Dokument-ID Dokumenttyp Autoren/innen Persönliche Herausgeber/innen Haupttitel Abstract Auflage Verlagsort Verlag Herausgeber (Institution) Erscheinungsjahr Titel des übergeordneten Werkes Jahrgang/Band ISBN Veranstaltung Veranstaltungsort Beginndatum der Veranstaltung Enddatum der Veranstaltung Ausgabe/Heft Erste Seite Letzte Seite URN DOI Lizenz Datum der Freischaltung OPUS4-55201 Zeitschriftenartikel Üstündag, Ömer; Bakir, Nasim; Gook, S.; Gumenyuk, Andrey; Rethmeier, Michael Hybrid laser‑arc welding of laser‑ and plasma‑cut 20‑mm‑thick structural steels It is already known that the laser beam welding (LBW) or hybrid laser-arc welding (HLAW) processes are sensitive to manufacturing tolerances such as gaps and misalignment of the edges, especially at welding of thick-walled steels due to its narrow beam diameter. Therefore, the joining parts preferably have to be milled. The study deals with the influence of the edge quality, the gap and the misalignment of edges on the weld seam quality of hybrid laser-arc welded 20-mm-thick structural steel plates which were prepared by laser and plasma cutting. Single-pass welds were conducted in butt joint configuration. An AC magnet was used as a contactless backing. It was positioned under the workpiece during the welding process to prevent sagging. The profile of the edges and the gap between the workpieces were measured before welding by a profile scanner or a digital camera, respectively. With a laser beam power of just 13.7 kW, the single-pass welds could be performed. A gap bridgeability up to 1 mm at laser-cut and 2 mm at plasma-cut samples could be reached respectively. Furthermore, a misalignment of the edges up to 2 mm could be welded in a single pass. The new findings may eliminate the need for cost and time-consuming preparation of the edges. Springer 2022 Welding in the World 2022 66 507 514 urn:nbn:de:kobv:b43-552013 10.1007/s40194-022-01255-y https://creativecommons.org/licenses/by/4.0/deed.de 2022-07-06 OPUS4-55226 Forschungsdatensatz Fabry, Cagtay; Hirthammer, Volker; Scherer, Martin K. weldx - welding data exchange format Scientific welding data covers a wide range of physical domains and timescales and are measured using various different sensors. Complex and highly specialized experimental setups at different welding institutes complicate the exchange of welding research data further. The WelDX research project aims to foster the exchange of scientific data inside the welding community by developing and establishing a new open source file format suitable for the documentation of experimental welding data and upholding associated quality standards. In addition to fostering scientific collaboration inside the national and international welding community an associated advisory committee will be established to oversee the future development of the file format. The proposed file format will be developed with regard to current needs of the community regarding interoperability, data quality and performance and will be published under an appropriate open source license. By using the file format objectivity, comparability and reproducibility across different experimental setups can be improved. Geneva Zenodo Bundesanstalt für Materialforschung und -prüfung (BAM) 2021 10.5281/zenodo.6563282 http://www.opensource.org/licenses/bsd-license.php 2022-07-11 OPUS4-55153 Vortrag Fabry, Cagtay WelDX - a file format for processing and archiving welding research data The talk gives an introduction into gas metal arc welding and its relation to plasma science as well as current challenges in welding research concerning research data management and the application of the FAIR principles. The WelDX project is introduced and the main goals are discussed and contrasted with the current features of the weldx API. Different internal and public facing use cases focusing on research data management and their implementation using weldx are presented. The interactive part of the presentation displays some advanced multi layer use cases and data analysis using the weldx API as well as the integration of materials properties into weldx. 2022 International Workshop on FAIR Data in Plasma Science Online meeting 16.05.2022 18.05.2022 2022-06-30 OPUS4-55123 Vortrag Ávila Calderón, Luis Alexander Low cycle fatigue behavior of DED-L Ti-6AL-4V Laser powder-based directed energy deposition (DED-L) is a technology that offers the possibility for 3D material deposition over hundreds of layers and has thus the potential for application in additive manufacturing (AM). However, to achieve broad industrial application as AM technology, more data and knowledge about the fabricated materials regarding the achieved properties and their relationship to the manufacturing process and the resulting microstructure is still needed. In this work, we present data regarding the low-cycle fatigue (LCF) behavior of Ti-6Al-4V. The material was fabricated using an optimized DED-L process. It features a low defect population and excellent tensile properties. To assess its LCF behavior two conventionally manufactured variants of the same alloy featuring different microstructures were additionally tested. The strain-controlled LCF tests were carried out in fully reversed mode with 0.3 % to 1.0 % axial strain amplitude from room temperature up to 400°C. The LCF behavior and failure mechanisms are described. For characterization, optical microscopy (OM), scanning electron microscopy (SEM), and micro-computed tomography (µCT) were used. The low defect population allows for a better understanding of the intrinsic material's properties and enables a fairer comparison against the conventional variants. The fatigue lifetimes of the DED-L material are nearly independent of the test temperature. At elevated test temperatures, they are similar or higher than the lifetimes of the conventional counterparts. At room temperature, they are only surpassed by the lifetimes of one of them. The principal failure mechanism involves multiple crack initiation sites. 2022 Ninth International Conference on Low Cycle Fatigue (LCF9) Berlin, Germany 21.06.2022 23.06.2022 2022-06-28 OPUS4-56173 Beitrag zu einem Tagungsband Raute, J.; Marquardt, R.; Biegler, M.; Rethmeier, Michael Untersuchung zum Elektronenstrahlschweißen additiv gefertigter Ni-Basis-Bauteile Die vorliegende Untersuchung befasst sich mit dem Einfluss des Additive Manufacturing auf die Schweißeignung von Bauteilen aus Inconel 718. Hierfür wurden Proben mittels DED und L-PBF hergestellt und ihr Verhalten in Blindschweißversuchen anhand eines Vergleichs mit konventionellen Gussblechen untersucht. Im zweiten Schritt wurden die verschiedenen additiv hergestellten Proben mit dem Gussmaterial im I-Stoß sowie untereinander verschweißt. Als Schweißverfahren wurde für alle Proben das Elektronenstrahlschweißen angewandt. Zur Auswertung wurde anhand von Schliffen das Nahtprofil vermessen und die Proben auf Poren und Risse untersucht. Zusätzlich wurde die Dichte vermessen und eine Prüfung auf Oberflächenrisse durchgeführt. Das AM-Material zeigte dabei Unterschiede in Nahtform und Defektneigung im Vergleich zum Gusswerkstoff. Insbesondere die DED-proben neigten unter bestimmten Parameterkonstellationen verstärkt zu Porenbildung. Risse konnten nicht beobachtet werden. Trotz auftretender Nahtunregelmäßigkeiten wurde in den kombinierten AM-Schweißproben die Bewertungsgruppe C erreicht. Eine Prüfung der bestehenden Regelwerke zur Schweißnahtbewertung anhand der gewonnenen Erkenntnisse zu additiv gefertigten Proben im Elektronenstrahlschweißprozess zeigte keinen Ergänzungsbedarf. DVS-Media GmbH 2022 DVS-Berichte 383 978-3-96144-202-7 #additivefertigung: Metall in bestForm Essen, Germany 26.10.2022 27.10.2022 81 92 2022-11-07 OPUS4-56242 Zeitschriftenartikel Meng, Xiangmeng; Putra, Stephen Nugraha; Bachmann, Marcel; Artinov, Antoni; Rethmeier, Michael Influence of the free surface reconstruction on the spatial laser energy distribution in high power laser beam welding modeling An accurate and efficient description of the spatial distribution of laser energy is a crucial factor for the modeling of laser material processing, e.g., laser welding, laser cutting, or laser-based additive manufacturing. In this study, a 3D heat transfer and fluid flow model coupled with the volume-of-fluid algorithm for free surface tracking is developed for the simulation of molten pool dynamics in high-power laser beam welding. The underlying laser-material interactions, i.e., the multiple reflections and Fresnel absorption, are considered by a raytracing method. Two strategies of free surface reconstruction used in the ray-tracing method are investigated: a typical piecewise linear interface calculation (PLIC)-based method and a novel localized level-set method. The PLIC-based method is discrete, resulting in noncontinuous free surface reconstruction. In the localized level-set method, a continuous free surface is reconstructed, and, thus, the exact reflection points can be determined. The calculated spatial laser energy distribution and the corresponding molten pool dynamics from the two methods are analyzed and compared. The obtained numerical results are evaluated with experimental measurements to assure the validity of the proposed model. It is found that distinct patterns of the beam multiple reflections are obtained with the different free surface reconstructions, which shows significant influence not only on the molten pool behaviors but also on the localized keyhole dynamics. Orlando, Fla. Laser Institute of America 2022 Journal of Laser Applications 34 4 042023-1 042023-8 urn:nbn:de:kobv:b43-562429 10.2351/7.0000739 https://creativecommons.org/licenses/by/4.0/deed.de 2022-11-14 OPUS4-56278 Zeitschriftenartikel Marko, A.; Bähring, S.; Raute, J.; Biegler, M.; Rethmeier, Michael Transferability of ANN-generated parameter sets from welding tracks to 3D-geometries in Directed Energy Deposition Directed energy deposition (DED) has been in industrial use as a coating process for many years. Modern applications include the repair of existing components and additive manufacturing. The main advantages of DED are high deposition rates and low energy input. However, the process is influenced by a variety of parameters affecting the component quality. Artificial neural networks (ANNs) offer the possibility of mapping complex processes such as DED. They can serve as a tool for predicting optimal process parameters and quality characteristics. Previous research only refers to weld beads: a transferability to additively manufactured three-dimensional components has not been investigated. In the context of this work, an ANN is generated based on 86 weld beads. Quality categories (poor, medium, and good) are chosen as target variables to combine several quality features. The applicability of this categorization compared to conventional characteristics is discussed in detail. The ANN predicts the quality category of weld beads with an average accuracy of 81.5%. Two randomly generated parameter sets predicted as "good" by the network are then used to build tracks, coatings,walls, and cubes. It is shown that ANN trained with weld beads are suitable for complex parameter predictions in a limited way. De Gruyter 2022 Material Testing 2022 64 11 1586 1596 10.1515/mt-2022-0054 2022-11-16 OPUS4-56284 Zeitschriftenartikel Marko, A.; Bähring, S.; Raute, J.; Biegler, M.; Rethmeier, Michael Prognose von Qualitätsmerkmalen durch Anwendung von KI-Methoden beim Directed 10 Energy Deposition Dieser Beitrag enthält die Ergebnisse eines im Rahmen der DVS Forschung entwickelten Ansatzes zur Qualitätssicherung im Directed Energy Deposition. Es basiert auf der Verarbeitung verschiedener während des Prozesses gesammelter Sensordaten unter Anwendung Künstlicher Neuronale Netze (KNN). So ließen sich die Qualitätsmerkmale Härte und Dichte auf der Datenbasis von 50 additiv gefertigten Probenwürfel mit einer Abweichung < 2 % vorhersagen. Des Weiteren wurde die Übertragbarkeit des KNN auf eine Schaufelgeometrie untersucht. Auch hier ließen sich Härte und Dichte hervorragend prognostizieren (Abweichung < 1,5 %), sodass der Ansatz als validiert betrachtet werden kann. Düsseldorf DVS Media 2022 Schweißen und Schneiden 74 10 672 679 2022-11-16 OPUS4-56058 Beitrag zu einem Tagungsband Raute, J.; Biegler, M.; Rethmeier, Michael Untersuchung zur Herstellung von Cu-Strukturen mittels Wire Electron Beam Additive Manufacturing Das Additive Manufacturing gewinnt zunehmend an Bedeutung für die Fertigung metallischer Bauteile im industriellen Umfeld. Hierbei wird zunehmend auch auf drahtförmige Ausgangswerkstoffe gesetzt, da diese Vorteile im Handling bieten, bereits in der Industrie etabliert sind und sich in der Regel durch geringere Beschaffungskosten auszeichnen. In den letzten Jahren entwickelte sich neben den bereits im großen Umfeld untersuchten Wire-DED-Verfahren auch eine Prozessvariante unter Nutzung des Elektronenstrahls zur industriellen Marktreife. Dabei zeigt die als Wire Electron Beam Additive Manufacturing bezeichnete Technologie besondere Vorteile gegenüber anderen, zumeist Laser- oder Lichtbogen-basierten DED-Prozessen. Das Verfahren bietet vor allem Potenzial für die Verarbeitung von hochleitfähigen, reflektierenden oder oxidationsgefährdeten Werkstoffen. Insbesondere für die Herstellung von Bauteilen aus Kupferlegierungen zeigt sich der Elektronenstrahl als besonders geeignet. Um das Verfahren einem breiten Anwenderkreis in der Industrie zugänglich zu machen, fehlen jedoch übergreifende Daten zu Leistungsfähigkeit, Prozessgrenzen und Anwendungsmöglichkeiten. Die vorliegende Untersuchung beschäftigt sich mit dieser Problemstellung am Beispiel zweier Cu-Werkstoffe. Dabei werden ein korrosionsbeständiger Werkstoff aus dem maritimen Bereich sowie eine Bronze mit guten Verschleißeigenschaften aus dem Anlagenbau getestet. Über mehrstufige Testschweißungen wurden die physikalisch möglichen Prozessgrenzen ermittelt und Rückschlüsse über die Eignung der Parameter zum additiven Aufbau gezogen. Hierfür wurden zunächst optimale Bereiche für den Energieeintrag anhand von Volumenenergie sowie mögliche Schweißgeschwindigkeiten untersucht. Anschließend wurde die Skalierbarkeit des Prozesses anhand von Strahlstrom und Drahtvorschub getestet. Als wesentliche Zielgrößen wurden dabei Spurgeometrie, Aufmischung und Härte herangezogen. Die Eignung der ermittelten Parameter wurde im letzten Schritt exemplarisch anhand einer additiven Testgeometrie in Form eines Zylinders nachgewiesen. DVS Media 2022 DVS-Berichte 382 978-3-96144-189-1 DVS Congress 2022 Große Schweißtechnische Tagung DVS CAMPUS Koblenz, Germany 19.09.2022 21.09.2022 446 454 2022-10-20 OPUS4-56461 Zeitschriftenartikel El-Batahgy, A.; Elkousy, M.; Al-Rahman, A.; Gumenyuk, Andrey; Rethmeier, Michael; Gook, S. Retaining Mechanical Properties of GMA-Welded Joints of 9%Ni Steel Using Experimentally Produced Matching Ferritic Filler Metal Motivated by the loss of tensile strength in 9%Ni steel arc-welded joints performed using commercially available Ni-based austenitic filler metals, the viability of retaining tensile strength using an experimentally produced matching ferritic filler metal was confirmed. Compared to the austenitic Ni-based filler metal (685 MPa), higher tensile strength in gas metal arc (GMA) welded joints was achieved using a ferritic filler metal (749 MPa) due to its microstructure being similar to the base metal (645 MPa). The microstructure of hard martensite resulted in an impact energy of 71 J (-196 °C), which was two times higher than the specified minimum value of _>34 J. The tensile and impact strength of the welded joint is affected not only by its microstructure, but also by the degree of its mechanical mismatch depending on the type of filler metal. Welds with a harder microstructure and less mechanical mismatch are important for achieving an adequate combination of tensile strength and notched impact strength. This is achievable with the cost-effective ferritic filler metal. A more desirable combination of mechanical properties is guaranteed by applying low preheating temperature (200 °C), which is a more practicable and economical solution compared to the high post-weld heat treatment (PWHT) temperature (580 °C) suggested by other research. MDPI 2022 materials 15 23 1 14 urn:nbn:de:kobv:b43-564610 10.3390/ma15238538 https://creativecommons.org/licenses/by/4.0/deed.de 2022-12-05 OPUS4-54226 Zeitschriftenartikel Ávila Calderón, Luis Alexander; Graf, B.; Rehmer, Birgit; Petrat, T.; Skrotzki, Birgit; Rethmeier, Michael Characterization of Ti-6Al-4V fabricated by multilayer laser powder-based directed energy deposition Laser powder-based directed energy deposition (DED-L) is increasingly being used in additive manufacturing (AM). As AM technology, DED-L must consider specific challenges. It must achieve uniform volume growth over hundreds of layers and avoid heat buildup of the deposited material. Herein, Ti-6Al-4V is fabricated using an approach that addresses these challenges and is relevant in terms of transferability to DED-L applications in AM. The assessment of the obtained properties and the discussion of their relationship to the process conditions and resulting microstructure are presented. The quality of the manufacturing process is proven in terms of the reproducibility of properties between individual blanks and with respect to the building height. The characterization demonstrates that excellent mechanical properties are achieved at room temperature and at 400 °C. Weinheim Wiley-VCH 2022 Advanced engineering materials 1 15 urn:nbn:de:kobv:b43-542262 10.1002/adem.202101333 https://creativecommons.org/licenses/by/4.0/deed.de 2022-01-19 OPUS4-56312 Vortrag Meng, Xiangmeng The influence of the free surface reconstruction on the spatial laser energy distribution in high power laser beam welding modeling An accurate and efficient description of the spatial distribution of laser energy is a crucial factor for the modeling of laser material processing, e.g., laser welding, laser cutting, or laser-based additive manufacturing. In this study, a 3D heat transfer and fluid flow model coupled with the volume-of-fluid algorithm for free surface tracking is developed for the simulation of molten pool dynamics in high-power laser beam welding. The underlying laser-material interactions, i.e., the multiple reflections and Fresnel absorption, are considered by a ray-tracing method. Two strategies of free surface reconstruction used in the ray-tracing method are investigated: a typical piecewise linear interface calculation (PLIC)-based method and a novel localized Level-Set method. The PLIC-based method is discrete, resulting in non-continuous free surface reconstruction. In the localized Level-Set method, a continuous free surface is reconstructed, and thus the exact reflection points can be determined. The calculated spatial laser energy distribution and the corresponding molten pool dynamics from the two methods are analyzed and compared. The obtained numerical results are evaluated with experimental measurements to assure the validity of the proposed model. It is found that distinct patterns of the beam multiple reflections are obtained with the different free surface reconstructions, which shows significant influence not only on the molten pool behaviors but also on the localized keyhole dynamics. 2022 The 41st annual International Congress on Applications of Lasers & Electro-Optics Orlando, FL, USA 17.10.2022 21.10.2022 2022-11-18 OPUS4-56319 Vortrag Yang, Chunliang Numerical analysis of ultrasonic vibration enhanced friction stir welding of dissimilar Al/Mg alloys The ultrasonic vibration enhanced friction stir welding (UVeFSW) process has unique advantages in joining dissimilar Al/Mg alloys. While there are complex coupling mechanisms of multi-fields in the process, it is of great significance to model this process, to reveal the influence mechanism of ultrasonic vibration on the formation of Al/Mg joints. In this study, the acoustic-plastic constitutive equation was established by considering the influence of both ultrasonic softening and residual hardening on the flow stress at different temperatures and strain rates. And the ultrasonic induced friction reduction (UiFR) effect on friction coefficient in different relative directions at the FSW tool-workpiece interface was quantitatively calculated and analyzed. The Al/Mg UVeFSW process model was developed through introducing the above acoustic effects into the model of Al/Mg friction stir welding (FSW). The ultrasonic energy is stronger on the aluminum alloy side. In the stirred zone, there is the pattern distribution of ultrasonic sound pressure and energy. The heat generation at the tool-workpiece contact interface and viscous dissipation were reduced after applying ultrasonic vi-bration. Due to the UiFR effect, the projection of friction coefficient and heat flux distributions at the tool-workpiece interface present a "deformed" butterfly shape. The calculated results show that ultrasonic vibration enhanced the material flow and promoted the mixing of dissimilar materials. 2022 The 13th International Seminar "Numerical Analysis of Weldability" Graz, Austria 04.09.2022 07.09.2022 2022-11-21 OPUS4-56367 Vortrag Rethmeier, Michael Welding of thick metal plates with laser - Where are the limits? -With modern high-power lasers (and vacuum) penetration around 100 mm is possible -Important for industrial applications: single-pass full penetration welds with tolerances -Contactless EM-backing helps to overcome many main restrictions: -Single-pass HLAW of up to 30 mm can be realized with 20 kW laser power -Increase of the gap bridgeability and misalignement of edges -Lower sensitivity to manufacturing tolerances and edge quality; samples can be prepared by a plasma-cut instead of time-consuming milling process -Gives the possibility to increase the welding parameter window and cooling rate so that the required mechanical properties can be reached -Improved filler wire mixing behaviour 2022 AKL22 - International Laser Technology Congress Aachen, Germany 04.05.2022 06.05.2022 2022-11-24 OPUS4-56368 Vortrag Üstündag, Ömer Einlagiges MSG-Hochleistungsschweißen von dickwandigen Baustählen mit kontaktloser elektromagnetischer Schmelzbadsicherung Diese Arbeit zeigt erstmals die Anwendung einer elektromagnetischen Schmelzbadstütze beim einlagigen MSG-Schweißen von dickwandigen Stählen. Die innovativen Entwicklungen im Bereich des Lichtbogenschweißverfahrens ermöglichen eine Erhöhung der Abschmelzleistung, um die Einschweißtiefe zu steigern. Somit kann die Lagenanzahl reduziert und die Produktivität gesteigert werden. Allerdings besteht insbesondere beim einlagigen Schweißen von dickwandigen Bauteilen in PA-Position ein erhöhtes Risiko für das gravitationsbedingte Austropfen der Schmelze an der Wurzel. Zur Verhinderung werden Badstützen eingesetzt, die mechanisch angebracht und nach dem Schweißen entfernt werden müssen, was zeit- und kostenintensiv ist. Die im Rahmen dieser Studie eingesetzte elektromagnetische Schmelzbadstütze wirkt dem gravitationsbedingten Austropfen der Schmelze entgegen und kompensiert den hydrostatischen Druck. Sie wirkt kontaktlos, was im Gegensatz zu herkömmlichen Badstützen vorteilhaft ist, so dass auf eine zeit- und kostenintensive Nachbearbeitung der Schweißnahtwurzel verzichtet werden kann. Das auf extern angelegten oszillierenden Magnetfeldern beruhende Verfahren wird dabei unterhalb des zu schweißenden Bauteils positioniert. Die Magnetfeldlinien sind quer zur Schweißrichtung ausgerichtet, sodass längs zur Schweißrichtung Wirbelströme im Werkstück und eine stets nach oben gerichtete Lorentzkraft generiert werden. Mit Hilfe der elektromagnetischen Badstütze konnten beim einlagigen MSG-Schweißen von 8 mm bis 12 mm die Tropfenbildung vermieden werden. Die innovative Technologie ermöglicht es dickwandige Bauteile einlagig zu schweißen und reduziert die Nachbearbeitungszeit deutlich. 2022 DVS Congress 2022 - Große Schweißtechnische Tagung Koblenz, Germany 19.09.2022 21.09.2022 2022-11-24 OPUS4-56369 Vortrag Üstündag, Ömer Improvement of Charpy impact toughness by using an AC magnet backing system at laser hybrid welding of thick S690QL steels The study deals with the influence of the heat input and the resulting cooling times on the microstructure and Charpy impact toughness of single-pass laser hybrid welded 20-mm thick high-strength steel S690QL. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured in-situ using a pyrometer and an optical fibre in three different depths of the seam where Charpy impact test specimens were also later taken. Thereby, three different heat inputs from 1.3 kJ/mm to 2 kJ/mm were investigated. Despite the observed decreased values of both t8/5-cooling time and the Charpy impact toughness in the root part of the seam, the required impact toughness of 38 J/cm2 could be reached in dependance on applied heat input, especially at the heat input of 1.6 kJ/mm. 2022 LANE 2022: 12th CIRP Conference on Photonic Technologies Fürth, Germany 04.09.2022 08.09.2022 2022-11-24 OPUS4-56371 Beitrag zu einem Tagungsband Üstündag, Ömer; Bakir, Nasim; Pittner, Andreas; Gumenyuk, Andrey; Rethmeier, Michael Einlagiges MSG-Hochleistungsschweißen von dickwandigen Baustählen mit kontaktloser elektromagnetischer Schmelzbadsicherung Diese Arbeit zeigt erstmals die Anwendung einer elektromagnetischen Schmelzbadsicherung beim einlagigen MSG-Schweißen von dickwandigen Stählen. Die innovativen Entwicklungen im Bereich des Lichtbogenschweißverfahrens ermöglichen eine Erhöhung der Abschmelzleistung, um die Einschweißtiefe zu steigern. Somit kann die Lagenanzahl reduziert und die Produktivität gesteigert werden. Allerdings besteht insbesondere beim einlagigen Schweißen von dickwandigen Bauteilen in PA-Position ein erhöhtes Risiko für das gravitationsbedingte Austropfen der Schmelze an der Wurzel. Zur Verhinderung werden Badsicherungen eingesetzt, die mechanisch angebracht und nach dem Schweißen entfernt werden müssen, was zeit- und kostenintensiv ist. Die im Rahmen dieser Studie eingesetzte elektromagnetische Schmelzbadsicherung wirkt dem gravitationsbedingten Austropfen der Schmelze entgegen und kompensiert den hydrostatischen Druck. Sie wirkt kontaktlos, was im Gegensatz zu herkömmlichen Badsicherungen vorteilhaft ist, so dass auf eine zeit- und kostenintensive Nachbearbeitung der Schweißnahtwurzel verzichtet werden kann. Das auf extern angelegten oszillierenden Magnetfeldern beruhende Verfahren wird dabei unterhalb des zu schweißenden Bauteils positioniert. Die Magnetfeldlinien sind quer zur Schweißrichtung ausgerichtet, sodass längs zur Schweißrichtung Wirbelströme im Werkstück und eine stets nach oben gerichtete Lorentzkraft generiert werden. Mit Hilfe der elektromagnetischen Badsicherung konnten beim einlagigen MSG-Schweißen von bis zu 10 mm dicken Blechen die Tropfenbildung vermieden werden. Die innovative Technologie ermöglicht es, dickwandige Bauteile einlagig zu schweißen und reduziert die Nachbearbeitungszeiten und -kosten deutlich. DVS Media GmbH 2022 DVS CONGRESS 2022 Große Schweißtechnische Tagung DVS CAMPUS 382 978-3-96144-189-1 DVS Congress 2022 - Große Schweißtechnische Tagung Koblenz, Germany 19.09.2022 21.09.2022 640 645 2022-11-24 OPUS4-56372 Zeitschriftenartikel Üstündag, Ömer; Bakir, Nasim; Brunner-Schwer, C.; Knöfel, F.; Gook, S.; Gumenyuk, Andrey; Rethmeier, Michael Laserstrahlhybridschweissen von Türmen für Windkraftanlagen Ökonomische und ökologische Vorteile Das Laserstrahlhybridschweißen ist beim Schweißen von Türmen für Windkraftanlagen eine Alternative zum Unterpulverschweißen von Dickblechen in Mehrlagentechnik und bietet hier ökonomische und ökologische Vorteile. Der industrielle Einsatz des Verfahrens ist jedoch durch prozessspezifische Herausforderungen eingeschränkt. Die im Beitrag beschriebene kontaktlose elektromagnetische Badstütze dient zur Erweiterung des Verfahrenspotenzials im Dickblechbereich >15 mm. DVS Media GmbH 2022 Der Praktiker 7 340 347 2022-11-24 OPUS4-56373 Zeitschriftenartikel Üstündag, Ömer; Bakir, Nasim; Gumenyuk, Andrey; Rethmeier, Michael Improvement of Charpy impact toughness by using an AC magnet backing system for laser hybrid welding of thick S690QL steels The study deals with the influence of the heat input and the resulting cooling times on the microstructure and Charpy impact toughness of single-pass laser hybrid welded 20-mm thick high-strength steel S690QL. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured in-situ using a pyrometer and an optical fibre in three different depths of the seam where Charpy impact test specimens were also later taken. Thereby, three different heat inputs from 1.3 kJ/mm to 2 kJ/mm were investigated. Despite the observed decreased values of both t8/5-cooling time and the Charpy impact toughness in the root part of the seam, the required impact toughness of 38 J/cm2 could be reached in dependance on applied heat input, especially at the heat input of 1.6 kJ/mm. Elsevier B.V. 2022 Procedia CIRP 111 12th CIRP conference on photonic technologies [lane 2022] Fürth, Germany 04.09.2022 08.09.2022 462 465 urn:nbn:de:kobv:b43-563731 10.1016/j.procir.2022.08.067 https://creativecommons.org/licenses/by-nc-nd/4.0/deed.de 2022-11-24 OPUS4-56374 Zeitschriftenartikel Jokisch, T.; Gook, S.; Marko, A.; Üstündag, Ömer; Gumenyuk, Andrey; Rethmeier, Michael Laser beam welding of additive manufactured components: Applicability of existing valuation regulations With additive manufacturing in the powder bed, the component size is limited by the installation space. Joint welding of additively manufactured parts offers a possibility to remove this size limitation. However, due to the specific stress and microstructure state in the additively built material, it is unclear to what extent existing evaluation rules of joint welding are also suitable for welds on additive components. This is investigated using laser beam welding of additively manufactured pipe joints. The welds are evaluated by means of visual inspection, metallographic examinations as well as computed tomography. The types of defects found are comparable to conventional components. This is an indicator that existing evaluation regulations also map the possible defects occurring for weld seams on additive components. DVS Media GmbH 2022 Welding and Cutting 2 109 113 2022-11-24 OPUS4-56375 Beitrag zu einem Tagungsband Üstündag, Ömer; Bakir, Nasim; Gumenyuk, Andrey; Rethmeier, Michael Elektromagnetische Schmelzbadbeeinflussung beim Laserhybridschweißen von Dickblechen Die technischen Entwicklungen in der Lasertechnologie in den letzten Jahrzehnten haben eine neue Generation von Hochleistungslasersystemen im Leistungsbereich bis zu 100 kW auf den Markt gebracht. Dennoch ist die industrielle Anwendung des Hochleistungslaserstrahlschweißens auf bis zu 15 mm dicke Bleche beschränkt. Mögliche Ursachen der Einschränkungen des Verfahrens sind z.B. die Sensibilität des Verfahrens auf Fertigungstoleranzen wie Spalt und Kantenversatz, die erhöhte Tropfenbildung bei höheren Blechdicken und eine inhomogene Verteilung des Zusatzwerkstoffes beim Laserhybridschweißen. In dieser Studie wird ein auf extern angelegte Magnetfelder basierte elektromagnetische Schmelzbadstütze eingesetzt, um die Grenzen des Verfahrens zu erweitern und die Herausforderungen zu minimieren. Der wesentliche Vorteil der elektromagnetischen Schmelzbadstütze ist, dass sie berührungslos arbeitet. Mit Hilfe der elektromagnetischen Schmelzbadstütze konnten bei 20 mm dicken Proben aus S355J2 die Tropfenbildung an der Wurzel vermieden werden. Zudem wurde der Einfluss der Kantenqualität auf die Schweißnahtqualität untersucht, wobei verschiedene Schneidverfahren zur Kantenvorbereitung eingesetzt wurden, wie z.B. Plasma-, Brenn- oder Laserschneiden. Es konnte gezeigt werden, dass auch bei schlechteren Kantenvorbereitung im Gegensatz zu gefrästen Bauteilen die Werkstoffe einlagig mittels Laserhybridschweißen bei einer hohen Schweißnahtqualität gefügt werden konnten. Bei plasmageschnittenen Proben wurden zudem eine Spaltüberbrückbarkeit bzw. Kantenversatz von bis zu 2 mm sicher überbrückt. Des Weiteren war es mit Hilfe der externen Magnetfelder möglich, die Durchmischung des Zusatzwerkstoffes über die gesamte Schweißnahttiefe deutlich zu homogenisieren. DVS Media GmbH 2022 DVS Berichte 42. Assistentenseminar Fügetechnik 385 42. Assistentenseminar der Wissenschaftlichen Gesellschaft Fügetechnik e.V. Blankenau, Germany 06.10.2021 08.10.2021 1 7 2022-11-24 OPUS4-56394 Zeitschriftenartikel Bakir, Nasim; Üstündag, Ömer; Gumenyuk, Andrey; Rethmeier, Michael Influence of the weld pool geometry on solidification cracking in partial penetration high power laser beam welding Solidification cracking is still a serious problem in laser beam welding, especially in the welding of thick-walled plates. The influence of weld pool geometry on solidification cracking in partial penetration welding of thick plates is investigated within scope of this study. Therefore, a specific experimental setup of steel and quartz glass in butt configuration and on the side with high-speed camera were used to record the weld pool shape. In addition, the influence of laser inclination angle on the weld pool geometry and on solidification crack formation was investigated. The results show a bulge in the weld pool root, which is separated from an upper region by a necking region. This leads to a case where there are three different longitudinal region lengths with different solidification zones. This temporal sequence of solidification strongly promotes the formation of solidification cracks in the weld root. Elsevier B.V. 2022 12TH CIRP Conference on photonic technologies (LANE 2022) 111 12th CIRP Conference on photonic technologies (LANE 2022) Fürth, Germany 04.09.2022 08.09.2022 397 400 urn:nbn:de:kobv:b43-563940 10.1016/j.procir.2022.08.174 https://creativecommons.org/licenses/by-nc-nd/4.0/deed.de 2022-11-28 OPUS4-56395 Vortrag Bakir, Nasim Influence of the weld pool geometry on solidification cracking in partial penetration high power laser beam welding Solidification cracking is still a serious problem in laser beam welding, especially in the welding of thick-walled plates. The influence of weld pool geometry on solidification cracking in partial penetration welding of thick plates is investigated within scope of this study. Therefore, a specific experimental setup of steel and quartz glass in butt configuration and on the side with high-speed camera were used to record the weld pool shape. In addition, the influence of laser inclination angle on the weld pool geometry and on solidification crack formation was investigated. The results show a bulge in the weld pool root, which is separated from an upper region by a necking region. This leads to a case where there are three different longitudinal region lengths with different solidification zones. This temporal sequence of solidification strongly promotes the formation of solidification cracks in the weld root. 2022 LANE 2022: 12th CIRP Conference on Photonic Technologies Fürth, Germany 04.09.2022 08.09.2022 2022-11-25 OPUS4-56328 Vortrag Yang, Fan Numerical analysis of the influence of an auxiliary oscillating magnetic field on suppressing the porosity formation in deep penetration laser beam welding of aluminum alloys The contactless magnetohydrodynamic technology has been considered as a potential and promising method to improve the weld qualities of deep penetration laser beam welding. In this paper, numerical investigations are conducted to study the influence of the auxiliary oscillating magnetic field on the porosity suppression in laser beam welding of 5754 aluminum alloy. To obtain a deeper insight into the suppression mechanism, a three-dimensional transient multi-physical model is developed to calculate the heat transfer, fluid flow, keyhole dynamic, and magnetohydrodynamics. A ray tracing algorithm is employed to calculate the laser energy distribution on the keyhole wall. A time-averaged downward Lorentz force is produced by an oscillating magnetic field. This force acts in the molten pool, leading to a dominant downward flow motion in the longitudinal section, which blocks the bubble migration from the keyhole tip to the rear part of the molten pool. Therefore, the possibility for the bubbles to be captured by the solidification front is reduced. The electromagnetic expulsive force provides an additional upward escaping speed for the bubbles of 1 m/s ~ 5 m/s in the lower and middle region of the molten pool. The simulation results are in a good agreement with experimental measurements. Based on the results obtained in this study, a better understanding of the underlying physics in laser beam welding enhanced by an auxiliary oscillating magnetic field can be provided and thus the welding process can be further optimized reducing the porosity formation. 2022 The 13th International Seminar "Numerical Analysis of Weldability" Graz, Austria 04.09.2022 07.09.2022 2022-11-21 OPUS4-56335 Vortrag Bachmann, Marcel Evaluation of narrowed weld pool shapes and their effect on resulting potential defects during deep penetration laser beam welding This study presents mechanisms of the evolution of a narrowed region in the weld pool center during deep penetration laser beam welding. In numerous numerical studies presented in this study, it was also found that the local reduction of the weld pool size can cause detrimental effects on the melt flow behavior and the resulting properties of the welds. A particularly large influence of this effect was identified in three aspects. First, the local variation of the solidification sequence of the weld pool causes an increase in the hotcracking susceptibility due to a locally delayed solidification. Second, it was proven that a change in the local length and width of the weld pool is associated with an adverse impact on the potential flow routes of the molten material that induces stronger local variations of its solidification. Thus, the element mixing, e.g., during the welding with filler materials, is blocked. This leads to a nonhomogeneous chemical composition of the final weld and can cause undesired effects on the final material properties. Finally, another observed effect is related to the reduced ability of process pores to reach the top surface. As this type of porosity is usually produced around the keyhole tip, the change of the fluid flow regime above this area plays a significant role in determining the final path of the pores until the premature solidification in the middle of the weld pool captures them. This study summarizes mainly numerical results that were supported by selected experimental validation results. 2022 International Congress of Applications of Lasers & Electro-Optics 2022 Orlando, FL, USA 17.10.2022 20.10.2022 2022-11-22 OPUS4-56532 Beitrag zu einem Tagungsband Bachmann, Marcel; Meng, Xiangmeng; Artinov, Antoni; Rethmeier, Michael Evaluation of narrowed weld pool shapes and their effect on resulting potential defects during deep penetration laser beam welding This study presents mechanisms of the evolution of a narrowed region in the weld pool center during deep penetration laser beam welding. In numerous numerical studies presented in this study, it was also found that the local reduction of the weld pool size can cause detrimental effects on the melt flow behavior and the resulting properties of the welds. A particularly large influence of this effect was identified in three aspects. Firstly, the local variation of the solidification sequence of the weld pool causes an increase in the hot-cracking susceptibility due to a locally delayed solidification. Secondly, it was proven that a change in the local length and width of the weld pool is associated with an adverse impact on the potential flow routes of the molten material that induces stronger local variations of its solidification. Thus, the element mixing, e.g. during the welding with filler materials, is blocked. This leads to a non-homogeneous chemical composition of the final weld and can cause undesired effects on the final material properties. Finally, another observed effect is related to the reduced ability of process pores to reach the top surface. As this type of porosity is usually produced around the keyhole tip, the change of the fluid flow regime above this area plays a significant role in determining the final path of the pores until the premature solidification in the middle of the weld pool captures them. This study summarizes mainly numerical results which were supported by selected experimental validation results. 2022 Proceedings of the ICALEO 2022, 41st International Congress on Applications of Lasers & Electro-Optics International Congress of Applications of Lasers & Electro-Optics 2022 Orlando, FL, USA 17.10.2022 20.10.2022 1 2022-12-12 OPUS4-56533 Beitrag zu einem Tagungsband Meng, Xiangmeng; Putra, Stephen Nugraha; Bachmann, Marcel; Artinov, Antoni; Rethmeier, Michael The influence of the free surface reconstruction on the spatial laser energy distribution in high power laser beam welding modeling An accurate and efficient description of the spatial distribution of laser energy is a crucial factor for the modeling of laser material processing, e.g., laser welding, laser cutting, or laser-based additive manufacturing. In this study, a 3D heat transfer and fluid flow model coupled with the volume-of-fluid algorithm for free surface tracking is developed for the simulation of molten pool dynamics in high-power laser beam welding. The underlying laser-material interactions, i.e., the multiple reflections and Fresnel absorption, are considered by a ray-tracing method. Two strategies of free surface reconstruction used in the ray-tracing method are investigated: a typical piecewise linear interface calculation (PLIC)-based method and a novel localized Level-Set method. The PLIC-based method is discrete, resulting in non-continuous free surface reconstruction. In the localized Level-Set method, a continuous free surface is reconstructed, and thus the exact reflection points can be determined. The calculated spatial laser energy distribution and the corresponding molten pool dynamics from the two methods are analyzed and compared. The obtained numerical results are evaluated with experimental measurements to assure the validity of the proposed model. It is found that distinct patterns of the beam multiple reflections are obtained with the different free surface reconstructions, which shows significant influence not only on the molten pool behaviors but also on the localized keyhole dynamics. 2022 Proceedings of the ICALEO 2022, 41st International Congress on Applications of Lasers & Electro-Optics International Congress of Applications of Lasers & Electro-Optics 2022 Orlando, FL, USA 17.10.2022 20.10.2022 1 9 2022-12-12 OPUS4-56672 Vortrag Winterkorn, René WAAM dickwandiger Bauteile aus höherfesten AL-MG-SI Legierungen Das Wire and Arc Additive Manufacturing (WAAM) ist dank hoher erreichbarer Aufbauraten prädestiniert für die Fertigung großvolumiger Bauteile. Dabei ist auf die Wirkmechanismen zwischen Prozessparametern und den daraus resultierenden mechanisch-technologischen Eigenschaften zu achten. Dies gilt insbesondere für die Fertigung dickwandiger Bauteile aus Al-Mg-Si-Aluminiumlegierungen, die eine hohe Anfälligkeit gegenüber Erstarrungsrissen und wasserstoffinduzierter Porosität aufweisen. Der Einfluss der Prozessparameter und des resultierenden Temperaturregimes auf die Bauteilqualität wurde durch die Analyse der Größe und Verteilung von Poren sowie der resultierenden Festigkeit untersucht. Darüber hinaus wurde der Einfluss einer Wärmenachbehandlungsstrategien auf das Festigkeitsverhalten analysiert. 2022 Additive Fertigung – Werkstoffe – Prozesse – Wärmebehandlung 2022 Bremen, Germany 29.06.2022 2022-12-22 OPUS4-56673 Beitrag zu einem Tagungsband Winterkorn, René; Pittner, Andreas; Rethmeier, Michael Lichtbogenbasierte additive Fertigung dickwandiger Strukturen aus einer höherfesten Al-Mg-Si-Aluminiumlegierungen Die lichtbogenbasierte, additive Fertigung ist dank hoher erreichbarer Aufbauraten und nahezu uneingeschränktem Bauraum zur Fertigung großvolumiger Bauteile prädestiniert. Die Kombination etablierter Maschinenkomponenten aus Robotertechnik, Schweißtechnik und Sensorik ermöglicht den präzisen schichtweisen Materialauftrag. Die Wirkmechanismen zwischen Prozessparametern und den daraus resultierenden mechanisch-technologischen Eigenschaften der additiv gefertigten Bauteile stellen eine Herausforderung dar. Dies gilt insbesondere auch für dickwandige Bauteile. Bei der Fertigung von Bauteilen aus höherfesten Al-Mg-Si-Aluminiumlegierungen ist aufgrund der hohen Anfälligkeit für Erstarrungsrisse und der Neigung zu wasserstoffinduzierter Porosität im besonderen Maße auf das Temperaturregime und die gewählte Aufbaustrategie zu achten. Der Einfluss der Prozessparameter auf die Bauteilqualität wurde durch die Analyse der Größe und Verteilung von Poren sowie der resultierenden Festigkeit untersucht. Darüber hinaus wurde der Einfluss einer Wärmenachbehandlungsstrategien auf das Festigkeitsverhalten analysiert. Es konnte gezeigt werden, dass dickwandige Strukturen aus höherfesten Al-Mg-Si-Aluminiumlegierungen mit mechanischen Kennwerten im Bereich des Referenzmaterials mittels MSGLichtbogenverfahren additiv gefertigt werden können. Bremen Arbeitsgemeinschaft Wärmebehandlung und Werkstofftechnik e. V. 2022 AWT Fachkonferenz 2022 Additive Fertigung Werkstoffe – Prozesse – Wärmebehandlung Additive Fertigung – Werkstoffe – Prozesse – Wärmebehandlung 2022 Bremen, Germany 29.06.2022 30.06.2022 169 181 2022-12-22 OPUS4-54506 Zeitschriftenartikel Artinov, Antoni; Meng, Xiangmeng; Bachmann, Marcel; Rethmeier, Michael Study on the transition behavior of the bulging effect during deep penetration laser beam welding The present work is devoted to the study of the transition behavior of the recently confirmed widening of the weld pool, known as the bulging effect, during high-power deep penetration laser beam welding of thick unalloyed steel sheets. A three-dimensional transient multi-physics numerical model is developed, allowing for the prediction of the bulge formation and the study of its temporal behavior. The model is generalized to account automatically for the transition from partial to complete penetration. Several experimental measurements and observations, such as drilling period, weld pool length, temperature, efficiency, and metallographic cross-sections are used to verify the model and assure the plausibility of the numerical results. The analysis of the calculated temperature and velocity distributions, as well as the evolution of the keyhole geometry, shows that the formation of a bulging region strongly depends on the penetration depth of the weld. Based on the numerical results, the bulge is found to occur transiently, having its transition from a slight bulge to a fully developed bulging between penetration depths of 6 mm and 9 mm, respectively. Elsevier Ltd. 2022 International Journal of Heat and Mass Transfer 184 122171 urn:nbn:de:kobv:b43-545067 10.1016/j.ijheatmasstransfer.2021.122171 https://creativecommons.org/licenses/by/4.0/deed.de 2022-03-21 OPUS4-54665 Zeitschriftenartikel Gook, Sergej; Üstündag, Ömer; Gumenyuk, Andrey; Rethmeier, Michael Method for defect-free hybrid laser-arc welding of closed circumferential welds This paper presents investigation results of a process for defect-free hybrid laser arc welding (HLAW) of closed circumferential welds. The process aims to avoid weld imperfections in the overlap area of a HLAW circumferential weld. A process control strategy for closing the circumferential weld was developed to achieve a defect-free overlap region by controlling the solidification conditions at the end of the weld. The controlled heat flow is achieved by adjusting the parameters of both welding processes involved, the laser beam as well as gas metal arc welding (GMAW) process. Experimental investigations were carried out on 12 mm to 15 mm thick tube sections. The influence of process parameters such as the laser ramp time, the change in magnification scale and the defocusing of the laser beam on the solidifi-cation conditions at the end of the circumferential weld was investigated to find an optimum strategy for ramping out the process energy. Within the framework of the experimental studies, it was demonstrated that defocusing the laser beam in the range between 60 mm and 100 mm over a short run-out area of the weld of approximately 15 mm led to a significantly better weld formation in the overlap area. A favourable cup-shaped weld shape could be achieved without a tendency to crack. The laser optics with a motor-driven lens system made it possible to increase the laser beam diameter without changing the position of the GMAW arc relative to the component surface. DVS Media 2021 Welding and Cutting 20 4 334 339 2022-04-20 OPUS4-54702 Zeitschriftenartikel Straße, Anne; Gumenyuk, Andrey; Rethmeier, Michael Study on Duplex Stainless Steel Powder Compositions for the Coating of thick Plates of Laser Beam Welding Duplex stainless steels combine the positive properties of its two phases, austenite and ferrite. Due to its good corrosion resistance, high tensile strength, and good ductility, it has multiple applications. But laser beam welding of duplex steels changes the balanced phase distribution in favor of ferrite. This results in a higher vulnerability to corrosion and a lower ductility. Herein, different powder combinations consisting of duplex and nickel for coating layers by laser metal deposition (LMD) are investigated. Afterward, laser tracks are welded, and the temperature cycles are measured. The ferrite content of the tracks is analyzed by feritscope, metallographic analysis, and electron backscatter diffraction. The goal is the development of a powder mixture allowing for a duplex microstructure in a two-step process, where first the edges of the weld partners are coated with the powder mixture by LMD and second those edges are laser beam welded. The powder mixture identified by the pretests is tested in the two-step process and analyzed by metallographic analysis, energy-dispersive X-ray spectroscopy, and Vickers hardness tests. The resulting weld seams show a balanced duplex microstructure with a homogenous nickel distribution and a hardness of the weld seam similar to the base material. Weinheim Wiley-VCH 2022 Advanced Engineering Materials 1 11 urn:nbn:de:kobv:b43-547024 10.1002/adem.202101327 https://creativecommons.org/licenses/by/4.0/deed.de 2022-04-27 OPUS4-54703 Zeitschriftenartikel Marko, A.; Bähring, S.; Raute, J.; Biegler, M.; Rethmeier, Michael Quality Prediction in Directed Energy Deposition Using Artificial Neural Networks Based on Process Signals The Directed Energy Deposition process is used in a wide range of applications including the repair, coating or modification of existing structures and the additive manufacturing of individual parts. As the process is frequently applied in the aerospace industry, the requirements for quality assurance are extremely high. Therefore, more and more sensor systems are being implemented for process monitoring. To evaluate the generated data, suitable methods must be developed. A solution, in this context, was the application of artificial neural networks (ANNs). This article demonstrates how measurement data can be used as input data for ANNs. The measurement data were generated using a pyrometer, an emission spectrometer, a camera (Charge-Coupled Device) and a laser scanner. First, a concept for the extraction of relevant features from dynamic measurement data series was presented. The developed method was then applied to generate a data set for the quality prediction of various geometries, including weld beads, coatings and cubes. The results were compared to ANNs trained with process parameters such as laser power, scan speed and powder mass flow. It was shown that the use of measurement data provides additional value. Neural networks trained with measurement data achieve significantly higher prediction accuracy, especially for more complex geometries. MDPI 2022 Applied Sciences 12 8 1 13 urn:nbn:de:kobv:b43-547039 10.3390/app12083955 https://creativecommons.org/licenses/by/4.0/deed.de 2022-04-27 OPUS4-54704 Zeitschriftenartikel Geisen, O.; Müller, V.; Graf, B.; Rethmeier, Michael Integrated weld preparation designs for the joining of L‑PBF and conventional components via TIG welding size limitations and high production costs of L-PBF make it competitive for smaller, highly complex components, while the less complex elements of an assembly are manufactured conventionally. This leads to scenarios that use L-PBF only where it's beneficial, and it require an integration and joining to form the final product. For example, L-PBF combustion swirlers are welded onto cast parts to produce combustion systems for stationary gas turbines. Today, the welding process requires complex welding fixtures and tack welds to ensure the correct alignment and positioning of the parts for repeatable weld results. In this paper, L-PBF and milled weld preparations are presented as a way to simplify the Tungsten inert gas (TIG) welding of rotationally symmetrical geometries using integrated features for alignment and fixation. Pipe specimens with the proposed designs are manufactured in Inconel 625 using L-PBF and milling. The pipe assembly is tested and TIG welding is performed for validation. 3D scans of the pipes before and after welding are evaluated, and the weld quality is examined via metallography and computed tomography (CT) scans. All welds produced in this study passed the highest evaluation group B according to DIN 5817. Thanks to good component alignment, safe handling, and a stable welding process, the developed designs eliminate the need for part-specific fixtures, simplify the process chain, and increase the process reliability. The results are applicable to a wide range of components with similar requirements. Springer 2022 Progress in Additive Manufacturing 1 11 urn:nbn:de:kobv:b43-547042 10.1007/s40964-021-00221-2 https://creativecommons.org/licenses/by/4.0/deed.de 2022-04-27 OPUS4-54701 Zeitschriftenartikel Gook, S.; El-Sari, B.; Biegler, M.; Rethmeier, Michael; Lichtenthäler, F.; Stark, M. Multiple-wire submerged arc welding of high-strength fine-grained steels Ensuring the required mechanical-technological properties of welds is a critical issue in the application of multi-wire submerged arc welding processes for welding high-strength fine-grained steels. Excessive heat input is one of the main causes for microstructural zones with deteriorated mechanical properties of the welded joint, such as a reduced notched impact strength and a lower structural robustness. A process variant is proposed which reduces the weld volume as well as the heat input by adjusting the welding wire configuration as well as the energetic parameters of the arcs, while retaining the advantages of multiwire submerged arc welding such as high process stability and production speed. Kiev Paton Publishing House 2022 The Patron Welding Journal 1 9 13 10.37434/tpwj2022.01.02 2022-04-27 OPUS4-54399 Vortrag Scheuschner, Nils Infrared Thermography of the DED-LB/M and PBF LB/M processes Infrared thermography is a technique that allows to measure the temperatures of objects by analyzing the intensity of the thermal emission without the need of direct contact with very high spatial and temporal resolution. As the temperature is a fundamental factor for the additive manufacturing processes of metals, infrared thermography can provide experimental data that can be used for the validation of simulations and improving the understanding of the processes as well as for in-situ process monitoring for nondestructive evaluation (NDE) for quality control. In this talk we will provide an overview over the possibilities of state of the art thermographic in-situ monitoring systems for the DED-LB/M and PBF-LB/M processes and the challenges such as phase transitions and unknown emissivity values in respect to the determination of real temperatures. We define the requirements for different camera systems in various configurations and give examples on the selection of appropriate measurement parameters and data acquisition techniques as well as on techniques for data analysis and interpretation. Finally, we compare in-situ monitoring methods against post NDE methods by analyzing the advantages and disadvantages of both. This research was funded by BAM within the Focus Area Materials. 2021 Coupled2021 - IX International Conference on Coupled Problems in Science and Engineering Online meeting 13.06.2021 16.06.2021 2022-02-28 OPUS4-53976 Zeitschriftenartikel El-Sari, B.; Biegler, M.; Rethmeier, Michael Verbesserung der Vorhersagegüte von künstlichen neuronalen Netzen zum Widerstandspunktschweißen durch Auswertung des dynamischen Widerstands Das Widerstandspunktschweißen ist ein etabliertes Fügeverfahren in der Automobilindustrie. Es wird vor allem bei der Herstellung sicherheitsrelevanter Bauteile, zum Beispiel der Karosserie, eingesetzt. Daher ist eine kontinuierliche Prozessüberwachung unerlässlich, um die hohen Qualitätsanforderungen zu erfüllen. Künstliche neuronale Netzalgorithmen können zur Auswertung der Prozessparameter und -signale eingesetzt werden, um die individuelle Schweißpunktqualität zu gewährleisten. Die Vorhersagegenauigkeit solcher Algorithmen hängt von dem zur Verfügung gestellten Trainingsdatensatz ab. In diesem Beitrag wird untersucht, inwieweit die Vorhersagegüte eines künstlichen neuronalen Netzes durch Auswertung einer Prozessgröße, dem dynamischen Widerstand, verbessert werden kann. 2021 Schweißen und Schneiden 785 789 2021-12-13 OPUS4-53979 Zeitschriftenartikel Raute, J.; Biegler, M.; Rethmeier, Michael Elektronenstrahl schweißt additiv gefertigte Nickel-Superlegierungen Die Additive Fertigung ist ideal zur Herstellung und Reparatur komplexer Bauteile aus hochfesten Werkstoffen. Doch es fehlen Fügeverfahren, die Heißrisse vermeiden. Die Lösung heißt Elektronenstrahl. 2021 MM Maschinenmarkt 1 6 2021-12-13 OPUS4-54244 Zeitschriftenartikel Ivanov, S.; Artinov, Antoni; Zemlyakov, E.; Karpov, I.; Rylov, S.; Em, V. Spatiotemporal Evolution of Stress Field during Direct Laser Deposition of Multilayer Thin Wall of Ti-6Al-4V The present work seeks to extend the level of understanding of the stress field evolution during direct laser deposition (DLD) of a 3.2 mm thick multilayer wall of Ti-6Al-4V alloy by theoretical and experimental studies. The process conditions were close to the conditions used to produce large-sized structures by the DLD method, resulting in specimens having the same thermal history. A simulation procedure based on the implicit finite element method was developed for the theoretical study of the stress field evolution. The accuracy of the simulation was significantly improved by using experimentally obtained temperature-dependent mechanical properties of the DLD-processed Ti-6Al4V alloy. The residual stress field in the buildup was experimentally measured by neutron diffraction. The stress-free lattice parameter, which is decisive for the measured stresses, was determined using both a plane stress approach and a force-momentum balance. The influence of the inhomogeneity of the residual stress field on the accuracy of the experimental measurement and the validation of the simulation procedure are analyzed and discussed. Based on the numerical results it was found that the non-uniformity of the through-thickness stress distribution reaches a maximum in the central cross-section, while at the buildup ends the stresses are distributed almost uniformly. The components of the principal stresses are tensile at the buildup ends near the substrate. Furthermore, the calculated equivalent plastic strain reaches 5.9% near the buildup end, where the deposited layers are completed, while the plastic strain is practically equal to the experimentally measured ductility of the DLD-processed alloy, which is 6.2%. The experimentally measured residual stresses obtained by the force-momentum balance and the plane stress approach differ slightly from each other. MDPI 2022 Materials 15 263 1 20 urn:nbn:de:kobv:b43-542444 10.3390/ma15010263 https://creativecommons.org/licenses/by/4.0/deed.de 2022-01-24 OPUS4-54331 Vortrag Gumenyuk, Andrey Influence of an external applied AC magnetic field on the melt pool dynamics at high-power laser beam welding The study deals with the determination of the influence of an externally applied oscillating magnetic field on the melt pool dynamics in high power laser beam and hybrid laser arc welding processes. An AC magnet was positioned under the workpiece which is generating an upward directed electromagnetic force to counteract the formation of the droplets. To visualise the melt flow characteristics, several experiments were carried out using a special technique with mild steel from S355J2 with a wall thickness of up to 20 mm and a quartz glass in butt configuration. The profile of the keyhole and the melt flow were recorded with a high-speed camera from the glass side. Additionally, the influence of the magnetic field orientation to the welding direction on the filler material dilution on laser hybrid welding was studied with variating oscillation frequency. The element distribution over the whole seam thickness was measured with X-ray fluorescence (XRF). The oscillation frequency demonstrated a greater influence on the melt pool dynamics and the mixing of the elements of the filler wire. The high-speed recordings showed, under the influence of the magnetic field, that the melt is affected under strong vortex at the weld root, which also avoids the formation of droplets 2022 The 18th Nordic Laser Materials Processing Conference Lulea, Sweden 18.01.2022 20.01.2022 2022-02-14 OPUS4-54332 Zeitschriftenartikel Bachmann, Marcel; Meng, Xiangmeng; Artinov, Antoni; Rethmeier, Michael Elucidation of the Bulging Effect by an Improved Ray-Tracing Algorithm in Deep Penetration Wire Feed Laser Beam Welding and its Influence on the Mixing Behavior Herein, an improved ray-tracing routine using a virtual mesh refinement approach is adopted in a 3D transientmultiphysics computational fluid Dynamics model for deep penetration wire feed laser beam welding. In a previous study, it was shown that the improved localization of the reflection points of the subrays within the keyhole leads to a more realistic development of the keyhole Depth being validated with experimental results. Another effect investigated in Detail herein is a drastic change in the flow behavior in the weld pool, which promotes the occurrence of a necking area in the solidification line and subsequent bulging under specific circumstances. This has a detrimental effect on the filler material element transport in the weld pool, leading to an inhomogeneous dilution of the added material. The numerical observations are backed up by experimentally obtained data, allowing to provide a clear physics-based explanation of the reduced mixing behavior of the filler wire in the melt pool. Wiley 2022 Advanced Engineering Materials 1 9 urn:nbn:de:kobv:b43-543322 10.1002/adem.202101299 https://creativecommons.org/licenses/by/4.0/deed.de 2022-02-14 OPUS4-54333 Vortrag Rethmeier, Michael The bulging effect and its relevance in high power laser beam welding The present work deals with the recently confirmed widening of the weld pool interface, known as a bulging effect, and its relevance in high power laser beam welding. A combined experimental and numerical approach is utilized to study the influence of the bulge on the hot cracking formation and the transport of alloying elements in the molten pool. A technique using a quartz glass, a direct-diode laser illumination, a high speed camera, and two thermal imaging cameras is applied to visualize the weld pool geometry in the longitudinal section. The study examines the relevance of the bulging effect on both, partial and complete penetration, as well as for different sheet thicknesses ranging from 8 mm to 25 mm. The numerical analysis shows that the formation of a bulge region is highly dependent on the penetration depth and occurs above 10 mm penetration depth. The location of the bulge correlates strongly with the cracking location. The obtained experimental and numerical results reveal that the bulging effect increases the hot cracking susceptibility and limits the transfer of alloying elements from the top of the weld pool to the weld root 2022 The 18th Nordic Laser Materials Processing Conference Lulea, Sweden 18.01.2022 20.01.2022 2022-02-14 OPUS4-54022 Zeitschriftenartikel Artinov, Antoni; Bachmann, Marcel; Rethmeier, Michael; Karkhin, V.; Khomich, P. Modeling of hydrodynamic and thermal processes at laser welding with through penetration A mathematical model for physical processes in fusion welding has been developed. It is based on the equivalent heat source concept and consists of two parts: thermo-hydrodynamics of the weld pool and heat conduction in the weldment outside the pool. In thermo-hydrodynamic problem, temperature - dependent material properties, keyhole shape, thermo-capillary and natural convection, phase transformations and other physical phenomena are taken into consideration. Solution of the thermo-hydrodynamic problem by the finite element method is demonstrated with keyhole laser beam welding of a 15 mm thick steel plate. Thermo-capillary convection is primarily responsible for the intricate convex-concave melt pool shape and pool enlargement near the plate surfaces. The calculated and experimental molten pool dimensions are in close agreement. Taylor & Francis Group 2021 Welding International 1 12 10.1080/09507116.2021.1989209 2021-12-15 OPUS4-53926 Beitrag zu einem Tagungsband Üstündag, Ömer; Bakir, Nasim; Gumenyuk, Andrey; Rethmeier, Michael Thermal Cycles and Charpy Impact Toughness of Single-Pass Hybrid Laser-Arc Welded Thick-Walled Structures The study deals with the influence of the heat input on the thermal cycles and Charpy impact toughness for hybrid laser-arc welding of 25 mm thick structural steel S355J2 using a 20-kW high-power laser in combination with an electromagnetic weld pool support. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured using a pyrometer in combination with an optical fibre in three different locations near to fusion lines corresponding to different heights of the seam. Also, Charpy impact specimens were taken from different parts of the weld joint corresponding to the different heights. The influence of the heat input was investigated for 1.8 kJ mm-1 and 3.2 kJ mm-1. Despite the observed decreased values of both t8/5-cooling time and the Charpy impact toughness in the root part of the seam, the required values could be reached in dependance on applied heat input. 2021 Lasers in Manufacturing Conference 2021 Lasers in Manufacturing Conference 2021 Online meeting 21.06.2021 24.06.2021 1 8 2021-12-08 OPUS4-53967 Beitrag zu einem Tagungsband Straße, Anne; Gumenyuk, Andrey; Scheuschner, Nils; Altenburg, Simon; Pignatelli, Giuseppe; Gornushkin, Igor B.; Baensch, Franziska; Rethmeier, Michael In-situ Prozessüberwachung beim Laser-Pulver-Auftragschweißen (LPA) mittels Thermografie, optischer Emissionsspektroskopie (OES) und Schallemissionsanalyse (SEA) Vor allem in den letzten Jahren ist das Interesse der Industrie an der additiven Fertigung deutlich gestiegen. Die Vorteile dieser Verfahren sind zahlreich und ermöglichen eine ressourcenschonende, kundenorientierte Fertigung von Bauteilen, welche zur stetigen Entwicklung neue Anwendungsbereiche und Werkstoffe führen. Aufgrund der steigenden Anwendungsfälle, nimmt auch der Wunsch nach Betriebssicherheit unabhängig von anschließenden kostenintensiven zerstörenden und zerstörungsfreien Prüfverfahren zu. Zu diesem Zweck werden im Rahmen des von der BAM durchgeführten Themenfeldprojektes „Prozessmonitoring in Additive Manufacturing" verschiedenste Verfahren auf ihre Tauglichkeit für den in-situ Einsatz bei der Prozessüberwachung in der additiven Fertigung untersucht. Hier werden drei dieser in-situ Verfahren, die Thermografie, die optische Emissionsspektroskopie und die Schallmissionsanalyse für den Einsatz beim Laser-Pulver-Auftragschweißen betrachtet. Düsseldorf DVS MEdia 2021 41. Assistentenseminar der Füge- und Schweißtechnik 370 978-3-96144-141-9 41. Assistentenseminar der Füge- und Schweißtechnik Magdeburg, Germany 02.09.2020 04.09.2020 132 140 2021-12-13 OPUS4-53970 Zeitschriftenartikel Rethmeier, Michael; Gumenyuk, Andrey; Bachmann, Marcel High-power laser beam welding for thick section steels - new perspectives using electromagnetic systems In recent years, it was shown that the introduction of additional oscillating and permanent magnetic fields to laser beam and laser-arc hybrid welding can bring several beneficial effects. Examples are a contactless weld pool support for metals of high thickness suffering from severe drop-out when being welded conventionally or an enhanced stirring to improve the mixing of added filler material in the depth of the weld pool to guarantee homogeneous resulting mechanical properties of the weld. The latest research results show the applicability to various metal types over a wide range of thicknesses and welding conditions. The observations made were demonstrated in numerous experimental studies and a deep understanding of the interaction of the underlying physical mechanisms was extracted from numerical calculations. Taylor & Francis Group 2021 Science and Technology of Welding and Joining 27 1 43 51 10.1080/13621718.2021.1999763 2021-12-13 OPUS4-53974 Vortrag Brunner-Schwer, Chr.; Biegler, M.; Rethmeier, Michael Investigation on laser cladding of rail steel without preheating The contact between train wheels and rail tracks is known to induce material degradation in the form of wear, and rolling contact fatigue in the railhead. Rails with a pearlitic microstructure have proven to provide the best wear resistance under severe wheel-rail interaction in heavy haul applications. High speed laser cladding, a state-of-the-art surface engineering technique, is a promising solution to repair damaged railheads. However, without appropriate preheating or processing strategies, the utilized steel grades lead to martensite formation and cracking during deposition welding. In this study, laser cladding of low-alloy steel at very high speeds was investigated, without preheating the railheads. Process speeds of up to 27 m/min and laser power of 2 kW are used. The clad, heat affected zone and base material are examined for cracks and martensite formation by hardness tests and metallographic inspections. A methodology for process optimization is presented and the specimens are characterized for suitability. Within the resulting narrow HAZ, the hardness could be significantly reduced. 2021 Lasers in Manufacturing Conference 2021 Erlangen, Germany 21.06.2021 2021-12-13 OPUS4-54057 Zeitschriftenartikel Biegler, M.; El-Sari, B.; Rethmeier, Michael; Finus, F. Schweißen unter Zug - LME-Eingangsprüfung für die Autoindustrie Der Trend zum Leichtbau und die Transformation zur E-Mobilität in der Automobilindustrie befeuern die Entwicklung neuer hochfester Stähle für den Karosseriebau. Derartige Werkstoffe sind beim Widerstandspunktschweißen besonders rissanfällig (LME). Das Schweißen unter Zug stellt eine effektive Methode um die LME-Anfälligkeit unterschiedlicher Werkstoffe qualitativ zu bestimmen. 2021 Blechnet 6 54 55 2021-12-16 OPUS4-54061 Posterpräsentation Meyerdierks, M.; Schreiber, V.; Böhne, Ch.; Jüttner, S.; Meschut, G.; Rethmeier, Michael Validierung von Methoden zur Vermeidung von Liquid Metal Embrittlement an realitätsnahen Prinzipbauteilen (IGF 21483 BG / P 1488) Ziel des Forschungsprojekts ist es, eine Korrelation zwischen Gleeble-Heißzug-Prüfverfahren und Widerstandspunktschweiß-basierten Prüfverfahren herzustellen. Es soll die Effektivität von Methoden zu Vermeidung von Liquid Metal Embrittlement an realitätsnahen Prinzipbauteilen bewertet werden. Weiterhin soll Kenntnis über Auswirkungen von LME Rissen auf das Tragverhalten von realitätsnahen Prinzipbauteilen gewonnen werden. 2021 30. Schweißtechnische Fachtagung Barleben, Germany 07.10.2021 2021-12-16 OPUS4-54067 Beitrag zu einem Tagungsband Müller, V.; Marko, A.; Kruse, T.; Biegler, M.; Rethmeier, Michael Analysis and recycling of bronze grinding waste to produce maritime components using directed energy deposition Additive manufacturing promises a high potential for the maritime sector. Directed Energy Deposition (DED) in particular offers the opportunity to produce large-volume maritime components like propeller hubs or blades without the need of a costly casting process. The post processing of such components usually generates a large amount of aluminum bronze grinding waste. The aim of the presented project is to develop a sustainable circular AM process chain for maritime components by recycling aluminum bronze grinding waste to be used as raw material to manufacture ship Propellers with a laser-powder DED process. In the present paper, grinding waste is investigated using a dynamic image Analysis system and compared to commercial DED powder. To be able to compare the material quality and to verify DED process parameters, semi-academic sample geometries are manufactured. 2021 LiM 2021 Munich, Germany 21.06.2021 24.06.2021 1 9 2021-12-20