The brake system is one of the key components of a high-speed train and the last guarantee to ensure the operation safety of such train. In braking conditions with relatively low speeds, brake disc-pad friction can cause unstable stick-slip vibration in the brake system. The stick−slip vibration poses a threat to the stability of the brake system and the safe operation of the vehicle. In actual operation conditions of the brake system, its dynamic characteristics are simultaneously influenced by the disc-pad friction interface and the structural parameters of the brake system. However, the current tribological tests and related dynamic analysis of the brake system are relatively independent, and have not been able to better reveal the dynamic characteristics of the brake system in operation.
Therefore, the block-on-disc stick−slip vibration test for pentagonal and hexagonal friction blocks commonly used in high-speed train brake system was carried out at relatively low speeds, to explore the influence of friction block shape on stick−slip vibration of high-speed train brake system. And then, the Stribeck friction parameters of disc−block interface were identified to reveal the relationship between the shape of the friction block, the friction coefficient, and the stick−slip vibration at the disc−block interface. Furthermore, a dynamic model of the high-speed train brake system considering disc−block friction, wheel−rail adhesion, and wheel−disc torsion was established. Then, the correlation between the disc−block interface friction characteristics and the dynamic response of the brake system was constructed by integrating the identified interface Stribeck friction parameters into the dynamic model.
Based on this, the influence of friction block shape on stick−slip vibration of the high-speed train brake system was studied. The block-on-disc experiments showed that both pentagonal and hexagonal friction blocks exhibited low-frequency stick−slip vibration under relatively low speed conditions. Among them, the amplitude of stick−slip vibration of hexagonal friction blocks was lower than that of pentagonal friction blocks, resulting in better system stability. The identified Stribeck friction parameters could reflect the stick-slip characteristics of the brake disc−block friction interface. The larger difference between the dynamic and static friction coefficients, the more elastic potential energy stored by the friction block during the adhesion stage, which caused the higher relative velocity between the disc and block during sliding stage, and the stronger stick−slip vibration. The larger exponential decay factor, the shorter period of stick−slip motion, and the higher the frequency of stick−slip vibration at the disk block interface.
Generally, the results indicated that the shape of the friction block affected the stick−slip vibration response and stability of the brake system by changing the friction characteristics of the disc−block interface. In addition, the specific shape of the friction block is beneficial for improving the friction characteristics of the disc−block interface, thereby reducing the stick−slip vibration of the brake system and improving its stability.
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