Historically, S-N curve has been expressed in the form of an exponential relationship between applied stress σ and number of cycles to failure N_f. This paper elucidates the essential structure of S-N curve based on the prediction method for fatigue life and limit of materials containing defects from the viewpoint of mechanics of small crack. The extended application of the proposed method to step loading and variable amplitude loading is discussed. The question about the applicability of Miner’s rule is also discussed from the viewpoint of continuous decrease in fatigue limit with number of stress cycles and crack growth.

中文翻译：

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S - N曲线的基本结构：疲劳寿命和缺陷材料的疲劳极限以及散布性质的预测

从历史上看，S - N曲线以施加应力σ与失效循环次数N _f之间的指数关系表示。从小裂纹的力学角度出发，基于疲劳寿命的预测方法和含缺陷材料的极限，阐明了S - N曲线的基本结构。讨论了该方法在阶跃加载和变幅加载中的扩展应用。从疲劳极限随着应力循环次数和裂纹扩展的不断降低的角度，还讨论了有关Miner规则的适用性的问题。