飞机铝合金壁板结构广布疲劳多裂纹扩展与剩余强度研究

Study on wide-spread fatigue multi crack propagation and residual strength of aircraft aluminum alloy plate structure

随着航空工业的发展,飞机经过长时间服役,其广布疲劳损伤带来的飞机服役可靠性问题日益受到关注。针对飞机铝合金壁板结构开展了疲劳裂纹扩展试验与剩余强度拉伸试验,以及数值仿真研究,并采用塑性区连通准则、表观断裂韧性准则、净截面屈服准则和韧带平均应力准则4种典型的多裂纹连通准则对其剩余强度进行了对比分析。结果表明:随着疲劳裂纹的逐渐扩展,裂纹尖端应力强度因子逐渐增大,裂纹扩展速率逐渐增大。对于含多裂纹的铝合金壁板结构,建立剩余强度与裂纹总长度的关系更能准确体现机身壁板在实际服役过程中的剩余强度变化。与其他3种准则相比,塑性区连通准则可以控制含等长度裂纹与非等长度裂纹的铝合金壁板结构剩余强度的预测结果与试验结果的相对误差在5%以内,是4种准则中预测精度最高的,因此,塑性区连通准则对飞机铝合金壁板结构广布疲劳损伤设计具有良好的指导意义。

With the development of aircraft industry, aircraft service reliability problem caused by wide-spread fatigue damage has attracted more and more attention after a long service.Fatigue crack propagation test, residual strength tensile test and numerical simulations were carried out for aircraft aluminum alloy plate structures.And four multi crack connectivity criteria, ligament yield criterion, K-apparent criterion, net ligament loss criterion and average stress criterion, were employed to analyze its residual strength.The results show that with the gradual growth of fatigue crack, the stress intensity factors at the crack tip increase and the crack growth rates increase. For the aluminum alloy plate structures with multiple cracks, the relationship between residual strength and total crack length can more accurately reflect the change of residual strength in the actual service process of fuselage panel. Compared with the other three criteria, the ligament yield criterion can control the relative error between the residual strength prediction results and the test results of aluminum alloy plate structure prefabricated with equal length crack and non-equal length crack no more than 5 %,which was the highest prediction accuracy among the four criteria.Therefore, the ligament yield criterion has good guiding significance for the wide-spread fatigue damage design of aircraft aluminum alloy plate structure.