Effect of creep rate at crack tip on stress corrosion crack propagation rate for nickel-based alloy 600
In order to simplify the quantitative calculation model of stress corrosion crack(SCC)propagation rate for nickel-based alloy 600,based on the analysis of Ford-Andresen model,creep rate at tip of SCC was taken as main driving force for crack propagation.Then,the material crack tip creep rate was proposed to replace the crack tip strain rate in the Ford-Andresen model,and a quantitative predic-tion model for SCC propagation rate with the crack tip creep rate as the mechanical parameter was obtained.Furthermore,based on creep characteristics and mechanical parameters of nickel-based alloy 600,the relationship between crack tip stress and crack tip stress intensity factor was obtained by finite element simulation,and a quantitative calculation model for creep rate characterized by crack tip stress inten-sity factor was further simplified and established.The results show that the larger the creep stress index and creep coefficient of nickel-based alloy 600,the higher the crack tip creep rate,which increases the driving force of crack propagation and accelerates the crack prop-agation.The hardening index of the material has a significant impact on crack tip creep rate and crack propagation rate,but crack propa-gation rate decreases with the increasing of crack tip current decay index.The crack propagation rate calculation model based on stress in-tensity factor as a mechanical parameter not only simplifies the calculation of crack tip strain rate,but also solves the problem of difficult to accurately obtain crack tip strain rate to a certain extent.
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