排气系统缠绕式金属软管断裂原因分析

Fracture Analysis of Spiral Flexible Metal Pipe in Exhaust System

卡车发动机排气系统中的缠绕式金属软管在行驶过程中发生断裂及卡死现象。通过宏观分析、断口观察、金相分析、能谱分析及硬度检测等手段,对金属软管断裂的原因进行分析:粘着磨损和磨粒磨损导致金属软管的截面厚度逐渐变薄,截面变薄后零件抗疲劳性能下降,最终发生疲劳断裂。发生卡死的原因是车辆在行驶过程中,由车轮激起的泥沙或其他异物逐渐进入金属软管空隙,在金属软管间隙内淤积,而卡死也加速了金属软管的断裂。针对失效原因,提出了防止金属软管发生卡死和断裂的方法。

A spiral flexible metal pipe in the exhaust system of a truck fractured and locked during service. Macro observation, fracture analysis, metallographic analysis, energy spectrum analysis and hardness testing were carried out to find out the failurecause. It is found that adhesive wear and abrasive wear gradually made the section of the pipe thin, resulting in the decrease ofthe fatigue performance of the pipe and the final fatigue fracture. While the truck was running, soil and other foreign matterssplashed up by the tyres gradually went into the clearance of the flexible pipe and deposited in the clearance, which finally resulted in the locking of the pipe. The locking accelerated the fatigue fracture of the pipe. Based on the failure cause, some methods were proposed to prevent locking and fracture.