The fractured flange bolt used for structural support of wind-poweredgenerator cabin was investigated by means of macro-morphology inspection,microstructureanalysis,fracture morphology analysis and numerical simulation.The investigation showedthe failure of flange bolt was fatigue fracture.The thicker decarburized layer in the threadwas the main cause of the fracture of the bolt.Put forward the suggestions to adopt thebolts manufactored in the same factories and with the same grade,and exchange theoriginal ...