Abstract
In this paper, the influence of oxidation of automatic transmission fluids (ATFs) and sliding distance on the friction coefficients of a wet clutch in approached running-in conditions was investigated. The ATFs were oxidized by a laboratory process approaching oxidation occurred in actual ATFs. Oxidation was evaluated by means of increase in carbonyl compounds and depletion of zinc dialkyldithiophosphates (ZDDPs) additives. Also, the changes in kinematic viscosity and viscosity index were evaluated. Pin-on-disk tests were conducted to replicate the actual sliding contact in a wet clutch. The pin specimens were cut from friction material composite plates and the disks were actual steel separators both from an automotive wet clutch. Friction coefficient, μ, was measured at progressive sliding velocity, ν, to obtain μ-ν curves at 26 and 100 ΰC. Three μ-ν tests were consecutively run using the same pair of specimens and oil. The cumulative sliding distance for each μ-ν test generated surface flattening using the oils. The friction coefficients of the wet clutch increased due to the ATFs oxidation meanwhile the dμ/dυ values decreased in most cases. It suggests that ATF oxidation can enhance torque capacity of the wet clutch, but it could reduce anti-shudder property. Progressive sliding distance improved the slopes in the μ-ν results using fresh ATFs meanwhile it generated a slope decrease by using aged ATFs.
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Acknowledgements
The authors would like to acknowledge to CNMNIPN for the support in the spectroscopic analyses of our oil samples. We also thank to “Laboratorio de Reología y Física de la Materia Blanda” from ESFM-Instituto Politécnico Nacional for the assistance and equipment support for the viscosity measurements of our oil samples.
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Leonardo Israel FARFAN CABRERA. He received his M.S. and Ph.D. degrees in mechanical engineering from Instituto Politécnico Nacional, Mexico, in 2014 and 2018, respectively. He joined the School of Engineering and Sciences and the Nanotechnology research group at Tecnologico de Monterrey since 2018. His current position is assistant professor. His research areas cover the tribology of automotive components and engineering polymers, bio-lubricants, and tribo-testing.
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Farfan-Cabrera, L.I., Gallardo-Hernández, E.A., Vite-Torres, M. et al. Influence of oxidation of automatic transmission fluids (ATFs) and sliding distance on friction coefficients of a wet clutch in the running-in stage. Friction 9, 401–414 (2021). https://doi.org/10.1007/s40544-020-0406-z
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DOI: https://doi.org/10.1007/s40544-020-0406-z