航空铝合金预腐蚀疲劳寿命退化规律

航空铝合金材料在服役过程中常因腐蚀损伤而导致疲劳断裂问题,通过采用扫描电镜及疲劳寿命测试等方法,研究了不同预腐蚀损伤对2xxx铝合金在不同应力比下疲劳寿命的影响,探讨了预腐蚀损伤对疲劳裂纹萌生扩展的影响机理.结果表明:预腐蚀损伤对2xxx铝合金材料疲劳寿命的影响显著,材料的疲劳性能随着腐蚀损伤程度的增加而明显下降.同时建立了预腐蚀损伤对材料疲劳极限的影响系数C-T-R模型,材料疲劳极限的影响系数C随着预腐蚀时间的增加或者应力比R的增加而变大.断口分析表明,预腐蚀损伤的存在导致裂纹萌生寿命大大缩短,裂纹萌生由单源转变为多源,并且均萌生于腐蚀坑处.

Fatigue Life Degenerating Rule of Pre-corroded Aviation Aluminum Alloy

Fatigue fracture usually happens in service process because of the corrosion damage for aerospace aluminum alloy. The effect of pre-corrosion damage on the fatigue life of 2xxx aluminum alloy without clad layers under different stress ratio was studied using stereo microscope， SEM and fatigue tests. The affecting mechanism of pre-corrosion damage on the initiation and propagation of fatigue crack was also discussed. The results show that pre-corrosion damage has a significant effect on the fatigue performance， i.e. fatigue strength decreases with the increase of pre-corrosion extent. A C-T-R effect model of pre-corrosion defect on the fatigue limit was proposed. The fatigue limit effect factor C increases with the increase of pre-corrosion time or stress ratio R. Fracture analysis shows that the pre-corroded damage would result in the emergence of crack changing from single source to multiple sources and the crack initiation life would decrease because of the pre-corroded damage.