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腐蚀环境下的疲劳性能是航空金属结构疲劳寿命设计的重要前提,为此,试验测定了2种航空铝合金材料(2E12-T3、7050-T7451)的光滑试样和缺口试样在干燥大气和3.5%Na Cl腐蚀环境下的疲劳性能,在试验数据的基础上进行性能对比,并对试样断口进行扫描电镜(SEM)分析,研究了3.5%Na Cl腐蚀环境与载荷联合作用对腐蚀疲劳性能的影响机理,研究结果表明:3.5%Na Cl腐蚀环境对2种铝合金材料的疲劳性能均产生不利影响,且腐蚀与疲劳载荷的交互作用随着应力水平的降低而增强,疲劳性能下降更明显;与光滑试样相比,腐蚀环境对铝合金2E12-T3缺口试样疲劳性能的影响更大,但对铝合金7050-T7451缺口试样疲劳性能的影响却变小;在腐蚀环境下,裂纹尖端易发生电化学反应产生腐蚀产物和[H]离子,腐蚀产物的存在会阻碍裂纹闭合,同时,[H]离子导致裂纹尖端的氢脆效应,加快裂纹扩展,使疲劳性能降低。
Fatigue performance under corrosive environment is an important prerequisite for fatigue life design of aeronautical metal structure. To this end, two smooth aluminum alloy specimens (2E12-T3, 7050-T7451) 3.5% Na Cl corrosive environment fatigue performance, the performance comparison based on the experimental data, and the specimen fracture analysis by scanning electron microscopy (SEM), 3.5% Na Cl corrosive environment and the combined effect of load on the corrosion fatigue properties The results show that 3.5% NaCl corrosive environment adversely affects the fatigue properties of two kinds of aluminum alloy materials, and the interaction between corrosion and fatigue load increases with the decrease of stress level and the fatigue performance decreases more obviously ; Compared with the smooth sample, the corrosion environment has a greater impact on the fatigue properties of the 2E12-T3 aluminum alloy notch specimens, but the impact on the fatigue properties of the aluminum alloy 7050-T7451 notch specimens becomes smaller; in the corrosive environment, cracks The tip is susceptible to electrochemical reactions to produce corrosion products and [H] ions. The presence of corrosion products hinders the crack closure, while [H] ions cause hydrogen embrittlement at the crack tip, accelerating crack propagation and fatigue Reduced.