Laserstrahlgeschweißte T-Stoß-Verbindungen in Stahlhohlplatten

Laser-stake welded T-joints of all-steel sandwich panels - Fatigue strength of laser-stake welded T-joints.

Laser-stake welding enables an economic production of all-steel sandwich panels that can be used for steel bridges as well as for decks in ro/ro ships. Deck plates of 10 mm thickness can be joined to interior web plates ensuring a weld throat thickness of 2 to 3 mm. Up to now the thickness of cover plates which could be stake welded in acceptable quality was limited to 4 mm. For this reason these sandwich panels could be used only for secondary structures in shipbuilding or similar only static strained structures. In the frame of FOSTA project P869 "Laser beam welded T-joints" (IGF 16935 BG) reliable welding parameter and technologies were developed to join cover plates up to 10 mm thickness to enable the use of sandwich panels in higher strained, fatigue loaded structures. Fatigue tests were performed with laser-stake welds subjected to axial, shear and multiaxial in-phase loading and assessed by the nominal and the notch stress approach. In addition to possible effects of gaps between deck and web plates or of the steel strength, the application of interaction formulae to laser-stake welds is checked as contained in Eurocode 3 and the IIW recommendations for the fatigue assessment of multiaxial loading. In this way, the basis is provided for a safe design of laser-stake welded T-joints. A technology for tractor-based assembly of these panels using laser beam and laser beam GMA welding was developed simultaneously.