TY - GEN A1 - Evdokimov, Anton A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Obrosov, Aleksei A1 - Weiß, Sabine A1 - Michailov, Vesselin T1 - Thermomechanical laser welding simulation of dissimilar steel-aluminum overlap joints T2 - International Journal of Mechanical Sciences N2 - Mixing of steel and aluminum within the weld pool during keyhole laser welding results in a complex dissimilar microstructure, which in turn, initiates a shift in weld metal mechanical properties. In this study, a numerical model for computation of distortions in laser-welded dissimilar overlap joints (austenitic stainless steel 304 – 6082-T6 aluminum alloy), which considers properties of the mixed steel-aluminum weld metal was developed. The required yield strength, Young's modulus, and strain hardening exponent of the weld metal were experimentally determined using the indentation technique coupled with energy-dispersive X-ray spectroscopy. The designed material model calculates the weld elastic-plastic properties as a function of the aluminum concentration. The softening of the alloys in the heat-affected zone was determined by physical simulations and considered as a function of maximum temperature. Computed and measured distortions showed good agreement for various welding regimes with an average deviation of 18.4%. The sensitivity analyses indicated that the application of the developed weld material model significantly improves the accuracy of the thermomechanical simulations. Y1 - 2021 U6 - https://doi.org/10.1016/j.ijmecsci.2020.106019 SN - 1879-2162 VL - 190 ER - TY - GEN A1 - Ginzburg, Svetlana A1 - Morozova, Iuliia A1 - Kloshek, Alexander A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin A1 - Bobrynina, Elizaveta A1 - Koltsova, Tatiana S. A1 - Tolochko, Oleg V. A1 - Koçak, Mustafa A1 - Ozbek, Sunullah A1 - Morozova, Iuliia T1 - Addition of nanoparticles to flux cored wires for the nucleation of acicular ferrite microstructure in weld metals of the high-strength low-alloy steel T2 - Welding and Cutting N2 - For the reliability of many welded structures like pipelines or offshore wind parks, it is necessary to ensure high mechanical properties such as strength and toughness of the entire material. In order to improve quality of weld joints, flux cored rods and wires containing different nanoparticles (ZrO2, LaB6 and Al2O3) were manufactured and welded with the TIG and MAG welding processes. Influence of these nanoparticles on the microstructure and mechanical properties of the weld joints were investigated. The acicular ferrite and improved strength of the weld metals were observed by the addition of 0.2 wt.% of iron powder with ZrO2 nanoparticles to the filling of flux cored wires. Y1 - 2020 SN - 1612-3433 VL - 19 IS - 1 SP - 48 EP - 53 ER - TY - GEN A1 - Baena-Moreno, Francisco Manuel A1 - González-Castaño, Miriam A1 - Navarro de Miguel, Juan Carlos A1 - Miah, Kamal Uddin Mohammad A1 - Ossenbrink, Ralf A1 - Odriozola, José Antonio A1 - Arellano-García, Harvey T1 - Stepping toward Efficient Microreactors for CO2 Methanation: 3D Printed Gyroid Geometry T2 - ACS Sustainable Chemistry & Engineering N2 - This work presents a comparative study towards the development of efficient micro-reactors based on 3D-printed structures. Thus, the study evaluates the influence of the metal substrate geometry on the performance of structured catalysts for the CO2 methanation reaction. For this purpose, 0.5%Ru–15%Ni/MgAl2O4 catalyst is wash coated over two different micro-monolithic metal substrates: a conventional parallel channel honeycomb structure and a novel 3D-printed structure with a complex gyroid geometry. The effect of the metal substrate geometry is analyzed for several CO2 sources including ideal flue gas atmospheres, the presence of residual CH4 and CO in the flue gas, as well as simulated biogas sources. The advantages of the gyroid-3D complex geometries over the honeycomb structures are shown for all evaluated conditions, providing at the best-case scenario a 14% improvement of CO2 conversion. Moreover, this contribution shows that systematically tailoring geometrical features of structured catalysts becomes an effective strategy to achieve improved catalysts performances independent of the flue gas composition. By enhancing the transport processes and the gas-catalyst interactions, the employed gyroid 3D metal substrates enable boosted CO2 conversions and greater CH4 selectivity within diffusional controlled regimes. KW - CO2 methanation KW - gyroid geometry KW - CH4 selectivity KW - gyroid-3D complex Y1 - 2021 U6 - https://doi.org/10.1021/acssuschemeng.1c01980 SN - 2168-0485 VL - 9 IS - 24 SP - 8198 EP - 8206 ER - TY - GEN A1 - Shapovalov, Oleg A1 - Shapovalova, Mariia A1 - Ossenbrink, Ralf A1 - Heckel, Thomas A1 - Michailov, Vesselin A1 - Weiß, Sabine A1 - Gaal, Mate T1 - Verbessern der Korrosionsbeständigkeit eines hochtemperaturbeständigen Ultraschalldämpfungskörpers mittels Laserstrahl-Auftragschweißen T2 - DVS Berichte 2021 N2 - Während in einem konventionellen Ultraschallprüfkopf ein Kunststoffdämpfungskörper mit Kleber oder Öl an einen Piezoschwinger angekoppelt ist, werden als Hochtemperaturlösung feinporöse sintermetallische Dämpfungsmaterialien mit einer Flüssigglasankopplung eingesetzt. Um dabei das Sintermetall vor dem korrosiven Angriff der Glasschmelze zu schützten, wird am Dämpfungskörper gegenwärtig Gold- oder Platinfolie zeit- und kostenaufwendig appliziert. In der aktuellen Arbeit wurde eine Methode zum Korrosionsschutz der sintermetallischen Oberfläche aus rostfreiem Stahl mittels Laser-Pulverauftragschweißen entwickelt. Im Laufe einer Schweißparameterstudie auf dem Substratmaterial aus massivem rostfreiem Stahl wurde die Eignung unterschiedlicher Auftragsmaterialien auf Nickel- und Kobaltbasis untersucht. Dabei wurde zunächst der Einfluss verschiedener Schweißparameter wie Laserleistung, Vorschubgeschwindigkeit und Pulvermenge auf die Auftragsqualität (Nahtform, Vermischungsgrad, Porosität) metallografisch bewertet. Anschließend wurden die aufgetragenen Schichten hinsichtlich ihrer Korrosionsbeständigkeit getestet. Der Kontakt mit einer flüssigen Glasmischung bei 500 °C hat bei keiner der beschichteten Proben sichtbare Korrosionswirkung gezeigt. Als Resultat der Schweißparameterstudie haben sich besonders die nickelbasierten Pulver als gut geeignete Materialien für den Prozess gezeigt. Die identifizierten Schweißparameter wurden im nächsten Schritt erfolgreich an das sintermetallische Substrat angepasst. Y1 - 2021 UR - https://www.dvs-ev.de/call4papers/abstract.cfm?vid=109&pid=7032 SN - 978-3-96144-147-1 SP - 370 EP - 377 PB - DVS Media GmbH CY - Düsseldorf ER - TY - GEN A1 - Kaneneks, Michael A1 - Kloshek, Alexander A1 - Morozova, Iuliia A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin A1 - Sembol, Ronny T1 - WAAM eines Zwischenstücks für die Bergbauausrüstung T2 - DVS Bericht 2021 N2 - Die lichtbogenbasierte additive Fertigung (WAAM) ist ein vielversprechendes Werkzeug, um die Ersatzteilbereitstellung von schwer verfügbaren oder aufwendig herstellbaren Einzelkomponenten in kürzester Zeit zu gewährleisten. Die Straffung innerbetrieblicher Abläufe sowie die Minimierung von Herstellungs- und Lagerkosten sind eine direkte Folge. Vor dem Einsatz im Betrieb muss sichergestellt werden, dass die Bauteile fehlerfrei additiv herstellbar sind und die mechanischen Eigenschaften den Anforderungen konventionell gefertigter Werkstücke entsprechen. Ein solcher Nachweis konnte am Beispiel eines additiv hergestellten Zwischenstücks für die Bergbauausrüstung mit einer abschließenden Charakterisierung der Werkstoffeigenschaften erfolgreich geführt werden. Das Zwischenstück mit einem Gewicht von ca. 31 kg zur Verbindung von geometrisch unterschiedlichen Profilen wurde ausgehend von einer Grundplatte aus S355-J2+N beidseitig additiv mit einem Massivdraht G3Si1 aufgebaut. Die Ermittlung geeigneter Parameter, Schweißfolgen und Zwischenlagentemperaturen erfolgte experimentell mit begleitenden metallografischen Untersuchungen. Nach erfolgreicher Fertigung wurden die mechanischen Eigenschaften des Zwischenstücks bestimmt sowie die Festigkeit und Zähigkeit mit den geforderten Werkstoffkennwerten des bisher eingesetzten konventionellen Konstruktionsmaterials verglichen. KW - Schweißtechnik KW - WAAM KW - Wire Arc Additiv Manufacturing KW - Additive Fertigung KW - Lichtbogenauftragschweißen Y1 - 2021 UR - https://www.dvs-ev.de/call4papers/abstract.cfm?vid=109&pid=7030 SN - 978-3-96144-147-1 VL - 2021 SP - 315 EP - 323 PB - DVS Media GmbH CY - Düsseldorf ER - TY - GEN A1 - Jokisch, Torsten A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin T1 - Heat source model for electron beam welding of nickel-based superalloys T2 - Materials testing : Materialprüfung Y1 - 2021 U6 - https://doi.org/10.1515/mt-2020-0002 SN - 2195-8572 SN - 0025-5300 VL - 63 IS - 1 SP - 17 EP - 28 ER - TY - GEN A1 - Valkov, Stefan A1 - Kotlarski, Georgi A1 - Ormanova, Maria A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Petrov, Peter A1 - Michailov, Vesselin T1 - Crystallography and Mechanical Properties of Wire Arc Additively Manufactured Al5356 Components T2 - Comptes Rendus de L'Academie Bulgare des Sciences N2 - In this study, we present results of the evolution of the crystallographic texture and imperfections, as well as the corresponding mechanical properties of wire and arc additively manufactured (WAAM) Al5356 specimens, studied by X-ray diffraction (XRD) and tensile testing, respectively. The results show that the phase composition is in the form of a face-centred cubic (fcc) crystal structure, corresponding to the base material, as well as some traces of oxide phase Al2O3. The WAAM specimen growing is accompanied by a slight change in the preferred crystallographic orientation, from (111) to (200) and a decrease in the imperfections concentration. Also, it was found that the ultimate tensile strength (UTS), yield strength (YS), and elongation slightly decrease from the initial to the more advanced stages of growth. KW - wire arc additive manufacturing KW - Al5356 alloy KW - crystallography KW - mechanical properties Y1 - 2021 U6 - https://doi.org/10.7546/CRABS.2021.06.03 SN - 1310-1331 VL - 74 IS - No. 6 SP - 820 EP - 827 ER - TY - GEN A1 - Wasilewski, Eric A1 - Kaneneks, Michael A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin T1 - Laserstrahlschweißen – Verzugs- und Kaltrissminimierung durch simulationsbasierte Steuerung T2 - DVD Congress 2020 : Große Schweißtechnische Tagung : DVS Campus : Vorträge der Online-Veranstaltungen vom 14. bis 18. September 2020 N2 - Leichtbau und das Streben nach Ressourcen- und Energieeffizienz fördern in den letzten Jahren vermehrt den Einsatz hochfester Stähle. Das Laserstrahlschweißen dieser Werkstoffe wird in der industriellen Großserienferti-gung zur effizienten Herstellung hochpräziser Bauteile und Komponenten mit höchsten Qualitätsanforderungen eingesetzt. Die Vermeidung schweißbedingter Fehler wie Schweißverzug und Kaltrissbildung sind dabei von ent-scheidender Bedeutung. Konventionelle Anwendungen erfüllen diesen Anspruch derzeit bedingt durch sehr enge Prozesstoleranzen und die Auswahl unkritischer Werkstoffe, was die Potentiale der Fügeverbindung begrenzt. Auf Basis von FE-Schweißprozesssimulationen konnten Konzepte entwickelt werden, welche eine Verzugs- und Riss-minderung durch aktive Steuerung des Laserschweißprozesses ermöglichen. Die zugrundeliegenden Modelle be-rücksichtigen zum einen das schweißbedingte Temperaturfeld, Gefügeumwandlungen und Eigenspannungen für die Berechnung des Verzugs. Zudem wird die lokale Wasserstoffkonzentration berechnet und die Ergebnisse der Schweißprozesssimulation mittels eines Kaltrisstools bewertet, welches werkstoffspezifische Risskriterien enthält. Die Fähigkeit das Verzugs- und Kaltrissverhalten abzubilden, eröffnet die Möglichkeit zur Parametervariation. Aus den erhobenen Daten wurden Konzepte der aktiven Krafteinleitung mit einer dynamischen Werkstückeinspannung abgeleitet, die zu Verzugs- und Kaltrissminimierung führen und die Schweißbarkeit hochfester Werkstoffe fördern. Y1 - 2019 SN - 978-3-96144-098-6 SP - 9 PB - DVS Media GmbH CY - Düsseldorf ER - TY - GEN A1 - Jokisch, Torsten A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin A1 - Böttger, Bernd A1 - Senger, Aleksej T1 - Analysis of temperature field during electron beam welding of hot crack sensitive nickel base alloy T2 - IEBW International Electron Beam Welding Conference: lectures of the 6th International Conference taking place online on 9 to 10 March 2021 N2 - The use of temperature-resistant nickel-based superalloys in the field of industrial gas turbines is increasing due to constantly rising operating temperatures. Among different joining methods the electron beam welding is commonly used for manufacturing of turbine components because it provides a reduced heat input. However, the highly localized beam impact causes high temperature gradients and leads to the formation of hot cracks. Welding of such material with a high brittle temperature range is challenging and needs an increasing effort of process adaption. Experiments indicate a significant improvement of hot crack susceptibility when welding outside the common welding parameter range. To understand these observations a study of the temperature field in the specimens using numerical simulations was carried out. For this purpose, a validated simulation model was used. Special attention was paid to the domain in close vicinity of the weld pool. The results illustrate the velocity of solidification isotherm as well as the temperature rates when crossing the melting point. Finally, the relations between thermal fields, crack types and distributions in the different specimens are discussed. Y1 - 2021 UR - https://www.dvs-media.eu/media/pdf/DVS_Bericht_368_Inhalt.pdf SN - 978-3-96144-133-4 SP - 81 EP - 87 PB - DVS Media GmbH CY - Düsseldorf ER - TY - GEN A1 - Piott, Michael A1 - Werber, Alexandra A1 - Schleuss, Leander A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin T1 - Numerical and experimental analysis of heat transfer in resistance spot welding process of aluminum alloy AA5182 T2 - International Journal of Advanced Manufacturing Technology N2 - In this work, a numerical model and experiments are used to investigate heat transfer processes during resistance spot welding process of aluminum. For this purpose, calibrated heat transfer conditions and thermal contact conductance are transferred from a previous work to a coupled thermal-electrical-mechanical finite element model. First, all domains of the numerical model are validated by an experimental study. The experimental setup includes the measurement of current, voltage drops, electrode force, electrode displacement, and temperatures while two sheets of aluminum alloy AA5182 are joined. Computational results show that most of the generated Joule heat (78%) is stored in the electrodes or transferred to cooling water until the end of weld time. Heat transfer by natural convection and thermal radiation is very small and can in general be neglected for complete process. Afterwards, the influence of electrode water-cooling on welding process is investigated numerically. The results indicate that the generation of Joule heat and thermal energy of the sheets during weld time is only slightly affected by electrode water-cooling. As a consequence, water-cooling conditions do not affect nugget formation. In contrast, electrode water-cooling highly influences cooling conditions during hold time. KW - Aluminum resistance spot welding KW - Heat transfer KW - FE-simulation KW - Electrode water-cooling KW - Instrumented experiments Y1 - 2020 U6 - https://doi.org/10.1007/s00170-020-06197-7 SN - 0268-3768 SN - 1433-3015 VL - Vol. 111 IS - 5-6 SP - 1671 EP - 1682 ER - TY - GEN A1 - Piott, Michael A1 - Werber, Alexandra A1 - Schleuss, Leander A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin T1 - A study of the heat transfermechanism in resistance spot welding of aluminum alloys AA5182 and AA6014 T2 - International Journal of Advanced Manufacturing Technology N2 - This work investigates heat transfer mechanism of aluminum resistance spot welding process. The main target is to determine thermal contact conductance and heat transfer coefficients for natural convection and thermal radiation at ambient air and forced convection inside the water-cooled electrodes. For this purpose, the heat transfer of hot sheets in a welding gun for aluminum alloys AA5182 and AA6014 is analyzed experimentally and numerically. The transient temperature field is measured by several thermocouples in a simplified experimental setup. Subsequent thermal-mechanical coupled finite element simulations of the experiments were used to calibrate the heat transfer coefficients. The heat transfer coefficient for natural convection and thermal radiation to ambient air is 13 W m2 K and the heat transfer coefficient for forced convection of electrode water-cooling is 25,000 W m2 K. The results indicate that the thermal contact conductance can be assumed ideal for welding process. Additionally, the finite element model is validated by the measured and calculated dissipated heat due to forced convection. Finally, a sensitivity analysis is performed to compare the influence of maximum and minimum heat transfer coefficients of forced convection (water-cooling) on transient temperature field and dissipated heat of sample AA5182. KW - Aluminum resistance spot welding KW - Heat transfer KW - FE simulation KW - Thermal contact conductance KW - Electrode water-cooling Y1 - 2020 U6 - https://doi.org/10.1007/s00170-020-05650-x SN - 0268-3768 SN - 1433-3015 VL - Vol. 111 SP - 263 EP - 271 ER - TY - GEN A1 - Jokisch, Torsten A1 - Doynov, Nikolay A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin T1 - Analysis of Local Strain Evolution during Electron Beam Welding of Hot Crack Sensitive Nickel Base Conventionally Cast Alloy 247 LC CC T2 - Journal of Materials Engineering and Performance N2 - Among different joining methods, the electron beam welding is recently applied for manufacturing of turbine components from temperature-resistant nickel-based conventionally cast Alloy 247 LC CC. However, the high tendency to hot cracking, in particular the formation of solidification cracks, remains a major challenge. Experiments indicate a significant reduction in hot cracks if the welding is performed outside the common welding parameter range. To understand these observations, a study of local thermo-mechanical conditions during electron beam welding of Alloy 247 samples was carried out using numerical simulations. The results were subsequently compared with reference test welds. For this purpose, a finite element model for coupled transient thermal and mechanical analysis was created and used. The work presents a comparative analysis of the evolution of strain components in brittle temperature range during cooling, considering the distribution and orientation of the cracks. Various relations between local strain kinetics and crack appearance, with notable influence of the plastic strain vector, were observed. Finally, the aspects of assessment of hot crack susceptibility with aid of thermo-mechanical welding simulation are discussed. KW - computational welding mechanics KW - electron beam welding KW - hot crack susceptibility KW - modeling of welding and joining KW - nickel-based alloys Y1 - 2022 U6 - https://doi.org/10.1007/s11665-022-06660-4 SN - 1544-1024 VL - 31 IS - 9 SP - 7009 EP - 7017 ER - TY - GEN A1 - Meeß, Joachim A1 - Anasenzl, Manuel A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin A1 - Singh, Reeti A1 - Kondas, Jan T1 - Cold Gas Spray Inner Diameter Coatings and Their Properties T2 - Journal of Thermal Spray Technology N2 - Due to recent developments, cold gas spraying technology can now be used to create inner diameter coatings for cylinder inner diameters > 70 mm. The present investigations focus on the process optimization and the specific properties of cold gas spray inner diameter coatings created with three different alloy steel powder variants. The cold gas spray coating properties were compared with the corresponding properties of coatings created with twin wire arc technology. The particle velocities and deposition efficiencies were measured with the aim of optimizing the process parameters. The most suitable process parameters were used to analyze the microstructure of the deposited coating in terms of porosity and interface quality. Furthermore, the hardness and adhesion strength properties of the coatings were measured. In addition, the different liners were honed, and the achievable surface roughness of each was determined. Finally, wear resistance was evaluated using ball-on-disk testing. The results reveal that with the maximum process parameters, the cold gas spray coating properties are comparable to the twin wire arc coating properties. Further investigations are necessary to determine whether cold gas spraying is a feasible alternative to the current series production process for cylinder surface coatings. KW - automotive KW - cold gas spraying (CGS) KW - cylinder block application KW - inner diameter coating KW - wear resistance Y1 - 2022 U6 - https://doi.org/10.1007/s11666-022-01365-5 SN - 1544-1016 VL - 31 SP - 1712 EP - 1724 ER - TY - GEN A1 - Meeß, Joachim A1 - Anasenzl, Manuel A1 - Ossenbrink, Ralf A1 - Michailov, Vesselin T1 - Influence of Particle Velocities on Adhesion Strength of Cold Spray Inner Diameter Coatings T2 - Journal of Thermal Spray Technology N2 - Due to the recent developments of hardware components and the hereby resulting ability to increase process parameters, the application area of the cold gas spray technology is expanding quickly. The present research focuses on the influence of working gas pressure and working gas temperature on the adhesive strength of inner diameter coatings, which were produced with two different alloy steel powder variants. Gas pressure and gas temperature were varied in four different parameter sets. At first, the powder variants were examined for morphology and particle size distribution. Secondly, the influence of four different process parameters on the achievable particle velocity was measured. In addition, the arithmetical mean height (Sa) of the coating was measured in order to determine the effect of the four parameter sets on the achievable surface roughness. Furthermore, the impact of the process parameters on the steel particles’ penetration depth into the aluminum substrate was examined. Finally, adhesion strength measurements of the inner diameter coatings were carried out. The results reveal that with rising process parameters, the particle velocity increases, and the achievable surface roughness is lowered. It was also shown that the penetration depth of the particles into the substrate increases with increasing particle velocity. In addition, this study demonstrated a dependence of the process parameters on the adhesion strength for inner diameter coatings. KW - adhesion strength KW - cold gas spraying (cgs) KW - cylinder block application KW - inner diameter coating KW - particle velocity Y1 - 2022 U6 - https://doi.org/10.1007/s11666-022-01439-4 SN - 1544-1016 VL - 31 IS - 7 SP - 2025 EP - 2038 ER -