针对部件服役过程中，在常幅循环加载中引入单个拉伸过载作用的行为，研究过载比、应力比和试样厚度对单个拉伸过载后的裂纹扩展行为和疲劳寿命产生的影响。采用Q345R标准紧凑拉伸试样为研究对象，开展不同过载比、应力比和厚度条件下，在常幅加载过程中引入单个拉伸过载作用下疲劳裂纹扩展行为的试验。试验结果表明：在保持应力比、过载比和试样厚度中的任意两个条件一致的情况下，过载比越大，迟滞效应越明显；应力比越高，迟滞效应越弱；试样厚度增加，迟滞效应减弱。利用半幅降载勾线法，研究由过载引起的沿试样厚度方向的裂纹扩展形貌的变化，并一定程度上解释了厚度效应对过载行为的影响。根据试验和分析结果，对于Q345R在实际服役过程中的寿命评定起重要作用。

For most engineering components/structures, it is frequent subjected the single tensile overload during constant amplitude loading. The influence of overload ratio, stress ratio and specimen thickness are analyzed and study on the fatigue crack growth behavior and fatigue life after the single tensile overload. A series of fatigue crack growth experiments subjected to a single tensile overload are conducted using compact tension specimens of Q345R steel. The experimental results of single tensile overload show that a larger overload ratio induces the more obvious retardation effect, retardation effect decreased with increased stress ratio, retardation effect decreased with increased specimen thickness. The crack growth shapes of specimens are obtained by using the marking method under overload and constant amplitude loading. The experimental results explain the fatigue crack growth behavior after overload. The crack growth experiment and analyze results is important to the life prediction of engineering components.