Study on fatigue crack growth prediction model of carbon steel based on surface observation of fatigue test specimen

Cumulative Usage Factor (CUF) is currently used for fatigue design and management to prevent fatigue failure. Fatigue damage is evaluated by CUF but CUF doesn't show the real extend of fatigue damage and cannot be used for probabilistic index for risk assessment. Therefore, in order to clarify relation between CUF and damage state, the introduction of postulated crack growth curve (P-curve) of stainless steel was examine by Kamaya. This curve was defined by single crack growth curve made from fatigue test and specimen surface observation. And construction of P-curve of stainless steel by Abe et al. substantiates that fatigue life can be predicted by simulation analysis of experiment-based crack growth behavior. In this study, in order to expand the knowledge of crack growth prediction, general crack growth curve model of carbon steel was developed using computer simulation. Based on specimen surface observation, scatter on crack initiation and propagation was quantified. Crack growth curve was developed by computer simulation with these results. Furthermore, differences of crack growth behavior between carbon steel and stainless steel are examined through comparison of them. (author)