Fatigue Strength of Laser- and Laser Hybrid Welded Joints

BESST - Breakthrough in European Ship and Shipbuilding Technologies

Workpackage on the potentials of laser welding for product performance

High value ships as cruise liner, ferries and navy vessels require light weight solutions. Fatigue properties of weld seams are a driving factor for the design of ship structures, as over its lifetime a ship has to endure many millions of load cycles. This project investigated the fatigue strength of thin plated ship structures.

The participating ship yards prepared butt and fillet weld joints of thin plates utilizing their laser, laser hybrid and conventional weld plants. Exhaustive experimental and theoretical studies were performed on the specimens; e.g. weld geometry statistics, microstructure and hardness profiles, SN-curves, FE Analysis.

The fatigue assessments prove strong impact of the weld process related misalignments and deflections. The relevant results were classified according to a classification society´s rules for use in daily engineering processes.  A FME(C) Analysis was conducted and some prototype designs of novel ship sections were created to prove the effects.

Partners: Aalto University, Center of Maritime Technologies, Fincantieri, Flensburger Schiffbau-Gesellschaft, Germanischer Lloyd, Meyer Werft, STX Finland, Hamburg University of Technology, ThyssenKrupp Marine Systems.

The project was funded within the 7th Frame Work Programme of the European Commission. The University of Southern Denmark awarded a PhD degree to FH Kiels graduate L. Molter for his research on laser, laser hybrid and arc shield welded 3 mm plates.