Now showing 1 - 10 of 2620
  • Publication
    Numerical and experimental assessment of liquid metal embrittlement in externally loaded spot welds
    ( 2024-01-30)
    Prabitz, Konstantin
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    Antretter, Thomas
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    ; ;
    Schubert, Holger
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    Hilpert, Benjamin
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    Gruber, Martin
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    Sierlinger, Robert
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    Ecker, Werner
    Zinc-based surface coatings are widely applied with high-strength steels in automotive industry. Some of these base materials show an increased brittle cracking risk during loading. It is necessary to examine electrogalvanized and uncoated samples of a high strength steel susceptible to liquid metal embrittlement during spot welding with applied external load. Therefore, a newly developed tensile test method with a simultaneously applied spot weld is conducted. A fully coupled 3D electrical, thermal, metallurgical and mechanical finite element model depicting the resistant spot welding process combined with the tensile test conducted is mandatory to correct geometric influences of the sample geometry and provides insights into the sample’s time dependent local loading. With increasing external loads, the morphology of the brittle cracks formed is affected more than the crack depth. The validated finite element model applies newly developed damage indicators to predict and explain the liquid metal embrittlement cracking onset and development as well as even ductile failure.
  • Publication
    KI zur Prozessüberwachung im Unterpulverschweißen
    Beim Unterpulverschweißen sind die Prozessgeräusche ein Indikator für eine gute Fügequalität. Diese Beurteilung kann i.d.R. nur von einer erfahrenen Fachkraft durchgeführt werden. Eine kürzlich entwickelte künstliche Intelligenz kann automatisch das akustische Prozesssignal anhand vortrainierter Merkmale klassifizieren und die Fügequalität anhand des Geräuschs beurteilen. Der Algorithmus, einmal richtig trainiert, kann den Prüfaufwand beim Unterpulverschweißen deutlich reduzieren.
  • Publication
    Process advantages of laser hybrid welding compared to conventional arc-based welding processes for joining thick steel structures of wind tower
    ( 2023-12-22) ;
    Üstündag, Ömer
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    Bakir, Nasim
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    The most common welding processes when joining thick-walled steels in the industry are arc-based welding processes such as GMAW or SAW. For this purpose, the sheets are joined in multi-layer technique, which can lead to productivity losses due to high welding times. The process-specific challenges in welding thick steels using multi-layer technique relate to the high heat input from the process. Therefore, alternative welding processes are being actively sought. A suitable alternative is provided by beam-based welding processes such as the laser hybrid welding processes, which are characterized by deep penetration welds and lower heat input. With implementation of the laser hybrid welding process in the heavy industry, such as the wind tower industry, economic benefits can be reached such as the increase in productivity by reducing the layer number, and the lower consumption of filler material and energy. When comparing SAW welded 25 mm thick steels in five to six layers and single-pass laser hybrid welding, the welding time can be reduced more than 80 % and the costs of filler material, flux and energy can be saved up to 90 %. However, the industrial use of the laser hybrid welding process is still limited to applications, where the material thickness does not exceed 15 mm due to some process-specific challenges such as the sagging, sensitivity to manufacturing tolerances such as gaps and misalignment, limited filler wire mixing, and deteriorated mechanical properties resulting from high cooling rates. To overcome these challenges, a contactless electromagnetic backing based on an externally applied AC magnetic field was used. Eddy currents are induced due to the oscillating magnetic field, and an upward-oriented Lorentz force is generated to counteract the droplets formed due to gravitational forces. It allows to weld up to 30 mm thick structural steels in a single-pass with a 20-kW fiber laser system. Additionally, the gap bridgeability and the misalignment of edges were increased to 2 mm when welding 20 mm thick steels. With the aid of the AC magnetic field, a vortex was formed in the weld root, which had a positive effect on the filler wire mixing.
  • Publication
    Tailor Welded Blanking Digital
    ( 2023-11-30)
    Weber, Joshua
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    Daniel, González
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    Höfemann, Matthias
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    Joos, Paul
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    Rys, Anastasia
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    Der immer effizientere Einsatz von Energie und Ressourcen bleibt eine große Herausforderung, die nur mit innovativen Lösungen zu bewältigen ist. Ein schneller, günstiger und ressourcenschonender Ansatz ist die Anwendung von digitalen Methoden. Vor allem bei anspruchsvolleren Fertigungsketten, wie die Herstellung von Karosseriebauteilen aus Tailor Welded Blanks, ist es sinnvoll, die Produktauslegung bzw. die Prozessauslegung vor der eigentlichen Produktion digital und ganzheitlich zu simulieren, um Werkzeuganpassungen und unnötige Versuche zu verhindern. Dies funktioniert mit der Benutzung eines sogenannten digitalen Zwillings für die Fertigungskette durch die Verknüpfung von numerischen Simulationen, die die einzelnen Prozessschritte abbilden.
  • Publication
    Mit Gaia-X Europas digitale Zukunft gestalten
    ( 2023-10) ;
    Rosa Cencic, Maiara
    Die digitale Revolution ist längst in vollem Gange, und Europa ergreift Maßnahmen, um sich in diesem Kontext wettbewerbsfähig zu halten. Im Mittelpunkt steht Gaia-X mit dem Ziel, die digitale Landschaft Europas umzugestalten.In diesem Artikel werfen wir einen Blick auf die Ausgangslage, die Vision und die wirtschaftlichen Auswirkungen von Gaia-X.
  • Publication
    Werkzeug zur datenbasierten kontinuierlichen Verbesserung (KVP) in produzierenden Unternehmen
    Die Einführung von kontinuierlicher Verbesserung stellt Unternehmen regelmäßig vor Herausforderungen. Angesichts der fortschreitenden Digitalisierung eröffnen sich neue Analysemöglichkeiten, die den kontinuierlichen Verbesserungsprozess (KVP) unterstützen. Dieser Beitrag zeigt auf, wie Prozessorientierung, Digitalisierung und operative Tätigkeiten systematisch für die Entwicklung und Integration eines datenbasierten KVP in produzierenden Unternehmen angewandt werden können.
  • Publication
    Sustainable product lifecycle management with Digital Twins: A systematic literature review
    ( 2023-07)
    Seegrün, Anne
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    Kruschke, Thomas
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    Mügge, Janine
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    Hardinghaus, Louis
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    Knauf, Tobias
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    A Digital Twin (DT) is a virtual replica of a product or product-service system, which can be used to provide transparency of a product's sustainability and to positively influence the ecological impact throughout its lifecycle by means of intelligent data analytics. This paper identifies current sustainability-focused application scenarios of DTs in the manufacturing industry and outlines the results of a systematic literature review (SLR). The identification of the state-of-the-art and the assessment of current DT concepts with regard to the addressed product lifecycle phases, technological maturity and sustainability scope point towards key directions to guide future research.
  • Publication
    Brennstoffzelle - wie sauber muss es sein?
    Die technische Sauberkeit ist bei der Brennstoffzelle eine wichtige Einflussgröße für die realisierte Produktqualität in Bezug auf Lebensdauer und Performanz. Wie an welcher Stelle der Prozesskette im Hinblick auf welche Grenzwerte gereinigt und geprüft werden sollte, wird aktuell im Rahmen eines Forschungsprojektes betrachtet.
  • Publication
    Investigation of the LME Susceptibility of Dual Phase Steel with Different Zinc Coatings
    The application of anti-corrosion coated, high-strength steels in the automotive industry has increased in recent years. In combination with various zinc-based surface coatings, liquid metal embrittlement cracking can be observed in some of these materials. A high-quality, crack-free spotwelded joint is essential to realize the lightweight potential of the materials. In this work, the LME susceptibility of different coatings, which will be determined by the crack length and the occurrence rate, will be investigated using a welding under external load setup. The uncoated specimens did not show any LME. EG, GI and GA showed significantly less LME than ZM coatings. The latter coatings showed much larger crack lengths than the EG, GI and GA coatings. Furthermore, two mechanisms regarding the LME occurrence rate were observed: the occurrence of LME in zinc-magnesium coatings was theorized to be driven by the material properties of the coatings, whereas the occurrence of LME at EG, GI and GA samples was forced mainly by the application of the external tensile load. In the experimental setup of this work, the materials were exposed to unusually high mechanical loads (up to 80% of their yield strength) to evoke LME cracks.