Crack Growth Path And Detailed Analyze Of Mechanical Field At Crack Tip In Dissimilar Metal Welded Joints

The environmental assisted cracking(EAC)is a crack growing behavior in welded structures under the synergistic action of sensitive material,mechanics and aqueous chemical environment nearby the micro-area at the tip of EAC in the primary circuit of pressurized water reactors,and the accurate analysis of EAC crack growing behavior is an important guarantee for the long-term safe operation of nuclear power equipment.Considering that the EAC crack growing path and the micro-mechanical state of the crack tip are key factors in determining the EAC growing behavior,and its versatility and complexity during processing and service.In this thesis,a method is proposed and developed by combining theoretical research,numerical simulation and experimental analysis,which can accurately predict the crack growing path and accurately analyze the mechanical field of the growing crack tip,and use the method to analyze the crack growing path in the local area of the dissimilar metal welded joint at the safety end of a nuclear power circuit,and accurately analyze the mechanical field of the dynamic growing crack tip.The main contents are as follows:The respective advantages of the extended finite element method(XFEM)and De-bond technique in analyzing crack growing are studied,and the advantages of the two analysis methods are combined with each other through sub-model to establish a method that can both accurately predict the crack expanding path and accurately analyze the mechanical field of the growing crack tip.The factors influencing the crack growing behavior of welded joints are analyzed,and the influence law of different material parameters,crack size,crack tilt angle and different crack locations on the mechanical state of the crack tip,the mechanical behavior of the crack tip during growing and the crack growing path are explored,and the main influencing factors of the crack growing behavior are determined.The use of microhardness test to obtain the hardness distribution of the local area of the dissimilar metal welded joint,and the corresponding analysis of the mechanical properties of the material;through the user-defined field method to achieve a continuous transition of the mechanical properties of the material in the local area of the welded joint;the use of XFEM to obtain the crack growing path in different locations of the welded joint under the action of heterogeneous mechanical properties.Based on the acquisition of the crack growing path at different locations of the welded joint under the action of heterogeneous mechanical properties,the mechanical field of the growing crack tip under constant load conditions is accurately analyzed in the local area of the crack tip through the sub-model using De-bond technique.