A Failure Assessment Diagram (FAD), developed for rolling contact, was specifically formulated for railway wheel steels. The FAD allows combining a multiaxial fatigue criterion with the linear elastic fracture mechanics concept; in particular, it was used to assess the fatigue failure in wet contact, related to the pressurization of the fluid entrapped in surface cracks. The approach was applied to the results of previous bi-disc tests carried out on three railway wheel steels, subjected first to a dry rolling-sliding contact step, then to a wet contact step. The crack size distribution after the dry contact step was evaluated by a statistical approach; subsequently, the stress intensity factor during the wet contact step was estimated by finite elements. The results of the FAD agreed with the damage observed on the cross section of the specimens at the end of the tests. Furthermore, the FAD was used to determine the maximum allowable crack to prevent rolling contact fatigue, this way showing its potential as a damage tolerant approach.

中文翻译：

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失效评估图法在铁路车轮钢接触疲劳损伤评估中的应用

为滚动接触开发的失效评估图 (FAD) 是专门为铁路车轮钢制定的。FAD 允许将多轴疲劳准则与线弹性断裂力学概念相结合；特别是，它被用来评估湿接触中的疲劳失效，这与表面裂纹中夹带的流体的加压有关。该方法应用于之前对三种铁路车轮钢进行的双盘测试的结果，首先进行干滚动-滑动接触步骤，然后进行湿接触步骤。通过统计方法评估干接触步骤后的裂纹尺寸分布；随后，湿接触步骤中的应力强度因子由有限元估计。FAD 的结果与试验结束时在试样横截面上观察到的损伤一致。此外，FAD 用于确定最大允许裂纹，以防止滚动接触疲劳，这种方式显示了其作为损伤容限方法的潜力。