Transferability of fatigue resistance data for welded joints

Abstract

The original notch stress approach for fatigue design is limited to thick sheet structures and a fixed notch radius of 1 mm. Concepts utilizing the effective notch stress claim to account for the variation of the weld shape parameters, however, size effects are not taken into account. Therefore, an expansion of the notch stress approach has been developed, which includes consideration of the geometrical and statistical size effect in order to extend the application to thin and thick sheet structures. It is also capable of evaluating highly localized three-dimensional stress concentrations at weld start and end points. To validate the quality of this approach, experimentally determined fatigue data for thin steel sheet specimens from the Institute of Material Mechanics, including weld start and end points, and data from the literature regarding conventional thick sheet components without weld start and end points were reevaluated. The final result is a unified scatter band of fatigue lives of thin and thick sheet specimens, with and without weld start and end points, including also several modes of seam weld end point loading: transversal and longitudinal tension compression as well as shear loading at seam welds.