Extent of Adhesion Losses in The Wheel- Rail Contact Under Contaminated Conditions

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Addis Ababa University


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.



Wheel tread–railhead contact, Contaminants, Adhesion, Slip, Twin disc