ISSN   1004-0595

CN  62-1224/O4

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高速列车用闸片摩擦学行为与磨损寿命研究

Evolution of Tribological Behavior and Wear Life of Brake Pads for High-Speed Trains

  • 摘要: 采用高速销-环式摩擦磨损试验机,对燕尾I-C型闸片在350 km/h速度水平下的摩擦学行为、闸片各组元的损伤机制和磨损寿命进行了系统的分析. 闸片平均摩擦耗散能为0.113 cm3/MJ,接近1:1制动试验台的测试结果0.14 cm3/MJ. 不同循环次数下的高速摩擦磨损试验中,主要发生磨粒磨损和黏着磨损,平均摩擦系数呈现一定波动性,介于0.4~0.44. 循环试验次数增加,闸片表面摩擦层的厚度和连续性增强,80次循环摩擦试验后环表面存在厚度不均的富Cu-Cr摩擦层. 经拟合计算,350 km/h速度水平的紧急制动工况下,闸片的磨损寿命大约为341次. 闸片半原位磨损试验表明:增强组元易于破碎脱落,特别是紧邻石墨组元的部分;磨屑可能会脱离摩擦界面、储存在闸片表面低洼处或压实成摩擦层;在剪切力、磨屑的犁削以及摩擦副的黏着作用下,表面的摩擦层会经历去除和生成的过程.

     

    Abstract: With the continuous improvement of high-speed train running speed and heavy load technology, the energy dissipation density and thermal shock between the braking pads- braking discs friction pair have also increased significantly, which undoubtedly constitutes a serious challenge for the friction and wear performance of the disc braking system, especially the braking pads material as a wearable and necessary part. In this paper, from the perspective of energy dissipation, the friction and wear behavior characteristics and wear life of dovetailed I-C type braking pads at a speed level of 350 km/h with different cumulative cycle times (service cycles) were thoroughly investigated using a high-speed pin-ring friction and wear tester instead of a 1:1 brake bench test equipment based on the principle of specific experimental parameter selection. In addition, semi-in-situ wear experiments were carried out in order to characterize in detail the damage mechanism of each component in the braking pads. The conclusions of this paper were as follows. The average friction coefficient of the pin-ring friction pair under different number of cyclic experiments was mainly distributed between 0.4 and 0.44, with certain fluctuation. 40 and 80 cyclic experiments resulted in similar wear surface morphology of the pin, with a large number of plow grooves, craters, fragmentation of reinforcing components, oxide adhesion, and edge spalling phenomena. The thickness and continuity of the friction layer on the wear surface of the pins (braking pads) increased with the growing number of cycles, and after 80 cycles, there were uneven thicknesses of friction layers enriched with Cu and Cr, bar attachments along the frictional sliding direction, and a large number of furrows on the ring surface. The 350 km/h condition of the braking pads was mainly characterized by abrasive and adhesive wear, and the reinforcing elements were fragmented and detached under cyclic shear and compressive stresses, especially the reinforcing elements immediately adjacent to the graphite elements. A large number of abrasive particles existed between the friction interfaces, resulting in severe abrasive wear. The abrasive particles may detach from the friction interface, be stored in the low-lying areas on the surface of the braking pads, or be compacted into a friction layer. The friction layer on the surface experienced a process of removal and generation under shear, plowing of the abrasive chips, and adhesion of the friction pair. The use of small-scale (laboratory-level) equipment and the adoption of certain experimental parameter selection principles could make the experimental results comparable with those of the 1:1 braking test bench. The average frictional dissipation energy of the braking pads at the speed level of 350 km/h was 0.113 cm3/MJ, which was close to that of the 1:1 braking test bench provided by the iron academy of science with the test result of 0.14 cm3/MJ. The wear life of the braking pads was 192 times, which corresponded to 341 times of emergency braking under the actual working condition of 350 km/h speed. The results of this paper could provide a reference for the improvement of the safety of the braking system and the development of new material systems for high-speed railroads from the point of view of tribological research.

     

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