Finite Element Simulation On Weld Deformation And Residual Stress Of Nuclear Reactor Pressure Vessel Inner Ring

Reactor pressure vessels(RPV)are mainly formed by wrought,but with the development of the reactor in the direction of miniaturization,weld become one of the most important method in the manufacture of RPV.Unavoidable residual stress and deformation in the weld process can resut in crack、destroy in welded joint,even affect the structure intensity and assembly accuracy.In this study,nuclear reactor pressure vessel inner ring is taken as research objects and an efficient numerical method which is suitable for the prediction of weld residual stress with large thickness was proposed through finite element method.After that,a number of factors like dimension of model、geometry and material model which may have effect on residual stress are analyzed.This study has important theoretical significance and value in engineering for design and manufacture of nuclear equipment.Weld and post weld heat treatment(PWHT)process of vessel shell and inner ring were simulated by finite element axisymmetric model with assigned temperature heat source model.The estimated results are in a fairly good agreement with the measured results and higher residual stress occurred near the weld joint surface.After PWHT,residual stress can be almost eliminated and the final residual stress level is hardly affected by PWHT during the welding process.Compared 3D model with 2D axisymmetric model,the results showed no significant difference,the stress level was high at the interface of cladding and inner ring and PWHT had no effect.A lot of simulation were conducted through FEM,we can find that the material type、constitutive model、weld sequence and geometry parameters et al can affect the residual stress and deformation more or less.On the basis of numerical method,lumped-pass method can further increase computational efficiency and guarantee the accuracy simultaneously.A more conservative strength evaluation can be achieved by a criterion that takes the effect of residual stress into account.