TY - GEN A1 - Nikitin, Alexander A1 - Turabov, Dashqin A1 - Ermilova, Evgeniia A1 - Evdokimov, Anton A1 - Ossenbrink, Ralf A1 - Seidlitz, Holger T1 - Using dynamic resistance to predict electrode surface degradation in resistance spot welding of 5182 aluminum alloy T2 - Welding in the World N2 - In this study, the correlation between dynamic resistance during the first 10 ms of welding time and the electrode surface condition in resistance spot welding of 5182 aluminum alloy has been investigated. The electrode surface rapidly degrades due to contamination and morphological changes, adversely affecting the weld spot surface. The accumulation of Cu-Al intermetallic phases on the electrode surface alters its roughness, leading to variations in dynamic resistance. By analyzing this correlation, optimal electrode milling intervals were identified to extend electrode life. This work focused on detecting crater formation on the electrode surface through dynamic resistance monitoring. The results indicate that resistance measurements provide a reliable approach for evaluating electrode wear, optimizing maintenance schedules, and reducing material removal during milling. KW - resistance spot welding KW - aluminum alloy KW - electrode wear KW - dynamic resistance KW - electrode surface Y1 - 2024 U6 - https://doi.org/10.1007/s40194-024-01872-9 VL - 69 SP - 449 EP - 458 ER - TY - GEN A1 - Ormanova, Maria A1 - Kotlarski, Georgi A1 - Kaisheva, Darina A1 - Nikitin, Alexander A1 - Ossenbrink, Ralf A1 - Doynov, Nikolay A1 - Valkov, Stefan T1 - Investigation of the thermal gradients formed during the process of cooling of WAAM built Al99.7 specimen T2 - Journal of Physics: Conference Series N2 - This work presents a preliminary experiment used to determine the possibility of developing a thermal model used to predict the thermal gradients formed during the process of wire and arc additive manufacturing (WAAM). For this purpose, an Al99.7 specimen was built using gas metal arc welding (GMAW) in the cold arc pulse mode. The temperature of both the substrate and each consecutive layer was measured using thermocouples and infrared thermometers and the experimental data was used for the calibration of the developed thermal model. The obtained results can be used for the further development of the thermal model. KW - Thermal model KW - Wire arc additve manufacturing KW - Waam KW - Gas metal arc welding KW - Gmaw KW - Aluminum KW - Al99.7 Y1 - 2024 U6 - https://doi.org/10.1088/1742-6596/2710/1/012038 SN - 1742-6596 VL - 2024 IS - 2710 ER - TY - GEN A1 - Kotlarski, Georgi A1 - Ormanova, Maria A1 - Nikitin, Alexander A1 - Ossenbrink, Ralf A1 - Doynov, Nikolay A1 - Valkov, Stefan A1 - Michailov, Vesselin ED - Tsankov, Plamen ED - Maximov, Jordan ED - Aleksandrov, Anatoliy ED - Todorov, Todor ED - Peneva, Petya T1 - Structure, morphology and hardness of a WAAM built Al99.7 specimen T2 - International Scientific Conference Unitech 2023, Gabrovo : selected papers N2 - The present work discusses the possibility of wire arc additive manufacturing (WAAM) of pure aluminum specimens (Al99.7). The manufactured specimen's structure was studied using X-ray diffraction (XRD) experiments. The morphology of the specimen at different stages of build-up was studied by examining prepared mechanical properties of the specimen, and for this reason the microhardness of the specimen was studied as well. The results of the present study were discussed regarding the change of the structure of the samples with the increase of the specimen's height during the manufacturing process and its influence on the resultant microhardness. KW - WAAM KW - Al99.7 KW - Structure KW - Morphology KW - Hardness Y1 - 2023 UR - https://unitech2023.tugab.bg/images/thematic-sessions/CHEMISTRY_PHYSICS_AND_ECOLOGY/s17_p149_v1.pdf U6 - https://doi.org/10.70456/PJKY7011 SN - 1313-230X VL - 2 SP - 349 EP - 353 PB - Union of Automation & Informatics CY - Gabrovo ER - TY - GEN A1 - Köhler, Marcel A1 - Nikitin, Alexander A1 - Sonnenfeld, Peter A1 - Ossenbrink, Ralf A1 - Jüttner, Sven T1 - Wire arc additive manufacturing of aluminum foams using TiH2-Laced Welding Wires T2 - Materials N2 - Composite materials made from aluminum foam are increasingly used in aerospace and automotive industries due to their low density, high energy absorption capacity, and corrosion resistance. Additive manufacturing processes offer several advantages over conventional manufacturing methods, such as the ability to produce significantly more geometrically complex components without the need for expensive tooling. Direct Energy Deposition processes like Wire Arc Additive Manufacturing (WAAM) enable the additive production of near-net-shape components at high build rates. This paper presents a technology for producing aluminum foam structures using WAAM. This paper’s focus is on the development of welding wires that are mixed with a foaming agent (TiH2) and produce a foamed weld metal as well as their processing using MIG welding technology. KW - MIG welding KW - wire arc additive manufacturing KW - direct energy deposition KW - aluminum foam KW - titanium hydride KW - foaming agent KW - metal-cored wires KW - continuous powder extrusion KW - energy absorption Y1 - 2024 U6 - https://doi.org/10.3390/ma17133176 SN - 1996-1944 VL - 17 IS - 13 PB - MDPI AG ER - TY - GEN A1 - Hagen, Christian A1 - Klinkenberg, Franz-Josef A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin T1 - Resistance spot welding of dissimilar material joints with a cold-gas-sprayed inlayer T2 - The International Journal of Advanced Manufacturing Technology N2 - In this publication, cold gas spraying (CGS) is investigated as an enabler for aluminum-steel joints. Using a powder-based coating process to adhere a steel layer to an aluminum substrate allows a steel component to be welded to the deposited layer by resistance spot welding. This method permits the metallurgical connection between similar materials to be separated, while mechanical bonding ensures the connection at the dissimilar aluminum-to-inlayer interface. A modification of the porous CGS layer, as well as the creation of the remelted zone in the aluminum, can be observed during the resistance spot welding process. Electron backscatter diffraction (EBSD) analyses show that the severely prestressed particles in the CGS coating recrystallize, which coincides with a decrease in defect density and hardness in the heat-affected zone. Microscopy of the aluminum substrate shows the creation of metallurgical pores as well as the expansion of pores attributed to the casting process. The rise in remelted aluminum hardness and decrease in the heat-affected zone of the CGS layer indicate the formation of a metallurgical notch. KW - resistance spot weld KW - rsw KW - cold gas spray KW - cgs KW - inlayer KW - dissimilar joint KW - aluminium-steel weld Y1 - 2023 UR - https://link.springer.com/article/10.1007/s00170-023-11897-x U6 - https://doi.org/10.1007/s00170-023-11897-x SN - 1433-3015 SN - 0268-3768 ER - TY - GEN A1 - Wasilewski, Eric A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin T1 - Investigations on the thermal conditions during laser beam welding of high-strength steel 100Cr6 T2 - Advances in Industrial and Manufacturing Engineering N2 - This study examines the thermal conditions during laser beam welding of 100Cr6 high-strength steel using a TruDisk5000 disc laser with a continuous adjustable power range of 100–5000 W. Two parameter sets, characterized by laser power and welding speeds, were analyzed by thermal-metallurgical FE simulations to determine their impact on the thermal conditions during welding. The results show a significant shift in heat coupling, with conduction transitioning to deep penetration welding. As a result of the high welding speeds and reduced energy input, extremely high heating rates up to 2∙104 K s−1 (set A) respectively 4∙105 K s−1 (set B) occur. Both welds thus concern a range of temperature state values for which conventional Time-Temperature-Austenitization (TTA) diagrams are currently not defined, requiring calibration of the material models through general assumptions. Also, the change in energy input and welding speed causes significantly steep temperature gradients with a slope of approximately 5∙103 K mm−1 and strong drops in the temperature rates, particularly in the heat affected zone. The temperature cycles also show very different cooling rates for the respective parameter sets, although in both cases they are well below a cooling time t8/5 of 1 s, so that the phase transformation always leads to the formation of martensite. Since the investigated parameters are known to cause a loss of technological strength and conditionally result in cold cracks, these results will be used for further detailed experimental and numerical investigation of microstructure, hydrogen distribution, and stress-strain development at different restraint conditions. KW - laser beam welding KW - welding temperature field KW - temperature rates KW - thermal-metallurgical FE simulation KW - high-strength steel Y1 - 2023 UR - https://www.sciencedirect.com/science/article/pii/S2666912923000077 U6 - https://doi.org/10.1016/j.aime.2023.100118 SN - 2666-9129 VL - 6 ER - TY - GEN A1 - Turabov, Dashqin A1 - Evdokimov, Anton A1 - Nikitin, Alexander A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin T1 - Vorhersage des Elektrodenverschleißes beim Widerstandspunktschweißen von Aluminium durch dynamische Widerstandsmessung T2 - DVS Congress 2023, Große Schweißtechnische Tagung, DVS Campus ; Kurzfassungen der Vorträge der Veranstaltung in Essen vom 11. bis 14. September 2023 ; (Langfassungen der Beiträge auf USB-Karte) N2 - Das Widerstandspunktschweißen ist ein weit verbreitetes Schweißverfahren, insbesondere bei der Karosserieherstellung in der Automobilbranche. Im Hinblick auf den Leichtbau werden zunehmend Aluminiumlegierungen verwendet. Das Hauptproblem beim Widerstandspunktschweißen von Aluminiumlegierungen ist der schnelle Elektrodenverschleiß. Dadurch wird die Qualität und Effizienz des Schweißprozesses beeinträchtigt. Die Elektrodenstandmenge ist erreicht, wenn die Schweißverbindung eines der Qualitätskriterien nicht erfüllt. Um die Elektrodenstandmenge zu ermitteln, werden in der Industrie im Rahmen der Schweißnahtqualifizierung zeit- und ressourcenaufwändige Methoden, u. a. zerstörende Prüfmethoden, verwendet. In dieser Arbeit wird eine Methode zur Vorhersage des kritischen Elektrodenverschleißes beim Aluminiumschweißen durch Messung des dynamischen Widerstandes vorgeschlagen. In umfangreichen Versuchsreihen an einer automobiltypischen Al-Legierung der 5000er Gruppe wurden dynamische Widerstandsmessungen durchgeführt. Aus den Widerstandsmesswerten konnte ein Indikator ermittelt werden, welcher auf das Auftreten von Poren in Schweißverbindung und auf einen bald auftretenden kritischen Elektrodenverschleiß hinweist. Y1 - 2023 UR - https://www.dvs-ev.de/call4papers/abstract.cfm?vid=116&pid=7816 SN - 978-3-96144-230-0 VL - 389 / 2023 SP - 780 EP - 787 PB - DVS Media GmbH CY - Düsseldorf ER - TY - GEN A1 - Kotlarski, Georgi A1 - Ormanova, Maria A1 - Nikitin, Alexander A1 - Morozova, Iuliia A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin A1 - Doynov, Nikolay A1 - Valkov, Stefan T1 - Microstructural and Mechanical Properties of CAP-WAAM Single-Track Al5356 Specimens of Differing Scale T2 - Materials N2 - The mass production of metallic components requires high agility in the working process conditioned by the necessity of building details of different shapes and sizes. Changing the size of the components theoretically influences the thermal dissipation capability of the same, which could lead to a change in their structure and mechanical properties. This is particularly important when aluminum alloys are concerned. For this reason, two Al5356 single-track specimens were built using the same technological conditions of layer deposition by varying only their geometrical size. In all cases, the specimens were wire and arc additively manufactured (WAAM) using a process based on gas metal arc welding (GMAW) in the cold arc pulse mode (CAP). The structure of both specimens was studied and defects along their surfaces were detected in the form of micro-pores and micro-cracks. A high concentration of undissolved Mg particles was also detected, along with some standalone Si particles. Uniformity in the build-up process was achieved, which led to the formation of nearly identical structures in the specimens. Subsequently, the resultant mechanical properties were also highly comparable. This indicates that the geometry-related variation in thermal conditions has an insignificant influence on the component’s structure and properties. KW - microstructure KW - WAAM KW - cold arc pulse (CAP) KW - AlMg5Cr KW - Al5356 KW - single-track KW - mechanical properties Y1 - 2024 U6 - https://doi.org/10.3390/machines12010072 SN - 2075-1702 VL - 12 IS - 1 ER - TY - GEN A1 - Kotlarski, Georgi A1 - Ormanova, Maria A1 - Nikitin, Alexander A1 - Parasar, Ashirwad A1 - Ossenbrink, Ralf A1 - Doynov, Nikolay A1 - Valkov, Stefan A1 - Michailov, Vesselin T1 - Wire arc deposition of specimens using a special-designed aluminum-cored wire with CNTs T2 - Journal of physics : conference series N2 - This work investigated the possibility of manufacturing components using an aluminum welding wire with an aluminum powder core reinforced with carbon nanotubes (CNTs). Appropriate technological conditions of deposition were selected for the successful manufacturing of a wall-shaped specimen. The last was built using a multi-track approach. The results indicated the presence of a large quantity of pores within the volume of the specimen with values of over 30%. Regardless of the high defect quantity within the specimen a number of successfully integrated carbon nanoparticles were detected in certain areas of the cross-section of the specimen in the form of an Al₄C₃ composite. Y1 - 2025 U6 - https://doi.org/10.1088/1742-6596/2994/1/012024 SN - 1742-6588 SN - 1742-6596 VL - 2994 IS - 1 SP - 1 EP - 6 PB - IOP Publishing CY - Bristol ER -