Regulatory Effect of Brake Pad Friction Block Size Design on the Vibration and Noise for High-Speed Train Braking

The friction braking mode of high-speed trains mainly converts the kinetic energy of the train into thermal energy through the frictional action between the brake pad and the brake disc to achieve deceleration. Therefore, there is a strong frictional action between the brake pad and the brake disc. The frictional action of the brake disc/pad is prone to generate high-frequency, high-intensity friction-induced vibration and noise, and temperature accumulation at the interface, which puts higher requirements and new challenges on the structural parameter design of the brake pad. As the friction material on the brake pad, the friction block needs to exhibit sufficient and stable tribological performance during the braking process of high-speed trains. The unreasonable design of the friction block will directly affect the tribological performance of the brake disc/pad, while the size, as an important variable in the structural design of the friction block, has not been clearly understood. Therefore, we conducted friction braking tests under different friction block size parameters on a self-developed high-speed train braking performance simulation test rig to obtain the influence law of friction block size parameters on the tribological behavior and friction-induced vibration and noise characteristics of the braking interface. Furthermore, based on the main structure of the test rig, we built its finite element model and developed a wear calculation method suitable for this research work. Then, we conducted friction block wear simulation under test conditions to obtain friction block surface wear morphology similar to the test results. Based on this, we conducted complex modal and transient dynamic analysis to explore the regulation effect and mechanism of friction block size parameters on friction braking friction-induced vibration and noise characteristics. The results showed that under the experimental conditions of this work, all friction blocks would produce high-frequency friction-induced vibration and generate certain intensity squeal noise when sliding with the brake disc. However, different friction block sizes led to significant differences in the friction-induced vibration and noise collected by the test in both time and frequency domains. The size of the friction block had a significant impact on the generation and evolution of friction-induced vibration and noise. Appropriate friction block size could effectively reduce the unstable vibration intensity of the braking system, resulting in smaller and more stable evolution rules of friction-induced vibration and noise intensity. However, an inappropriate friction block size parameter design would significantly enhance the unstable vibration of the braking system, inducing high-intensity friction-induced vibration and noise with unpredictable evolution rules. During the sliding friction process between the friction block and the brake disc, the frictional heat at the braking interface was mainly concentrated in the incision end region. A properly sized friction block could distribute the frictional heat evenly at the braking interface and improve its contact characteristics and tribological behavior, thereby suppressing friction-induced vibration and noise. Under the experimental conditions in this article, the friction block size did not significantly affect the inherent characteristics of the braking system, but significantly affected the distribution and value of contact stress and wear at the braking interface. The maximum contact stress decreased with increasing friction block size. Therefore, the size of the friction block had a significant impact on the contact characteristics of the braking interface and the friction-induced vibration and noise. A reasonable design of the friction block size could achieve effective regulation of the friction-induced vibration and noise. In the parameter design of high-speed train brake pads, the influence of the friction block size on the characteristics of friction-induced vibration and noise should be fully considered in combination with the structure and service conditions of the braking system, and then reasonable friction block size parameters should be designed.