This paper intensively explores the critical issues related to the quantitative and accurate evaluations of FCG behavior in the early stage,macro fatigue fracture toughness,and the critical crack size for damage toler...This paper intensively explores the critical issues related to the quantitative and accurate evaluations of FCG behavior in the early stage,macro fatigue fracture toughness,and the critical crack size for damage tolerance in nuclear graphite.To address these issues,scale-span FCG tests were carried out using two typical specimens,CT and SEM in-situ specimens.These results indicate that the FCG threshold and the effective FCG length have a significant correlation with the modified maximum loop stress theory for a mixed I/II mode.In particular,the effective FCG length(aeq)and the applied stress threshold of polycrystalline graphite are important parameters for fatigue damage tolerance design in engineering application.The influencing factors ofΔKth,eq and aeq were discussed in detail using the mixed I/II mode,respectively.In addition,the scattered values ofΔKIC for this graphite can be quantitatively estimated using the Weibull distribution equation.The predicated parameters and experimental results demonstrate a strong correlation.展开更多
基金supported by the National S&T Major Project(Grant No.ZX06901)Additional funding was provided by the National Natural Science Foundation of China(Grant Nos.11572170 and 11872225).
文摘This paper intensively explores the critical issues related to the quantitative and accurate evaluations of FCG behavior in the early stage,macro fatigue fracture toughness,and the critical crack size for damage tolerance in nuclear graphite.To address these issues,scale-span FCG tests were carried out using two typical specimens,CT and SEM in-situ specimens.These results indicate that the FCG threshold and the effective FCG length have a significant correlation with the modified maximum loop stress theory for a mixed I/II mode.In particular,the effective FCG length(aeq)and the applied stress threshold of polycrystalline graphite are important parameters for fatigue damage tolerance design in engineering application.The influencing factors ofΔKth,eq and aeq were discussed in detail using the mixed I/II mode,respectively.In addition,the scattered values ofΔKIC for this graphite can be quantitatively estimated using the Weibull distribution equation.The predicated parameters and experimental results demonstrate a strong correlation.
