2024铝合金振动疲劳特性及断口分析

Vibration Fatigue and Fracture Performance of Aluminum Alloy 2024

研究激振频率对铝合金悬臂梁结构振动疲劳特性的影响。在不同激振频率下测试2024铝合金悬臂梁相同初始应力幅值下的振动疲劳寿命。利用体式显微镜及扫描电镜对疲劳断口进行微观分析。结果表明:初始应力相同时,处于共振状态的悬臂梁振动疲劳寿命最长,瞬断区面积最小。微观分析表明,疲劳裂纹源萌生于材料表面的最大应力区,在裂纹源区有明显的放射状条纹、贝壳线和大量刻面;在疲劳裂纹扩展区,除疲劳条带外,还观察到大量的二次疲劳裂纹;疲劳瞬断区则由大量韧窝构成,表现出典型的韧性断裂特征。微观分析可知合金内强化相颗粒对疲劳裂纹扩展有明显的阻碍作用。

A series of vibration fatigue tests with the same initial stress amplitude were carried out on aluminum alloy 2024 cantilever beam aimed to explore the effect of excitation frequency on vibration fatigue lives. The experiment results show that the longest-life vibration fatigue of cantilever beam appears, and the least fatigue failure region of fracture surface is found, while the excitation frequency is equal to the natural frequency of sample. The fatigue fracture surface was studied by optical microscope and scanning electron microscope. The results show that the crack initiations mostly derive from the surface flaw or inclusion. The crack propagation regions are characterized by fatigue striation and secondary crack. There are lots of dimples in fatigue failure region of fracture surface. The tiny strengthening phase particles play a role of restraining the propagation of fatigue crack.