Finite Element Simulation and Test Verification of the Effect of Microgrooved Textures on the Stick-slip Vibration of Brake Friction Blocks in High-speed Trains

High-speed train braking systems experience stick-slip vibrations during low-speed braking, particularly before new brake pads reach a stable wear stage. Stick-slip vibrations lead to the abnormal wear and fracture of the friction blocks, threatening train braking safety. Moreover, they produce significant braking noise, which impacts passenger comfort and the everyday lives of residents along the route as well as leads to numerous complaints. Therefore, an in-depth study of the stick-slip vibration mechanism of high-speed train braking systems and the development of effective suppression strategies are crucial for enhancing train safety and passenger comfort. Stick-slip vibration, a typical friction-induced phenomenon, is significantly influenced by interface contact characteristics. Researchers have focused on studying interface contact characteristics and suggested that controlling these characteristics may suppress stick-slip vibrations. Considering the role of the surface texture in improving tribological performance, a series of parallel microgrooved textures of varying quantities are designed on the surfaces of the friction blocks. Finite element simulations and experimental analyses are combined to assess the effectiveness of microgrooved surface textures in suppressing stick-slip vibrations during high-speed train braking. Initially, finite element simulations reveal the effects of the number of surface microgrooved textures of the friction block on the contact stress, wear depth, interface contact degree, and vibration characteristics. These results indicate that the surface-microgrooved textures extended the primary load-bearing area in the direction of the texture, increase the contact area, and achieve a more uniform distribution of the contact stress. As the number of surface-microgrooved textures increases, the degree of interface contact gradually improves, and the amplitude of the displacement and velocity of the friction blocks decreases, transitioning from complex motion to more regular motion. However, finite element analysis alone struggles to account for the effects of wear debris generation and flow during friction, changes in wear surface morphology, and system vibrations, resulting in an incomplete reflection of the interface control function of the microgrooved surface textures. Therefore, friction tests must be conducted to verify the actual effects of surface-microgrooved textures in suppressing stick-slip vibrations. The experimental results indicate that surface-microgrooved textures effectively suppress high-frequency irregular vibrations and reduce the intensity of stick-slip vibrations. An analysis of the contact behavior reveals that microgrooved surface textures increase the actual contact area between the brake disc and friction block and thus play a role in reducing wear and dispersing interface contact stress, thereby favoring a rapid transition to a stable wear state. In addition, the design of surface-microgrooved textures optimizes the flow of interface wear debris, thereby facilitating their easy detachment and ejection, maintaining stable fluctuations in the friction force, and further weakening the intensity of the stick-slip vibration. Consequently, enhancing the friction interface contact state is the key to diminishing the stick-slip vibration intensity, and the optimal interface contact degree and mild wear characteristics contribute significantly to this improvement. The conclusions drawn from this study underscore the significance of enhancing the friction interface contact state to reduce stick-slip vibration intensity. The optimal degree of interface contact and mild wear characteristics are key contributors to this improvement. This study demonstrates that surface-microgrooved textures on friction blocks hold significant potential for mitigating friction-induced stick-slip vibrations during the bedding-in phase. The innovation of this study lies in its comprehensive approach to addressing the stick-slip vibration problem in high-speed train braking systems. Integrating finite element simulations with experimental validation provides a thorough analysis of the effectiveness of surface microgrooved textures. The mechanism by which these textures suppress stick-slip vibrations is elucidated, and practical insights into the design and optimization of friction blocks for high-speed trains are offered.