Extent of adhesion losses in the wheel-rail contact under contaminated conditions

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 and on the other, low adhesion during deceleration will extend the braking distance, which is a safety issue.

This research work examines the influence of the contaminants, i.e., water, mud, leaves, oil and grease, with a twin disc machine which is designed and constructed as part of this study to simulate wheel tread-railhead contact. Thus, the research methodology is a laboratory test without and with the different contaminants aimed at studying the extent of adhesion coefficients of each contaminant over the range of slip values 0 to 10% and comparing which of them are the worst to cause loss of adhesion. As the lab results revealed, oil, grease and water have been found to cause less adhesions than leaves. Unlike the research made justifying leaves, they were found the worst in causing adhesion losses.

Keywords: Wheel tread, railhead contact, contaminants, adhesion, slip, twin disc and breaking distance