Transient elastohydrodynamic analysis of elliptical contacts. Part 1: Isothermal and Newtonian lubricant solution

A simplified semi-analytical solution for the film thickness fluctuations in the normalapproach problem of elastohydrodynamic lubrication (EHL) contacts has been obtained. The model is based on an inlet analysis to include squeeze-film effects together with the variation of lubricant entrainment speed that is induced by the changes of contact radius as the load oscillates. The results obtained are in excellent agreement with numerical solutions and suggest that the fluctuations in entrainment speed are the main cause for the observed film modulations. The modified semi-analytical solution seems applicable in many practical cases. The amplitude of the film thickness fluctuations produced by fluctuations in the load is in this way related to a single parameter.

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“…Thus, using equation (5) to describe the inlet entrainment velocity, equation (1) can now be written as…”

Section: Analytical Solution Improvementmentioning

confidence: 99%

Film thickness fluctuations in time-varying normal loading of rolling elastohydrodynamically lubricated contacts

Félix-Quiñonez

Morales-Espejel

2010

Proceedings of the Institution of Mechanical Engineers, Part C:

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“…Taking this into account, substituting expressions (6) and (7) into equation (4), and equating coefficients at identical power of y the following expressions can be obtained…”

Section: Problem Statementmentioning

confidence: 99%

Effects of lubricant viscoelasticity on film thickness in elastohydrodynamic line contacts during start-up

Usov

2015

Proceedings of the Institution of Mechanical Engineers, Part J:

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By means of numerical simulation the elastohydrodynamic lubricating film formation during start-up of motion of a line contact from rest is studied. The transition from solid contact to lubricated contact is of importance in investigating the start-up process and its effects on bearing performance. The numerical results of and others, concerning point contact and Newtonian lubricant, are not in good agreement with the known experimental data. The numerical film thickness is significantly smaller than the experimental values and the experimental velocity at which lubricant travels through the conjunction does not equal the entrainment velocity of numerical results. In the current paper, a lubricant with viscoelastic properties is considered. The Maxwell model of a lubricant at pure rolling of elastic cylinders is used. Also, as well as in work of Usov (2008) the model assumes the division of the whole area of contact into three zones: the dry contact of surfaces, the transient zone and the zone in which the surfaces are separated by a liquid lubricant layer. The rigid body model is assumed for the lubricant in the transient zone. The effects of viscoelasticity and size of transient zone on film thickness and the velocity at which the lubricant moves through the contact are studied. It is shown that viscoelasticity raises film thickness in a start of the motion and lowers the velocity at which the lubricant moves through the contact. This velocity is lower than the entrainment velocity in the first half of the contact, as in the experimental results with point contact. In the second half of the contact, this velocity may be lower or higher than the entrainment velocity depending on the size of the transient zone. The film thickness may increase considerably at the start of motion when the size of the transient zone increases.

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“…Mongkolwongrojn, Aiumporsin and Thammakosol (Mongkolwongrojn, et al, 2006) investigated the film temperature and film thickness of liquid-solid lubricants in contact region with non-Newtonian lubricants under sudden overloads and showed the significant effect of solid particles on transient TEHL. Jin, Yang, Cui and Dowson (Jin, et al, 2004 and2005) have analyzed transient EHL of elliptical contacts with Newtonian lubricant to predict the film pressure and film thickness. The results showed that, transient TEHL are similar to EHL.…”

Section: Introductionmentioning

confidence: 99%

Effect of nanoparticle additives on rough surface cylinder in line contact under TEHL with non-Newtonian lubricant

Mongkolwongrojn

Rattapasakorn

2014

JAMDSM

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This paper presents the results of a transient analysis of thermal elastohydrodynamic lubrication (TEHL) of a rough cylinder on a rough flat surface in line contact with non-Newtonian lubricant blended with Al 2 O 3 nanoparticles. The simultaneous systems of time-dependent modified Reynolds equation, elasticity equation and energy equation with initial conditions were solved numerically using multigrid multilevel with full approximation technique. In this study, the effect of Al 2 O 3 nanoparticle additives, surface roughness and sudden overload on TEHL of two surfaces in line contact were examined. The minimum film thickness and the pressure spike increase slightly with an increase in nanoparticle concentration. For TEHL with Al 2 O 3 nanoparticle additives, the film temperature increases very little due to thermal enhancement of nanofluids.

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Transient elastohydrodynamic analysis of elliptical contacts. Part 1: Isothermal and Newtonian lubricant solution

Cited by 35 publications

References 18 publications

Film thickness fluctuations in time-varying normal loading of rolling elastohydrodynamically lubricated contacts

Film thickness fluctuations in time-varying normal loading of rolling elastohydrodynamically lubricated contacts

Effects of lubricant viscoelasticity on film thickness in elastohydrodynamic line contacts during start-up

Effect of nanoparticle additives on rough surface cylinder in line contact under TEHL with non-Newtonian lubricant

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