Engineering questions: Statistics show that the total mileage of railway which lies in desert environment is close to 15,000 km, mainly distributing in the northwest of China. Considering that the brake system generally operates in an open environment due to the need of heat dissipation, therefore, the effect of desert environment on the brake interfacial behaviors must be considered. The tribological behaviors of the brake system would be extremely complex when sand particles are involved in the brake interface, which may lead to abnormal wear of braking material and brings to severe safety threat to the train. Methodology: In this work, a sand feeder was developed and mounted on a customized small-scale brake dynamometer, and the feed rate of sand particles can be manually controlled. The effect of sand particles on the tribological behavior of high-speed train brake pad was investigated through a series of experiments. Taking two typical sand particles (Gobi sand and desert sand) as the research medium, the friction and wear behavior of braking material was studied. Then, the effect of desert sand with different sizes on tribological behavior of braking material was investigated. The worn morphology evolution of material surface during the experiments is concerned emphatically. Results: The results show that the original friction layer on block surface, the graphite component in superficial surface and the copper matrix could be destroyed by the intrusive sand particles in turn. Sand particles with small size are more easily to enter the braking interface, which consequently forms a mixed frictional layer in which plenty of sand can be found, causing serious damage to the material surface. Additionally, the friction and wear characteristics of the friction material have a significant effect on the temperature distribution on the brake interface and the vibration and noise characteristics of brake system. Limitations of this study: The wind has not been considered yet and a brake system of full size which can simulate the brake process more realistically is needed. What does the paper offer that is new in the field in comparison to other works of the author? Reports concerning the influence of desert environment on tribological behavior of high-speed train braking materials are extremely limited. This research work can provide experimental basis and guidance for the design and optimization of brake material in high speed train brake system under harsh environments. Conclusion: More desert sand is found to accumulate in the brake interface at the same feeding rate due to its relatively small particle size compared with the Gobi sand. This results in the formation of the mixed accumulation layer of desert sand and wear debris, causing serious damage to the matrix material of the friction block. Moreover, it will consequently cause uneven thermal distribution on disc surface and brake vibration and noise with high intensity.

Dr. Bin Tang, Lecturer, Guiyang University; Dr. Zaiyu Xiang, Lecturer, Guangxi University; Dr. Zhiyong Fan, Lecturer, Southwest Jiaotong University; Mr. Shuangxi Feng, No, Southwest Jiaotong University; Mr. Zhou Yu, No, Southwest Jiaotong University; Dr. Jiliang Mo, Professor, Southwest Jiaotong University