Numerical Simulation Of Residual Stress On Safety End Welded Joint Of Reactor Pressure Vessel In Nuclear Power Plants

The dissimilar metal welded joint of the pressure vessel safety end is the crucial structure, and its security greatly influence the safe operation in nuclear power plants.It is one of main factors of the welded joint failure that the welded residual stress produced in welding process of safety end.To understand the distribution of residual stress in dissimilar metal welded joint in the pressure vessel safety end, the researches by using FEM numerical simulation is as following in this thesis.(1) As a subject of study, the finite element model of dissimilar metal double V-groove welded plate is established by using the ANSYS software. The welding process is numerically simulated, in which the loading way with moving heat source, the convecting heat transfer coefficient and the multi-pass welding process are adopted, and the thermal cycle curve and the temperature field distribution are obtained.(2) Indirect coupling of thermal-stress is used in ANSYS software. The residual stress field in welded plate is calculated in the coupling of temperature, in which switching element type, defining material parameters, imposing reasonable boundary conditions and using the method of “Beath and Death” are adopted.(3) Under the conditions of nuclear power welding technology, the change of welding temperture field as well as welding residual stress field in the dissimilar metal welded joint of the pressure vessel safety end is analysised.Moreover, the effects of welding sequence and layer on welding residual stress pattern is also discussed.The reasearched results provide a basis for quantitative prediction fatigue crack growth and fracture in the dissimilar metal welded joint of the pressurized vessel safety end under residual stress field.