Citation

Beagley TM, Pritchard C. Wear 1975; 35(2): 299-313.

Copyright

(Copyright © 1975, Elsevier Publishing)

DOI

10.1016/0043-1648(75)90078-2

PMID

unavailable

Abstract

Water from the atmosphere affects all rails, depositing in quantities far greater than the minute amounts of oily contamination normally present. Laboratory experiments are described which show how water reduces friction between rail and tyre steel surfaces. Depending on the amount of oily contamination the friction coefficient is reduced to a value between 0.3 (no oil present) and the friction which is characteristic of an excess of the oil. Lower friction on oil-free surfaces is observed using laboratory machines which involve continuous rolling; water mixes with wear debris or surface rust to form a lubricating paste and friction coefficients as low as 0.05 result. The lowest friction occurs when the ratio of water to debris is small and a viscous (non-Newtonian) paste is formed which is observed on the laboratory rigs for a few seconds whenever wetted surfaces are on the point of drying completely. Trains similarly encounter low adhesion in slightly wet conditions, most noticeably on little used lines where a substantial coverage of debris particles is present on the wear band.