Failure Reasons of Rotor Connection Bolts of Seawater Filter in a Nuclear Power Plant

To figure out the reasons for fracture failure of rotor connection bolts of seawater filter in a nuclear power plant, the fracture morphology of the bolts was observed by means of stereo microscopy and scanning electron microscopy, and the composition of corrosion products was analyzed by energy dispersive spectroscopy. The stress distributions in bolts under shear load and axial tensile load respectively were simulated by Marc finite element software, and the failure mechanism of bolts was discussed. The results show that the first screw thread nearest to the flange support face bore the greatest load. Under the long-term action of radial alternating shear load and the axial tensile load, the micro crack at the screw root expanded along the tangent direction of arc, and finally led to fatigue fracture.