PSI - Issue 79

Benjamin Möller et al. / Procedia Structural Integrity 79 (2026) 493–500

494

Nomenclature A

elongation at break

diameter of the inner optical core fiber diameter of the outer optical ring fiber

d C d R

spot diameter for the core spot diameter for the ring energy per unit length

d SC d SR E L

force amplitude tensile force focal length collimation length

F a F t

f f f c

cycles to crack initiation power of the laser core beam

N i P C P L P R R m

laser output power

power of the laser ring beam

tensile strength yield strength sheet thickness groove depth penetration depth

R p0.2

t

thickness of the adapter (segment)

t a t g t P t U t W v w

undercut

width of a single weld

welding speed weld angle

α

1. Introduction An increased environmental consciousness is the reason for an advanced lightweight design in ship building. Lightweight construction materials, such as aluminum, decrease the fuel consumption and the total shipping weight. Furthermore, aluminum alloys have also been applied in joining material combinations to adjust the center of gravity. Costly explosive welding is currently used to join steel to aluminum, especially in the field of yachts. The joining by an explosive-welded adapter is explained in more detail by Buijs (2004). Recent research by Lipiäinen, K. et al. (2025) shows that the failure locations of explosion-cladded steel-to-aluminum transition joints either were in the weld root or toe of the connecting element at the aluminum side or in the explosion cladded areas. Based on an overview of the various mechanical and thermal technologies for joining steel to aluminum given by Lahdo et al. (2016), using a high-power laser beam welding (LBW) system, joining dissimilar materials in maritime applications is used to produce a purpose-built adapter of steel and aluminum. However, intermetallic phases are unavoidable due to a low solubility of iron in aluminum. It is already known in the thermal joining of hybrid materials, that the formation of intermetallic phases causes embrittlement, which must be considered, as described by Klock and Schroer (1977) and Kreimeyer et al. (2004). Taking the specific framework and welding conditions into account, it was shown by Lahdo, R. et al. (2018) and Lahdo, R. (2021) that it is possible to produce steel-aluminum lap joints with comparatively high joint strength and low weld seam imperfections in the thick sheet range. Although it was found that this joining method was limited to further improve microstructural properties and joints strengths, e.g. a max. cross tension force of approx. 3.5 kN resulted. Quality and especially strength of the weld depend on the local weld geometry between steel and aluminum as well as the resulting crack formation. For this reason, welding process parameters for the minimization of aluminum-rich microstructures have been optimized, a process control of the penetration depth has been realized, and filler material has been used in previous research work in Lahdo, R. et al. (2023) and Lahdo, R. et al. (2025). The feasibility of such a joining process is shown by the adapters manufactured