Simulation And Measurement Of Welding Residual Stress In The SC Structure Of Nuclear Power Plant

The SC structure of nuclear power plant is a steel plate concrete structure,which is an important part of the CAP1400 nuclear power plant shield plant.The stress and distortion of SC structure caused by welding directly affect the assembly accuracy and service safety of SC structure.Accurately simulating and measuring the welding residual stress of SC structure of nuclear power plant has important theoretical significance and practical engineering value for evaluating the service performance and safety performance of the structure.This paper takes the two most typical welded joints of Q345 B horizontal and vertical welding with 40 mm thick in SC structure of nuclear power plant as the research object.The welding stress and distortion of the two typical joints in SC structure of nuclear power plant were simulated by the finite element method,and compared with the actual measurement results to verify and modify the numerical model.On this basis,the effects of cutting methods and dimensions on the welding residual stresses of SC structure of nuclear power plant during the sampling and measuring of analog parts were analyzed.The thermal elastoplastic finite element method was used to simulate the welding thermal cycle,the distribution of stress and distortion of two typical joints,and compared with the actual measurement results.The results are basically consistent,indicating that the established finite element model is accurate and reliable.The stress distribution on the surface of horizontal welding and vertical welding is consistent,and there is a significant stress gradient in the transverse stress of the two joints in the weld area.The longitudinal peak stress of transverse welding is higher than the room temperature yield strength of the filler metal.The longitudinal and transverse peak stress of transverse welding is about 60 MPa higher than that of vertical welding.The angular distortion of the horizontal welding joint is about 12.9 °,and the angular distortion of the vertical welding joint is about 9.8 °.As the weld bead increases,the angular distortion of the two joints changes inconsistently.Welding heat input affects both the angular distortion of horizontal and vertical welding,and when the heat input parameter is at a medium size,the corresponding angular distortion is rather large.In terms of stress value and distribution,the symmetrical cutting method on both sides is less affected by the change in cutting size than single-sided cutting,and is closer to the original size.Longitudinal cutting changes the size perpendicular to the weld direction,the transverse restraint of the specimen decreases and the transverse stress significantly decreases.When the transverse size is greater than 600 mm,the longitudinal stress maintains the same size and distribution as the original size.The transverse cutting changes the size along the weld direction,the longitudinal restraint of the specimen decreases.The bidirectional cutting changes the size of the specimen in both directions,the restraint in both directions decreases.Transverse cutting and bidirectional cutting have similar influence laws on stress,in which the influence on transverse stress is small,the influence on longitudinal stress is obvious and the stress changes of small samples between adjacent sizes are also obvious.On the center line of the specimen perpendicular to the weld,when the longitudinal size is less than 600 mm,the longitudinal stress near the weld changes from the tensile stress to the compressive stress.