当量加速腐蚀条件下7B04-T6高强度铝合金疲劳裂纹扩展规律研究

The fatigue crack growth rule of 7B04-T6 high strength aluminum alloy under equivalently accelerated corrosion environment

基于编制的机场环境加速试验谱,针对关键结构高强度铝合金件进行当量腐蚀试验,在实验室条件下成功地模拟和再现了服役环境条件的腐蚀损伤,借助复型法观测得到了腐蚀损伤的演化规律;通过预腐蚀疲劳试验和疲劳断口扫描电镜定量分析,得到了裂纹长度a与循环次数N数据集,分析了裂纹扩展速率da/d N与应力强度因子幅值ΔK的对应关系,定量表征了不同程度腐蚀损伤对疲劳裂纹扩展行为的影响规律.结果表明,在腐蚀初期,疲劳裂纹扩展过程中有经典的小裂纹扩展阶段;随着腐蚀损伤的加重,小裂纹行为不明显;腐蚀损伤越严重,疲劳裂纹扩展速率越快,结构抗疲劳性能显著退化.

Based on an accelerated corrosion testing spectrum complicated for the servicing field environment, the equivalently accelerated corrosion testing of high strength aluminum alloy 7B04-T6 specimens for critical structure were carried out. Corrosion damage under the field environment was successfully simulated and reappeared, and corrosion damage evolvement rule was obtained. By prior?corrosion fatigue testing and fractography quantitative analysis, the fatigue crack length (a) and fatigue cycles (N) were gotten, and relationship between fatigue crack growth rate (da/dN) and stress intensify factors rang (ΔK) was analyzed. Moreover the effect of different corrosion damage on fatigue crack growth behavior was quantitatively characterized. The result shows that there is obvious short crack growth behavior during early corrosion stage, the fatigue crack growth rate increases when the corrosion damage is more serious, and the fatigue performance is greatly degraded.