以LD2航空铝合金材料为研究对象，通过加速腐蚀试验，得到不同腐蚀时间下的试验件，并在MTS-810疲劳机上对不同腐蚀时间下的试验件进行疲劳试验，得到不同腐蚀年限下的疲劳断口形貌。通过断口判读分析，得到不同腐蚀年限下的裂纹扩展数据。从不同腐蚀时间下的裂纹扩展数据研究分析，得到裂纹长度与循环次数符合指数函数的形式，即裂纹扩展速率与裂纹长度成正比，其斜率依赖于腐蚀损伤与疲劳载荷两个因素，而且在同一应力水平下，其斜率与腐蚀时间成线性关系，并且其截距与应力水平也成线性关系。
The accelerated corrosion tests and then the fatigue tests on LD2 aerospace aluminum alloy test samples were executed under different corrosion times. The fatigue rupture morphologies of the test samples with different corrosion times were gained. The crack growth datum under different corrosion times were measured by judgment of the rupture morphologies. By fitting the datum , it can be found that the relation between crack length and cycle number is of exponential, and the crack growth rate is direct ratio to the crack length where the slope of the crack growth rate vs the crack length depends on the factors of corrosion damage and the fatigue load level. Furthermore, by fatigue tests under different corrosion times and different stress levels, it can be also found that the relation between the slope and the corrosion time is of linear under the same stress level and the slope values under different stress levels are nearly the same, while the intercept of the line of crack growth rate also varies linearly as the stress level.
[1] Mu Zhitao. The analyzing method for fatigue life of aircraft structures under corrosive environment [J]. China Engineering Science, 2002, (3): 68-72. (in Chi-nese) .
穆志韬. 腐蚀环境下飞机结构疲劳寿命的分析方法[J]. 中国工程科学, 2002, (3): 68-72.
[2] Mu Zhitao Jin Ping, Duan Chengmei. The corrosion fatigue and life of aircraft structure in servicing [J]. China Engineering Science, 2000, 2(4): 34-38. (in Chi-nese)
穆志韬, 金平, 段成美. 现役飞机结构腐蚀疲劳及寿命研究[J]. 中国工程科学. 2000, 2(4): 34-38.
[3] Zhou Xiyuan. Equivalent environment spectrum and accelerated test spectrum of aircraft structure [J]. Acta Aeronoutica et Astronautica Sinica, 1996, 17(5): 613-616. (in Chinese)
周希沅. 飞机结构的当量环境谱与加速试验谱[J]. 航空学报, 1996, 17(5): 613-616.
[4] Zhang Dong. Accelerated corrosion test of the aircraft structure under equivalent environment spectrum and the computing method for the calendar life [J]. Acta Aeronoutica et Astronautica Sinica, 2000, 21(3): 196-201. (in Chinese)
张栋. 飞机结构件在当量环境谱下加速腐蚀试验和日历寿命计算方法[J]. 航空学报, 2000, 21(3): 196-201.
[5] Liu Wenting, Zhao Yanxiang. Back-calculating method for determining parameters of a da/dN equation of rela-tively small crack.[J]. Acta Aeronoutica et Astronautica Sinica, 1993, 4(2): 033-B038. (in Chinese)
刘文珽，赵燕湘．确定相对小裂纹da/dN公式系数的计算反推法[J]．航空学报, 1993，14(2)：B033-B038.
[6] Polak J. Mechanisms and kinetics of the early fatigue damage in crystalline materials. Mater Sci Eng A, 2007, 33(9): 468-470.
[7] Nakajima M, Tokaji K. Fatigue Life Distribution and Growth of Corrosion Pits in A Medium Carbon Steel in 3% NaCl Solution[J]. Fatigue Fract Engng Mater Struct. 1995: 18(3): 345-351.
[8] Jisa D. I.iskutin P. Kruml T. Polak J. Small fatigue crack growth in aluminum alloy EN-AW 6082/T6. Interna-tional Journal of Fatigue. 2010, 32: 1913-1920
[9] Li Xudong. Small crack growth of aluminum alloy under corrosive environment [D]. Beijing: Master’s degree thesis of Tsinghua University. 2011.7. (in Chinese)
李旭东. 腐蚀环境下铝合金材料微裂纹扩展分析[D]. 北京: 清华大学硕士毕业论文.2011.7.
[10] Xue Yibin. Modeling fatigue small-crack growth with confidence - A multistage approach. Int J Fatigue, 2010, 32(3): 1210~1219.
[11] Wang XS, Fan JH. SEM online investigation of fatigue crack initiation and propagation in notched cast magne-sium specimens. Journal of Materials Science, 2004, 39(7): 2617~2620.
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