To define the fatigue crack propagation mode for the prediction and classification of the experimental results based on its evolution mechanism, successive mesoscopic observations of a fatigue process under pure cyclic mode II loading are performed. Thus, damage accumulation, which is considered to be a vacancy accumulation, is found to be a mechanism. The phenomena occur not at the crack tip but ahead of it. Thus, “plastic deformation mode” and “damage accumulation mode” are the terms proposed to represent the fatigue crack propagation modes instead of “tensile mode” and “shear mode,” respectively. Moreover, as a method to classify both the fatigue crack propagation modes using the experimental results, it is proposed to identify the plastic strain in the wake of the crack tip.

中文翻译：

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疲劳裂纹扩展模式：塑性变形模式和损伤累积模式

为了定义疲劳裂纹扩展模式以根据其演化机制对实验结果进行预测和分类，我们对纯循环模式 II 加载下的疲劳过程进行了连续细观观察。因此，发现被认为是空位累积的损伤累积是一种机制。这种现象不是发生在裂纹尖端，而是发生在裂纹尖端。因此，“塑性变形模式”和“损伤累积模式”是提议用来表示疲劳裂纹扩展模式的术语，而不是分别代表“拉伸模式”和“剪切模式”。此外，作为使用实验结果对两种疲劳裂纹扩展模式进行分类的方法，建议识别裂纹尖端的塑性应变。