Study On Creep Characteristics At Tip Of Stress Corrosion Cracking In Dissimilar Metal Weld Joint Of Nuclear Power Plants

The stress corrosion cracking(SCC) is a main failure of safe-end dissimilar metal welded joints in primary circuit of nuclear power plants in service, SCC is a process of the oxide-film rupture and reformation dominated by the co-action of micro mechanics and electrochemistry at the crack tip. The recent researches indicate that the creep in high stress area at the tip of SCC would affect SCC growth rate. To understand the properties of the creep in high stress region at the crack tip and the effect of the creep on SCC growth rate, the stress and strain field at the tip of SCC in the welded joint is investigated by using ABAQUS software. The main task performed in this dissertation is as follows:(1) The creeping process at crack tip in high stress at low temperature was researched by using ABAQUS Finite Element Software and its restart function on welding material nickel based alloy 182, the variation law of micro-mechanical field and related mechanical parameters those influenced by the proceeding of creeping time was obtained.(2) Taking into account of the material heterogeneity, the numerical simulation modeled of weld joints were set up. The distribution of mechanical field and law of creep were analyzed in detail based on the simplified model of dissimilar metal welds composed of nickel based alloy 182, heat affected zone(HAZ) and stainless316 L. In addition, the creeping and stress parameters were discussed when the initial cracks are located in welding metal and heat affected zone respectively.(3) The creep rate at crack tip of SCC and crack growth rate which were dominated by low temperature and high stress creep based on the improved oxide-film rupture prediction model(Ford-Andresen model) were calculated, The effect of welded joint material mechanical heterogeneity on SCC crack growth rate was acquired.