Welded joints in ship structures are subject to several variable loadings which may lead to fracture after a relatively low number of cycles. This behaviour is not always fully described by high-cycle fatigue predictions, so low-cycle fatigue has also to be assessed, considering plastic deformation. Local approaches are applied in these cases and are mainly based on local displacement and strain measurements by strain gauges. These approaches have physical limitations when high stress concentrations regions have to be analyzed.

The present research activity has the aim to study different approaches (i.e. the notch strain approach) in order to evaluate the fatigue life of fillet welded joints. Two full-field techniques were applied: Digital Image Correlation and infrared thermography. Elastic-plastic finite element analysis were also performed, using different cyclic stress-strain curves for base material, heat affected zone and weld metal. The finite element analyses were validated by the experimental measurements and effective notch strain values from these calculations were used to assess fatigue life.

The proposed method and the comparison with experimental measurement gave interesting information about the effective notch strain evaluation and the fatigue life of fillet welded joints used in the naval sector.