@misc{JokischDoynovOssenbrinketal., author = {Jokisch, Torsten and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Analysis of Local Strain Evolution during Electron Beam Welding of Hot Crack Sensitive Nickel Base Conventionally Cast Alloy 247 LC CC}, series = {Journal of Materials Engineering and Performance}, volume = {31}, journal = {Journal of Materials Engineering and Performance}, number = {9}, issn = {1544-1024}, doi = {10.1007/s11665-022-06660-4}, pages = {7009 -- 7017}, abstract = {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.}, language = {en} } @misc{MeessAnasenzlOssenbrinketal., author = {Meeß, Joachim and Anasenzl, Manuel and Ossenbrink, Ralf and Michailov, Vesselin and Singh, Reeti and Kondas, Jan}, title = {Cold Gas Spray Inner Diameter Coatings and Their Properties}, series = {Journal of Thermal Spray Technology}, volume = {31}, journal = {Journal of Thermal Spray Technology}, issn = {1544-1016}, doi = {10.1007/s11666-022-01365-5}, pages = {1712 -- 1724}, abstract = {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.}, language = {en} } @misc{MeessAnasenzlOssenbrinketal., author = {Meeß, Joachim and Anasenzl, Manuel and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Influence of Particle Velocities on Adhesion Strength of Cold Spray Inner Diameter Coatings}, series = {Journal of Thermal Spray Technology}, volume = {31}, journal = {Journal of Thermal Spray Technology}, number = {7}, issn = {1544-1016}, doi = {10.1007/s11666-022-01439-4}, pages = {2025 -- 2038}, abstract = {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.}, language = {en} } @misc{EvdokimovJasiewiczDoynovetal., author = {Evdokimov, Anton and Jasiewicz, Filip and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Simulation of surface heat treatment with inclined laser beam}, series = {Journal of Manufacturing Processes}, volume = {81}, journal = {Journal of Manufacturing Processes}, issn = {1526-6125}, doi = {10.1016/j.jmapro.2022.06.051}, pages = {107 -- 114}, abstract = {The beam inclination leads to a change in the laser spot size on the material surface. The higher the inclination, the larger the irradiated area and the lower the laser intensity. Moreover, if the material surface is outside of the beam focal plane, the intensity distribution profile becomes asymmetric. In this study, a heat source model, which calculates the intensity distribution on the workpiece surface as a function of beam parameters (beam waist, divergence half-angle) and process parameters (laser power, incidence angle, and distance to focal plane) was developed. The applicability of the heat source model was demonstrated by simulating 4 different laser hardening regimes. Once the heat efficiency coefficient had been calibrated the developed finite-element model allowed computation of temperatures while hardening with perpendicular laser beams as well as with inclined beams. The open-source software FEniCSx was used for the finite element computations. The mathematical formulation, required for performing temperature simulations with FEniCSx was briefly introduced.}, language = {en} } @misc{ShapovalovSeidlitzOstetal., author = {Shapovalov, Oleg and Seidlitz, Holger and Ost, Lucas and Doynov, Nikolay and Kuke, Felix and Ambrosio, Marcello and Michailov, Vesselin}, title = {Substitution von metallischen Schubfeldern im Fahrzeugbau durch f{\"u}getechnische Integration von FKV-Schalen}, series = {DVS Congress 2022, Große Schweißtechnische Tagung, DVS Campus ; Kurzfassungen der Vortr{\"a}ge der Veranstaltung in Koblenz vom 19. bis 21. September 2022 ; (Langfassungen der Beitr{\"a}ge auf USB-Karte)}, journal = {DVS Congress 2022, Große Schweißtechnische Tagung, DVS Campus ; Kurzfassungen der Vortr{\"a}ge der Veranstaltung in Koblenz vom 19. bis 21. September 2022 ; (Langfassungen der Beitr{\"a}ge auf USB-Karte)}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-189-1}, pages = {385 -- 393}, abstract = {Durch den strukturellen Einsatz von Faser-Kunststoff-Verbunden (FKV) lassen sich hochwertige gewichtsoptimierte Karosserien in Mischbauweise umsetzen. Die untersuchte CMT-Pin-Schweißtechnik zur Verbindung von thermoplastischen Organoblechen mit St{\"a}hlen bietet, im Vergleich zu anderen Verfahren, neben einer einseitigen Zug{\"a}nglichkeit, ein hohes Leichtbaupotenzial. Das Vorhaben wurde auf eine werkstoff-, prozess- und konstruktionsgerechte Umsetzung des Verfahrens ausgerichtet. Auf Basis experimenteller und numerischer Untersuchungen wurde eine Methode zum Vorw{\"a}rmen von Organoblechen mittels Infrarotstrahlung entwickelt. Die Eignung der CMT-Pin-Technologie wurde sowohl f{\"u}r das F{\"u}gen von karbon- als auch glasfaserverst{\"a}rktem PA6 betrachtet. Als Bewertungskriterien wurden das Schweißgut sowie der Faser- und Matrixerhalt in Abh{\"a}ngigkeit der Schweißparameter untersucht. Das entwickelte Verfahren wurde mit herk{\"o}mmlichen F{\"u}gemethoden bzgl. der in Kopf- und Scherzugversuchen ermittelten Festigkeiten verglichen. Zur Bestimmung der Best{\"a}ndigkeit der Verbindungen gegen unterschiedliche Witterungsbedingungen wurden Salzspr{\"u}hnebel- und Wechselkorrosionstests durchgef{\"u}hrt. Mit dem F{\"u}gen von Hutprofilen wurde die Anwendung der entwickelte CMT-Pin-Technik am Tunnel sowie den L{\"a}ngs- und Quertr{\"a}gern der Bodenstruktur eines Kraftfahrzeugs demonstriert.}, language = {de} } @misc{MorozovaKrolickaObrosovetal., author = {Morozova, Iuliia and Kr{\´o}licka, Aleksandra and Obrosov, Aleksei and Yang, Yitong and Doynov, Nikolay and Weiß, Sabine and Michailov, Vesselin}, title = {Precipitation phenomena in impulse friction stir welded 2024 aluminium alloy}, series = {Materials Science and Engineering: A}, journal = {Materials Science and Engineering: A}, issn = {0921-5093}, doi = {10.1016/j.msea.2022.143617}, pages = {1 -- 11}, abstract = {Microhardness variations across the friction stir welded (FSW) and impulse friction stir welded (IFSW) AA2024-T351 joints have been elucidated by the transformations of the S-Al2CuMg phase with a special focus on a distinguished hardness peak within the heat-affected zone (HAZ) of the impulse welds. The increase in hardness within the stir zone (SZ) originated from the partial re-precipitation of the initial Guinier-Preston-Bagaryatsky zones (GPB) and metastable S needles, previously dissolved.) Formation and growth of stable S precipitates via coalescence accounted for the softening through the thermo-mechanically affected zone (TMAZ). The peak strengthening within the HAZ of the IFSW joints was mainly caused by the dense needle-shaped S particles, which can be explained by a mutual influence of the process specific temperature and strain cycles. Dislocations and subgrain boundaries introduced to the material due to plastic deformation facilitated the nucleation of strengthening S precipitates in the HAZ. It demonstrates that the impact of deformation should be considered by the characterization of the precipitation development in the HAZ.}, language = {en} } @misc{HantelmannFritzscheMichailovetal., author = {Hantelmann, Cord and Fritzsche, Sebastian and Michailov, Vesselin and Boywitt, Ralf}, title = {Entwicklung geschweißter Konstruktionen aus Aluminiumsandwich}, series = {DVS Congress 2022, Große Schweißtechnische Tagung, DVS Campus ; Kurzfassungen der Vortr{\"a}ge der Veranstaltung in Koblenz vom 19. bis 21. September 2022 ; (Langfassungen der Beitr{\"a}ge auf USB-Karte)}, journal = {DVS Congress 2022, Große Schweißtechnische Tagung, DVS Campus ; Kurzfassungen der Vortr{\"a}ge der Veranstaltung in Koblenz vom 19. bis 21. September 2022 ; (Langfassungen der Beitr{\"a}ge auf USB-Karte)}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-189-1}, pages = {245 -- 251}, abstract = {Im vorgestellten Projekt wurden werkstoff- und konstruktionsgerechte Knotenformen aus Aluminiumschaumsandwich gestaltet und mit unterschiedlichen Schweißverfahren, wie dem Metall-Inertgas-Schweißen und dem R{\"u}hrreibschweißen, gef{\"u}gt und gepr{\"u}ft. In umfangreichen Untersuchungen wurden die Knoten, der Sandwichverbund und die Einzelkomponenten des Sandwich, Schaum und Decklagen, anhand der statischen Festigkeit und Schwingfestigkeit bewertet. Zus{\"a}tzlich wurden innere Sch{\"a}digungsmechanismen betrachtet. Mit experimentellen und numerischen Nachweismethoden konnte die anwendungssichere Knotengestaltung, -anbindung und -berechnung der unterschiedlichen Verbindungstypen umgesetzt werden. Die Ergebnisse wurden im Rahmen der Nachweisf{\"u}hrung gegen{\"u}bergestellt und hinsichtlich eines praxisgerechten Einsatzes nach FKM-Richtlinie bzw. Eurocode9 bewertet. Mit den ermittelten Ergebnissen wurde die bisherige Gestaltungs- und F{\"u}gerichtlinie um neue Verbindungstypen erweitert.}, language = {de} } @misc{KotlarskiOrmanovaOssenbrinketal., author = {Kotlarski, Georgi and Ormanova, Maria and Ossenbrink, Ralf and Nikitin, Alexander and Doynov, Nikolay and Valkov, Stefan and Michailov, Vesselin}, title = {Fabrication and Characterization of Wire Arc Additively Manufactured AlSi5 Structures}, series = {Metals}, volume = {12}, journal = {Metals}, number = {11}, issn = {2075-4701}, abstract = {For the purpose of this research, single track details were manufactured in the shape of thin walls with a length of 100 mm and a height of 80 mm. Two welding speeds were chosen for this experiment-13.3 mm/s and 20.0 mm/s corresponding to the following heat inputs: 120 J/mm and 80 J/mm. The gas metal arc welding (GMAW) method was used for the build-up of the specimens in the cold arc pulse mode. The structure of the specimens was studied using X-ray diffraction (XRD) analysis carried out with CuKα radiation with a wavelength of 1.5406 Ǻ, optical microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). Furthermore, the Vickers hardness of the samples was determined using a ZwickRoell DuraScan 10/20 G5 unit at a force of 1 N. A preferred crystallographic orientation towards the (200) plane was observed in all cases, however a vastly textured structure was observed with inclusions of peaks in the (111), (220), and (311) crystallographic planes. The full width at half maximum (FWHM) of samples taken from different stages of build-up was calculated indicating an increase of the dislocation density at the more advanced stages of specimen growth. Despite that an increase of the hardness was observed towards the top of both specimens. This is attributed to the change in the structure of the αAl + Si formations from an irregular one at the bottom of the specimens, towards a fibrous one at the top. The results are discussed in regard to the optimization of the build-up process during wire arc additive manufacturing (WAAM).}, language = {en} } @misc{MiahKloshekGonzalezCastanoetal., author = {Miah, Kamal Uddin Mohammad and Kloshek, Alexander and Gonz{\´a}lez-Casta{\~n}o, Miriam and Kehm, Christian and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Herstellen hocheffektiver Mikroreaktoren durch selektives Laserstrahlschmelzen}, series = {DVS Congress 2022, Große Schweißtechnische Tagung, DVS Campus ; Kurzfassungen der Vortr{\"a}ge der Veranstaltung in Koblenz vom 19. bis 21. September 2022 ; (Langfassungen der Beitr{\"a}ge auf USB-Karte)}, journal = {DVS Congress 2022, Große Schweißtechnische Tagung, DVS Campus ; Kurzfassungen der Vortr{\"a}ge der Veranstaltung in Koblenz vom 19. bis 21. September 2022 ; (Langfassungen der Beitr{\"a}ge auf USB-Karte)}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-189-1}, pages = {708 -- 713}, abstract = {Das pulverbasierte 3D-Metalldrucken erm{\"o}glicht die Fertigung von hochkomplexen Integralbauteilen, die als Tr{\"a}gerstruktur f{\"u}r Mikroreaktoren benutzt werden. Nach einer Beschichtung der Struktur mit einem Katalysatormaterial, k{\"o}nnen diese Mikroreaktoren h{\"o}chst effizient f{\"u}r die CO2-Methanisierung eingesetzt werden. Durch die additive Fertigung mit dem selektiven Laserstrahlschmelzen (SLM) wurden adaptierte dreidimensionale periodische Gitterstrukturen mit sehr geringen Wandst{\"a}rken hergestellt. Diese weisen ein sehr g{\"u}nstiges Verh{\"a}ltnis von Oberfl{\"a}che zu Volumen (TPMS - Triply periodic minimal surface) auf. Des Weiteren zeigen die TPMS-Strukturen vorteilhafte Str{\"o}mungseigenschaften, die sowohl f{\"u}r die Beschichtung mit dem Katalysator-Material als auch die Durchstr{\"o}mung mit den Reaktionsmedien im Betrieb essentiell sind. So ist es beispielsweise m{\"o}glich, durch die Variation der Dimension einer TPMS-Struktur die Oberfl{\"a}che pro Volumeneinheit, den hydraulischen Durchmesser des Reaktors und somit auch den Transportprozess des Fluids deutlich zu verbessern. Diese Faktoren erm{\"o}glichen eine effektivere Gas-Katalysator-Reaktion. Im Vergleich zu Mikroreaktorstrukturen aus den traditionellen Herstellungsverfahren liefern die additiv gefertigten Strukturen sowohl eine h{\"o}here CO2-Umwandlungsrate als auch eine CH4-Selektivit{\"a}t innerhalb des diffusionskontrollierten Bereichs.}, language = {de} }