高强预腐蚀铝合金单轴拉-拉疲劳断口定量分析

目的通过断口定量分析获得7A09铝合金的疲劳裂纹扩展规律,为7A09铝合金结构的寿命评估提供依据。方法使用EXCO溶液对试验件进行预腐蚀,利用疲劳拉伸机进行疲劳加载直至断裂,使用扫描电镜对疲劳断口进行定量化分析。结果疲劳裂纹在试件的腐蚀坑处萌生,从自由界面附近向纵深发展导致试件的断裂。通过断口分析和Paris公式确定了裂纹的萌生寿命和扩展寿命。结论腐蚀之后的试件裂纹萌生寿命占总寿命的比例下降,当裂纹扩展程度较大之后,受腐蚀影响减轻,得出裂纹扩展速率和应力强度因子的关系。

Quantitative Analysis on Tension-Tension axial Fatigue Fractography of High Strength and Toughness Aluminum Alloy

Objective To obtain fatigue crack propagation behaviors of 7A09 aluminum alloy by quantitative analysis of crack to provide basis for its fatigue life analysis. Methods EXCO solution was used to have pre-corrosion on test specimen. The fatigue tension machine was used to load fatigue till cracking. The scanning electron microscope was applied to carry out quantitative analysis on fatigue fracture. Results The fatigue crack appeared at the corrosion pit of the specimen and developed in depth and breadth from adjacent of free interface and lead to fracture. Initiation life and propagation of crack were determined by fracture analysis and Paris formula. Conclusion The ratio of crack initiation life of specimen after corrosion decreased. When the crack extent is larger, the corrosion effect is reduced. The relationship between the crack propagation rate and the stress intensity factor was obtained.