航空铝合金预腐蚀疲劳寿命退化规律

Fatigue Life Degenerating Rule of Pre-corroded Aviation Aluminum Alloy

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