Research On Mechanical State At Crack Tip Of Welded Structure Under Residual Stress Field In Nuclear Power Plants

A132is widely used in welding metal of safety end in nuclear power plants. It hasbecome one of the key issues affecting plant safety and life that the stress corrosion crackingin weld metal layer induced by interaction of environment, mechanics, material, because ofthe long running process of nuclear power structure in high temperature water environment.By using numerical simulation method and the sub models technique, the stress and strainfield at the tip of SCC in A132safety end welded metal of nuclear power plants is analyzedand studied in this paper.Main research works performed are as follows:(1) Residual stress field is researched by using three common methods to simulate. Theappropriate method is selected by comparing the results of three common methods with thatof actual distribution.(2) Through analyzing the stress and strain parameters of crack tip under residual stresswhen the crack length is constant, the relationship between stress-strain field and residualstress field is researched.(3) The relationship between stress-strain field and residual stress field is researched,through studying the stress-strain parameters by adjusting the crack length under residualstress field. In order to obtain how the crack length effect the redistribution of residual stressfield, the redistribution of residual stress field at the crack tip after crack propagation isresearched.(4) The parameters of stress-strain at the crack tip are studied separately when tensile andcompressive stress with residual stress field to analyze the effect of tensile and compressivestress on residual stress field.(5) Two material properties in residual stress field are researched when the crack in different length. With which the stress-strain parameters are obtained. And then quantitativelyanalyzed the rate of crack growth, the relationship of material properties and residual stressdistribution with strain rate in crack tip are concluded.The results of this investigation provide a theoretical foundation for quantitativeprediction of SCC growth rate of weld joint under residual stress in the high temperaturewater environments.