Research Of Crack Propagating Characteristics In Dissimilar Metal Welded Joint Based On XFEM

The dissimilar metal welded joints in the safe end of nuclear reactor pressure vessel are affected by various complex factors,which are prone to environmental assisted cracking behavior represented by stress corrosion cracking.The crack propagation behavior and its hazards in different parts of the welded joints are unpredictable.The safety evaluation and crack propagation path prediction of dissimilar metal welded joint are the best way to minimize the damage.This paper takes the safety end of dissimilar metal welded joint as the research object.The crack propagation path and crack tip mechanical field distribution law under different working conditions are studied by using the extended finite element method(XFEM)in ABAQUS.The main work performed in this thesis are as follows:(1)Clarified the application range of the two methods,By comparing XFEM and the Debond technology to simulate crack propagation.Based on the extended finite element method(XFEM),a new finite element model of crack propagation in elastic-plastic materials was established.(2)The crack propagation behavior of dissimilar metal welding joint base metal and four welding materials with different yield strength and tensile strength was analyzed,the stress change and plastic deformation law at crack tip was explored so as to obtain the influence of relevant parameters on the length and direction of propagation path.(3)The interfacial crack growth behavior of materials with yield strength and tensile strength loss ratio of 1.2,1.4,0.8 and 0.6 were compared and analyzed,both the mechanical field at crack tip and the possibility that the extension path will penetrate the interface and deflect in the growth process were investigated.(4)The influence of crack positions on the propagation is studied,which provides the basis for the selection of welding joints and the replacement of components containing defects.