某型飞机转接环和发动机安装边的连接螺钉发生断裂。采用宏观观察、化学成分分析、扫描电镜及能谱分析、金相检验、十字槽深度检测、力学性能测试等方法对螺钉断裂原因进行分析。结果表明:飞机服役时,含有氯元素的腐蚀性介质沉积在螺钉十字槽处,且螺钉的十字槽深度超出标准要求,使该部位产生应力集中,在二者的综合作用下,十字槽根部发生应力腐蚀开裂,裂纹由十字槽根部向外表面扩展,最终导致螺钉发生断裂。

The connecting screw between the adapter ring and the engine mounting edge of a certain type aircraft was broken. The causes of screw fracture were analyzed by macroscopic observation, chemical composition analysis, scanning electron microscopy and energy spectrum analysis, metallographic examination, cross groove depth detection and mechanical property test. The results show that the corrosive medium containing chlorine element was deposited at the cross slot of the screw during the service of the aircraft, and the depth of the cross slot of the screw exceeded the standard requirement, which caused stress concentration in this part. Under the combined action of the two, the stress corrosion cracking of the screw occurred at the root of the cross slot, and the crack extended from the root of the cross slot to the outer surface, which eventually led to the fracture of the screw.