symbols Amentioning

confidence: 97%

“…Preliminary tests showed the temperature rise in pure rolling to be very small which necessitated an adaptation of the experimental method used previously by authors to study sliding-rolling contact [1,3].…”

Section: List Of Symbols Amentioning

confidence: 99%

Compression Heating and Cooling in Elastohydrodynamic Contacts

2009

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In this study, the infrared temperature mapping technique, originally developed by Sanborn and Winer (Trans ASME J Tribol 93: [262][263][264][265][266][267][268][269][270][271] 1971) and extended by Spikes et al. (Tribol Lett 17(3):593-605, 2004), has been made more sensitive and used to study the temperature rise of elastohydrodynamic contacts in pure rolling. Under such conditions lubricant shear heating within the contact is considered negligible and this allows temperature changes due to lubricant compression to be investigated. Pure rolling surface temperature distributions have been obtained for contacts lubricated with a range of lubricants, included a group I, and group II mineral oil, a polyalphaolefin (group IV), the traction fluid Santotrac 50 and 5P4E, a five-ring polyphenyl-ether. Resulting maps show the temperature rise in the contact increases in the inlet due to compression heating and then decreases and in most cases becomes negative in the exit region due to the effect of decompression. Temperature changes increase with entrainment speed but in the current tests are always very small, and less than 1°C. Contact temperature rises from compression were compared to those from sliding contacts (where a slide-roll ratio of 0.5 was applied). Here the contribution to the contact temperature from compression is shown to decrease dramatically with entrainment speed. The lubricant 5P4E is found to behave differently from other lubricants tested in that it showed a peak in temperature at the outlet. This effect becomes more pronounced with increasing speed, and has tentatively been attributed to a phase change in the exit region. Using moving heat source theory, the measured temperature distributions have been converted to maps showing rate of heat input into each surface and the latter compared with theory. Qualitative agreement between theory and experiment is found, and a more accurate theoretical comparison is the subject of ongoing study.

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Viscosity modification of high‐oleic sunflower and castor oils with acid oils‐derived estolides for lubricant applications

García‐Zapateiro

Franco

Valencia

et al. 2013

Euro J Lipid Sci & Tech

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The use of estolides as additives to increase the viscosity of vegetable oils for lubricant applications was investigated. For this purpose, high‐oleic sunflower (HOSO) and castor (CO) oils were blended with estolides derived from acid oils resulting from vegetable oil refining process (HOSO and olive pomace acid oils). These blends were characterized from both viscous and tribological point of views. Significant increments in viscosity were generally found when added estolides were synthetized using sulphuric acid as catalyst, compared to p‐toluensulphonic acid catalyst. Estolides prepared from these two by‐products gave rise to similar viscosity modification in HOSO, yielding maximum viscosity increments of 322 and 362%, at 10°C, respectively. Smaller viscosity modifications were obtained for CO/estolide blends, with maximum increments in kinematic viscosity of 84 and 152%, respectively. Generally, the addition of estolides to HOSO yielded a significant increase in the temperature dependence of viscosity. The addition of acid oils‐derived estolides slightly improved CO thermal dependence of viscosity for lubricant applications. Although wear was significantly reduced by adding these estolides to any of these vegetable oils, the addition of acid oils‐derived estolides to CO increased the friction coefficient at low rotational speeds, extending the boundary lubrication regime to higher Sommerfeld number values. On the contrary, a single Stribeck master curve was obtained for HOSO/estolide blends.

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Measurement of the Rheology of Lubricant Films Within Elastohydrodynamic Contacts

Cited by 33 publications

References 8 publications

3D Measurements of Lubricant and Surface Temperatures Within an Elastohydrodynamic Contact

3D Measurements of Lubricant and Surface Temperatures Within an Elastohydrodynamic Contact

Compression Heating and Cooling in Elastohydrodynamic Contacts

Viscosity modification of high‐oleic sunflower and castor oils with acid oils‐derived estolides for lubricant applications

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