This study investigated the retardation mechanisms and modeling methodology for the fatigue crack growth (FCG) of a high-strength Q500qE steel after a single overload. Different stress ratios ( = 0.1, 0.3, and 0.5) and overload ratios (OLR = 1.5, 2.0, and 2.5) were considered as key parameters. The digital image correlation (DIC) testing technique was used to capture the deformation at the crack tip during the tests. The crack closure response in the crack wake region was investigated using a virtual extensometer. The results show that, under an identical stress ratio, the fatigue life was increased as the OLR increased. The FCG was completely arrested when OLR reached 2.5 when ≥0.3. Under an identical stress ratio, the residual strain before the crack tip and the residual deformation in the crack wake region increased with the rise of the overload ratio after a single overload. It’s found that the FCG was retarded or completely arrested due to the constraint of the crack tip plastic zone caused by single overload. Finally, a modified Wheeler model was proposed to predict the FCG rate based on the measured plastic zone size at the crack tip, and the predicted results agree well with the experimental findings.

中文翻译：

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单次过载后高强度钢疲劳裂纹扩展的延迟机制和建模

本研究研究了高强度 Q500qE 钢在单次过载后疲劳裂纹扩展 (FCG) 的延迟机制和建模方法。不同的应力比（= 0.1、0.3 和 0.5）和过载比（OLR = 1.5、2.0 和 2.5）被视为关键参数。数字图像相关（DIC）测试技术用于捕获测试过程中裂纹尖端的变形。使用虚拟引伸计研究了裂纹尾流区域的裂纹闭合响应。结果表明，在相同应力比下，疲劳寿命随着OLR的增加而增加。当OLR≥0.3时达到2.5时FCG完全停止。在相同应力比下，单次过载后，随着过载比的增大，裂纹尖端前的残余应变和裂纹尾迹区的残余变形增大。结果发现，由于单次过载引起的裂纹尖端塑性区的约束，FCG被延迟或完全停止。最后，提出了一种改进的Wheeler模型，根据测量的裂纹尖端塑性区尺寸来预测FCG率，预测结果与实验结果吻合良好。