某型航空发动机飞附吊挂机匣的转角出现裂纹。采用宏观观察、断口分析、应力分析和有限元模拟分析等方法,对该飞附吊挂机匣裂纹产生的原因进行了分析。结果表明:该裂纹为起始应力较大的疲劳裂纹;飞附吊挂机匣与风扇机匣装配时,将定位销敲击进入销钉孔的过程会导致飞附吊挂机匣发生局部变形,从而在裂纹部位形成较大的初始应力,在振动的工作环境下,飞附吊挂机匣产生裂纹并扩展。保证风扇机匣与飞附吊挂机匣的安装边装配尺寸为间隙配合、在装配定位销前使用工艺螺钉先固定飞附吊挂机匣可以避免该类问题的发生。

Cracks occured at the corners of the aircraft accessories suspension casing of an aeroengine. By means of macroscopic observation, fracture analysis, stress analysis and finite element simulation analysis, the causes of cracks in the aircraft accessories suspension casing were analyzed. The results show that the cracks were fatigue cracks with large initial stress. When the aircraft accessories suspension casing was assembled with the fan casing, the process of knocking the locating pin into the pin hole would lead to local deformation of the aircraft accessories suspension casing, thus forming a large initial stress at the crack location. Under the vibration working environment, the aircraft accessories suspension casing would produce cracks and expand. This kind of problem could be avoided by ensuring that the mounting side assembly dimensions of the fan casing and the aircraft accessories suspension casing were clearance fit, and using process screws to fix the aircraft accessories suspension casing before assembling the positioning pin.