Research Of Stress Corrosion Crack Propagation In Safety End Of Nuclear Power Plants Based On XFEM

The residual stress of dissimilar metal welding is one of the main factors that lead to the stress corrosion cracking(SCC)at the safety end.In this dissertation,the finite element methods(XFEM)is used to simulate the crack propagation process under the influence of residual stress in the welded joints of nuclear safety.The stress-strain field in the crack tip region during the crack propagation process is studied by the sub-model technique.Main works were performed as follows:(1)Residual stress is loaded into the safely end model using the predefine temperature field methods.Under the residual stress field,the crack propagation dynamic simulation of the safety end elastic-plastic material based on the maximum principal stress expansion criterion is realised(2)The distribution of the stress-strain on the extended path is studied when the crack extended to different lengths.It is studied that the interaction law between crack propagation and residual stress field.Thc influence of the crack on the stress and strain field of the crack tip is studied by using the sub-model technique to determine the crack propagation,crack cease and prediction of crack propagation direction.(3)In the welding material and the interface position,influence rules of the initial crack length to the crack propagation characteristics of the elastoplastic material was analyzed.The results shows that the initial crack length is related to the crack driving force,the crack extension rate and the stress concentration of crack tip.And the crack growth at the interface position is affected by the material properties on both sides of the interface.(4)The distance between the crack to interface was analyzed and discussed,which is located on the sub-interface A508 base metal and the sub-interface Alloy52Mw welding material.The influence of the nonuniformity of the mechanical properties at the interface on the stress,strain distribution,crack growth rates,and the offset of the extended path is obtained.The results of this dissertation provide a theoretical basis and technical means for the study of crack propagation characteristics of stress corrosion cracking in welded joints of nuclear power plant safety end.