Friction modifiers (FM's) are substances deliberately applied to the top-of-the-rail in the field in order to control the traction coefficient. In this work, two FM's, a commercial (FM1) and a custom-made (FM2), and a gauge lubricant (CGL) were evaluated in the laboratory using rheological and tribological tests. Two rheological tests were done: oscillatory (frequency and strain sweeps) and flow tests (viscosity vs. shear rate). Tribological tests were done in a twin disk machine to obtain the traction coefficient under different slip values. Retentivity tests were also done in the same machine. Several physical–chemical tests were also done to characterise the products. The results of rheological tests showed that there are notable differences that can influence the performance of FMs. From the studied materials, the FM2 product tends to be more viscous even for high-shear rates. The tribological tests showed that the traction coefficient is different for all the studied materials and changes from 0.15 to 0.45 depending on the creepage. The retentivity of FM2 is 1.9 times higher than FM1. The results show a good correlation between the rheological behaviour and the coefficient of traction and retentivity.

中文翻译：

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轮轨应用摩擦改进剂的流变学和摩擦学评估

摩擦改进剂 (FM) 是在现场特意应用于轨道顶部以控制牵引系数的物质。在这项工作中，在实验室中使用流变学和摩擦学测试评估了两种 FM，一种商业 (FM1) 和一种定制 (FM2)，以及一种量规润滑剂 (CGL)。进行了两项流变测试：振荡（频率和应变扫描）和流动测试（粘度与剪切速率）。在双盘机上进行摩擦学测试，以获得不同滑差值下的牵引系数。保持力测试也在同一台机器上进行。还进行了几次物理化学测试来表征产品。流变测试结果表明，存在显着差异会影响 FM 的性能。从研究的材料来看，即使在高剪切速率下，FM2 产品也往往更粘稠。摩擦学测试表明，所有研究材料的牵引系数都不同，并且根据爬电距离从 0.15 变化到 0.45。FM2 的保持力是 FM1 的 1.9 倍。结果表明流变行为与牵引系数和保持力之间存在良好的相关性。