NUMERICAL METHODS RESEARCH AND FRACTURE FAILURE ANALYSIS FOR CRITICAL CRACK SIZE

Abstract

Safety analysis of fracture mechanics is an important part of structural integrity assessment and critical crack size is one ofmain concerns for fracture failure. From the perspective of mathematics, the calculation of critical crack size is the solving and analysis for nonlinear equation f(x)=0. About the solution of nonlinear equation, there are the bisection method, the false position method, the simple iteration method, the newton method and the secant method. For the complexity of load imposed on nuclear power equipment, there may be the multi-value phenomenon of critical crack size in analyzing fracture failure problems. Considering that the corresponding mechanical states of the shallow crack and the deep crack are different when the fracture failure occurs, the crack toughness factor needs to be considered in the fracture failure analysis of shallow cracks. Connecting the bottom head of nuclear power plant main equipment, the pipeline large break transient of accident condition and the welding research council bulletin 175, the algorithm and the convergence of multi-value phenomenon of critical size are studied. Using the crack toughness factor, the fracture failure critical crack size is deeply analyzed and discussed. The algorithm and fracture failure theory in the present study can provide the technical support for the prolonging operation life projects of nuclear power plant main equipment in future.