Field of research: Fatigue Strength, Ship Structural Design
Duration: 01.04.2000 – 31.03.2004
Project leader: Prof. Dr.-Ing. W. Fricke
Funded by: EU (FKZ GRD1-1999-10558) – 13 partners (Coordinator: TNO)
The overall objective of the project was to pave the way for the realisation of a new generation of fast (50 knots), large (> 160m), cost efficient and safe ships (monohulls) based on high-tensile steel with a yield strength of 690 MPa. Today the yield stress of steels used for the design of ship structures is limited to 390 MPa by the classification societies. The future application of very high tensile steel with a yield stress of 690 MPa (VHTS 690) in shipbuilding brings up several problems, e.g. fatigue and buckling. As no rolled profiles of this material are available, new designs had to be appied. Trapezoidal stiffeners bent from plate material were chosen for the stiffening of deck structures.
In order to investigate the consequences of the above mentioned problems as well as the new kind of stiffening on future designs a large program of theoretical investigations and experiments was carried out. Our contribution was to accomplish fatigue tests and accompaniing calculations. Our part of the test program comprehended about 250 simple specimens, 20 semi-complex specimens and three full-scale tests. The full scale tests dealt with a deck structure stiffened by trapezoidal profiles. The test models were loaded in a realistic manner by a moving wheel. The project had shown by means of a target ship that a conventional construction based on the new material according to the design rules of the classification societies is impossible. The construction is made possible by direct calculations. Fatigue has proven to be the dominant aspect for dimensioning, as ships are welded structures.
Concerning fatigue the designs have to be free of sharp notches. Also the workers have to specially trained in order to ensure a very good workmanship.
Today the application of the new material came out to be possible in parts of the ships structure, e.g. for lightweight car decks or in the bottom of the foreship area to avoid slamming damage. There is further demand for research on the sealoads of such fast ships. In the future individual calculations to simulate the loads (response of the structure) will be required. This was carried out by the classification societies for the target ship.
G. Janssen and J. Struijk: HIGH TENSILE STEEL 690 IN FAST SHIP STRUCTURES. Final Report TD.04.71.09.04, Brussels (confidential)
S. Eylmann, H. Paetzold, B. Bohlmann (2004): Fatigue Behaviour of Car Decks made of VHTS 690. Proc. of PRADS 2004, Schiffbautechnische Ges., Hamburg.
S. Eylmann, W. Fricke und H. Paetzold: Betriebsfestigkeitsverhalten von LKW-Decks auf Fähren aus hochfestem Stahl. In: Fügen und Betriebsfestigkeit, DVM-Bericht 132, S. 99-108, Deutscher Verband für Materialforschung und prüfung, Berlin 2005.
S. Eylmann, W. Fricke and H. Paetzold: Investigation of New Designs for Wheel Loaded Truck Decks in Ferries. Proc. of Fatigue Design, Senlis 2005.
W. Fricke, S. Eylmann und J.-O. Probst: Schweißkonstruktionen im Schiffbau. Tagungsband der 6. Sondertagung Schweißen im Schiffbau und Ingenieurbau, Hamburg 2005, und HANSA 142 (2005), Nr. 9, S. 64-68.