Equivalent crack approach for fatigue life assessment of welded joints

An equivalent crack approach for estimating the fatigue strength of welded structures based on one experimental data point is presented. The experimental data point reflects and quantifies the stress concentration effects at the fatigue critical location. These effects are then assumed approximately equivalent to having a crack in an unwelded plate. The crack propagation from this initial equivalent flaw to final fracture is calculated using the Paris law. The approach has been applied to constant amplitude fatigue data. The results show good agreement between the calculated and experimental fatigue lives. Extension of the approach to variable amplitude loading is proposed.