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Energetic coefficient of friction applied to cylinder liners lab tests

Joao Luiz do Vale (Surfaces and Contact Lab. (LASC), UTFPR – Universidade Tecnológica Federal do Paraná, Londrina, Brazil)
Carlos Henrique da Silva (Surfaces and Contact Lab. (LASC), Universidade Tecnológica Federal do Paraná, Curitiba, Brazil)
Giuseppe Pintaude (Surfaces and Contact Lab. (LASC), Universidade Tecnológica Federal do Paraná, Curitiba, Brazil)

Industrial Lubrication and Tribology

ISSN: 0036-8792

Article publication date: 6 February 2020

Issue publication date: 9 November 2020

131

Abstract

Purpose

This paper aims to present a proposal for evaluating the coefficient of friction (COF), under a reciprocating test that considers the energy dissipated by the friction force. In addition, this new parameter is compared to average COF, which is often used to evaluate COF in reciprocating tests.

Design/methodology/approach

Samples of compacted graphite iron were extracted directly from an internal combustion engine block. The piston ring used was a nitrided martensitic stainless steel with an asymmetrical profile, and the lubricant oil was the SAE 30 CF, controlled at 40°C. Different testing conditions were carried out in a CETR-UMT-Bruker tribometer, varying loads between 25-125 N, frequencies between 1-12.5 Hz and track length between 3-10 mm. Three maps comparing the average COF and the energetic definition were built, allowing to discuss their similarities.

Findings

In general, both parameters had similarities especially for low frequencies and small tracks. However, for test conditions that imposed higher accelerations (i.e. longer track lengths and higher frequencies), the energetic COF (COFe) was lower than the average COF (COFa) and presented better agreement in Stribeck-like curves – independent on the experienced lubrication regime along the stroke. As the COFe can be interpreted as a weighted average of instantaneous COF in relation to in-track displacements, an immediate consequence is that instantaneous COF closest to mid-stroke is considered more significant. Furthermore, perturbations associated with the intrinsic accelerations of the movement test are minimized in the COFe formulation.

Originality/value

The energetic COF parameter (COFe) is presented and compared to the average COF. The new parameter presented less data dispersion and is attractive to evaluate the COF behavior in reciprocating tests, as its formulation minimizes perturbations associated with the intrinsic accelerations of the movement (mainly in the initial and final part of the track where the acceleration has its greatest magnitude).

Peer review

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0324

Keywords

Acknowledgements

The authors would like to thank the support given by Tupy S.A. for the financial support through the cooperation ACT 10/2015 TUPY-UTFPR, and for Mahle Metal Leve S.A. for providing the samples of piston rings. One of authors, G. Pintaude, thanks to CNPq by the financial support through Process 308416/2017-1.

Citation

do Vale, J.L., da Silva, C.H. and Pintaude, G. (2020), "Energetic coefficient of friction applied to cylinder liners lab tests", Industrial Lubrication and Tribology, Vol. 72 No. 9, pp. 1103-1108. https://doi.org/10.1108/ILT-08-2019-0324

Publisher

:

Emerald Publishing Limited

Copyright © 2019, Emerald Publishing Limited

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