Low adhesion still remains a problem on the railway network, as exemplified by the recent passenger train collision near Salisbury. Contaminated railhead often caused by leaves or “wet-rail” (small amounts of water mixing with any metal oxide present – forming a slippery paste) causes safety concerns due to the impact it has on braking.
Furthermore, this can lead to performance issues and delays and widespread passenger dissatisfaction. Great effort is put into managing the railhead during Autumn by all stakeholders, however a greater understanding is needed of how effective current mitigation techniques are and how best to deploy them (e.g. comparisons of water-jetting and traction gels applied wayside and via rail head treatment trains (RHTTs)) in order to make further improvements on the current solution. Some investigation of how new railhead cleaning technologies could be best utilized to fill existing gaps is also required. One example of this is the dry-ice cleaning technique that can be implemented through various platforms, with the benefit of being deployable where RHTTs are unable to run.
While much has been learnt in recent years about low adhesion mechanisms, once contamination is present, there is a critical gap in terms of how the contamination layers form initially from a leaf adhering to the railhead; how they are removed (by passage of trains and/or dedicated mitigation techniques) and how they then regenerate, post removal.
This has been complicated further by the emergence of incidents where there are ‘non-visible contaminants’ – that is to say, low friction has been reported by drivers in a specific area, but upon visible inspection by lineside safety experts, no obvious causes for low adhesion are observed, hence the likelihood of a non-visible layer/phase in the formation.
This knowledge could help develop models and novel solutions that inform a more rigorous rail cleaning strategy, supported by the use of interdisciplinary tribological and surface chemistry techniques.
Wheels as well as rails become contaminated which causes extra problems. In Scotland some wheels are sprayed with a citrus derived cleaner, but there is currently little data to show how effective this is so this is another gap that can be investigated. Comparing various solvents against citrus based cleaning products would be relatively easy and allow changing to a greener solution than the current one, that is also more effective.
This 3.5 year “iCASE” project will involve carrying out research to gain a physical understanding of the key stages of formation/propagation and termination of railhead contaminants. This will potentially allow for a model of the initial process of railhead contamination to be created, as well as a model for removal by passage of eithers trains (either RHTTs or via high pressure, physical removal) or by the various treatments available. Currently the industry employs a variety of techniques: mechanical scrubbing, cleaning solvents, high pressure sprays, novel cleaning systems).
This goal will be achieved both in the laboratory and out on mainline infrastructure, ensuring real world validity. A useful output for this would be a standardized tests methodology – defining future good industry practice and approaches to cleaning railheads. This project may draw on various key areas including: railhead characterization parameters from roughness measurements; profilometry; tribochemistry; surface chemistry/effects, friction etc. Thus enable an effective, fair analysis to be made of the current treatments, by an unbiased non-industrial entity (UoS).
There will a portion of time set aside to undertake a secondment as part of the Network Rail team during the project.
For further information on the project please contact Professor Roger Lewis: [Email Address Removed] or Dr Joe Lanigan: [Email Address Removed].
Funding providers: Network Rail and the Department of Mechanical Engineering, The University of Sheffield
Subject areas: Railway engineering; Tribology; Tribochemistry; Surface analysis
Project start date: 1st October 2022
Eligibility
Candidates must normally hold an undergraduate degree at 2.1 level (or Non-UK equivalent as defined by The University of Sheffield) in Engineering or similar relevant science discipline.
Due to funding restrictions, this scholarship is open to applicants eligible to pay tuition fees at the UK rate only.
Funding
This scholarship covers the full cost of UK tuition fees and an annual stipend of £18,000.
Additional research expenses (to cover field testing etc.) will also be available as well as funds to travel to at least one international conference.
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