Fracture Analysis of 40Cr Connecting Rod Bolt of Diesel Engine for Ship

The fracture sample of 40 Cr connecting rod bolt of diesel engine for ship was analyzed by macro analysis,metallographic analysis,elemental analysis,SEM morphology analysis and mechanical testing.It was showed that the fracture of connecting rod bolt is shear ductile fracture caused by fatigue,stress concentration induced by processing scratches,irregular defects on bolt root surface is the main reason of fatigue sources.