6. Conclusion

The fatigue resistance of welded joints is much lower than that of the base materials. This poor performance can be explained by the inherent presence of geometric singularities at the weld, which result in stress concentrations, and by the high residual tensile stresses caused by welding shrinkage.

In some cases, this fatigue resistance can be improved by modifying the design of the welded joint, the shape of the bead, or the residual stresses.

In order to evaluate the fatigue resistance of welded assemblies, various calculation methods exist. Some are based on the use of S-N curves expressed either in nominal stress, geometric stress, or notch stress, and others on linear elastic fracture mechanics approaches, considering an initial defect. These approaches are described in various standards or recommendations.

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