Fracture Analysis of Spiral Flexible Metal Pipe in Exhaust System

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 failure cause. It is found that adhesive wear and abrasive wear gradually made the section of the pipe thin, resulting in the decrease of the fatigue performance of the pipe and the final fatigue fracture. While the truck was running, soil and other foreign matters splashed 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.