Railroad products suffer fatigue since they are used in a condition of cyclic loading when railroad vehicles run. Key products are the most important mechanical parts, which are wheels, axles, discs, and truck frames. They are such fail-out components, as can cause the fatal failure of vehicles, when the components fail. Among such components, wheels and axles are the most critical railroad components, since they can cause the derailment. Tremendous efforts to the research and development have been devoted in the area of railroad industry. However, the rail accident of German railroad in 1998 clarified that we need to study more deeply. Fracture Mechanics are now used as an ordinary tool to apply to design products, and knowledge of fatigue characteristics is common. This paper summarizes how the railroad product in Japan were developed using the knowledge of fatigue characteristics and fracture mechanics, and considers the future research. The issues are whether fatigue limit exists based on the scientific explanation, whether the retardation of crack extension can happen with appropriate ground, and whether a crack extends under large compressive cyclic loading. The author had engaged in the area for 35 years, and the summary adding such experience is explained.

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