Engineering questions: Stick-slip vibrations are inclined to be induced in the braking process of high-speed trains at low operation speed and high braking pressure, especially for the new brake pads in the early unstable wear stage. Stick-slip vibration not only causes chatter, limit cycle oscillation, creep groan, and many other negative problems, but also leads to system instability and brake safety hazards (abnormal wear and rupture of friction blocks). Surface modification of the braking interface is a potential solution to improve the interfacial tribological behavior and suppress friction-induced vibration. Methodology: This study proposes a surface modification solution by designing micro-grooved textures on the surface of the friction block to reduce stick-slip vibration by regulating the interface contact state. Specifically, micro-grooved textures with different numbers (0, 3, 5, 7, 9) were machined on the block samples, and a series of stick-slip vibration tests were conducted on the self-developed vehicle braking performance simulation test bench. Results: The experimental results showed that the surface micro-grooved textures reduced the vibration amplitude and the probability of stick-slip motion. Moreover, it also spread the interface contact stress, which consequently improved the interfacial wear state. The finite element simulation results showed that changing the number of surface micro-grooved textures hardly affects the frequency and vibration pattern of unstable vibration, but significantly affects the unstable vibration intensity of the brake system, and suppresses the relatively higher frequency vibration of the friction interface. The best performance in suppressing the stick-slip vibration was achieved by 9 strips of micro-grooved textures on the surface of the hexagonal friction block in this study. Limitations of this study: The friction and sound signals during the test were too weak to capture precisely at this stage. Subsequently, tests needed to be carried out on a full-size brake system to further verify whether the proposed strategies apply to high-speed train brake systems. What does the paper offer that is new in the field in comparison to other works of the author? This work reproduced low-frequency chatter caused by stick-slip vibration occurring in the high-speed train brake system using a self-developed friction brake simulator and demonstrated the effectiveness of micro-grooved textures on the friction block surface to improve the friction interface contact state and suppress stick-slip vibration. Conclusion: This work realized the direct regulation of the friction contact interface by surface treatment technology, revealed the mechanism of surface micro-grooved texture to suppress stick-slip vibration, and proposed a surface treatment scheme to effectively suppress stick-slip vibration, which provides a potential method to solve the problems of friction block rupture and abnormal wear caused by low-frequency chatter in the early unstable wear stage.
Mr. Qixiang Zhang, No, Southwest Jiaotong University; Prof. Dr. Jiliang Mo, Professor, Southwest Jiaotong University; Dr. Zaiyu Xiang, Lecturer, Guangxi University; Mr. Caizhou Zhai, Engineer, CRRC Qishuyan Institute Co.; Mr. Song Zhu, Senior engineer, CRRC Qishuyan Institute Co.; Mr. Qingbing Gou, Senior engineer, CRRC Qishuyan Institute Co.