Brake disc fastening bolts endure complex thermomechanical loads and are susceptible to loosening during emergency braking, making comprehensive analysis of their thermomechanical response and failure mechanism critical. This study developed and experimentally validated a thermal-mechanical coupling model for a C/C-SiC axle-mounted brake disc system, investigating the bolt’s thermodynamic responses under emergency braking at different initial speeds and pressures. During the emergency braking process, a non-uniform temperature field and deformation field are generated in the bolt, causing it to bend slightly towards the brake flange. Significant stress concentration consistently occurs at the root of the first engaged thread, identifying it as the critical region for loosening initiation. Higher initial speeds elevate bolt maximum temperature and equivalent stress. Under 400 km/h emergency braking condition, the bolt reaches a maximum temperature of 159.91 °C, a maximum equivalent stress of 849.00 MPa, and a stress amplitude of 98.66 MPa. Braking pressure also exerts significant effects. The optimal strategy for a 400 km/h emergency braking is determined as follows: a braking pressure of 26 kN is applied when the speed exceeds 300 km/h, and 28 kN when the speed drops below 300 km/h. With this strategy, the bolt’s maximum temperature, maximum equivalent stress, and stress amplitude are reduced by 17.02%, 1.41%, and 4.33%, respectively.
Yao et al. (Sun,) studied this question.