Fatigue strength of laser-welded thin-plate ship structures based on nominal and structural hot-spot stress approach

Journal
Ships and offshore structures  
Volume
10
Issue
1
Start Page
39
End Page
44
Citation
Ships and Offshore Structures 1 (10): 39-44 (2015)
Publisher DOI
10.1080/17445302.2013.850208
Scopus ID
2-s2.0-84924858955
Publisher
Taylor and Francis
To improve the energy efficiency, the demand for new light-weight solutions has been increased significantly in the last decades. The weight reduction of the current ship structures is possible using thinner plates, that is, plate thickness between 3 and 4 mm. However, at present this is, in normal cases, not possible due to the 5 mm minimum plate thickness requirement given by classification societies. The present paper investigates the fatigue strength of thin-plated ship structures. In the European research project BESST – ‘Breakthrough in European Ship and Shipbuilding Technologies’ – the extensive fatigue test programme was carried out for butt- and fillet-welded specimens, which were manufactured by the arc, laser and laser-hybrid welding methods. The test programme also covered the different production quality and thus a large variation of misalignments was included. Fatigue test results were analysed using the nominal as well as the structural stress approach, where the actual geometry of the specimens was taken into account. The results show that the present design S–N curve with slope value of 3 is applicable to thin plates, but it is slightly non-conservative. The fatigue test results for thin plates show better agreement with the slope value of 5. For thin plates and slender ship structures, the secondary bending stress due to angular misalignment plays an important part and changes in a non-linear way with the applied tension load. Therefore, it is important to consider the plate straightening effect in structural stress analysis.
Subjects
fatigue strength
laser-welded joint
structural stress approach
thin plate
DDC Class
620: Ingenieurwissenschaften
More Funding Information
European Community's Seventh Framework Programme (FP7/2007-2013) [grant agreement number 233980].