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在不同幅值循环载荷条件下对7075-T7451铝合金紧凑拉伸(CT)试样进行拉伸疲劳试验,对其疲劳裂纹扩展速率和应力强度因子幅值ΔK进行了研究,并用扫描电子显微镜观测试样的断口形貌。结果表明:随着循环载荷幅值的增大,试样的疲劳寿命缩短,裂纹的扩展速率增大;试样宏观断口形貌的裂纹稳态扩展区域减小,而瞬时断裂区域增大。稳态扩展区主要以疲劳条带扩展机制为主,且疲劳条带间距随循环载荷幅值的增大而增大;瞬断区的断口形貌以韧窝断裂为主,韧窝尺寸随循环载荷幅值的增大而减小。
Tensile fatigue tests were carried out on the 7075-T7451 aluminum alloy compact tensile (CT) specimens under different cyclic loading conditions. The fatigue crack growth rate and the magnitude of stress intensity factor ΔK were studied. Scanning electron microscopy Fracture morphology of the specimen. The results show that the fatigue life of specimens decreases with the increase of cyclic loading amplitude, and the crack growth rate increases. The steady state crack propagation area of the macroscopic fracture surface decreases and the instantaneous fracture area increases. The steady-state extension zone is dominated by the fatigue-strip expansion mechanism, and the fatigue-stripe spacing increases with the increase of the cyclic loading amplitude. The fracture morphology of the instantaneous fracture zone is dominated by ductile fracture with dimple size Load amplitude increases and decreases.