To successfully fight climate change, it is essential to replace fossil fuels with renewable energies. Offshore wind energy will significantly contribute to this transition. Since the required future bottom-fixed offshore wind farms will be located further away from shore and in greater water depth, in addition to (XL-) monopiles, jacket foundations are a reasonable alternative. To increase the competitiveness of jacket substructures, a modular jacket concept was developed within the offshore industry, combining prefabricated robot-welded tubular joints with standardized pipes. With regard to fatigue strength in particular, the automatically welded tubular joints have a large potential due to the reproducible fabrication process resulting in highly uniform welds. However, this potential cannot be adequately considered for the fatigue assessment due to the lack of suitable S-N curves. Up to now, serial fatigue tests to determine statistically validated S-N curves have only been conducted on manually welded tubular joints. Nevertheless, some robot-welded tubular joints were tested regarding fatigue strength, but neither the influence of an inner root welding nor the existing weld geometry was systematically evaluated. Against this background, the fatigue resistance of automatically manufactured tubular joints is determined within this thesis. Furthermore, this work focuses on the characterization of the uniform weld seam geometry as a prerequisite for an additionally proposed weld geometry optimization using bionic approaches. To determine a statistically validated S-N curve, serial fatigue tests were performed on 16 single- and 16 double-sided automatically welded tubular X-joints, whereby these joints were medium-scaled compared to real jacket dimensions. During these tests, the fatigue damage evolution was digitized using the digital image correlation method, enabling a detailed analysis of the tubular joints' fatigue behavior including crack initiation. The obtained fatigue resistance of the robot-welded ...
Fatigue Behavior of Automatically Welded Tubular Joints for Offshore Wind Energy Substructures
2021-01-01
Hochschulschrift
Elektronische Ressource
Englisch
Automatically welded tubular joints , fatigue strength , digital image correlation , weld geometry , real notch stresses , bionic optimization , Automatisiert geschweißte Rohrknoten , Ermüdungsfestigkeit , Bildkorrelationsverfahren , Schweißnahtgeometrie , reale Kerbspannungen , bionische Optimierung , ddc:620
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