New observations on the effect of roughness and third-body layers on friction at the wheel/rail interface

Friction at the wheel/rail interface is critical for safe and efficient operation of railways. Low friction due to leaf layers or the “wet-rail” phenomenon can cause safety issues and delays. High friction can lead to increased energy consumption, accelerated wheel and rail damage, and plays a role in wheel climb derailments. These can occur after or rail grinding operations which increase roughness of wheel and rail surfaces thereby increasing the lateral forces present at the interface. Although these rough surfaces wear in relatively quickly, there is a period where the risk of an accident is raised.

Rail roughness effects on friction have not been extensively studied. One reason for this is the difficulty in measuring roughness evolution.

In this work novel friction measurements were taken using a high-pressure torsion approach. Wheel and rail specimens were used and different initial rail roughness’. Friction was recorded cycle by cycle along, uniquely, with roughness. Dry tests were run with tests using third body layers. New relationships between friction and roughness and unique friction datasets have been determined that could now be integrated into multi-body dynamics simulations, via a creep force model, designed to predict wheel/rail interface behaviour in similar rail roughness conditions.