Heat cracks in brake discs for heavy vehicles

Abstract

Existing models describing the formation of heat cracks in heavy-duty vehicles are not detailed enough to predict the sensitivity of brake discs for heat cracks. In this paper, results from a dynamometer experiment are discussed. They allow a deeper understanding of the processes that result in the failure of brake discs. The experiment described is a standardized heat crack test, which was performed over 300 cycles and ended with a through-thickness crack. During the test, the brake disc was monitored via a thermographic camera, a pyrometer, two sliding thermocouples, a set of capacitive displacement sensors, and an eddy current crack detector. The results show that the current explanation model might not consider several factors that contribute to the crack propagation. Cyclic shear movements at the disc surface are observed, which are likely caused by the cooling channel pins. The variation of the coning of the disc correlates with the maximum disc surface temperature and the crack growth rate. The consequences of the observations are discussed to develop a more detailed model to explain the formation of heat cracks.