新型航空铝合金材料复杂形貌点蚀损伤应力集中效应分析

根据7B04铝合金材料试件模拟加速点蚀试验检测结果,并结合铝合金材料点蚀行为机制、微观结构特征与随机性过程本质,构建由多个微观椭球体合成的楔入型与合围型两种典型复杂形貌点蚀损伤模型。采用ANSYS有限元方法建模并基于线弹性断裂力学,对上述两种点蚀损伤模型的应力集中效应进行计算与分析。研究发现:两种复杂形貌特征的点蚀损伤模型产生的应力集中系数数值基本相当,各个微观椭球体蚀坑分别对应力分布产生影响并相互干涉与叠加,造成复杂形貌点蚀损伤模型的应力集中系数数值增大;两种复杂形貌点蚀损伤模型的应力主要集中在各个微观椭球体蚀坑交会的位置,大都位于宏观点蚀损伤的侧边;两种复杂形貌点蚀损伤模型的应力集中效应作用区域的尺寸与铝合金材料微观晶粒尺寸、点蚀萌生的短裂纹初期尺寸基本相当。

Stress concentration effect analysis of new aviation aluminum alloy pitting corrosion damage with complex morphology

Based on simulation accelerated pitting corrosion test results of 7B04 aluminum alloy specimen, which combined with the pitting corrosion mechanization and microstructure of aluminum alloy and stochastic process essence of pitting corrosion, two typical damage models with complex morphology which were composed of many micro-ellipsoid corrosion pits were erected through finite element method, two models were named wedging model and encircling model respectively. The stress concentration effect which was embodied by stress concentration factor and stress nephogram was calculated and analyzed through ANSYS software and linear elastic fracture mechanics. The results show that the stress concentration effect of wedging model and encircling model is very different from the results of simplified ellipsoid corrosion pits model. The stress concentration factor value of wedging model and encircling model is almost the same, and may increase because of interference and influence and superposition of each single micro-ellipsoid corrosion pits. The obvious area or location of stress concentration effect of wedging model and encircling model almost locates at the intersection region between each micro-ellipsoidal corrosion pit, the intersection regions almost are on the side of the macro corrosion pits. The size range of wedging model and encircling model stress concentration effect are well matched with the microscopic grain size and small crack size of aluminum alloy.