Thermal fatigue damage assessment of high-speed train brake discs under multiple braking conditions

Brake discs are important components for ensuring train safety, and its failure is usually caused by cracks on the friction surface. In this paper, a thermal fatigue damage assessment method for brake discs based on Paris law and Miner’s rule is proposed. The thermomechanical analysis of the fatigue specimens is carried out by constructing an elastic-plastic finite element model, and the stress results under different temperatures are obtained. Utilizing the crack growth model, the stress intensity factor was calculated based on the J-integral, and the conversion relationship between the crack growth rate and the stress intensity factor under different temperatures was established. Then, the typical braking conditions are analyzed on a full-scale brake disc model, and the residual crack growth life is predicted. The research results indicate that the fatigue damage to brake discs increases significantly as the initial crack grows. Compared to a shorter radial crack, a longer one leads to a noticeably higher damage and a substantial reduction in the number of allowable braking cycles. Overall, the presence of a longer crack accelerates fatigue progression and shortens the remaining service life. This research provides theoretical support for the life evaluation and maintenance strategy optimization of brake discs.