Fatigue assessment of welded joints using stress averaging and critical distance approaches

This paper comprises a brief methodical analysis and practical application of both the stress averaging approach according to Neuber and the critical distance approach according to Taylor for a fatigue assessment on welded steel structures under axial loading. The stress averaging approach, as established theoretically by Neuber, is discussed and compared to the effective notch stress approach with a reference radius r(ref)=1 mm and also to the r(ref)=0.05 mm concept which is usually applied for thin-walled structures. Furthermore, both approaches are applied for an assessment of 38 individual test series. As a result of the evaluations, a microstructural length rho*=0.40 mm is recommended. For the critical distance approach, a distance a=0.10 mm was derived. Fatigue design ( FAT) values are recommended for the practical application. Compared to the notch stress approach with a radius r(ref)=0.05 mm, it was possible to improve the assessment quality significantly. The non-local approaches should be preferred to the r(ref)=0.05 mm concept, especially for welded components using thin sheets for which the radius of 1 mm cannot be applied.