Watson, M., White, B., Lanigan, J. et al. (2 more authors) (2020) The composition and friction-reducing properties of leaf layers. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 476 (2239). 20200057. ISSN 1364-5021
Abstract
Every autumn rail networks across the world suffer delays, accidents and schedule changes due to low friction problems caused by leaves landing on the rails. These leaves form a layer that can reduce the friction between the wheel and the rail to a similar level as that between ice and an ice-skate (μ=0.01–0.05). Previous works have generated several hypotheses for the chemical reactions and low friction mechanism associated with these layers. In this work, the reaction between an aqueous extract of sycamore leaves and metallic iron is investigated. This reaction has been shown to produce a black precipitate, which matches field observations of leaf layers, while friction tests with these extracts produce characteristic ultra low friction. The reaction is investigated through FTIR, XPS, CHNS and ICP-MS analysis as well as wet chemical testing. The impact of the reaction on friction is investigated through three rounds of tribological testing. The results indicate that the black precipitate produced is iron tannate, formed by complexation of tannins with dissolved iron ions. Friction testing showed that eliminating tannins from the leaf extract resulted in a significant increase in the friction coefficient compared with the control.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2020 The Authors. This is an author-produced version of a paper subsequently published in Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | tribology; friction; rail; leaf layer |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Mechanical Engineering (Sheffield) |
Funding Information: | Funder Grant number Engineering and Physical Sciences Research Council EP/R001766/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 11 Jun 2020 07:50 |
Last Modified: | 12 Jan 2021 08:29 |
Status: | Published |
Publisher: | The Royal Society |
Refereed: | Yes |
Identification Number: | 10.1098/rspa.2020.0057 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:161648 |