The Effect of Sand Particles Entering the Braking Interface of a High-Speed Train on the Friction and Wear Behavior of Friction Block

With the continuous development of high-speed railway operation speed and the adaptability requirements of operating environment, the mechanical braking performance of high-speed trains and the friction and wear performance of brake pad urgently need to be improved. However, the mechanical braking system of high-speed trains operates in an open environment, and the entry of external pollutants such as rain, snow, oil stains, sand and dust into the braking interface will further increase the randomness and complexity of the friction and wear characteristics of the friction block surface, leading to degradation of braking performance and endangering the safety of train operation. Currently, most areas in northwest China are located in severe sandstorm environments, and train brake pads often experience varying degrees of cracking. Therefore, in order to further develop the railway industry and high-speed trains, it is necessary to study the friction and wear behavior of train brake interfaces in sandstorm environments. In this research work, based on the self-developed high-speed train braking friction and wear test bench, an experimental study was conducted on the impact of Gobi sand and desert sand on the friction and wear behavior of friction blocks, in response to the problem of train braking friction and wear on railways in sandy areas. The focus was on exploring the evolution process of the friction and wear characteristics and the interfacial friction heat after the two different types of sand particles enter braking interface. The results showed that two types of sand particles with different particle sizes (Gobi sand and desert sand) intervened in the braking interface and affected the interface friction behavior. Moreover, there were significant differences in the interface friction coefficient, wear behavior of friction block surface, and frictional thermal characteristics between the two cases. After the Gobi sand intervenes in the braking interface, the original debris accumulation layer on the surface of the friction block was destroyed, and more graphite components were exposed on the material surface. Due to the lubrication characteristics of graphite, debris was not easy to remain on the worn surface of the friction block, which meant it was not easy to form a stable friction layer, resulting in a decrease in the interface friction coefficient and average temperature. Compared to the situation of Gobi sand, desert sand with smaller average particle size was more likely to enter the braking interface, and a large amount of desert sand entering the interface not only led to an increase in friction coefficient. It also destroyed the original debris accumulation layer on the surface of the friction block, as well as the graphite and matrix material on the surface of the material, and gradually formed a mixed accumulation layer of sand debris mainly composed of sand particles in the peeling pits and grooves, ultimately causing more serious damage to the material surface.