Reason analysis on fracture of anchor bolt with a subway

Anchor bolt of a subway during using process occurred fracture failure.By fracture appearance examination,scanning electron microscope(SEM) observation,chemical composition analysis,hardness testing,metallurgical microstructure analysis and other methods,the fracture mode and failure reasons of the bolt were analyzed.The results show that the fracture mode of the bolt is fatigue fracture.With bolt thread rolling forming,the thread root place form strain groove surface defect,to reduce its anti-fatigue performance,and the thread root place during using process easy to produce stress concentration,so as to promote the fatigue crack initiation and propagation,which eventually led to the bolt fracture failure.