Threshold and near-threshold fatigue crack growth (FCG) is critical for the total life prediction as majority of time is spent in this regime. The proposed study includes the fatigue crack growth near-threshold in the time-based subcycle model for fatigue life prediction under arbitrary loading conditions. A novel fatigue-life prediction methodology combining a subcycle fatigue crack growth analysis and equivalent initial flaw size (EIFS) concept is proposed. A previously developed time-based subcycle fatigue crack growth model is extended to near threshold regime and under multiaxial loadings. A new temporal kernel function to include intensity factor corresponding to near threshold region is proposed. The multiaxial load scenario is considered for mixed-mode FCG using a critical plane approach. Model predictions under arbitrary are compared with experimental data from open literatures and internal testing. Most of the predicted fatigue life results lie with error factor range of 2, which shows a good prediction for fatigue life.
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