Abstract
The “wet-rail” phenomenon results in low adhesion between wheel and rail throughout the year, occurring transiently on a slightly wet, or drying railhead. It has been previously proposed that it is caused by a mixture of iron oxides and small amounts of water (from dew or precipitation) on the railhead that form a friction reducing paste. This paper outlines a novel combination of rheology, modelling and experimental work using a twin disc test rig to determine how the rheology of this iron oxide paste affects adhesion. The yield strength of different types of iron oxides, along with solid oxide fraction of the friction reducing paste, was assessed and used as an input into an “adhesion model” for assessing water and oxide suspensions. The rheological and modelling results were compared against very low adhesion recorded in twin disc experimental validation when simulating the wet-rail phenomenon.
Highlights
IntroductionLow adhesion has been well-documented throughout the autumn season due to organic contamination [1, 2], and takes place throughout the year when no visible contamination is seen on the railhead, due to what is known in the UK as the “wet-rail” phenomenon
Low adhesion between wheel and rail is a recurrent problem for the rail industry
Using a combination of rheological measurements, adhesion modelling and twin disc traction testing this work provides novel information of the role that different types, particle sizes and moisture content of iron oxides play in affecting the friction coefficient when present as a paste in the wheel/ rail interface
Summary
Low adhesion has been well-documented throughout the autumn season due to organic contamination [1, 2], and takes place throughout the year when no visible contamination is seen on the railhead, due to what is known in the UK as the “wet-rail” phenomenon. Previous analysis of Network Rail station overruns showed that during the autumn season, no railhead leaf contamination was seen for approximately 50% of incidents [3]. It showed an increase in low adhesion incidents during morning and evening hours where no precipitation
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