Notches, local stress raisers within structural components, are one of the most important locations for fatigue crack initiation. It is well known that fatigue is governed by the effective stresses in the vicinity of notches. Within this study, differences in prediction accuracy between different types of theory of critical distance methods, that is, point and line methods, are systematically investigated in conjunction with a sensitivity study regarding mesh refinement, assumed strength hypothesis and material behaviour. For this purpose, a finite element analysis parameter study on notched structures is performed and recommendations for the application of stress gradient methods are presented. Difference in effective stress of up to 30%, and hence a significant difference in fatigue life (e.g., 185% for a slope of S‐N curve of k = 4), is found for typical notch shapes, for example, in welded joints.

中文翻译：

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基于临界距离理论的缺口结构基于应力梯度的疲劳评估要求

槽口是结构部件内的局部应力升高点，是引起疲劳裂纹的最重要位置之一。众所周知，疲劳是由切口附近的有效应力控制的。在这项研究中，结合关于网格细化，假定强度假设和材料行为的敏感性研究，系统地研究了不同类型的临界距离方法理论（即点线方法）之间的预测准确性差异。为此，对缺口结构进行了有限元分析参数研究，并提出了应用应力梯度法的建议。有效应力的差异最大为30％，因此疲劳寿命也有显着差异（例如，对于S-N曲线的斜率为185％）k = 4），适用于典型的缺口形状，例如在焊接接头中。