油箱积水环境下航空铝合金2 E12-T3和7050-T7451疲劳性能实验

摘要

Fatigue properties in typical corrosion environments are the premise of fatigue life design for metallic structures in aircraft. Therefore, fatigue tests were performed on smooth and notched specimens subjected to constant amplitude loading in two environments of dry air and fuel tank ponding respectively to determine pure and corrosion fatigue properties of aluminum alloys 2E12-T3 and 7050-T7451. Corrosion fatigue properties in the two environments were analyzed and compared with each other, and the interaction mecha-nisms between corrosion and fatigue were deduced from fractographical studies by using scanning election microscope ( SEM ) . It is showed that fuel tank ponding has a detrimental influence on fatigue properties and the adverse effect increases with the decreasing stress level. In addition, the notch of specimen enhances the severity of corrosion effects. Fatigue crack is easily initiate from the corro-sion pits on the rough fatigue surface, and crack propagation is enhanced by the corrosion products and the hydrogen embrittlement effects at crack tips, thus the degradation of fatigue properties and the reduction of fatigue life are caused.%典型腐蚀环境下的疲劳性能是航空金属结构疲劳寿命设计的前提，为此，实验测定航空铝合金2E12-T3和7050-T7451光滑试样和缺口试样在干燥大气环境和油箱积水环境下的疲劳性能S-N曲线，观测实验现象，根据实验数据结果进行疲劳性能对比，并对试样断口进行扫描电镜( SEM)分析，研究油箱积水腐蚀环境和载荷联合作用对疲劳性能的影响机理，结果表明：油箱积水环境对材料的疲劳性能产生不利影响，疲劳载荷的降低和试样的缺口均加剧腐蚀环境对材料疲劳性能的不利影响；腐蚀引起的试样表面粗糙状况更容易萌生疲劳裂纹，裂纹尖端发生的电化学反应和氢脆效应加快裂纹扩展，使得疲劳性能降低和疲劳寿命缩短。