Fatigue of laserwelded connections

: Sonsino, C.M.; Müller, F.

Abstract
Hitherto only a small amount of fatigue data for laser welded steel plates are available. For that reason the fatigue behaviour of several basic types of laser weldments was determined under constant amplitude axial loading. The specimens were machined of the steel St 14 with a thickness of 0.8 mm and 2.0 mm. Also test series on specimens with a zinc layer on the surface were foreseen (material thickness 0.9 mm). The results of the examinations were interpreted in terms of nominal tensile stress amplitudes as well as structural equivalent stress amplitudes to give the design engineer a reliable database for construction. Additionally, component-like hollow sections with wall thicknesses of 0.8 mm and 2.0 mm were examined under constant and variable amplitude torsion loading. The application of the laser technique led to a clear improvement of the fatigue strength under constant amplitude loading when compared to butt welded specimens of the same size. The positive results of the laser technology were also visible in the case of variable amplitude loading: the laser welded specimens with a wall thickness of 0.8 mm rather failed by buckling during the higher amplitudes than by cracking in the weldment.