In this study, an experimental method predicting for fatigue crack initiation lives of welded structures is proposed. Fatigue test specimens were extracted from the welded structures containing embedded defects detected with a time-of-flight diffraction technique by electric discharge machining. The fatigue test conditions were set to be equal to the operating conditions of the welded structures. The validity of the operation conditions was confirmed by finite element analysis.

The fatigue tests found a good correlation between a stress intensity factor range and a number of cycles to fatigue crack initiation life within a factor of 2 scatter bands. This correlation of the stress intensity factor range was more accurate than one of a net cross-sectional stress range. Using the correlation, the fatigue crack initiation lives of the welded structures are predicted within the factor of 2 scatter bands by calculating the stress intensity factor ranges of the embedded defects.