Statistics of Weld Geometry for Laser-Hybrid Welded Joints and its Application within Notch Stress Approach

During the past few decades the shipbuilding industry has shown an increasing interest in laser welding. In particular, laser-hybrid welding offers special advantages over arc welding such as low levels of welding distortion because of the different welding processes used. In the present study, the influence of weld geometry on notch stresses in butt-welded joints was studied experimentally and numerically using a notch stress approach. The results of hybrid-welded joints were compared to those of laser- and arc-welded joints. In the case of laser-based joints the weld height, weld width and notch depth are the dominant geometrical parameters. The flank angle of the weld has a minor influence, unlike in an arc-welded joint, because of the difference in the weld bead size. The weld dimensions showed a large statistical variation, and this resulted in significant differences in the stress concentration factor values between the critical and mean weld geometries. The analysis of fatigue test results indicated that the statistical variation of the weld dimensions should be included in the notch stress analysis in order to improve the accuracy of fatigue strength prediction.