Elastohydrodynamic modelling of heat partition in rolling-sliding point contacts

Clarke, Alastair; Sharif, Khairi; Evans, Henry Peredur; Snidle, Raymond Walter

doi:10.1243/13506501jet219

Cited by 10 publications

(9 citation statements)

References 31 publications

(65 reference statements)

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“…Their result largely agreed with those found in this article that heat partition favoured the faster moving surface. To understand the origins of these phenomena, Evans et al compared their experimental heat partition with a thermal EHL analysis using a range of rheological models of lubricant behaviour [34]. It was found that heat partition results agreed only when wall-slip occurred at the faster moving surface (i.e.…”

Section: Temperature Mapsmentioning

confidence: 99%

Improved infrared temperature mapping of elastohydrodynamic contacts

Reddyhoff

Spikes

Olver

2009

Proceedings of the Institution of Mechanical Engineers, Part J:

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An effective means of studying lubricant rheology within elastohydrodynamic contacts is by detailed mapping of the temperature of the fluid and the bounding surfaces within the lubricated contact area.In the current work, the experimental approach initially developed by Sanborn and Winer and then by Spikes et al., has been advanced to include a high specification infrared (IR) camera and microscope. Besides the instantaneous capture of full field measurements, this has the advantage of increased sensitivity and higher spatial resolution than previous systems used. The increased sensitivity enables a much larger range of testable operating conditions: namely lower loads, speeds, and reduced sliding. In addition, the range of test lubricants can be extended beyond high shearing traction fluids.These new possibilities have been used to investigate and compare the rheological properties of a range of lubricants: namely a group I and group II mineral oil, a polyalphaolephin (group IV), the traction fluid Santotrac 50, and 5P4E, a five-ring polyphenyl-ether. As expected, contact temperatures increased with lubricant refinement, for the mineral base oils tested.Using moving heat source theory, the measured temperature distributions were converted into maps showing rate of heat input into each surface, from which shear stresses were calculated. The technique could therefore be validated by integrating these shear stress maps, and comparing them with traction values obtained by direct measurement. Generally there was good agreement between the two approaches, with the only significant differences occurring for 5P4E, where the traction that was deduced from the temperature over-predicted the traction by roughly 15 per cent.Of the lubricants tested, Santotrac 50 showed the highest average traction over the contact; however, 5P4E showed the highest maximum traction. This observation is only possible using the IR mapping technique, and is obscured when measuring the traction directly. Both techniques showed the effect of shear heating causing a reduction in traction.

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Section: Temperature Mapsmentioning

confidence: 99%

Improved infrared temperature mapping of elastohydrodynamic contacts

Reddyhoff

Spikes

Olver

2009

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…The work presented by Merritt [9] indicates that if "the oil film offers no resistance to heat flow" and the flash contact temperatures of the disks are equal, then calculation of equal Block flash temperatures for the disks leads to Table 1 are higher than this as might be expected given that the mean surface temperature difference between the disks varies between 15 °C and 53 °C over the experiments, with the higher temperature in the faster disk. Numerical analyses of the EHL oil film using a variety of viscosity and non-Newtonian rheological models [12] have shown that the values of b obtained from thermal EHL considerations are generally less than 0.5 if the shear heating is dissipated in a distributed way across the oil film, and values of b greater than 0.6 are only obtained if the rheological model results in lubricant slip within the film at or near to the higher temperature surface. It is instructive to note that, for all of the combinations of viscosity and rheological models considered in [12], the calculated frictional traction matched that measured in experiment.…”

Section: Discussionmentioning

confidence: 99%

“…Evaluating Q film and Q fr for the contacts used in the experiment using data for film temperature and thickness from [11] and [12] shows that Q fr exceeds Q film by a factor of between 500 and 1200, and consequently that Q film can be disregarded as being negligible.…”

Section: Thermal Model Of Test Diskmentioning

confidence: 99%

“…However these results required heat transfer coefficients to be specified for all surfaces of the rotating disk and shaft, a source of some uncertainty. Subsequent work by Clarke et al [12] considered the question of heat partition behaviour as a means of discriminating between various candidate rheological and viscosity models in smooth surface EHL simulations. It was found that, when compared to the experimental results of [10], the mechanism for heat dissipation within the contact which gave similar heat partition results to Clarke's thermal model was one which involved slip at or near the faster surface.…”

Section: Introductionmentioning

confidence: 99%

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Experimental determination of heat partition in elastohydrodynamic contacts

Al-Hamood

Clarke

Evans

2015

Proceedings of the Institution of Mechanical Engineers, Part J:

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Experimental and theoretical analyses are reported to study the heat generation and partition in an elastohydrodynamic rolling/sliding point contact. Heat is generated within the lubricant in the Hertzian region by shearing and compression of the oil film. This heat is essentially conducted to the contacting surfaces as the amount convected from the Hertzian zone by the lubricant can be neglected due to the very low lubricant mass flowrate.A two-disk test rig was used for the experimental tests using crowned, superfinished 76.2 mm diameter disks fixed on parallel shafts. Each disk was fitted with six thermocouples in two rows of three located 3 mm and 6 mm below the surface to measure the temperature distribution of the disks during the tests. In addition, the disks were insulated on both plane sides by ceramic washers to minimise heat transfer to the surroundings over those surfaces.A numerical model was developed to calculate the circumferential mean disk temperature distribution in the outer 6 mm annular ring using the inner row of thermocouples to provide a boundary condition. The model was used to predict the temperature distribution for given values of the fraction of the total heat entering the fast disk, b, and the heat transfer coefficient, h, for the disk running surfaces.Minimisation of error between predicted and experimentally measured temperatures at the thermocouple positions, together with consideration of the physical relationship between fast and slow shaft heat transfer coefficients led to the conclusion that b lies in the range 0.71 to 0.77 for the experiments reported in the paper and that approximately 75% of the frictional heat dissipated within the lubricant film flows

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“…This assumption appears reasonable for small and moderate sliding velocities, which was the case in these experiments. Clarke et al [31] studied the high sliding velocity case and concluded that shearing occurs near the faster surface, with effects on temperature distribution and heat transfer of the contact surfaces.…”

Section: Traction Modelmentioning

confidence: 99%

An approach for determination of lubricant properties at elliptical elastohydrodynamic contacts using a twin-disc test device and a numerical traction model

Kleemola

Lehtovaara

2008

Proceedings of the Institution of Mechanical Engineers, Part J:

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High-pressure lubricant properties are important when friction coefficients and power losses are evaluated in elastohydrodynamic (EHL) contacts. An approach was developed to determine the limiting shear stress and actual viscosity properties of lubricants using a numerical traction model based on elliptical EHL contact and traction curves, measured at a wide range of temperatures and pressures with a twin-disc test device. The tests were carried out in pure fluid film at high Hertzian pressures with finely polished surfaces. Each lubricant was tested at 135 test points, where traction coefficients and bulk temperatures were measured. The lubricant parameters in the traction model were adjusted so that the calculated results matched the experimental measurements at all test points. In general, there is a good correlation between the calculated results and the experimental measurements. The influence of pressure on limiting shear stress and actual viscosity is less significant for polyalphaolefin (PAO) oil than for mineral oil.

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Elastohydrodynamic modelling of heat partition in rolling-sliding point contacts

Cited by 10 publications

References 31 publications

Improved infrared temperature mapping of elastohydrodynamic contacts

Improved infrared temperature mapping of elastohydrodynamic contacts

Experimental determination of heat partition in elastohydrodynamic contacts

An approach for determination of lubricant properties at elliptical elastohydrodynamic contacts using a twin-disc test device and a numerical traction model

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