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

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.