Fatigue predictions of welded joints and the effective notch stress concept

Several research papers on a new concept of the effective notch stress of a welded joint were recently published. The toe of the weld is modelled with a prescribed radius. A parameter for the severity of the stress distribution at the weld can then be expressed as a Kt-value to be calculated with FE analysis. The new concept offers interesting applications for designing against fatigue crack initiation and predictions on the fatigue limit. It is argued that the radius concept should be replaced by a ratio of two dimensions and a proposal is made for this purpose. The fatigue assessment should be based on the calculated Kt-value. Limitations of the present codes are discussed.

► The initiation of fatigue cracks in welded structures is covered by a new design concept.
► The similarity between structures in service and laboratory specimens is explained.
► A new parameter for the fatigue performance of a welded joint is proposed.
► Shortcomings of the classical design codes are indicated.