State of the Art
Highly loaded parts in the structure of large ships (e.g. window corners in cruise ships) are currently strengthened with thick sections of conventional steel, or the design (e.g. radius of the notches) needs to be modified. High tensile steels (HTS) can offer significant weight saving (5-20%, case-dependant), improved strength and more design freedom. While feasibility of HTS in shipbuilding has been shown in previous projects; joining processes and joint properties are currently weakening HTS structures and decreasing practical use.
Solution
Welding procedures and weld post-processing techniques (friction stir processing, over-lamination) are systematically investigated and tested to improve quality and increase fatigue life of welds in design details made of different HTS types, e.g. for longitudinal bulkheads. Knowledge will be enhanced related to the effects of process parameters, design variations and post-processing on the fatigue performance and corrosion behaviour of typical complex HTS details in maritime structures. Failure mechanisms and approval criteria will also be defined. Thanks to numerical simulation and statistical models, process reliability will be verified thus to obtain pre-approval for similar applications. Smaller, real-scale specimens, sufficient to achieve fully valuable SN-curves, will be produced in realistic production environments.
Potential
Process parameters and post-treatment methods developed in the demo are applicable for a wide variety of large structures in ships and offshore structures, including renewable energy devices. Further application is possible in land based steel structures, like bridges or buildings.