Extent of Adhesion Losses in The Wheel- Rail Contact Under Contaminated Conditions
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Date
2014-12
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Addis Ababa University
Abstract
Railway vehicles require a certain level of adhesion between wheel and rail to operate
efficiently, reliably, and economically. Different levels of adhesion are needed
depending on the vehicle running conditions. In the wheel tread–railhead contact, the
dominant problem is low adhesion, as low adhesion on the railhead negatively affects
railway operation: on one hand, the vehicle will lose traction resulting in delay when
driving on low-adhesion tracks; on the other hand, low adhesion during deceleration
will extend the braking distance, which is a safety issue.
This thesis examines the influence of several contaminants, i.e., water, mud, leaves, oil
and grease, on the adhesion in the wheel tread–railhead contact. This study will also
improve our knowledge of the low-adhesion mechanism and of how various
contaminants influence adhesion.
In this thesis, the adhesion conditions were assessed using a twin disc test machine.
Thus the research methodology used was a laboratory test; the aim of which was to
study the extent of adhesion coefficients over a range of slip values with and without
contaminants. Thus the outcomes from lab test were the coefficients of adhesions of
each contaminant within 0 to 10% slip values so as to sort out which of them are the
worst to cause loss of adhesion. With this regard oil and grease have been found to
create less adhesion than leaves unlike the researches made abroad so far.
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Keywords
Wheel tread–railhead contact, Contaminants, Adhesion, Slip, Twin disc