Abstract Recent interest in emergency shoe braking in high-speed trains stimulated research on the damage due to sliding contact between brake blocks and wheel treads. Bi-disc tests, with rolling–sliding contact between specimens extracted from wheels and brake blocks, were previously performed in constant working conditions to reproduce the temperature of the wheel during braking. However, braking is often a discontinuous operation, obtained by intermittent contact between brakes and tread, to prevent excessive heating. In this article, braking is simulated by discontinuous tests, periodically interrupted to cool down the specimens. Three wheel steels (HYPERLOS, SANDLOS, and CLASS B) were tested against the same cast iron brake material. Measurements of the friction coefficient, contact surface temperature, and weight variation were performed. Moreover, optical microscopy observations and hardness tests were done on the cross section of the wheel specimens. Material transfer from the brake to the wheel disc with the formation of a discontinuous third-body layer was observed. This layer, when worn away, likely contributes to surface crack nucleation. In addition, the debris of both materials enhances abrasive wear. If compared with the continuous tests, the intermittent tests showed higher friction coefficient fluctuations and in some cases significantly different weight variation. Among the steels, the weight loss and subsurface hardening of HYPERLOS was higher in the discontinuous tests than in the longest continuous tests. CLASS B showed similar behavior in both tests. An effect of the temperature cycles on the friction coefficient and the wear behavior was hypothesized.

中文翻译：

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高速列车车轮踏面断续蹄制动损伤的小规模试验研究

摘要 最近对高速列车紧急制动蹄制动的兴趣激发了对制动块和车轮踏面之间滑动接触造成的损坏的研究。双盘测试，在从车轮和制动块中提取的样本之间进行滚动-滑动接触，之前在恒定的工作条件下进行，以重现制动过程中车轮的温度。然而，制动通常是不连续的操作，通过制动器和胎面之间的间歇接触来获得，以防止过热。在本文中，制动是通过不连续的测试来模拟的，周期性地中断以冷却样品。三种车轮钢（HYPERLOS、SANDLOS 和 CLASS B）针对相同的铸铁制动材料进行了测试。进行摩擦系数、接触表面温度和重量变化的测量。此外，对车轮试样的横截面进行了光学显微镜观察和硬度测试。观察到材料从制动器转移到轮盘，形成不连续的第三体层。该层磨损后，可能会导致表面裂纹成核。此外，两种材料的碎屑都会增强磨料磨损。如果与连续测试相比，间歇测试显示出更高的摩擦系数波动，并且在某些情况下重量变化显着不同。在钢种中，HYPERLOS 的失重和次表面硬化在不连续试验中高于最长连续试验。B 类在两个测试中表现出相似的行为。假设温度循环对摩擦系数和磨损行为的影响。对车轮试样的横截面进行了光学显微镜观察和硬度测试。观察到材料从制动器转移到轮盘，形成不连续的第三体层。该层磨损后，可能会导致表面裂纹成核。此外，两种材料的碎屑都会增强磨料磨损。如果与连续测试相比，间歇测试显示出更高的摩擦系数波动，并且在某些情况下重量变化显着不同。在钢种中，HYPERLOS 的失重和次表面硬化在不连续试验中高于最长连续试验。B 类在两个测试中表现出相似的行为。假设温度循环对摩擦系数和磨损行为的影响。对车轮试样的横截面进行了光学显微镜观察和硬度测试。观察到材料从制动器转移到轮盘，形成不连续的第三体层。该层磨损后，可能会导致表面裂纹成核。此外，两种材料的碎屑都会增强磨料磨损。如果与连续测试相比，间歇测试显示出更高的摩擦系数波动，并且在某些情况下重量变化显着不同。在钢种中，HYPERLOS 的失重和次表面硬化在不连续试验中高于最长连续试验。B 类在两个测试中表现出相似的行为。假设温度循环对摩擦系数和磨损行为的影响。