航空导管弯曲试验的疲劳裂纹萌生寿命

飞行器液压导管受接头和卡箍等约束，在使用的振动环境中，会因弯曲应力而导致破裂，影响到飞行安全．本文对飞行器液压系统通用的不锈钢导管的裂纹萌生寿命进行了试验研究．首先在对8 mm、12 mm 无缺陷导管和含U 型缺口8 mm 导管的疲劳试验和有限元分析的基础上，得到了导管的最大拉应变-裂纹萌生寿命数据．然后采用基于强度极限和弹性模量估算法的Manson-Coffin 公式来预测导管裂纹萌生寿命．最后引入加载类型修正系数、表面质量修正系数、试样尺寸修正系数、应力集中敏感系数和有效应力集中系数，使修正后的公式对三种类型的导管均有较好的裂纹萌生寿命预测精度．

Fatigue Crack Initiation Life of Aviation Pipe in Bending Test

Aircraft hydraulic pipe which is constrained by the joint, clamp and others used in the vibration environment, is vulnerable to rupture due to the bending stress, undermining the flight safety. In this paper, the crack initiation life of the stainless steel pipe used in aircraft hydraulic system is studied. On the basis of fatigue test and finite element analysis of 8 mm, 12 mm pipes without defects and 8 mm pipe with U-notch, the maximum tensile strain-crack initiation life data of the pipe were obtained. Then the crack initiation life was predicted by Manson-Coffin formula of strength limit and elastic modulus estimation method. Finally, the correction coefficient of loading type, the correction coefficient of surface quality, the correction coefficient of sample size, the sensitivity coefficient of stress concentration and the effective stress concentration coefficient are introduced, so that the revised formula has a better prediction accuracy of the crack initiation life for the three types of pipe.