Fatigue assessment of cruciform joints: Comparison between Strain Energy Density predictions and current standards and recommendations

The main aim of the present work is to investigate the effects of different design parameters on the fatigue strength of cruciform welded joints through an energy based approach, the Strain Energy Density. The most important design parameters taken into account in the present work for investigating the fatigue strength are the plates dimensions, the scale effect, the lack of welding bead penetration and the weld leg length. The results of the numerical analysis carried out have been also compared with the fatigue strength predicted by the most known design guidance for the fatigue assessment of steel welded joints: Eurocode 3; British Standard; International Institute of Welding; DNV-GL. The attached plate thickness severely affects the fatigue strength of the joint compared to the transverse plate one, as well as the weld leg length. The scale effect for this joint class can be predicted adopting the mode I Williams’ eigenvalues. The welding bead penetration, besides the codes provide fragmented information, has been predicted and the optimal design dimensions have been found. Several differences between the codes, with overestimation or underestimation of the cruciform joint fatigue strength, have been found due to their lack of consideration of the aforementioned design parameters.