Micro-geometry effects on the sliding friction transition in elastohydrodynamic lubrication

Morales-Espejel, Guillermo E.; Wemekamp, A.W.; Félix-Quiñonez, A

doi:10.1243/13506501jet787

Cited by 34 publications

(51 citation statements)

References 26 publications

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“…First, operating conditions and lubricant rheology parameters are entered along with representative measured 3D topography maps of both contacting surfaces. A fast, isothermal non-Newtonian (Eyring) mixed lubrication model described in [28] is used to calculate the stress history per load cycle of each surface point by solving the problem at different time steps as the surfaces slide-roll against each other. This fast approach to modelling micro-elasto-hydrodynamic lubrication (micro-EHL) conditions determines the clearance between the mating surfaces and the pressure fluctuations arising from the passage of roughness asperities through the contact in mixed lubrication conditions.…”

Section: Modelling Methodsmentioning

confidence: 99%

Prediction of micropitting damage in gear teeth contacts considering the concurrent effects of surface fatigue and mild wear

Morales-Espejel

Rycerz

Kadiric

2018

Wear

136

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A B S T R A C TThe present paper studies the occurrence of micropitting damage in gear teeth contacts. An existing general micropitting model, which accounts for mixed lubrication conditions, stress history, and fatigue damage accumulation, is adapted here to deal with transient contact conditions that exist during meshing of gear teeth. The model considers the concurrent effects of surface fatigue and mild wear on the evolution of tooth surface roughness and therefore captures the complexities of damage accumulation on tooth flanks in a more realistic manner than hitherto possible. Applicability of the model to gear contact conditions is first confirmed by comparing its predictions to relevant experiments carried out on a triple-disc contact fatigue rig. Application of the model to a pair of meshing spur gears shows that under low specific oil film thickness conditions, the continuous competition between surface fatigue and mild wear determines the overall level as well as the distribution of micropitting damage along the tooth flanks. The outcome of this competition in terms of the final damage level is dependent on contact sliding speed, pressure and specific film thickness. In general, with no surface wear, micropitting damage increases with decreasing film thickness as may be expected, but when some wear is present micropitting damage may reduce as film thickness is lowered to the point where wear takes over and removes the asperity peaks and hence reduces asperity interactions. Similarly, when wear is negligible, increased sliding can increase the level of micropitting by increasing the number of asperity stress cycles, but when wear is present, an increase in sliding may lead to a reduction in micropitting due to faster removal of asperity peaks. The results suggest that an ideal situation in terms of surface damage prevention is that in which some mild wear at the start of gear pair operation adequately wears-in the tooth surfaces, thus reducing subsequent micropitting, followed by zero or negligible wear for the rest of the gear pair life. The complexities of the interaction between the contact conditions, wear and surface fatigue, as evident in the present results, mean that a full treatment of gear micropitting requires a numerical model along the lines of that applied here, and that use of overly simplified criteria may lead to misleading predictions.

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Section: Modelling Methodsmentioning

confidence: 99%

Prediction of micropitting damage in gear teeth contacts considering the concurrent effects of surface fatigue and mild wear

Morales-Espejel

Rycerz

Kadiric

2018

Wear

136

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“…This can be accomplished by iteratively solving the system (3) and Eq. (8), similarly to the algorithm of Morales-Espejel et al [29]. However, it was found to be timeconsuming and a different single-loop approach was developed, which is described in Appendix 2.…”

Section: Numerical Lubrication Modelmentioning

confidence: 99%

“…Multilevel multi-integration was used to facilitate the calculations. A load-sharing concept-based approach which employs the half-space theory was also implemented by Morales-Espejel et al [29]. They used Hertz' theory [23] to calculate the average pressure, and the mean film thickness was obtained from ''central film thickness formula,'' such as the Dowson and Higginson fit [10] be it with the extension of an equivalent roughness using the perturbation method.…”

Section: Introductionmentioning

confidence: 99%

On a Model for the Prediction of the Friction Coefficient in Mixed Lubrication Based on a Load-Sharing Concept with Measured Surface Roughness

et al. 2015

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A new model was developed for the simulation of the friction coefficient in lubricated sliding line contacts. A half-space-based contact algorithm was linked with a numerical elasto-hydrodynamic lubrication solver using the load-sharing concept. The model was compared with an existing asperity-based friction model for a set of theoretical simulations. Depending on the load and surface roughness, the difference in friction varied up to 32 %. The numerical lubrication model makes it possible to also calculate lightly loaded contacts and can easily be extended to solve transient problems. Experimental validation was performed by measuring the friction coefficient as a function of sliding velocity for the stationary case.

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“…Friction calculations in mixed lubrication frequently combine models for boundary lubrication and fluid-film conditions. Morales-Espejel et al 16 and Popovici and Schipper 17 have published approaches for deterministic microcontact models and Eyring fluids.…”

Section: Introductionmentioning

confidence: 99%

“…[18][19][20] In this article, the Carreau equation is considered, bearing in mind that Jang et al, 20 Chapkov et al 21 and Liu et al 22 have reported an extensive set of numerical solutions and comparisons with experiments, which reveal that the Carreau model properly characterises the shear-thinning effects, in particular for the case of the mineral base and the polyalphaolefin lubricants [23][24][25] used in this work. Concerning the mixed lubrication analysis, unlike models based on the detailed geometry of the asperities 16,17 which generally complicate the use of analytical or semi-analytical algorithms, we use a macroscopical approach that only requires the use of a standardised statistical roughness parameter. In this way, we aim for an approach even more simplified than the aforementioned models, in order to develop a fully analytical model.…”

Section: Introductionmentioning

confidence: 99%

Friction coefficient in mixed lubrication: A simplified analytical approach for highly loaded non-conformal contacts

Otero

Ochoa

Tanarro

et al. 2017

Advances in Mechanical Engineering

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This article presents an analytical model for predicting friction in mixed lubrication regime. The calculations consider load shared between roughness asperities and the lubricant film, as well as the appearance of thermal effects in the contact and the influence of the lubricant rheology. Tests using tribometers have been performed to measure the friction coefficient in non-conformal surfaces for both point and line contacts. This allows verifying the results of the model under a broad range of experimental conditions with an influence on the lubrication conditions. Reasonably good precision has been found in the results obtained, which combined with a simplicity of use confers the model a high practical utility for rough estimates of the friction coefficient under mixed lubrication.

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Micro-geometry effects on the sliding friction transition in elastohydrodynamic lubrication

Abstract: International audienc

Cited by 34 publications

References 26 publications

Prediction of micropitting damage in gear teeth contacts considering the concurrent effects of surface fatigue and mild wear

Prediction of micropitting damage in gear teeth contacts considering the concurrent effects of surface fatigue and mild wear

On a Model for the Prediction of the Friction Coefficient in Mixed Lubrication Based on a Load-Sharing Concept with Measured Surface Roughness

Friction coefficient in mixed lubrication: A simplified analytical approach for highly loaded non-conformal contacts

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