Study On SCC Propagation Behavior And Fracture Parameter Change Of Welded Joints Based On XFEM

The dissimilar metal welded joints of the nuclear power safety end will be affected to many complex loads in high temperature and high pressure water environment,which will cause SCC(stress corrosion cracking)behavior.In order to clarify the crack propagation process in dissimilar material of the welded joints,this thesis established a new method to study the change of crack path and crack tip mechanical field during crack growth based on XFEM combined with the sub-mode technology.This thesis study the crack propagation behavior of the crack in the dissimilar metal bimaterial interface region.Furthermore,the crack propagation behavior under the combined effect of material heterogeneity and residual stress is investigated,and on this basis,the change of the fracture mechanical parameters of the nuclear power welded joint was analyzed.The main research contents are shown as follows:(1)Based on XFEM and sub-model technology,taking into account the advantages of sub-model analysis of local area crack propagation path changes,a new method for analyzing crack path and crack tip mechanical field changes during crack propagation is established,and the correctness of the method is verified.(2)Using the established XFEM technology combined with the sub-model processing method,the interface crack propagation behavior under different material yield strength mismatches is analyzed,and the relationship between the material strength mismatch ratio and the crack propagation path deflection direction is obtained;this thesis also discuss the influence of crack propagation law in different material interface angles.(3)This thesis creat a three-dimensional calculation model of welded joints in accordance with actual conditions,analyze the growth paths of planar cracks and semi-elliptical inner surface cracks under the combined effect of material inhomogeneity and residual stress,and obtain the propagation path of cracks at different positions.residual stress,and obtain the propagation path of cracks at different positions.(4)After deeply study the crack propagation behavior of the welded joints,based on the XFEM module,the fracture mechanical parameter K at the crack tip will be obtained,and the influence rule of the welding residual stress on the stress intensity factor will be analyzed.