Analysis on Fracture Reason of Bolt on Piston Compressor Coupling

A bolt on the piston compressor coupling was broken during their maintenance period. By means of chemical composition analysis, hardness testing, metallographic examination, fracture and energy spectrum analysis, the fracture reason was analyzed. The results showed that there was an undercut on the bolt root, which led to stress concentration to create initial crack. All of these led to bolt fatigue fracture after long-serving.