Research On Creep Characteristics At Crack Tip Of Environmentally Assisted Cracking Of Stainless Steel In High Temperature Water Environment

Stress corrosion cracking as a representative of environmentally assisted cracking is themost important forms of destruction failure of nuclear power equipment. In serviceenvironment, nuclear structure containing material defects at high strain crack tip will appearcreep phenomenon. The creep has led to a re-distribution of the crack tip stress, thus affectingthe crack growth rate of stress corrosion cracking. In the research of this thesis, standardcompact tension specimens for the study, using elastic-plastic finite element method andsub-model techniques, creep and stress and strain distribution of the crack tip are acquired.Four mechanical parameters, temperature, stress intensity factor, yield strength, stressexponent, are selected, and the stress and strain around crack tip are analyzed and comparedbefore and after creep. Main work completed is as follows:(1) Based on slip dissolution theory and Ford-Andresen model, newton creep model isselected as crack tip creep constitutive equation. Creep and creep rate at crack tip in keynuclear material of high temperature water environment are analyzed, and the law of creepand creep rate variation with time at crack tip are achieved.(2) Standard compact tension specimens for the study, using finite element method,influences of creep on stress and strain at crack tip are researched.(3) Standard compact tension specimen for global model and creep at crack tip forsub-model, effects of temperature, load, material yield strength and creep stress exponent oncreep laws at crack tip are performed, and then the stress and strain contours of at crack tipregion, stress-strain curves in different directions along the passivation radius at crack tip,radiuses of plastic zone at crack tip can be simulated, and from the three perspectives, effectsof four different mechanical parameters on stress and strain at crack tip region are analyzedand compared.The conclusions in this thesis provide a base for quantitative prediction of SCC growth rate in stainless steel in high temperature environments of the nuclear power plant.