Tensile and Fatigue Strength of Laser-Beam Welded Steel-Aluminum Adapters for Applications in Shipbuilding

This study investigates the tensile and fatigue performance of steel-aluminum adapters produced by an innovative laser beam welding (LBW) process, aimed at enhancing lightweight design and manufacturing alternatives in shipbuilding. Currently, costly explosive welding is used for joining in shipbuilding. The developed LBW process and adapter made from S355 steel and AA6082 aluminum alloy makes use of additional filler material and a form fit by an undercut using two intersecting laser beams in addition to the firmly bonded welded joint. Experimental results reveal that the steel-aluminum adapters with form fit achieve maximum tensile forces of approx. 35 kN, surpassing the yield strength of conventionally used AA5083 by about 37 %. While the adapters fail outside the steel-aluminum joint under tensile loading, axial fatigue loading generates full fracture in the aluminum alloy with crack initiation at the root notch between steel and aluminum. However, the fatigue strength is increased by a factor of 2 to 3 for the adapters with form fit and filler material compared to previous designs without it. The results demonstrate the robustness of the adapter realized by the developed LBW process, with no significant reduction in fatigue performance observed under corrosive conditions, i. e. salt corrosion fatigue, on a random basis, affirming its general suitability for maritime applications.