弯管接头开裂分析

某飞机飞行后例行检查时,2次发现回油路上与油滤相连的铝直角弯管接头出现漏油现象,经检查弯管接头螺纹部位发生开裂。通过外观检查、断口宏微观观察、断口定量分析、能谱分析、硬度检测和金相检验等方法对开裂铝直角弯管接头进行了分析。结果表明:弯管接头开裂性质为疲劳断裂,裂纹起源于弯管接头外壁表面;A弯管接头受到较大起始应力,在振动应力的作用下裂纹进一步扩展;B弯管接头螺牙底部的裂纹应在较大应力下快速扩展形成。

Failure Analysis of Bend Joint

Leakage occurred to two bend joints after serving for a time, and the bend joints were found to have cracks at the thread region. The failure mode and cause of the bend joints were analyzed by appearance observation, micro and macro observation on fracture surfaces, quantitative analysis, energy spectrum analysis, hardness testing and. metallographic examination. The results show that the failure mode of the bend joints is fatigue failure. The cracks initiated from the outside surface. The cracks of bend joint A initiated at greater stress, and propagated under vibration stress. The thread bottom crack of bend joint B propagated fast under greater stress.