This study investigated the effects of multiaxial cyclic loading on the initiation and propagation of fatigue cracks in an industrial-grade aluminum alloy. Four different loading cases, including 90° out-of-phase and asynchronous loading, were used under the control of strain. The study used cellulose acetate film replication and SEM fractography techniques to increase the understanding of the evolution of fatigue damage on specimen surfaces. The material exhibited a shear damage mechanism with a significant amount of small cracks coalescence. It was explained why, despite a high agreement with the assumptions of the critical plane approach, the predicted fatigue life was overestimated at high loading levels. A correlation between the crack initiation period and overall fatigue life, regardless of loading case, was presented, which has a potential for practical applications.

中文翻译：

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PA38-T6(6060-T6)铝合金多轴疲劳载荷下小裂纹行为研究

本研究研究了多轴循环载荷对工业级铝合金疲劳裂纹萌生和扩展的影响。在应变控制下使用了四种不同的加载情况，包括 90° 异相加载和异步加载。该研究使用醋酸纤维素薄膜复制和 SEM 断口分析技术来加深对样品表面疲劳损伤演变的了解。该材料表现出剪切损伤机制，并有大量小裂纹合并。解释了为什么尽管与临界平面方法的假设高度一致，但在高负载水平下预测的疲劳寿命被高估了。提出了无论载荷情况如何，裂纹萌生期和总体疲劳寿命之间的相关性，这具有实际应用的潜力。