Structural strain approach for low-cycle fatigue life prediction of ship welded joints

Fatigue life assessment of welded joints used in ship structures is of outmost importance and sometimes it is not sufficient to refer to the high-cycle fatigue regime, since high levels of plastic deformation can occur. The aim of this research activity is to study the low-cycle fatigue behaviour of welded joints commonly used in shipbuilding. Experimental tests were performed using the Digital Image Correlation technique, which is a non-contact full-field technique. The Digital Image Correlation technique allowed the detection of displacement and strain patterns, with particular attention to stress concentration areas. Furthermore, a Finite Element model, matched with the experimental data, was performed by applying the structural strain approach, which is mesh insensitive and requires only the elastic parameters. The values obtained from the structural strain approach were used to predict the fatigue life of the investigated welded joints.