An investigation into the effects of overload mode-mixity on crack growth behavior and governing micromechanisms of AA7075 T6 has been conducted. Cruciform AA7075 T6 specimens were subjected to constant amplitude planar biaxial fatigue with single overloads, and key fatigue damage behavior, including fatigue life, crack growth rate, and recovery distance, were investigated and correlated to overload parameters. Additionally, SEM fractography was conducted to identify and relate fracture surface features to governing fatigue damage micromechanisms. An increase in fatigue life was observed for all cases of mode-mixity, with the minimum increase occurring at 45°. The mix-mode overloads also caused crack retardation in all cases. In the shear dominant overloads, however, initial post-overload crack acceleration occurred and was immediately followed by crack retardation. Microscale analysis showed distinct fracture features in the pre-overload, transient, and post-overload regions for both tensile and shear dominant overloads.

已经研究了过载模式混合对AA7075 T6裂纹扩展行为和控制微观机制的影响。对十字形AA7075 T6试样进行单振幅恒定振幅的平面双轴疲劳，并研究了疲劳疲劳寿命，裂纹扩展速率和恢复距离等关键疲劳损伤行为，并将其与过载参数相关联。此外，进行了SEM断层扫描以识别断裂表面特征并将其与支配疲劳损伤的微观机制联系起来。在所有模式混合情况下，疲劳寿命均增加，最小增加发生在45°。在所有情况下，混合模式过载也会导致裂纹延迟。但是，在剪力过载中，最初出现了过载后的裂纹加速现象，然后立即出现裂纹延迟现象。微观分析表明，对于拉伸和剪切支配的超载，在超载前，瞬态和超载后区域都有明显的断裂特征。