发动机燃油供油导管断裂失效分析

Fracture Failure Analysis of a Fuel Pipe in an Aero-engines

某型发动机连续发生两起由于与主输油圈连接的U形燃油供油导管在连接处断裂引起的空中漏油故障。对断裂导管的安装位置、结构特点及装配情况进行了检查,对同型发动机进行了开车试验,对导管断口进行了分析。结果表明,两根导管的断裂性质相同,均为起始应力较大的高周疲劳断裂,疲劳裂纹起始于U形导管内侧或外侧的焊缝部位。U形导管装配应力大是导致导管疲劳裂纹早期萌生的主要原因,高压燃油冲击和脉动引起的弯曲应力对裂纹的萌生也有一定的影响,导管焊缝处存在的焊接缺陷对裂纹的萌生具有促进作用。

Two oil leaking failures of one type of aero-engine happened continuously, which were resulted from fracture of U-pipes at the joint connecting with the main pipe laying. Fix position, structure characteristics and assembly state of fracture U-pipes were inspected and the fracture surface was observed. And trial run of the same type of aero-engine was conducted. The results show that the fracture model of two pipes are the same high cycle fatigue fracture due to high original stress. Fatigue crack originated from welding line at inboard or outboard of U-pipes. The main cause of fatigue crack origination was excessive assembly stress. Bend stress resulted from shock and pulse of high pressure oil also have some effects on the crack origination. The welding defects existed in welding line promoted the origination of crack.