Study on the mechanism of mechanical properties deterioration of brake disc materials of high-speed train

Abstract

The mechanical properties of high-speed train brake disc will deteriorate after service, it is necessary to study the degradation mechanism in order to better understand the service process of the material. In this study, the microstructure evolution of the material in the hot spot area of the brake disc was observed by microstructure analysis, and a mixed structure of coarse and fine grains was formed. Through DIC tensile test and in-situ tensile test, the mechanism of mechanical property degradation of brake disc was obtained. The fine grain zone in the hot spot area forms a constraint effect on the coarse grain zone, resulting in uncoordinated deformation. It further causes strain localization and micro-cracks, resulting in a decrease in the bearing capacity and strength of the material. According to EBSD analysis, it is found that the distribution difference of grain boundary orientation further increases the degree of uncoordinated deformation between coarse and fine grains, resulting in stress concentration at the junction and inducing the formation of microcracks. The research results provide guidance for crack damage identification of brake disc. It is suggested that attention should be paid to the change of microstructure during the condition-based maintenance of brake disc, which is of great significance to ensure the safe operation of high-speed trains.