Two-Phase Fatigue Life Prediction of Small-Scale Welded Specimens Based on the Experimental Results

The study aims to calibrate parameters of two-phase fatigue prediction model based on the results of the small-scale fatigue test experiments for zero stress ratio and without residual stresses, and then to investigate their applicability for different stress ratios and in the presence of residual stresses. Total fatigue life using the two-phase model consists of crack initiation phase, calculated by strain-life approach, and crack propagation phase, calculated by fracture mechanic’s approach. Calibration of the fatigue parameters is performed for each phase by fitting numerical to the experimental results. Comparative analysis of calculated and measured fatigue lives is then conducted for different stress ratios, in both stress-relieved and as-welded conditions. Given that calculation parameters are calibrated for the basic case, uncertainty of predictions is large, showing that application of the method for real-life complex marine structures is challenging.