Thermally induced roughness of tread braked railway wheels, Part 1: Brake rig experiments

Artikel i vetenskaplig tidskrift, 1999

Roughness (corrugation, waviness) on the tread of a rolling railway wheel leads to vibrations in wheels, bogies and superstructure and also in rails, sleepers and roadbed. These vibrating components radiate noise to the surroundings. A lowering of the noise levels from tread-braked freight cars is of utmost importance for the future of rail traffic. The thermomechanical interaction between brake block and wheel tread during braking has been found to cause hot spots on the wheel tread. This phenomenon is believed to be a main contributor to the development of a wavy tread surface. Due to thermal expansion of the rim material, the hot spots will protrude from the wheel tread and be more exposed to wear during the wheel/block contact than the rest of the tread surface. The non-even wear results in roughness on the tread of the wheel after cooling. In the present paper, full-scale tread braking experiments on an inertia dynamometer are reported. Mainly cast iron but also composition and sinter material brake blocks are tested. A stationary pattern of temperature rises (hot spots) on the wheel tread is recorded which is found to correlate well with the measured roughness. In a companion paper results of modelling and field measurements are presented.