Fatigue damage and fracture of metals are the major failure modes of mechanical structures. Studying the fatigue crack growth (FCG) behaviour under overload effects can better explain the loading interactions and develop more accurate FCG prediction models. This research innovatively designed and established the experimental system that is suitable for FCG test under variable amplitude loading (VAL). Systematically, FCG experiments were carried out by introducing single tensile overload, single compressive overload and tensile/compressive sequential overload in constant amplitude loading (CAL). The effects of overload ratio, stress intensity factor (SIF) range ∆K and tensile/compressive overload sequence on the FCG behaviour of 7050‐T7451 aluminium alloy were comparatively analysed. The retardation or acceleration effects on the macro FCG and the micro crack deflection, crack bifurcation and particle falling effects of different overloads as well as their interactions were revealed.

中文翻译：

---

过载对7050-T7451铝合金疲劳裂纹扩展行为的实验研究

疲劳损伤和金属断裂是机械结构的主要失效模式。研究过载效应下的疲劳裂纹扩展（FCG）行为可以更好地解释载荷相互作用并开发更准确的FCG预测模型。该研究创新性地设计并建立了适用于可变振幅载荷（VAL）下FCG测试的实验系统。通过在恒定振幅负载（CAL）中引入单拉伸过载，单压缩过载和拉伸/压缩顺序过载来进行FCG实验。过载率，应力强度因子（SIF）范围∆ K的影响并分析了7050-T7451铝合金的FCG行为的拉伸和压缩过载顺序。揭示了对宏观FCG的延迟或加速作用以及不同过载的微裂纹偏转，裂纹分叉和落粒效应及其相互作用。