An experimental study of transient traction characteristics between rail and wheel under low slip and low speed conditions

This paper describes an experimental investigation of the transient traction coefficient at the wheel/rail interface under dry or unlubricated conditions with varying humidity and temperature. A twin-disc type of rolling–sliding frictional machine is used to simulate the actual contact conditions of a wheel and a rail, at low slip ratios and rolling speeds. The results report the influence of rolling speed, contact pressure, slip ratio, and such environmental variables as temperature and relative humidity on the traction characteristics. Three types of transient traction characteristics are observed for various slip ratios. In addition, the paper investigates the relation between the observed transient changes in traction with sliding distance and the corresponding changes in surface roughness and hardness.