THEORETICAL AND EXPERIMENTAL COMPARISON OF THE HEATING FROM SHOE-WHEEL AND PAD-DISK BRAKING SYSTEMS FOR RAILROAD FREIGHT CARS

摘要

Brazilian freight cars use brake shoes directly applied onto the wheels. This system causes wheel heating, which in turn gives rise to thermal stresses and loss of mechanical strength. An alternate solution is a system of brake disks and pads, which would not heat the wheels. This system is not used in high load railroads. Because temperature is one of the major factors affecting braking performance, a study of the viability of replacing shoe brakes by disk brakes must evaluate and compare the heating of wheels and disks. The present work evaluates the heating of disk-pad systems when used for braking freight cars. Preliminary numerical simulations were done to check whether the expected temperatures would exceed the limits and damage friction materials and systems. Following that, real scale tests were conducted in critical braking conditions for both types of brake systems. Dynamometer tests were performed in real scale at the Railroad Laboratory of the State University of Campinas, Brazil. Results showed that, as far as system heating is concerned, there is nothing to prevent the replacement of the current system by a disk-pad system.