Investigations on the fatigue strength of beam-welded butt joints taking the weld quality into account

Abstract

For the fatigue design of welded structures under constant amplitude loading, often the nominal stress approach based on design S-N curves is used. The design S-N curves, which can be found in commonly used guidelines, cover arc welds as well as beam welds. However, the experimental data basis for the guideline consists mainly of arc-welded joints. Beam-welded components on the other hand show different weld geometries (e.g., weld width, weld enforcement, weld radii) compared with arc-welded components. The local geometry of weldments as well as imperfections can affect the fatigue strength, theoretically in dependence of the ultimate strength. Therefore, the fatigue strength of beam-welded samples in the high cycle fatigue range made from S355J2+N and S960Q was tested in this study. Additionally, the weld geometry of all samples was measured and classified according to the weld quality groups in ISO 13919-1. Furthermore, numerical notch stress calculations were conducted to cover imperfections and weld geometries that were not covered by the experimental investigations. Finally, recommendations for the fatigue resistance of beam-welded butt joints are given. Correlations between the fatigue strength and certain quality groups of selected geometrical features and imperfections are shown.