Temperature-dependent wear of tread-braked railway wheels

Abstract

The paper describes the results of brake dynamometer experiments conducted to evaluate the influence of the tread temperature caused by tread braking on the wear rate of railway wheel tread. Employing a full-scale tread brake dynamometer composed of a brake block, a wheel, and a railwheel, wheel-rail rolling contact was imposed on the wheel tread surface heated under several braking scenarios. In dynamometer tests simulating the braking patterns of an actual vehicle exposed to unexpected hollow tread wear, no tread wear was observed after repetitive station stop braking, whereas tread wear was observed only for the rolling contact region after repetitive holding braking for load cases in which the internal tread temperature reached 300 °C. The wear rate of the rolling contact region was determined for various temperatures by performing experiments in which rolling contact was imposed at a constant tread temperature. The wear rate of the wheel tread increased rapidly with temperature at the tread surface for internal temperatures of 200 °C–300 °C. The wear volume obtained in the experiment was converted and generalized to determine the temperature dependence of the wear rate of the wheel tread as a function of the travel distance. The surface temperature of the tread and the internal temperature distribution were computed by FEM. The maximum temperature on the tread surface was estimated to range from 240 °C to 380 °C. The hollow wear of tread-braked railway wheels is primarily attributed to plastic deformation of the tread surface caused by hot rolling, i.e., rolling under a softened state with an increased temperature of the wheel steel on the tread surface. Verification of thermally activated process using Arrhenius equation confirms this conclusion.