@inproceedings{SchleussBrobeckOssenbrinketal., author = {Schleuß, Leander and Brobeck, Andreas F. W. and Ossenbrink, Ralf and Polzin, Ralf and Michailov, Vesselin}, title = {Neuartige Elektroden zum Rollennahtschweißen mit nichtlinearem Schweißpfad}, series = {Große Schweißtechnische Tagung, 15.-17.09.15}, booktitle = {Große Schweißtechnische Tagung, 15.-17.09.15}, publisher = {DVS Media}, address = {D{\"u}sseldorf}, isbn = {978-3-945023-46-4}, pages = {185 -- 190}, abstract = {Beim Rollennahtschweißen von Blechen mit eingebrachten Versteifungselementen wie Sicken oder regelm{\"a}ßig angeordneten Strukturen f{\"u}hren lineare Schweißpfade unter Verwendung klassischer Rollenelektroden zur teilweisen bzw. vollst{\"a}ndigen Einebnung dieser Versteifungselemente. Dadurch kann die positive Wirkung der Versteifungselemente reduziert bzw. vollst{\"a}ndig aufgehoben werden. Somit m{\"u}ssen neue Wege f{\"u}r das Rollennahtschweißen von gesickten oder strukturierten Blechen erarbeitet werden. Es wurden zwei neuartige Elektroden mit ver{\"a}nderten Geometrien an den Kontaktfl{\"a}chen entwickelt, welche die Topologie der Bleche ber{\"u}cksichtigen und eine Einebnung vermeiden. Eine der Elektroden besitzt eine periodisch unterbrochene Kontaktfl{\"a}che, die zweite eine laterale Profilierung mit in Schweißrichtung nichtlinearer Form der Kontaktfl{\"a}che. Das Verhalten beim Schweißen wurde durch Schweißversuche bestimmt. Es wurden Schweißbereichsdiagramme bzw. Prozessfenster abgeleitet. Die Verbindungseigenschaften wurden durch Metallografie-, Festigkeits-, Druck- und Dichtheitsuntersuchungen validiert. Als Vergleich und Referenz dienen Schweißuntersuchungen mit konventionellen Rollennahtelektroden. Die geschweißten Bleche haben Wabenstrukturen als regelm{\"a}ßig angeordnete Versteifungselemente mit unterschiedlichen Elementtiefen. Diese Bleche finden vorrangig Anwendung im Fahrzeugbau, in der Investitionsg{\"u}terindustrie und im Bauwesen. Aufgrund dieser Branchen und f{\"u}r zuk{\"u}nftige Anwendungen im W{\"a}rmetauscher- und Beh{\"a}lterbau sowie zur Ermittlung grundlegender Kenntnisse wurden die Untersuchungen an Werkstoffqualit{\"a}ten DC04 und 1.4301 mit Blechdicken von 0,5 mm und 0,7 mm durchgef{\"u}hrt. Die Untersuchungsergebnisse zeigen Unterschiede bei den Prozessparametern und der Auspr{\"a}gung der Verbindung in Abh{\"a}ngigkeit von der geschweißten Struktur, dem ausgew{\"a}hlten Schweißpfad und des geschweißten Werkstoffes gegen{\"u}ber den Referenzschweißungen. Eine anschließende Optimierung f{\"u}hrte zu einer vergleichbar guten Schweißnahtqualit{\"a}t sowohl bei Erhalt der Versteifungselemente mit den neuen Elektroden als auch bei deren Einebnung mit konventionellen Elektroden in Referenz zu Schweißuntersuchungen am ebenen Blech.}, language = {de} } @inproceedings{SchleussBrobeckOssenbrinketal., author = {Schleuß, Leander and Brobeck, Andreas F. W. and Ossenbrink, Ralf and Polzin, Ralf and Michailov, Vesselin}, title = {Rollennahtschweißen strukturierter Bleche mit neuartigen Elektroden}, series = {Widerstandsschweißen, 23. Sondertagung in Duisburg am 29. und 30. Juni 2016}, booktitle = {Widerstandsschweißen, 23. Sondertagung in Duisburg am 29. und 30. Juni 2016}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-945023-75-4}, pages = {230 -- 240}, abstract = {Bleche mit regelm{\"a}ßig angeordneten steifigkeitserh{\"o}henden Strukturen werden zunehmend in Kon-struktionen zur Erh{\"o}hung der Steifigkeit d{\"u}nner Bleche bzw. von kompletten Bauteilen verwendet. Damit diese Bauteile wirtschaftlich verarbeitet werden k{\"o}nnen, bietet das Rollennahtschweißen mit seinen hohen Prozessgeschwindigkeiten und ohne notwendigen Einsatz von Zusatzwerkstoffen bzw. Schweißhilfsstoffen eine kosteng{\"u}nstige Alternative zu anderen Verfahren. Beim Rollennahtschweißen strukturierter Bleche f{\"u}hren jedoch klassische Rollennahtelektroden zur teilweisen bzw. vollst{\"a}ndigen Einebnung der Versteifungselemente, sodass deren positive Wirkung reduziert bzw. vollst{\"a}ndig auf-gehoben werden kann. Die geschweißten Bleche haben Wabenstrukturen mit unterschiedlichen Elementtiefen als regelm{\"a}ßig angeordnete Versteifungselemente. Die Bleche finden vorrangig Anwendung im Fahrzeugbau und im Bauwesen. Aufgrund dieser Branchen und f{\"u}r zuk{\"u}nftige Anwendungen im W{\"a}rmetauscher- und Beh{\"a}l-terbau wurden die Untersuchungen an Werkstoffqualit{\"a}ten DC04 und X5CrNi 18-10 mit Blechdicken von 0,5 mm und 0,7 mm durchgef{\"u}hrt. Die entwickelten neuartigen Elektroden ber{\"u}cksichtigen die Topologie der Bleche, um eine Einebnung der strukturierten Bleche zu vermeiden. Daher wurden Elektroden mit ver{\"a}nderten Geometrien an den Elektrodenarbeitsfl{\"a}chen gestaltet. Eine der Elektroden besitzt eine periodisch unterbrochene und die zweite eine laterale Profilierung mit in Schweißrichtung nichtlinearer Form der Elektrodenarbeitsfl{\"a}che. Das Verhalten beim Schweißen wurde in Schweißversuchen bestimmt und Schweißbereichsdiagram-me bzw. Prozessfenster abgeleitet. Die Verbindungseigenschaften wurden durch Metallografie-, Fes-tigkeits-, Druck- und Dichtheitsuntersuchungen validiert. Als Vergleich und Referenz dienen Schweiß-untersuchungen mit konventionellen Rollennahtelektroden. Die Untersuchungsergebnisse zeigen Unterschiede bei den Prozessparametern und der Auspr{\"a}gung der Verbindung in Abh{\"a}ngigkeit von der geschweißten Struktur, dem ausgew{\"a}hlten Schweißpfad und des geschweißten Werkstoffes gegen{\"u}ber den Referenzschweißungen. Eine anschließende Optimie-rung f{\"u}hrte zu einer vergleichbar guten Schweißnahtqualit{\"a}t sowohl bei Erhalt der Versteifungselemen-te mit den neuen Elektroden als auch bei deren Einebnung mit konventionellen Elektroden in Referenz zu Schweißuntersuchungen am ebenen Blech. Anschließend wurde ein Vergleich der Verbindungsfestigkeiten mit dem Widerstandspunktschweißen und dem Metall-Aktivgas-Schweißen durchgef{\"u}hrt.}, language = {de} } @inproceedings{SchleussSpringerZoekeetal., author = {Schleuß, Leander and Springer, Katrin and Zoeke, J{\"o}rg and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Qualifizierung von w{\"a}rmearmen MSG-Schweißverfahren f{\"u}r Leichtbaukonstruktionen mit strukturierten Halbzeugen}, series = {Internationaler Fachkongress der Schweiß- und Verbindungstechnik Join-Ex 2012 Wien, 10. + 11. Oktober 2012, Congress Center der Messe Wien}, booktitle = {Internationaler Fachkongress der Schweiß- und Verbindungstechnik Join-Ex 2012 Wien, 10. + 11. Oktober 2012, Congress Center der Messe Wien}, publisher = {Schweißtechnische Zentralanstalt e.V.}, address = {Wien}, pages = {75 -- 83}, language = {de} } @misc{KazakSchleussOssenbrinketal., author = {Kazak, Fedor and Schleuß, Leander and Ossenbrink, Ralf and Michailov, Vesselin and Weiß, Sabine}, title = {Particularities of testing structured sheet metals in 3-point bending tests}, series = {Materials Testing}, volume = {58}, journal = {Materials Testing}, number = {6}, issn = {0025-5300}, doi = {10.3139/120.110883}, pages = {495 -- 500}, abstract = {Thin sheet metals from deep drawing steel DC04 are very often used in the production of car body and case parts. Quality improvement of sheet metal components by new constructive solutions (structuring) as well as adapted joining technology is going on. Structured sheet metals differ from each other by their high bending stiffness. At the same time, they show certain anisotropy due to the structure. Therefore a typical testing method of structured semi-finished parts (single sheet metals, sandwiches)is the bending test. The literature review revealed that in many studies no special demands on tests of structured materials were made. This concerns particularly the structure arrangement, structure direction and structure location of the specimen relative to the mandrel position during bending tests, i. e., the direction of the fixed load relative to the structure. The aim of this study was to determine the influence of the test specification on flexural behavior. In the present paper, honeycomb-structured sheet metals were examined using 3-point bending tests. Bending stiffness and lightweight potential were calculated with respect to the location of load application and compared for different structure arrangements,directions and locations. The influence of the anisotropy on flexural behavior of the honeycomb-patterned sheet metals was moderate.}, language = {en} } @misc{JakobsenZhangDoynovetal., author = {Jakobsen, Daniel and Zhang, Wei and Doynov, Nikolay and B{\"o}hm, Anna and Malzbender, J{\"u}rgen and Michailov, Vesselin and Roosen, Andreas}, title = {Thermal shock behaviour of laminated multilayer refractories for steel casting applications reinforced by residual stresses}, series = {Ceramics International}, volume = {42}, journal = {Ceramics International}, number = {12}, issn = {0272-8842}, doi = {10.1016/j.ceramint.2016.05.149}, pages = {13562 -- 13571}, language = {en} } @misc{ZhangDoynovOssenbrinketal., author = {Zhang, Wei and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Physical and FE-Simulation of Thermal Shock Behaviour of Refractory Ceramics}, series = {refractories WORLDFORUM}, volume = {8}, journal = {refractories WORLDFORUM}, number = {2}, issn = {1868-2405}, pages = {110 -- 117}, language = {en} } @inproceedings{ZhangPrieferOleninaetal., author = {Zhang, Wei and Priefer, Marian and Olenina, Mariia and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Additive manufacturing by laser beam build-up welding}, series = {6th International Conference on Additive Technologies - iCAT 2016, N{\"u}rnberg, Germany, 29. - 30. November 2016}, booktitle = {6th International Conference on Additive Technologies - iCAT 2016, N{\"u}rnberg, Germany, 29. - 30. November 2016}, isbn = {978-961-285-537-6}, pages = {324 -- 327}, language = {en} } @inproceedings{ZhangSchrammKaneneksetal., author = {Zhang, Wei and Schramm, Maximilian and Kaneneks, Michael and Michailov, Vesselin and Fleischhauer, Matthias}, title = {Laserstrahl-Auftragschweißen mit pulverf{\"o}rmigen keramischen und metallischen Zusatzwerkstoffen zur Herstellung von Gradientenwerkstoffen}, series = {Große Schweißtechnische Tagung, N{\"u}rnberg, 15. - 17. September 2015}, booktitle = {Große Schweißtechnische Tagung, N{\"u}rnberg, 15. - 17. September 2015}, publisher = {DVS Media}, address = {D{\"u}sseldorf}, isbn = {978-3-945023-46-4}, pages = {842 -- 845}, language = {de} } @inproceedings{ZhangDoynovOssenbrinketal., author = {Zhang, Wei and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin and Scheithauer, Uwe and Michaelis, Alexander}, title = {Investigation of thermal shock behaviour of refractory ceramics based on the calcium-aluminate}, series = {14th Biennial Worldwide Congress Unified International Technical Conference on Refractories (UNITECR) 2015, Vienna, Austria, September 15-18, 2015}, booktitle = {14th Biennial Worldwide Congress Unified International Technical Conference on Refractories (UNITECR) 2015, Vienna, Austria, September 15-18, 2015}, address = {Hannover}, isbn = {978-3-9815813-1-7}, language = {en} } @misc{AtangaZhangDreibatietal., author = {Atanga, Valetine Kubong and Zhang, Wei and Dreibati, Ossama and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin and Scheffler, Michael}, title = {Alumina-mullite Materials for Refractory Applications: Microstructure, Physical and Finite Element Simulation of Thermal Shock Behaviour}, series = {refractories WORLDFORUM}, volume = {4}, journal = {refractories WORLDFORUM}, number = {1}, issn = {1868-2405}, pages = {159 -- 164}, language = {en} } @misc{HantelmannFritzscheMichailovetal., author = {Hantelmann, Cord and Fritzsche, Sebastian and Michailov, Vesselin and Boywitt, Ralf and Risse, Steffen and Paulinus, Dietmar}, title = {Utilisation of aluminium foam sandwich components in welded structures}, series = {Welding and Cutting}, journal = {Welding and Cutting}, number = {5}, issn = {1612-3433}, pages = {317 -- 325}, language = {en} } @misc{HantelmannFritzscheMichailovetal., author = {Hantelmann, Cord and Fritzsche, Sebastian and Michailov, Vesselin and Boywitt, Ralf and Risse, Steffen and Paulinus, Dietmar}, title = {Einsatz von Aluminiumschaum-Sandwich-Bauteilen in Schweißkonstruktionen}, series = {Schweissen und Scheiden}, volume = {68}, journal = {Schweissen und Scheiden}, number = {3}, issn = {0036-7184}, pages = {106 -- 114}, language = {de} } @misc{GenchevDoynovOssenbrinketal., author = {Genchev, Gancho Vladimirov and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Modelling the Local Microstructure Properties due to Multi-Pass Welding}, series = {Materials Science Forum}, volume = {Vol. 879}, journal = {Materials Science Forum}, issn = {0255-5476}, doi = {10.4028/www.scientific.net/MSF.879.595}, pages = {595 -- 600}, language = {en} } @misc{MichailovDoynov, author = {Michailov, Vesselin and Doynov, Nikolay}, title = {Analytical-Numerical Modeling Approach for Calculation of the Structural Distortions after Welding and Thermal Straightening}, series = {Journal of Mechanics Engineering and Automation}, volume = {6}, journal = {Journal of Mechanics Engineering and Automation}, number = {5}, issn = {2159-5283}, doi = {10.17265/2159-5275/2016.05.004}, pages = {246 -- 253}, language = {en} } @inproceedings{HantelmannFritzscheMichailovetal., author = {Hantelmann, Cord and Fritzsche, Sebastian and Michailov, Vesselin and Paulinus, Dietmar}, title = {Einsatz von Aluminiumschaumsandwich in Schweißkonstruktionen}, series = {DVS Congress 2014, Große Schweißtechnische Tagung, DVS-Studentenkongress, Vortr{\"a}ge der Veranstaltungen in Berlin am 15. und 16. September 2014}, booktitle = {DVS Congress 2014, Große Schweißtechnische Tagung, DVS-Studentenkongress, Vortr{\"a}ge der Veranstaltungen in Berlin am 15. und 16. September 2014}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-945023-03-7}, language = {de} } @inproceedings{SeidlitzFritzscheSchleussetal., author = {Seidlitz, Holger and Fritzsche, Sebastian and Schleuß, Leander and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Neuartige F{\"u}getechnologie zum Herstellen von hochbelastbaren Multi-Material-Bauweisen aus textilverst{\"a}rkten Kunststoffen und Metallen bei einseitiger Zug{\"a}nglichkeit der F{\"u}gestelle}, series = {DVS Congress 2016, Große Schweißtechnische Tagung, Vortr{\"a}ge der Veranstaltungen in Leipzig am 19. und 20. September 2016}, booktitle = {DVS Congress 2016, Große Schweißtechnische Tagung, Vortr{\"a}ge der Veranstaltungen in Leipzig am 19. und 20. September 2016}, publisher = {DVS-Verlag}, address = {D{\"u}sseldorf}, isbn = {978-3-945023-74-7}, pages = {424 -- 428}, language = {de} } @misc{KoltsovaMichailov, author = {Koltsova, Tatiana S. and Michailov, Vesselin}, title = {Hybrid Composite Materials Aluminum-Carbon Nanostructures}, series = {Materials science medziagotyra}, volume = {21}, journal = {Materials science medziagotyra}, number = {3}, issn = {1392-1320}, pages = {372 -- 375}, language = {en} } @misc{KoltsovaTolochkoMichailov, author = {Koltsova, Tatiana S. and Tolochko, Oleg V. and Michailov, Vesselin}, title = {Effect of hot pressing modes on the structure and properties of an aluminum-carbon nanofibers' composite material}, series = {Metal Science and Heat Treatment}, volume = {56}, journal = {Metal Science and Heat Treatment}, number = {9-10}, issn = {0026-0673}, doi = {10.1007/s11041-015-9793-6}, pages = {525 -- 530}, language = {en} } @inproceedings{NaumovChenikovGolubevetal., author = {Naumov, Anton and Chenikov, Evgenii V. and Golubev, Iurii and Michailov, Vesselin}, title = {Numerical simulation and microstructure analysis of friction stir welded Al 6082}, series = {METAL 2015, 24th International Conference on Metallurgy and Materials, conference proceedings, June 3rd-5th 2015, Brno}, booktitle = {METAL 2015, 24th International Conference on Metallurgy and Materials, conference proceedings, June 3rd-5th 2015, Brno}, publisher = {Tanger}, address = {Ostrava}, isbn = {978-80-87294-62-8}, language = {en} } @inproceedings{GenchevDoynovOssenbrinketal., author = {Genchev, Gancho Vladimirov and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Schweißtechnische Simulation der lokalen Eigenschaften in der W{\"a}rmeeinflusszone von Mehrlagenschweißungen}, series = {ANSYS Conference \& 33rd CADFEM Users' Meeting, 24. - 26. Juni, Bremen, conference proceedings}, booktitle = {ANSYS Conference \& 33rd CADFEM Users' Meeting, 24. - 26. Juni, Bremen, conference proceedings}, publisher = {CADFEM GmbH}, address = {Grafing}, language = {de} } @inproceedings{DoynovKukeMichailov, author = {Doynov, Nikolay and Kuke, Felix and Michailov, Vesselin}, title = {Thermal straightening simulation of welded structures}, series = {Proceedings, METEC \& 2nd ESTAD 2015, European Steel Technology and Application Days, D{\"u}sseldorf, Germany, CCD Congress Center D{\"u}sseldorf, 15 - 19 June 2015}, booktitle = {Proceedings, METEC \& 2nd ESTAD 2015, European Steel Technology and Application Days, D{\"u}sseldorf, Germany, CCD Congress Center D{\"u}sseldorf, 15 - 19 June 2015}, publisher = {TEMA Technologie Marketing AG}, address = {Aachen}, isbn = {978-3-00-049542-7}, pages = {P 709, 1 -- 6}, language = {en} } @inproceedings{FritzscheSeidlitzWinkelmannetal., author = {Fritzsche, Sebastian and Seidlitz, Holger and Winkelmann, Kai and Michailov, Vesselin}, title = {Structural reinforced FRP sandwich constructions for lightweight floor panels}, series = {Conference papers, APT '15, 11th International Conference Advances in Plastics Technology, Sosnowiec, 13 - 15 October 2015}, booktitle = {Conference papers, APT '15, 11th International Conference Advances in Plastics Technology, Sosnowiec, 13 - 15 October 2015}, editor = {Pająk, Anna}, address = {Gliwice}, isbn = {978-83-63555-47-4}, language = {en} } @inproceedings{GolubevNaumovMichailov, author = {Golubev, Iurii and Naumov, Anton and Michailov, Vesselin}, title = {Developing finite element model of the friction stir welding for temperature calculation}, series = {METAL 2014, International Conference on Metallurgy and Materials, May 21 st - 23rd 2014, Brno}, booktitle = {METAL 2014, International Conference on Metallurgy and Materials, May 21 st - 23rd 2014, Brno}, isbn = {978-80-87294-54-3}, pages = {1242 -- 1248}, language = {en} } @misc{GenchevDoynovOssenbrinketal., author = {Genchev, Gancho Vladimirov and Doynov, Nikolay and Ossenbrink, Ralf and Bokuchava, Gizo and Petrov, Peter and Michailov, Vesselin}, title = {Numerical and Experimental Study of Residual Stress Distribution in Laser Beam Welded Joint}, pages = {S. 20}, language = {en} } @misc{Michailov, author = {Michailov, Vesselin}, title = {Prediction of the Properties of Heat-Affected Zone of Welded Joints of Sheets from Aluminum Alloys with Structured Surface}, series = {Metal Science and Heat Treatment}, volume = {58}, journal = {Metal Science and Heat Treatment}, number = {1-2}, issn = {0026-0673}, pages = {46 -- 50}, language = {en} } @misc{KarkhinGarkovMichailov, author = {Karkhin, Victor A. and Garkov, Sergey Vladimirovich and Michailov, Vesselin}, title = {Calculation of thermal processes in welding thick plates with moving axisymmetric heat sources}, series = {Welding International}, volume = {30}, journal = {Welding International}, number = {9}, issn = {0950-7116}, pages = {708 -- 711}, language = {en} } @inproceedings{IvanovPanchenkoKarkhinetal., author = {Ivanov, Sergey Y. and Panchenko, Oleg V. and Karkhin, Victor A. and Michailov, Vesselin and Velichko, Olga V.}, title = {Comparative study of mechanical inhomogeneity of laser and friction stir welded joints of Al-Mg-Si alloy}, series = {METAL 2015, 24th International Conference on Metallurgy and Materials, conference proceedings, June 3rd-5th 2015, Brno}, booktitle = {METAL 2015, 24th International Conference on Metallurgy and Materials, conference proceedings, June 3rd-5th 2015, Brno}, publisher = {Tanger}, address = {Ostrava}, isbn = {978-80-87294-62-8}, language = {en} } @inproceedings{KukeKloshekMichailov, author = {Kuke, Felix and Kloshek, Alexander and Michailov, Vesselin}, title = {Untersuchung des Einflusses von rohrf{\"o}rmigen Stahlelektroden auf das Prozessverhalten und den Werkstoff{\"u}bergang beim MSG-Schweißen}, series = {DVS Congress, September 2015, N{\"u}rnberg}, booktitle = {DVS Congress, September 2015, N{\"u}rnberg}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-945023-46-4}, pages = {615 -- 620}, language = {de} } @inproceedings{NaumovChenikovGolubevetal., author = {Naumov, Anton and Chenikov, Evgenii V. and Golubev, Iurii and Michailov, Vesselin}, title = {Research of temperature distribution during friction stir welding of 2 mm Aw 6082 sheets}, series = {METAL 2015, 24th International Conference on Metallurgy and Materials, conference proceedings, June 3rd-5th 2015, Brno}, booktitle = {METAL 2015, 24th International Conference on Metallurgy and Materials, conference proceedings, June 3rd-5th 2015, Brno}, publisher = {Tanger}, address = {Ostrava}, isbn = {978-80-87294-62-8}, pages = {651 -- 653}, language = {en} } @misc{SchleussRichterOssenbrinketal., author = {Schleuß, Leander and Richter, Thomas and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Plasma Cutting of Structured Sheet Metals in Comparison with Laser Beam Cutting}, series = {Journal of Materials Science and Engineering}, volume = {5}, journal = {Journal of Materials Science and Engineering}, number = {3-4}, issn = {2161-6221}, doi = {10.17265/2161-6221/2015.3-4.004}, pages = {135 -- 144}, language = {en} } @book{MichailovKarkhinPetrov, author = {Michailov, Vesselin and Karkhin, Victor A. and Petrov, Peter}, title = {Principles of welding}, publisher = {Polytechnic Univ. Publ.}, address = {St. Petersburg}, isbn = {978-5-7422-5569-7}, pages = {283}, language = {en} } @inproceedings{PetrovBokuchavaPapushkinetal., author = {Petrov, Peter and Bokuchava, Gizo and Papushkin, Igor and Genchev, Gancho Vladimirov and Doynov, Nikolay and Michailov, Vesselin and Ormanova, Maria}, title = {Neutron diffraction studies of laser welding residual stresses}, series = {19th International Conference and School on Quantum Electronics: Laser Physics and Applications, 26-30 September 2016 Sozopol, Bulgaria}, booktitle = {19th International Conference and School on Quantum Electronics: Laser Physics and Applications, 26-30 September 2016 Sozopol, Bulgaria}, publisher = {SPIE}, address = {Bellingham, Wash.}, isbn = {978-1-5106-0953-2}, doi = {10.1117/12.2261802}, language = {en} } @misc{NikitinSchleussOssenbrinketal., author = {Nikitin, Alexander and Schleuß, Leander and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Corrosion Behavior of Brazed Zinc-Coated Structured Sheet Metal}, series = {International Journal of Corrosion}, volume = {2017}, journal = {International Journal of Corrosion}, issn = {1687-9333}, doi = {10.1155/2017/4768505}, pages = {4768505}, language = {en} } @incollection{TolochkoMichailovRudskoy, author = {Tolochko, Oleg V. and Michailov, Vesselin and Rudskoy, Andrey I.}, title = {Metal Matrix/Nanocarbons Composites Based on Copper and Aluminum}, series = {Industry 4.0 : Entrepreneurship and Structural Change in the New Digital Landscape}, booktitle = {Industry 4.0 : Entrepreneurship and Structural Change in the New Digital Landscape}, editor = {Devezas, Tessaleno and Leit{\~a}o, Jo{\~a}o and Sarygulov, Askar}, publisher = {Springer International Publishing}, address = {Cham}, isbn = {978-3-319-49604-7}, pages = {205 -- 217}, language = {en} } @misc{IvanovKarkhinMichailovetal., author = {Ivanov, Sergey Y. and Karkhin, Victor A. and Michailov, Vesselin and Martikainen, J. and Hiltunen, E.}, title = {Modellierung der Entstehung von Heißrissen beim Laserschweißen von Al-Mg-Si-Legierungen}, series = {Izvestija Tul'skogo Gosudarstvennogo Universiteta}, volume = {6}, journal = {Izvestija Tul'skogo Gosudarstvennogo Universiteta}, number = {2}, issn = {2071-6168}, pages = {66 -- 74}, language = {ru} } @misc{IvanovKarkhinMichailov, author = {Ivanov, Sergey Y. and Karkhin, Victor A. and Michailov, Vesselin}, title = {Modellierung thermodynamischer Prozesse beim Schweißen von ungeraden N{\"a}hten}, series = {Izvestija Tul'skogo Gosudarstvennogo Universiteta}, volume = {6}, journal = {Izvestija Tul'skogo Gosudarstvennogo Universiteta}, number = {2}, issn = {2071-6168}, pages = {62 -- 66}, language = {ru} } @inproceedings{KloshekKaneneksDuedingetal., author = {Kloshek, Alexander and Kaneneks, Michael and D{\"u}ding, Michael and Wolf, Matthias and Michailov, Vesselin}, title = {Unterpulverschweißen in Steig- und Querposition}, series = {Tagungsband, 24. Schweißtechnische Fachtagung, Halle (Saale), 05.11.2014}, booktitle = {Tagungsband, 24. Schweißtechnische Fachtagung, Halle (Saale), 05.11.2014}, publisher = {Schweißtechnische Lehr- und Versuchsanstalt}, address = {Halle/Saale}, pages = {51 -- 58}, language = {de} } @misc{IsupovGaninTcemenkoetal., author = {Isupov, Fedor and Ganin, Sergey and Tcemenko, Valeriy and Michailov, Vesselin}, title = {Numerical simulation of sheet profiling process from aluminum alloy}, series = {METAL 2015, 24th International Conference on Metallurgy and Materials, Brno, Czech Republic, June 3rd-5th, 2015, Conference proceedings}, journal = {METAL 2015, 24th International Conference on Metallurgy and Materials, Brno, Czech Republic, June 3rd-5th, 2015, Conference proceedings}, publisher = {Tanger}, address = {Ostrava}, isbn = {978-80-87294-62-8}, pages = {1463 -- 1468}, language = {en} } @inproceedings{GolubevNaumovChernikovetal., author = {Golubev, Iurii and Naumov, Anton and Chernikov, Evgenii V. and Michailov, Vesselin}, title = {Temperature distribution and welding distortion measurements after FSW of Al 6082-T6 sheets}, series = {Friction Stir Welding and Processing VIII, 144th Annual Meeting and Exhibition, 15.03.2015, Orlando}, booktitle = {Friction Stir Welding and Processing VIII, 144th Annual Meeting and Exhibition, 15.03.2015, Orlando}, editor = {Mishra, Rajiv S. and Mahoney, Murray W. and Sato, Yutaka and Hovanski, Yuri}, publisher = {Springer}, address = {Cham}, isbn = {978-3-319-48604-8}, doi = {10.1007/978-3-319-48173-9}, pages = {289 -- 295}, language = {en} } @inproceedings{IvanovPanchenkoKarkhinetal., author = {Ivanov, Sergey Y. and Panchenko, Oleg V. and Karkhin, Victor A. and Michailov, Vesselin}, title = {Optimization technique for arc welding of structured sheet}, series = {METAL 2015, 24th International Conference on Metallurgy and Materials, conference proceedings, June 3rd-5th 2015, Brno}, booktitle = {METAL 2015, 24th International Conference on Metallurgy and Materials, conference proceedings, June 3rd-5th 2015, Brno}, publisher = {Tanger}, address = {Ostrava}, isbn = {978-80-87294-62-8}, language = {en} } @book{MichailovStapelfeld, author = {Michailov, Vesselin and Stapelfeld, Christoph}, title = {Erweiterung eines analytisch-numerischen Hybridmodells f{\"u}r die Verzugssimulation von Großstrukturen}, publisher = {Verlag und Vertriebsgesellschaft mbH}, address = {D{\"u}sseldorf}, isbn = {978-3-942541-35-0}, pages = {132}, language = {de} } @misc{KoltsovaShakovVoznyakovskiyetal., author = {Koltsova, Tatiana S. and Shakov, Fedor M. and Voznyakovskiy, A. A. and Lyashkov, A. I. and Tolochko, Oleg V. and Rudskoy, Andrey I. and Nasibulin, Albert G. and Michailov, Vesselin}, title = {Fabrication of a Compacted Aluminum-Carbon Nanofiber Material by Hot Pressin}, series = {Technical Physics}, volume = {59}, journal = {Technical Physics}, number = {11}, issn = {1063-7842}, doi = {10.1134/S1063784214110139}, pages = {1626 -- 1630}, language = {en} } @inproceedings{KrawczynskiDoynovMichailov, author = {Krawczynski, Damian and Doynov, Nikolay and Michailov, Vesselin}, title = {Minimization of Residual Welding Stress and Distortins in Aluminium-Steel Hybrid Structure}, series = {Innowacje w procesach produkcyjnych, technologicznych i bezpieczeństwie : XXXVIII Studencka Sesja Naukowa, Częstochowa, 29 maj 2014 : praca zbiorowa}, booktitle = {Innowacje w procesach produkcyjnych, technologicznych i bezpieczeństwie : XXXVIII Studencka Sesja Naukowa, Częstochowa, 29 maj 2014 : praca zbiorowa}, publisher = {Wydawnictwo Wydziału Inżynierii Produkcji i Technologii Materiał{\´o}w Politechniki Częstochowskie}, address = {Częstochowa}, isbn = {879-83-63989-02-6}, pages = {59 -- 63}, language = {en} } @misc{BobryninaAlkhalafShamshurinetal., author = {Bobrynina, Elizaveta and Alkhalaf, Ahmad A. and Shamshurin, Aleksey and Tolochko, Oleg V. and Michailov, Vesselin}, title = {Synthesis of Fe-ZrO2 composite powders by thermochemical method}, series = {Key Engineering Materials}, volume = {721}, journal = {Key Engineering Materials}, issn = {1662-9795}, doi = {10.4028/www.scientific.net/KEM.721.285}, pages = {285 -- 289}, language = {en} } @misc{HartelIlinSonntagetal., author = {Hartel, Udo and Ilin, Alexander and Sonntag, Steffen and Michailov, Vesselin}, title = {Nonlinear optimization methods for the determination of heat source model parameters}, series = {Materials Science Forum}, volume = {879}, journal = {Materials Science Forum}, issn = {1662-9752}, doi = {10.4028/www.scientific.net/MSF.879.2008}, pages = {2008 -- 2013}, language = {en} } @misc{HartelIlinMichailovetal., author = {Hartel, Udo and Ilin, Alexander and Michailov, Vesselin and Gibmeier, Jens and Bantel, Christoph}, title = {Finite Element Modelling for the Structural Analysis of Al-Cu Laser Beam Welding}, series = {Physics Procedia}, volume = {83}, journal = {Physics Procedia}, issn = {1875-3892}, doi = {10.1016/j.phpro.2016.08.147}, pages = {1404 -- 1414}, language = {en} } @inproceedings{ZhangPrieferOssenbrinketal., author = {Zhang, Wei and Priefer, Marian and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Neue M{\"o}glichkeiten f{\"u}r die Additive Fertigung durch Laser-Pulver-Auftragschweißen}, series = {DVS Congress 2017, Große Schweißtechnische Tagung, DVS Studentenkongress, Vortr{\"a}ge der Veranstaltungen in D{\"u}sseldorf vom 26. bis 29. September 2017}, booktitle = {DVS Congress 2017, Große Schweißtechnische Tagung, DVS Studentenkongress, Vortr{\"a}ge der Veranstaltungen in D{\"u}sseldorf vom 26. bis 29. September 2017}, publisher = {DVS Media}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-008-5}, pages = {278 -- 282}, language = {de} } @misc{GenchevDoynovOssenbrinketal., author = {Genchev, Gancho Vladimirov and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin and Bokuchava, Gizo and Petrov, Peter}, title = {Residual stresses formation in multi-pass weldment: A numerical and experimental study}, series = {Journal of Constructional Steel Research}, volume = {138}, journal = {Journal of Constructional Steel Research}, issn = {0143-974X}, doi = {10.1016/j.jcsr.2017.08.017}, pages = {633 -- 641}, abstract = {In this study, the residual stresses distribution induced by multi-pass arc welding of the steel S355J2+N are investigated experimentally and numerically. An extended approach is used for the simulations, which considers the change of the local microstructure properties due to multiple reheating. Experimental material data obtained from physical welding simulations with Gleeble® are used for the model calibration. The experimental stress study is performed using a neutron diffraction method on a fourier stress diffractometer. Numerical analysis of the welding stresses formation in the weldment is performed and compared to the experimental study. The results explain the influence of the welding thermal history on the resulting local thermo-mechanical properties in the heat-affected zone and, thus, on the residual stress distribution. The consideration of the local microstructure properties in the welding simulation leads to a significant increase in accuracy of the numerical results. The major influence factor on the residual stress formation is the change in the interpass microstructure yield strength. When a root pass with short cooling times is subjected to re-austenitisation in the fine-grained zone, the yield strength increases in this area and affects consequently the residual stress distribution. The influence of the reheating is detectable in the depth of the weldment, but it is less significant for the residual stress formation near the surface of the welded joint.}, language = {en} } @misc{DoynovMichailov, author = {Doynov, Nikolay and Michailov, Vesselin}, title = {Distortion analysis of heat spot straightening thin-walled welded structures: part 2: analytical-numerical approach}, series = {International Journal of Advanced Manufacturing Technology}, volume = {95}, journal = {International Journal of Advanced Manufacturing Technology}, number = {1-4}, issn = {0268-3768}, doi = {10.1007/s00170-017-1214-0}, pages = {469 -- 478}, abstract = {An analytical model based on a theoretical model established in the previous work (part 1) is developed. The analytical model considers the particular case of an instantaneous high-density heat source acting on a thin pre-stressed plate. It calculates the plastic strain and the area of the zone of plastic deformation. A theoretical study is performed in order to quantify the major factors that influence the plastic strain formation. Furthermore, the work presents a calculation procedure for distortion analysis of lar ge and complex structures, intended to be used for solving industrial tasks. The calculation procedure consists of a combination of the analytical solution and an elastic finite element analysis with the aid of the inherent strain approach. Various aspects of its application are also discussed. The calculation procedure is finally explained using a simple example. Its reliability and practicability are demonstrated through verification and validation studies. The work is dedicated to the thermal straightening of thin-walled welded structures; however, it can also be related to other processes.}, language = {en} } @book{MichailovDoynovKuke, author = {Michailov, Vesselin and Doynov, Nikolay and Kuke, Felix}, title = {Anwendungsnahe Simulation des thermischen Richtens : Forschungsvorhaben P 1008/IGF-Nr. 17970 BR}, publisher = {Verlag und Vertriebsgesellschaft mbH}, address = {D{\"u}sseldorf}, isbn = {978-3-946885-03-0}, pages = {XV, 122}, language = {de} } @misc{KondratyevMorozovaGolubevetal., author = {Kondratyev, Alex and Morozova, Iuliia and Golubev, Iurii and Hantelmann, Cord and Naumov, Alexander and Michailov, Vesselin}, title = {Микроструктура и механические свойства швов после различных режимов импульсной сварки Al - Mg - Si сплавов трением с перемешиванием}, series = {Metallovedenie i termicheskaya obrabotka metallov}, journal = {Metallovedenie i termicheskaya obrabotka metallov}, number = {11}, issn = {0026-0819}, pages = {25 -- 30}, abstract = {Welded joints of aluminum alloy 6082-T6 formed by the method of pulse friction stir welding are studied. The effect of the power and frequency of the pulses on the microstructure and mechanical properties of the welded joints is determined. Application of an additional pulse during the welding affects the surface quality and the shape of the weld, the distribution of the oxide layer and of particles of the hardening phase, and the grain size in the zone of dynamic recrystallization.}, language = {ru} } @misc{IvanovKarkhinMichailov, author = {Ivanov, Sergey Y. and Karkhin, Victor A. and Michailov, Vesselin}, title = {Optimization of welding conditions for curvilinear}, series = {Welding International}, volume = {31}, journal = {Welding International}, number = {12}, issn = {0950-7116}, doi = {10.1080/09507116.2017.1353276}, pages = {929 -- 933}, language = {en} } @misc{DoynovMichailov, author = {Doynov, Nikolay and Michailov, Vesselin}, title = {Distortion analysis of heat spot straightening thin-walled welded structures: part 1: analytical-numerical approach}, series = {The International Journal of Advanced Manufacturing Technology}, volume = {94}, journal = {The International Journal of Advanced Manufacturing Technology}, number = {1-4}, issn = {0268-3768}, doi = {10.1007/s00170-017-0911-z}, pages = {667 -- 676}, abstract = {The work deals with the elastic-plastic thermo-mechanical deformation process after spot heating of large thin plates. It promotes a new theoretical model of the process. The main target is to clarify the kinetics of the plastic strain formation during thermal straightening and to explore the main interactions. For this purpose, a simplified mechanical problem is formulated and applied. As a result, definite thermo-mechanical relations between temperature, initial strain, and accumulated plastic strain are obtained. Finally, a verification study is presented and discussed. The results contribute to extending the knowledge about the process and to establishing a theoretical background for development of applied analytical or analytical-numerical approaches for practical use in the designing and planning phases in welding production. An application to a particular case is described in an accompanying paper (part 2).}, language = {en} } @incollection{GolubevDoynovHantelmannetal., author = {Golubev, Iurii and Doynov, Nikolay and Hantelmann, Cord and Michailov, Vesselin}, title = {W{\"a}rmequellemodell und FE-Temperaturfeldsimulation f{\"u}r das R{\"u}hrreibschweißen}, series = {DVS Congress 2017 : Große Schweißtechnische Tagung : DVS-Studentenkongress : Vortr{\"a}ge der Veranstaltungen in D{\"u}sseldorf vom 26. bis 29. September 2017}, booktitle = {DVS Congress 2017 : Große Schweißtechnische Tagung : DVS-Studentenkongress : Vortr{\"a}ge der Veranstaltungen in D{\"u}sseldorf vom 26. bis 29. September 2017}, publisher = {DVS Media}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-008-5}, pages = {112}, language = {de} } @misc{EvdokimovSpringerDoynovetal., author = {Evdokimov, Anton and Springer, Katrin and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Heat source model for laser beam welding of steel-aluminum lap joints}, series = {International Journal of Advanced Manufacturing Technology}, volume = {93}, journal = {International Journal of Advanced Manufacturing Technology}, number = {1-4}, issn = {0268-3768}, doi = {10.1007/s00170-017-0569-6}, pages = {709 -- 716}, abstract = {In this study, a three-dimensional thermal conduction model based on the finite element analysis was established to predict a heat distribution during laser welding in overlap configuration of austenitic stainless steel 1.4301 and hardenable aluminum alloy 6016. A hybrid model based on two expanded curve-rotated volumetric heat sources is suggested to capture the complex weld geometry. Since thermal flow in the overlap area is a crucial part of the model, an analytic calculation of a thermal contact conductance between the plates and its subsequent implementation in the FE model through a superposition of two contact surfaces are described in details in this paper. Full thermal cycles, weld shapes, and thus mixing grades were successfully predicted by means of the developed model for different parameter combinations.}, language = {en} } @misc{ShapovalovHantelmannMichailovetal., author = {Shapovalov, Oleg and Hantelmann, Cord and Michailov, Vesselin and Kodgaspirov, G. E.}, title = {Influence of welding method on fatigue strength and destruction character of aluminum foam sandwiches}, series = {Deformatsiya i Razrushenie materialov}, journal = {Deformatsiya i Razrushenie materialov}, number = {5}, issn = {1814-4632}, abstract = {An influence of the arc welding and the laser welding on fatigue properties and destruction mechanisms of aluminum foam sandwich has been studied. It was found that specimens made by the arc welding had the best fatigue strength. Comparative results of four point bending fatigue tests of the non-welded specimens such as butt welded joints made by different welding methods are presented.}, language = {ru} } @inproceedings{PanchenkoIvanovKol'Tsovaetal., author = {Panchenko, Oleg V. and Ivanov, Sergey Y. and Kol'Tsova, Tatyana and Michailov, Vesselin}, title = {Survivability of Carbon Nanotubes During Arc Welding}, series = {Nanocon 2016, conference proceedings, 8th international conference, October 19th-21st, 2016, Brno, Czech Republic, EU}, booktitle = {Nanocon 2016, conference proceedings, 8th international conference, October 19th-21st, 2016, Brno, Czech Republic, EU}, publisher = {Tanger}, address = {Ostrava}, isbn = {978-80-87294-71-0}, pages = {59 -- 63}, language = {en} } @inproceedings{GolubevMorozovaNaumovetal., author = {Golubev, Iurii and Morozova, Iuliia and Naumov, Anton and Hantelmann, Cord and Doynov, Nikolay and Michailov, Vesselin}, title = {Numerical simulation and experimental investigation on Numerical simulation of 6082-T6 aluminum alloy}, series = {Materials Science and Technology 2017, (MS\&T17), Pittsburgh, Pennsylvania, USA, October 8-12, 2017, volume 2}, booktitle = {Materials Science and Technology 2017, (MS\&T17), Pittsburgh, Pennsylvania, USA, October 8-12, 2017, volume 2}, publisher = {Curran Associates, Inc.}, address = {Red Hook, NY}, isbn = {978-1-5108-5058-3}, pages = {987 -- 994}, abstract = {The series of impulse friction stir welding (IFSW) experiments for aluminum alloy 6082-T6 butt joints was performed to obtain micrographs, tensile and hardness test samples and to receive the validation data for a numerical model of the process. Impulse force and frequency were varied to determine the effect of individual process parameters on microstructure evolution and mechanical properties of the welded butt joints. A three-dimensional model was established to simulate temperature distribution, heat generation and contact state between the tool and the workpiece during IFSW. Based on the numerical simulation, the influence of the impulses on heat input, maximum weld temperatures and contact state was found. The combination of impulse force and frequency effected the grain refinement. The influence of impulses on the elongation and hardness of the welded joints during IFSW were determined.}, language = {en} } @incollection{HantelmannFritzscheMichailovetal., author = {Hantelmann, Cord and Fritzsche, Sebastian and Michailov, Vesselin and Boywitt, Ralf}, title = {Einsatz von Aluminiumschaumsandwich in Schweißkonstruktionen}, series = {DVS Congress 2017 : Große Schweißtechnische Tagung : DVS-Studentenkongress : Vortr{\"a}ge der Veranstaltungen in D{\"u}sseldorf vom 26. bis 29. September 2017}, booktitle = {DVS Congress 2017 : Große Schweißtechnische Tagung : DVS-Studentenkongress : Vortr{\"a}ge der Veranstaltungen in D{\"u}sseldorf vom 26. bis 29. September 2017}, publisher = {DVS Media}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-008-5}, pages = {173}, abstract = {In der vorgestellten Arbeit wird die Anwendbarkeit von Aluminiumschaumsandich in Schweißkonstruktionen vorgestellt. Systematische Betrachtungen zur Schweißbarkeit mittels Laserstrahlschweißen, MSG - Kurzlichtbogen und R{\"u}hrreibschweißen sowohl im gesch{\"a}umten als auch im ungesch{\"a}umten Zustand werden beschrieben. Dazu wurden verschiedene Knotenformen wie I-Stoß- bzw. T-Stoßverbindungen hergestellt und deren mechanischtechnologische Eigenschaften ermittelt. Neben der quasistatischen Pr{\"u}fung, wurde jede Ausf{\"u}hrungsform des Knotens auf deren Schwingfestigkeit hin gepr{\"u}ft und die Anwendbarkeit bestehender Regelwerke wie die FKMRichtlinie oder der Eurocode 9 f{\"u}r die Nachweisf{\"u}hrung betrachtet. Die Ergebnisse sind abschließend in einem Gestaltungskatalog als Hilfsmittel f{\"u}r den Konstrukteur zusammengefasst. Parallel dazu wurden die experimentellen Untersuchungen mittels FEM begleitet. Es wird die FE-Modellentwicklung f{\"u}r die Berechnung des Sandwichverbundes an sich als auch von F{\"u}geknoten dargestellt wie auch die Modellvalidierung mit einem Musterbauteil aus einer Hubarbeitsb{\"u}hne.}, language = {de} } @misc{IvanovKarkhinMichailovetal., author = {Ivanov, Sergey Y. and Karkhin, Victor A. and Michailov, Vesselin and Martikainen, J. and Hiltunen, E.}, title = {Оценка чувствительности сварных соединений Al - Mg - Si-сплавов к ликвационным трещинам при лазерной сварке}, series = {Metallovedenie i termicheskaya obrabotka metallov}, journal = {Metallovedenie i termicheskaya obrabotka metallov}, number = {12}, issn = {0026-0819}, language = {ru} } @misc{EvdokimovObrosovOssenbrinketal., author = {Evdokimov, Anton and Obrosov, Aleksei and Ossenbrink, Ralf and Weiß, Sabine and Michailov, Vesselin}, title = {Mechanical properties of dissimilar steel-aluminum weld}, series = {Materials Science and Engineering: A}, volume = {Volume 722}, journal = {Materials Science and Engineering: A}, issn = {0921-5093}, doi = {https://doi.org/10.1016/j.msea.2018.03.019}, pages = {242 -- 254}, abstract = {Knowledge of the properties of dissimilar welds is of great significance for the development of multi-material lightweight structures. In this study, stainless steel (1.4301) and aluminum alloy (6082-T6) sheets were welded in overlap configuration in keyhole mode. The resulting weld metals were investigated with respect to their mechanical properties. Several samples were cut out of different locations along the welds and their cross-sections were subjected to indentation testing and energy dispersive X-ray (EDS) analysis. Young's modulus E, yield stress σy, and strain hardening exponent n, were determined by means of reverse analysis of the indentation load (P) - depth (h) curves, allowing construction of true stress - true strain relations. An essential increase in yield stress in comparison to the one of the base alloys was observed inside the weld metal. In contrary, Young's modulus and strain hardening exponent of the welds were almost identical to corresponding values of the base steel metal. Due to the sensitivity of yield stress to the aluminum content, slight variations of the welding parameters lead to significant changes in elastic-plastic behavior of the weld metal.}, language = {en} } @inproceedings{StapelfeldLaunertPasternaketal., author = {Stapelfeld, Christoph and Launert, Benjamin and Pasternak, Hartmut and Doynov, Nikolay and Michailov, Vesselin}, title = {Numerische Festigkeitsberechnung einer versteiften Struktur unter Ber{\"u}cksichtigung realit{\"a}tsnaher geometrischer und struktureller Imperfektionen}, series = {110 Jahre DASt und 21. DASt-Forschungskolloquium an der Technischen Universit{\"a}t Kaiserslautern, 6./7. M{\"a}rz 2018}, booktitle = {110 Jahre DASt und 21. DASt-Forschungskolloquium an der Technischen Universit{\"a}t Kaiserslautern, 6./7. M{\"a}rz 2018}, publisher = {Deutscher Ausschuß f{\"u}r Stahlbau DASt}, address = {D{\"u}sseldorf}, isbn = {978-3-941687-27-1}, pages = {245 -- 249}, abstract = {Die Festigkeitsberechnung von Strukturen, zum Beispiel Platten oder Schalen, mittels der Finite-Elemente-Methode geh{\"o}rt schon seit l{\"a}ngerem zum Stand der Technik. Ber{\"u}cksichtigt werden bei der Berechnung sowohl geometrische Nichtlinearit{\"a}ten als auch das nichtlineare Verhalten des Werkstoffs. Die geometrischen und strukturellen Imperfektionen werden bei der Ermittlung der Festigkeit zumeist in ausschließlich geometrischen Imperfektionen, wie bspw. Kombinationen aus Fertigungstoleranzen und den Ergebnissen von Beulanalysen zusammengefasst. Zur Rechtfertigung dieser Vorgehensweise werden die geometrischen Imperfektionen gem{\"a}ß DIN EN 1993-1-5 erh{\"o}ht. In einem Kommentar zur selben Norm findet sich ebenfalls eine Empfehlung zur Ber{\"u}cksichtigung von Schweißimperfektionen in Form von vereinfachten L{\"a}ngseigenspannungsverl{\"a}ufen. Diese werden in Abh{\"a}ngigkeit der Fließgrenzspannung des Werkstoffs bei Raumtemperatur und der Dicken der F{\"u}gepartner angenommen. Sowohl die Annahme rein geometrischer Imperfektionen als auch die Ber{\"u}cksichtigung vereinfachter Eigenspannungszust{\"a}nde, sind mit Sicherheitszuschl{\"a}gen behaftet. Durch eine realit{\"a}tsn{\"a}here Ber{\"u}cksichtigung von strukturellen und geometrischen Imperfektionen, hervorgerufen durch Schweißprozesse, kann die tats{\"a}chliche Tragf{\"a}higkeit einer Struktur wesentlich exakter bestimmt werden. Inhalt dieses Artikels ist die Anwendung eines analytisch-numerischen Hybridmodells zur Schweißimperfektionsberechnung an einer doppelt versteiften Platte und einer anschließenden Festigkeitsanalyse. Eingangs wird das analytische Modell vorgestellt und auf die grundlegenden physikalischen Zusammenh{\"a}nge eingegangen. Es folgt die Erl{\"a}uterung des Kopplungsalgorithmus zwischen analytischem Modell und der numerischen Berechnung. Angewendet an der doppelt versteiften Platte, wird ein realit{\"a}tsnaher geometrischer und struktureller Imperfektionszustand berechnet. Eine anschließende Traglastanalyse gibt Aufschluss {\"u}ber das Verformungsverhalten unter achsialer Krafteinwirkung. Zur Bewertung der Ergebnisse wird ein Modell gleicher geometrischer Abmessungen und Werkstoffkennwerte aus der Literatur herangezogen. Berechnet wurden die ersten 6 Eigenformen mittels analytischer und numerischer Modelle sowie die Last-Verformungskurven unter der Annahme unterschiedlicher geometrischer Imperfektionen. Um die Vergleichbarkeit der Ergebnisse zu sichern, wird eingangs die Lagerung des Modells sowie der Kraftangriffspunkt in L{\"a}ngsrichtung invers, durch den Vergleich der ersten 6 Beulformen sowie der Last-Verformungskurven dreier Imperfektionen, bestimmt. Darauf aufbauen wird die Last-Verformungskurve f{\"u}r einen {\"u}berlagerten Imperfektionszustand berechnet, wobei die geometrischen Imperfektionen aus den Fertigungstoleranzen abgeleitet und die strukturellen idealisiert, gem{\"a}ß DIN EN 1993-1-5, gew{\"a}hlt werden. Abschließend werden alle Last-Verformungskurven einander gegen{\"u}bergestellt. Anhand des Vergleichs kann quantifiziert werden, wie konservativ die einzelnen angenommenen Imperfektionen sind und wie sich der Verformungsverlauf darstellt, berechnet man diesen unter Verwendung realit{\"a}tsnaher geometrischer und struktureller Imperfektionen.}, language = {de} } @misc{BrobeckMichailovOssenbrinketal., author = {Brobeck, Andreas F. W. and Michailov, Vesselin and Ossenbrink, Ralf and Polzin, Ralf and Schleuß, Leander}, title = {Rollennahtelektrode}, abstract = {Eine Rollennahtelektrode zur Verwendung beim Rollennahtschweißen umfasst eine segmentf{\"o}rmige Elektrodenfl{\"a}che (2) zur Anpressung der zu verbindenden Bauteile und zur Einleitung des Schweißstroms und der Schweißspannung. Die Elektrodenfl{\"a}che (2) ist derart dreieckf{\"o}rmig oder m{\"a}anderf{\"o}rmig oder zueinander beabstandet ausgebildet, dass in der ebenen Abwicklung der Elektrodenfl{\"a}che (2) ein Zickzack-Muster oder ein Wellen-Muster oder ein Steppnaht-Muster oder ein Rechteck-Muster vorliegt.}, language = {de} } @misc{KloshekMichailov, author = {Kloshek, Alexander and Michailov, Vesselin}, title = {Schweißeinrichtung, Verfahren zur Herstellung eines Bauteils mittels Schweißung und Verwendung einer Elektrode aus Schweißzusatzwerkstoff}, abstract = {Schweißeinrichtung (1) zum Schweißen von Werkst{\"u}cken (100), umfassend eine Laserstrahlquelle (10) zur Emission eines Laserstrahls (11), eine Vorschubeinrichtung zur Realisierung einer Vorschubbewegung einer abzuschmelzenden Elektrode (70) aus Schweißzusatzwerkstoff (30) in einer Transportrichtung (21) in eine Abschmelzzone, und eine Stromkontakteinheit (60) zur Anlegung einer elektrischen Spannung an die abzuschmelzende Elektrode (70), wobei die Laserstrahlquelle (10), die Vorschubeinrichtung und die Stromkontakteinheit (60) derart relativ zueinander angeordnet und ausgebildet sind, dass die L{\"a}ngsachse des von der Laserstrahlquelle (10) aussendbaren Laserstrahls (11) im Wesentlichen parallel zur Transportrichtung (21) der Elektrode (70) verl{\"a}uft, dadurch gekennzeichnet, dass sie eine Elektrodenformungseinrichtung (40) aufweist, mit der ein Querschnitt der Elektrode (70) erzeugbar ist, der den von der Laserstrahlquelle (10) aussendbaren Laserstrahl (11) zumindest in einem Winkelbereich von 180° umgibt.}, language = {de} } @misc{MichailovOssenbrinkSchleussetal., author = {Michailov, Vesselin and Ossenbrink, Ralf and Schleuß, Leander and Springer, Katrin and Zoeke, J{\"o}rg}, title = {Strukturierte Tailored Blanks}, abstract = {Die Erfindung betrifft ein strukturiertes Tailored Blank, umfassend mindestens zwei F{\"u}gepartner, wobei mindestens ein F{\"u}gepartner ein strukturierter F{\"u}gepartner ist und wobei der strukturierte F{\"u}gepartner regelm{\"a}ßig angeordnete Versteifungselemente umfasst und wobei der strukturierte F{\"u}gepartner an mindestens einen weiteren F{\"u}gepartner gef{\"u}gt ist.}, language = {de} } @misc{SchleussSeidlitzMichailov, author = {Schleuß, Leander and Seidlitz, Holger and Michailov, Vesselin}, title = {Neue F{\"u}getechnologie f{\"u}r Mischverbindungen}, language = {de} } @misc{Kondrat’evMorozovaGolubevetal., author = {Kondrat'ev, Sergey and Morozova, Iuliia and Golubev, Iurii and Hantelmann, Cord and Naumov, Alexander and Michailov, Vesselin}, title = {Microstructure and Mechanical Properties of Welds of Al - Mg - Si Alloys After Different Modes of Impulse Friction Stir Welding}, series = {Metal Science and Heat Treatment}, volume = {59}, journal = {Metal Science and Heat Treatment}, number = {11-12}, issn = {0026-0673}, doi = {10.1007/s11041-018-0213-6}, pages = {697 -- 702}, abstract = {Welded joints of aluminum alloy 6082-T6 formed by the method of impulse friction stir welding are studied. The effect of the power and frequency of the pulses on the microstructure and mechanical properties of the welded joints is determined. Application of an additional pulse during the welding affects the surface quality and the shape of the weld, the distribution of the oxide layer and of particles of the hardening phase, and the grain size in the zone of dynamic recrystallization.}, language = {en} } @misc{MichailovFritzscheHantelmannetal., author = {Michailov, Vesselin and Fritzsche, Sebastian and Hantelmann, Cord and Ossenbrink, Ralf}, title = {Aluminium foam sandwiches for lightweight structures}, series = {Metal Science and Heat Treatment}, volume = {60}, journal = {Metal Science and Heat Treatment}, number = {1-2}, issn = {1573-8973}, doi = {10.1007/s11041-018-0238-x}, pages = {44 -- 49}, abstract = {The properties of sandwiches with aluminum foam and the special features of their use in lightweight welded structures are determined. The weldability of such sandwiches in foamed and non-foamed conditions is analyzed under friction stir welding, laser beam welding and short arc welding in protective gas. The process and mechanical properties of the welds are studied. The results are generalized in a catalog that may be useful for materials scientists and designers.}, language = {en} } @misc{WasilewskiWolfZhangetal., author = {Wasilewski, Eric and Wolf, Matthias and Zhang, Wei and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Cu/LaCrO₃ joining by local melt infiltration through laser cladding}, series = {Journal of the American Ceramic Society}, volume = {101}, journal = {Journal of the American Ceramic Society}, number = {10}, issn = {1551-2916}, doi = {10.1111/jace.15767}, pages = {4472 -- 4472}, abstract = {Direct bonding of copper and porous LaCrO₃ without an extra filler interlayer was successfully completed using local and fast Cu-infiltration through laser cladding. This significantly reduced the susceptibility of the ceramic to cracking. A high-speed camera investigation into the wetting and infiltration behavior of a Cu-melt into LaCrO₃ with a porosity of ~63 vol\% was performed. By adjusting the focal distance with a constant laser power of 300 W, the Cu-melt was rapidly infiltrated into the ceramic preform in 10 seconds. This was completed under atmospheric air conditions, without added inert gas. The joining process developed can be used to fabricate ceramic/metal joints with targeted (micro-) structure properties by adjusting the infiltrated melt and the infiltration depth, which would be suitable for many applications, such as multifunctional devices, solid oxide fuel cells or heating elements.}, language = {en} } @misc{IvanovPanchenkoMichailov, author = {Ivanov, Sergey Y. and Panchenko, Oleg V. and Michailov, Vesselin}, title = {Comparative analysis of non-uniformity of mechanical properties of welded joints of Al - Mg - Si alloys in friction stir welding and laser welding}, series = {Metal Science and Heat Treatment}, volume = {60}, journal = {Metal Science and Heat Treatment}, issn = {0026-0673}, doi = {10.1007/s11041-018-0289-z}, pages = {393 -- 398}, abstract = {The properties of the welded joints of 6082-T6 alloy produced by friction stir welding (FSW) and laser welding(LW) were studied. The maximum temperature and microhardness fields in the friction stir-welded joints were shown to be asymmetrical. The concentrated energy input during laser welding yields a narrow heat-affected zone (HAZ) with sharp changes in mechanical properties. The strength of the FSW joint constitutes 72\% and that of the LWjoint—67\% of the base metal strength. In case of LW, the minimum hardness of the joint corresponds to the metal of the welded joint, while in case of FSW, it corresponds to the heat-affected zone. At the same maximum heating temperature, the hardness of the heat-affected zone of the friction stir-welded joint is lower compared to laser welding due to substantially lower rates of heating and cooling.}, language = {en} } @inproceedings{StapelfeldLaunertPasternaketal., author = {Stapelfeld, Christoph and Launert, Benjamin and Pasternak, Hartmut and Doynov, Nikolay and Michailov, Vesselin}, title = {Strength Calculation of Stiffened Structures Taking Into Consideration Realistic Weld Imperfections}, series = {European Conference on Residual Stresses 2018, ECRS-10, Leuven, Belgium, 11-14th September, 2018}, booktitle = {European Conference on Residual Stresses 2018, ECRS-10, Leuven, Belgium, 11-14th September, 2018}, editor = {Seefeldt, Marc}, publisher = {Materials Research Forum LLC}, address = {Millersville, PA}, isbn = {978-1-945291-88-3}, doi = {10.21741/9781945291890-39}, pages = {245 -- 250}, abstract = {The topic of this article is the application of an analytical numerical hybrid model for a realistic prediction of imperfections induced by welds. At the beginning, the analytical model, its physical basis as well as the physical interrelationships are explained. This is followed by the explanation of the coupling procedure between the analytical model and the numerical calculation. Afterwards, the coupled hybrid model is applied on the investigated stiffened curved structure for the determination of the weld imperfections. An ultimate load analysis gives information about the load carrying behavior under axial loading. The results are compared against the traditional approach using eigenmode-based imperfections. The comparison underlines the potential additional utilization of load bearing capacity by this new approach.}, language = {en} } @misc{StapelfeldLaunertPasternaketal., author = {Stapelfeld, Christoph and Launert, Benjamin and Pasternak, Hartmut and Doynov, Nikolay and Michailov, Vesselin}, title = {Traglastberechnung versteifter Platten und Schalen unter Ber{\"u}cksichtigung realer Schweißimperfektionen}, series = {Bauingenieur}, volume = {93}, journal = {Bauingenieur}, number = {10}, issn = {0005-6650}, pages = {403 -- 411}, abstract = {Imperfektionen, die bei Traglastberechnungen Ber{\"u}cksichtigung finden m{\"u}ssen, haben ihre Ursachen in Herstellungs- und Fertigungstoleranzen oder werden durch das Schweißen und den damit zumeist einhergehenden Nachbehandlungen in den Bauteilen hervorgerufen. Durch die W{\"a}rmewirkung des Schweißens entstehen sowohl sehr große Verformungen als auch signifikante Zug und Druckspannungen. Der strukturelle und geometrische Imperfektionsgrad wird somit maßgeblich von der Anzahl und der Lage der Schweißn{\"a}hte sowie den Schweißparametern bestimmt. F{\"u}r die Ber{\"u}cksichtigung in Traglastberechnungen ist ein physikalisch fundiertes Modell erforderlich, welches die Schweißimperfektionen schnell und pr{\"a}zise berechnet. Das gekoppelte analytisch numerische Hybridmodell erf{\"u}llt diese Kriterien. Die mathematischen Grundlagen des analytischen Modells sowie die Kopplung mit der numerischen Finite-Elemente-Berechnung werden eingangs vorgestellt und die Anwendung zur Berechnung von Verz{\"u}gen an einer Schiffsektion demonstriert. Darauffolgend wird das Hybridmodell an einer eben und einer gekr{\"u}mmten versteiften Platte zur Berechnung der Schweißimperfektionen angewendet. Anschließende Traglastberechnungen sowie der Vergleich mit den Ergebnissen unter der Annahme einer geometrischen Ersatzimperfektion in Form des kritischsten Eigenwerts gibt Auskunft dar{\"u}ber, welches Potenzial die realit{\"a}tsnahe direkte Ber{\"u}cksichtigung von Schweißimperfektionen birgt.}, language = {de} } @inproceedings{StapelfeldLaunertPasternaketal., author = {Stapelfeld, Christoph and Launert, Benjamin and Pasternak, Hartmut and Doynov, Nikolay and Michailov, Vesselin}, title = {The Influence of Geometrical and Welding Imperfections on the Strength of Stiffened Structures}, series = {High Performance Steel Structures Research Council (HPSSRC), Delft, Netherlands, 2018}, booktitle = {High Performance Steel Structures Research Council (HPSSRC), Delft, Netherlands, 2018}, pages = {191 -- 201}, abstract = {The strength calculation of stiffened plates and shells via finite element simulation has been part of the state of the art for a long time. Geometrical nonlinearities as well as the nonlinear material behavior are considered within the calculation. To simplify, both types of imperfections, geometrical and structural ones, are mostly combined in these strength calculations being considered as equivalent geometrical imperfections. Values for standard cases are included in EN 1993-1-5 in case of plated structures or 1-6 in case of shells. A second possibility is the separate definition of fabrication tolerances and residual stresses, as far as they are known. With increasing complexity of the structure, less information are however available on geometrical and particularly structural imperfections. Nevertheless, by means of a more realistic consideration of these values, the actual ultimate load can be determined significantly more exactly and the performance of high performance steel structures is increased. In the investigated cases, deformations and stresses arise mainly due to welding. Therefore, the topic of this article is the application of an analytical numerical hybrid model for predicting imperfections induced by welds. This is presented on an example of a stiffened steel structure and a subsequent ultimate load calculation. At the beginning the analytical model, its physical basis as well as the physical interrelationships are introduced and explained. This is followed by the explanation of the coupling procedure between the analytical model and the numerical calculation for the calculation of weld-induced deformations and residual stresses. The significance of the hybrid model is proven by means of a few sample applications. For a realistic determination of the weld imperfections in the investigated stiffened structure, the coupled hybrid model is used afterwards. An ultimate load analysis gives information about the load carrying behavior under axial loading. The results are compared with the results of an ultimate load analysis from a literature example assuming different eigenvalues with different scaling. The results underline the potential additional utilization of load bearing capacity by this new approach.}, language = {en} } @inproceedings{GinzburgMorozovaKlosheketal., author = {Ginzburg, Svetlana and Morozova, Iuliia and Kloshek, Alexander and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Schweißen von Stahl mit Nanopartikel modifizierten F{\"u}lldr{\"a}hten - Schweißnahtgef{\"u}ge und -eigenschaften}, series = {DVS Congress 2018 : Große Schweißtechnische Tagung, DVS-Studentenkongress, Vortr{\"a}ge der Veranstaltungen in Friedrichshafen am 17. und 18. September 2018}, booktitle = {DVS Congress 2018 : Große Schweißtechnische Tagung, DVS-Studentenkongress, Vortr{\"a}ge der Veranstaltungen in Friedrichshafen am 17. und 18. September 2018}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-036-8}, pages = {40 -- 46}, abstract = {Analyse des Schweißnahtgef{\"u}ges und -eigenschaften beim Schweißen von Stahl mit Nanopartikel modifizierten F{\"u}lldr{\"a}hten}, language = {de} } @inproceedings{FritzscheKloshekDietzetal., author = {Fritzsche, Sebastian and Kloshek, Alexander and Dietz, Eric and Michailov, Vesselin and Seidlitz, Holger and Ossenbrink, Ralf}, title = {SLM gefertigte Verbindungsknoten f{\"u}r Leichtbaurahmenelemente}, series = {DVS Congress 2018 : Große Schweißtechnische Tagung, DVS-Studentenkongress, Vortr{\"a}ge der Veranstaltungen in Friedrichshafen am 17. und 18. September 2018}, booktitle = {DVS Congress 2018 : Große Schweißtechnische Tagung, DVS-Studentenkongress, Vortr{\"a}ge der Veranstaltungen in Friedrichshafen am 17. und 18. September 2018}, number = {264}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-036-8}, abstract = {SLM gefertigte Verbindungsknoten f{\"u}r Leichtbaurahmenelemente}, language = {de} } @inproceedings{DoynovOssenbrinkMichailov, author = {Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Unterst{\"u}tzung beim thermischen Richten von geschweißten Großstrukturen durch praktikable Computersimulationen}, series = {DVS Congress 2018 : Große Schweißtechnische Tagung, DVS-Studentenkongress, Vortr{\"a}ge der Veranstaltungen in Friedrichshafen am 17. und 18. September 2018}, booktitle = {DVS Congress 2018 : Große Schweißtechnische Tagung, DVS-Studentenkongress, Vortr{\"a}ge der Veranstaltungen in Friedrichshafen am 17. und 18. September 2018}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-036-8}, pages = {364 -- 369}, abstract = {Unterst{\"u}tzung beim thermischen Richten von geschweißten Großstrukturen durch praktikable Computersimulationen}, language = {de} } @misc{BokuchavaPetrovGenchevetal., author = {Bokuchava, Gizo and Petrov, Peter and Genchev, Gancho Vladimirov and Michailov, Vesselin and Doynov, Nikolay and Ossenbrink, Ralf}, title = {Residual stress analysis in welded joints by neutron difffraction and comouter modeling}, series = {Romanian Journal of Physics}, volume = {Vol. 63}, journal = {Romanian Journal of Physics}, number = {7-8}, issn = {1221-146X}, pages = {16}, abstract = {Numerical models for thermo-mechanical simulation of the welding residual stresses in laser beam and multi-pass arc welded joints are developed. The models describe the resulting microstructure as a function of the peak temperature, austenization time, cooling time and take into account the microstructure formed after single or multiple thermal cycles. The results of simulations are validated by neutron diffraction experiments performed on FSD diffractometer at the IBR-2 pulsed reactor in FLNP JINR (Dubna, Russia). The elaborated numerical models are in good agreement with obtained neutron diffraction data, which enable to study the influence of different conditions and process parameters on the distribution of residual welding stresses.}, language = {en} } @misc{ZhangEvdokimovSchleussetal., author = {Zhang, Wei and Evdokimov, Anton and Schleuß, Leander and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Laser beam build-up welding of AlSi12-powder on AlSi1MgMn-alloy substrate}, series = {Progress in Additive Manufacturing}, volume = {4}, journal = {Progress in Additive Manufacturing}, number = {2}, issn = {2363-9512}, pages = {117 -- 129}, abstract = {In the present work, laser beam build-up welding of AlSi12 alloy powder on AlSi1MgMn-alloy (EN AW-6082) substrate has been studied to determine the laser deposition strategy for fabrication of 3-D structure. First, the influence of laser power, scanning speed and powder feeding rate on the output parameters, such as clad geometry, dilution ratio, powder efficiency and porosity were analysed for deposition of a single track. Mathematical relationships were then established and the optimal parameters were identified by the desirability approach. Second, these optimal process parameters are furthermore adjusted to fabricate rectangular, cylindrical and complex combination volumes; different layer deposition strategies are used and evaluated. Finally, by using an adapted deposition strategy, one prototype consisted of different complexly shaped elements on one curved Al-alloy substrate without welding fusion defects was manufactured. The average tensile strength of deposited samples with four different layer deposition directions (vertical 0°/90°; horizontal 0°/90°; horizontal 0° and horizontal 90°) was measured, respectively, which are comparable strengths or higher than those of cast samples. The microstructure of the laser-deposited material is investigated using optical microscopy and scanning electron microscopy as well as microcomputed tomography. Microstructure and hardness of deposited multilayers exhibit inhomogeneous distributions, which vary with the deposit location}, language = {en} } @misc{IvanovKarkhinMichailovetal., author = {Ivanov, Sergey Y. and Karkhin, Victor A. and Michailov, Vesselin and Martikainen, J. and Hiltunen, E.}, title = {Assessment of the Sensitivity of Welded Joints of Al -Mg - Si Alloys to Liquation Cracks Under Laser Welding}, series = {Metal Science and Heat Treatment}, volume = {Vol. 59}, journal = {Metal Science and Heat Treatment}, number = {11-12}, issn = {0026-0673}, doi = {10.1007/s11041-018-0225-2}, pages = {773 -- 778}, abstract = {The microstructure and the distribution of chemical elements in laser-welded joints of Al - Mg - Si alloy 6005-T6 are studied. Segregations of chemical elements are detected over grain boundaries in the heat-affected zones of the welded joints. The joints fracture by the intergrain mechanism. A Gleeble 3800 device is used to determine the temperature dependences of the mechanical properties of the alloy with allowance for the special features of the welding cycle. Amethod for evaluating the sensitivity of welded joints of aluminum alloys to formation of liquation cracks with allowance for the local properties of the metal, the welding conditions, and the rigidity of the construction is suggested.}, language = {en} } @misc{BobryninaLarionovaKoltsovaetal., author = {Bobrynina, E. V. and Larionova, T. V. and Koltsova, Tatiana S. and Ginzburg, S. A. and Michailov, Vesselin}, title = {Effect of alumina addition on weld deposits microstructure at the welding of carbon steel}, series = {Materials Physics and Mechanics}, volume = {Vol. 38}, journal = {Materials Physics and Mechanics}, number = {1}, issn = {1605-8119}, doi = {10.18720/MPM.3812018_4}, pages = {26 -- 32}, abstract = {The formation of acicular ferrite in the structure of weld deposits when welding carbon steels is often associated with the introduction of nonmetallic additives into the electrode material. Fe-alumina composite powders with alumina particles less than 1 µm were used as a filler for cored welding wire and the influence of aluminum oxide additives up to 2,5 wt.\% on the structure of the welded seam was studied. It was shown that the addition of aluminum oxide to the welding wire led to the initiation of the formation of intragranular acicular ferrite in the weld deposit and to a more even distribution of hardness through the zones of weld seam.}, language = {en} } @misc{DoynovStapelfeldMichailovetal., author = {Doynov, Nikolay and Stapelfeld, Christoph and Michailov, Vesselin and Pasternak, Hartmut and Launert, Benjamin}, title = {Distortion analysis of large scaled welded structures}, series = {Mathematical Modelling of Weld Phenomena 12 : selected peer reviewed papers from the 12th International Seminar Numerical Analysis of Weldability : September 23-26, 2018, Graz, Schloss Seggau - Austria}, journal = {Mathematical Modelling of Weld Phenomena 12 : selected peer reviewed papers from the 12th International Seminar Numerical Analysis of Weldability : September 23-26, 2018, Graz, Schloss Seggau - Austria}, editor = {Sommitsch, Christof and Enzinger, Norbert and Mayr, Peter}, publisher = {Verlag der Technischen Universit{\"a}t Graz}, address = {Graz}, isbn = {978-3-85125-615-4}, doi = {10.3217/978-3-85125-615-4}, pages = {254 -- 280}, abstract = {The work presents an innovative approach for simulation of welding induced distortions, which allows taking into consideration the local effects of the welding process as well as the global interactions in the structure. The approach bases on an integration of analytical and numerical calculation's procedures in a hybrid model, realized with the aid of the inherent strain concept. The analytical procedure calculates the shrinkage strain components and area of the plastic deformed zone, caused by welding. The calculated strains are then transferred to the global finite element model in order to predict the distortions and stresses in the structure after every welding stage, as well as their final state. The consideration of welding scenarios, weld sequence, clamping conditions and the assembling stages is done by taking into account the intermediate variation of the strain state during the manufacturing steps. The article gives the theoretical basis of the analytical model. The consideration of the essential physical relations is put into discussion. The application of the model is illustrated on complex structures. Its reliability and practicability are demonstrated by means of a validation study.}, language = {en} } @misc{StapelfeldLaunertPasternaketal., author = {Stapelfeld, Christoph and Launert, Benjamin and Pasternak, Hartmut and Doynov, Nikolay and Michailov, Vesselin}, title = {Improve load capacity calculations by considering realistic imperfections induced by welding for plates and shells}, series = {Stability and ductility of steel structures 2019 : proceedings of the International Colloquia on Stability and Ductility of Steel Structures (SDSS 2019), September 11-13, 2019, Prague, Czech Republic}, journal = {Stability and ductility of steel structures 2019 : proceedings of the International Colloquia on Stability and Ductility of Steel Structures (SDSS 2019), September 11-13, 2019, Prague, Czech Republic}, publisher = {CRC Press}, address = {Boca Raton}, isbn = {978-0-367-33503-8}, pages = {1059 -- 1067}, language = {en} } @misc{NaumovMorozovaRylkovetal., author = {Naumov, Anton and Morozova, Iuliia and Rylkov, Evgenii and Obrosov, Aleksei and Isupov, Fedor and Michailov, Vesselin and Rudskoy, Andrey I.}, title = {Metallurgical and Mechanical Characterization of High-Speed Friction Stir Welded AA 6082-T6 Aluminum Alloy}, series = {Materials}, volume = {12}, journal = {Materials}, number = {24}, issn = {1996-1944}, doi = {10.3390/ma12244211}, pages = {16}, abstract = {The objective of this study was to investigate the effect of the high welding speed on the mechanical properties and their relations to microstructural characteristics of butt friction stir welded joints with the use of 6082-T6 aluminum alloy. The aluminum sheets of 2.0 mm thick were friction stir welded at low (conventional FSW) and high welding speeds (HSFSW) of 200 and 2500 mm/min, respectively. The grain size in the nugget zone (NZ) was decreased; the width of the softened region was narrowed down as well as the lowest microhardness value located in the heat-affected zone (HAZ) was enhanced by HSFSW. The increasing welding speed resulted in the higher ultimate tensile strength and lower elongation, but it had a slight influence on the yield strength. The differences in mechanical properties were explained by analysis of microstructural changes and tensile fracture surfaces of the welded joints, supported by the results of the numerical simulation of the temperature distribution and material flow. The fracture of the conventional FSW joint occurred in the HAZ, the weakest weld region, while all HSFSW joints raptured in the NZ. This demonstrated that both structural characteristics and microhardness distribution influenced the actual fracture locations.}, language = {en} } @misc{MorozovaBonnelRosertetal., author = {Morozova, Iuliia and Bonnel, Jean-Marie and Rosert, Reinhard and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Einfluss der Schweißposition beim MSG-F{\"u}lldrahtschweißen auf die Kerbschlagz{\"a}higkeit von hoch- und niedriglegierten St{\"a}hlen}, series = {DVS Congress 2019Große Schweißtechnische Tagung : DVS-Studentenkongress : Vortr{\"a}ge der Veranstaltungen in D{\"u}sseldorf vom 16. bis 17. September 2019}, journal = {DVS Congress 2019Große Schweißtechnische Tagung : DVS-Studentenkongress : Vortr{\"a}ge der Veranstaltungen in D{\"u}sseldorf vom 16. bis 17. September 2019}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-066-5}, pages = {310 -- 318}, abstract = {Die Schweißposition beeinflusst erheblich die mechanischen Eigenschaften der Schweißnaht, insbesondere die Kerbschlagz{\"a}higkeit. Dies zeigt ein umfassender Vergleich der mechanischen Eigenschaften von Schweißg{\"u}tern, die in der Steigposition (PF) und Wannenlage (PA) ausgef{\"u}hrt wurden. Schweißg{\"u}ter von Kohlenstoff-Mangan-St{\"a}hlen weisen in der PF-Position eine reduzierte Kerbschlagarbeit im Vergleich zur PA-Position auf. Dagegen ist bei austenitischen und Duplexst{\"a}hlen der Einfluss der Schweißposition auf die Kerbschlagarbeit genau entgegengesetzt. Der Vortrag fasst den Einfluss der Schweißpositionen auf die mechanischen Eigenschaften zusammen und liefert eine Erkl{\"a}rung f{\"u}r die gegens{\"a}tzlichen Auswirkungen auf die Kerbschlagz{\"a}higkeit der Schweißg{\"u}ter. Der Schwerpunkt liegt dabei auf hochlegierten F{\"u}lldr{\"a}hten mit einer schnell erstarrenden Schlacke. Die Schlackeneigenschaften, Schweißgutmikrostruktur, Delta-Ferrit-Gehalte f{\"u}r Schweißg{\"u}ter vom Typ Duplexstahl (2209) und von austenitischen Schweißg{\"u}tern (308L) sowie die Auswirkungen der Schweißposition auf die Richtung des Schweißkornwachstums werden erl{\"a}utert. Zum Vergleich werden Kohlenstoff-Mangan-Rutil-F{\"u}lldr{\"a}hte mit schnell erstarrender Schlacke herangezogen.}, language = {de} } @misc{NaumovMorozovaIsupovetal., author = {Naumov, Anton and Morozova, Iuliia and Isupov, Fedor and Golubev, Iurii and Michailov, Vesselin}, title = {Temperature Influence on Microstructure and Properties Evolution of Friction Stir Welded Al-Mg-Si Alloy}, series = {Key Engineering Materials}, volume = {822}, journal = {Key Engineering Materials}, issn = {1662-9795}, doi = {10.4028/www.scientific.net/KEM.822.122}, pages = {122 -- 128}, abstract = {The temperature influence on the microstructure evolution and microhardness of the agehardenable aluminium alloy 6082 T6 during friction stir welding was defined. In order to achieve this aim, the thermocycles calculated using the developed 3D Finite Element Model were physically simulated on the Gleeble-3800 in the points which located in the different zones of the weld. The microstructure in the chosen points after Gleeble testing was investigated as well as the microhardness was measured. The results were consequently compared with the relevant results obtained after friction stir welding. It was shown that the microstructure and microhardness profile are influenced not only by temperature but by deformation. The increase in hardness in different zones after FSW compared to Gleeble testing can be explained by the grain refinement in the nugget zone as well as the hardening precipitate distribution along the weld which can occur more rapidly due to the deformation influence.}, language = {en} } @misc{GolubevMorozovaNaumovetal., author = {Golubev, Iurii and Morozova, Iuliia and Naumov, Anton and Hantelmann, Cord and Doynov, Nikolay and Michailov, Vesselin}, title = {Numerical Simulation and Experimental Investigation on Impulse Friction Stir Welding of 6082-T6 Aluminum Alloy}, series = {Papers from Materials Science and Technology 2017 (MS\&T17), October 8 - 12, 2017, David L. Lawrence Convention Center, Pittsburgh, Pennsylvania USA}, journal = {Papers from Materials Science and Technology 2017 (MS\&T17), October 8 - 12, 2017, David L. Lawrence Convention Center, Pittsburgh, Pennsylvania USA}, doi = {10.7449/2017/mst_2017_987_994}, pages = {987 -- 994}, abstract = {The series of impulse friction stir welding (IFSW) experiments for aluminum alloy 6082-T6 butt joints was performed to obtain micrographs, tensile and hardness test samples and to receive the validation data for a numerical model of the process. Impulse force and frequency were varied to determine the effect of individual process parameters on microstructure evolution and mechanical properties of the welded butt joints. A three-dimensional model was established to simulate temperature distribution, heat generation and contact state between the tool and the workpiece during IFSW. Based on the numerical simulation, the influence of the impulses on heat input, maximum weld temperatures and contact state was found. The combination of impulse force and frequency effected the grain refinement. The influence of impulses on the elongation and hardness of the welded joints during IFSW were determined.}, language = {en} } @misc{EvdokimovOssenbrinkDoynovetal., author = {Evdokimov, Anton and Ossenbrink, Ralf and Doynov, Nikolay and Michailov, Vesselin}, title = {Laser beam welding of steel-aluminum joints - influence of weld metal elastic-plastic properties on the distortions}, series = {Mathematical Modelling of Weld Phenomena 12 : selected peer reviewed papers from the 12th International Seminar Numerical Analysis of Weldability : September 23-26, 2018, Graz, Schloss Seggau - Austria}, journal = {Mathematical Modelling of Weld Phenomena 12 : selected peer reviewed papers from the 12th International Seminar Numerical Analysis of Weldability : September 23-26, 2018, Graz, Schloss Seggau - Austria}, editor = {Sommitsch, Christof and Enzinger, Norbert and Mayr, Peter}, publisher = {Verlag der Technischen Universit{\"a}t Graz}, address = {Graz}, isbn = {978-3-85125-615-4}, doi = {10.3217/978-3-85125-615-4}, pages = {431 -- 440}, abstract = {Great attention is focused nowadays on laser welding of dissimilar steel-aluminum joints in overlap configuration in key-hole mode. It was found that elastic-plastic properties of the weld metal exhibit strong difference to those of the base alloys and can be defined as a function of aluminum content in the weld metal. A developed Finite-Element simulation model allows prediction of the aluminum content as a function of welding parameters and subsequently the elastic-plastic properties of the weld metal as a function of the determined content. The main goal of the present study is to show the impact of the weld metal properties on welding distortions and residual stresses. For that purpose, a sensitivity analysis of the thermomechanical model was performed, where the distortions and residual stresses were computed as a function of welding parameters and therefore as a function of corresponding weld metal properties. The analysis showed that the influence of the weld metal is essential, and its properties should be taken into consideration in the models for better prediction accuracy.}, language = {en} } @misc{KaishevaBokuchavaPapushkinetal., author = {Kaisheva, Darina and Bokuchava, Gizo and Papushkin, Igor and Genchev, Gancho Vladimirov and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin and Petrov, Peter}, title = {Determination of residual stresses in fiber laser welded stainless steel joints by neutron diffraction method}, series = {Proc. SPIE 11047, 20th International Conference and School on Quantum Electronics: Laser Physics and Applications}, journal = {Proc. SPIE 11047, 20th International Conference and School on Quantum Electronics: Laser Physics and Applications}, address = {Nessebar}, doi = {10.1117/12.2516421}, pages = {7}, abstract = {This study presents an experimental results of residual stress states in stainless steel plate samples with size 100 x 50 x 10 mm welded using a high-power fiber laser. The technological parameters of the welding process were: laser power Q = 15 kW; laser spot size = 0.65 mm; welding speed V = 3 m/min; 4 m/min; 5 m/min, using 30 L/min of protective Ar gas. The neutron diffraction method was used to determine the residual stresses in the bulk of the material. The neutron experiments were performed on the FSD diffractometer at the IBR-2 pulsed reactor in the Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research - Dubna, Russian Federation. The measured residual stress distributions exhibit maxima at weld seam centers. As expected, for all specimens the residual stress is falling down in regions distant from the weld zone. Maximal residual stress value of 492 MPa was observed for sample welded with speed of V = 5 m/min.}, language = {en} } @misc{ShapovalovKodzhaspirovHantelmannetal., author = {Shapovalov, Oleg and Kodzhaspirov, Georgii and Hantelmann, Cord and Michailov, Vesselin}, title = {Effect of a Welding Method on the Fatigue Strength and Fracture of Foam-Aluminum Sandwiches}, series = {Russian Metallurgy (Metally)}, volume = {Vol. 2019}, journal = {Russian Metallurgy (Metally)}, number = {10}, issn = {0036-0295}, doi = {10.1134/S0036029519100239}, pages = {1063 -- 1066}, abstract = {The influence of argon-arc welding and laser welding on the fatigue properties and the fracture of a foam-aluminum sandwich is studied. Argon-arc-welded samples are found to have the highest fatigue strength.}, language = {en} } @misc{EvdokimovDoynovOssenbrinketal., author = {Evdokimov, Anton and Doynov, Nikolay and Ossenbrink, Ralf and Obrosov, Aleksei and Weiß, Sabine and Michailov, Vesselin}, title = {Thermomechanical laser welding simulation of dissimilar steel-aluminum overlap joints}, series = {International Journal of Mechanical Sciences}, volume = {190}, journal = {International Journal of Mechanical Sciences}, issn = {1879-2162}, doi = {10.1016/j.ijmecsci.2020.106019}, pages = {18}, abstract = {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.}, language = {en} } @misc{GinzburgMorozovaKlosheketal., author = {Ginzburg, Svetlana and Morozova, Iuliia and Kloshek, Alexander and Ossenbrink, Ralf and Michailov, Vesselin and Bobrynina, Elizaveta and Koltsova, Tatiana S. and Tolochko, Oleg V. and Ko{\c{c}}ak, Mustafa and Ozbek, Sunullah and Morozova, Iuliia}, title = {Addition of nanoparticles to flux cored wires for the nucleation of acicular ferrite microstructure in weld metals of the high-strength low-alloy steel}, series = {Welding and Cutting}, volume = {19}, journal = {Welding and Cutting}, number = {1}, issn = {1612-3433}, pages = {48 -- 53}, abstract = {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.}, language = {en} } @misc{MorozovaObrosovNaumovetal., author = {Morozova, Iuliia and Obrosov, Aleksei and Naumov, Anton and Kr{\´o}licka, Aleksandra and Golubev, Iurii and Bokov, Dmitry O. and Doynov, Nikolay and Weiß, Sabine and Michailov, Vesselin}, title = {Impact of Impulses on Microstructural Evolution and Mechanical Performance of Al-Mg-Si Alloy Joined by Impulse Friction Stir Welding}, series = {Materials}, volume = {14}, journal = {Materials}, number = {2}, issn = {1996-1944}, doi = {https://doi.org/10.3390/ma14020347}, abstract = {Impulse Friction Stir Welding (IFSW) was utilized to join 6082-T6 alloy plates at various impulse frequencies. A distinctive feature of IFSW is the generation of mechanical impulses that enhances the forging action of the tool, and thereby, alters the weld microstructure. The microstructural evolution in the Stir Zone (SZ) with special focus on the strengthening precipitation behavior, and overall mechanical properties of the IFSW joints have been investigated. It was demonstrated that the strengthening β″ precipitates reprecipitated in the SZ of the IFSW joints during natural aging. In contrast, no precipitates were found in the SZ of the Friction Stir Welding (FSW) weld. Partial reversion of β″ after IFSW is supposed to occur due to more developed subgrain network and higher dislocation density introduced by impulses that accelerated precipitation kinetics. Dynamic recrystallisation was facilitated by impulses resulting in a fine, homogeneous structure. There was no significant difference between the microhardness in the SZ, tensile and yield strength of the FSW and IFSW joints. However, the application of impulses demonstrated the smoothing of the hardness reduction in the transition region at the advancing side. The shift of the fracture location from the Heat-Affected Zone (HAZ) by FSW to the SZ as well as higher elongation of the joints by IFSW of lower frequencies could be related to the grain refinement and the change of the grain orientation.}, language = {en} } @misc{ShapovalovShapovalovaOssenbrinketal., author = {Shapovalov, Oleg and Shapovalova, Mariia and Ossenbrink, Ralf and Heckel, Thomas and Michailov, Vesselin and Weiß, Sabine and Gaal, Mate}, title = {Verbessern der Korrosionsbest{\"a}ndigkeit eines hochtemperaturbest{\"a}ndigen Ultraschalld{\"a}mpfungsk{\"o}rpers mittels Laserstrahl-Auftragschweißen}, series = {DVS Berichte 2021}, journal = {DVS Berichte 2021}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-147-1}, pages = {370 -- 377}, abstract = {W{\"a}hrend in einem konventionellen Ultraschallpr{\"u}fkopf ein Kunststoffd{\"a}mpfungsk{\"o}rper mit Kleber oder {\"O}l an einen Piezoschwinger angekoppelt ist, werden als Hochtemperaturl{\"o}sung feinpor{\"o}se sintermetallische D{\"a}mpfungsmaterialien mit einer Fl{\"u}ssigglasankopplung eingesetzt. Um dabei das Sintermetall vor dem korrosiven Angriff der Glasschmelze zu sch{\"u}tzten, wird am D{\"a}mpfungsk{\"o}rper gegenw{\"a}rtig Gold- oder Platinfolie zeit- und kostenaufwendig appliziert. In der aktuellen Arbeit wurde eine Methode zum Korrosionsschutz der sintermetallischen Oberfl{\"a}che 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 zun{\"a}chst der Einfluss verschiedener Schweißparameter wie Laserleistung, Vorschubgeschwindigkeit und Pulvermenge auf die Auftragsqualit{\"a}t (Nahtform, Vermischungsgrad, Porosit{\"a}t) metallografisch bewertet. Anschließend wurden die aufgetragenen Schichten hinsichtlich ihrer Korrosionsbest{\"a}ndigkeit getestet. Der Kontakt mit einer fl{\"u}ssigen 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 f{\"u}r den Prozess gezeigt. Die identifizierten Schweißparameter wurden im n{\"a}chsten Schritt erfolgreich an das sintermetallische Substrat angepasst.}, language = {de} } @misc{KaneneksKloshekMorozovaetal., author = {Kaneneks, Michael and Kloshek, Alexander and Morozova, Iuliia and Ossenbrink, Ralf and Michailov, Vesselin and Sembol, Ronny}, title = {WAAM eines Zwischenst{\"u}cks f{\"u}r die Bergbauausr{\"u}stung}, series = {DVS Bericht 2021}, volume = {2021}, journal = {DVS Bericht 2021}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-147-1}, pages = {315 -- 323}, abstract = {Die lichtbogenbasierte additive Fertigung (WAAM) ist ein vielversprechendes Werkzeug, um die Ersatzteilbereitstellung von schwer verf{\"u}gbaren oder aufwendig herstellbaren Einzelkomponenten in k{\"u}rzester Zeit zu gew{\"a}hrleisten. Die Straffung innerbetrieblicher Abl{\"a}ufe 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 Werkst{\"u}cke entsprechen. Ein solcher Nachweis konnte am Beispiel eines additiv hergestellten Zwischenst{\"u}cks f{\"u}r die Bergbauausr{\"u}stung mit einer abschließenden Charakterisierung der Werkstoffeigenschaften erfolgreich gef{\"u}hrt werden. Das Zwischenst{\"u}ck 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 Zwischenst{\"u}cks bestimmt sowie die Festigkeit und Z{\"a}higkeit mit den geforderten Werkstoffkennwerten des bisher eingesetzten konventionellen Konstruktionsmaterials verglichen.}, language = {de} } @misc{JokischDoynovOssenbrinketal., author = {Jokisch, Torsten and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Heat source model for electron beam welding of nickel-based superalloys}, series = {Materials testing : Materialpr{\"u}fung}, volume = {63}, journal = {Materials testing : Materialpr{\"u}fung}, number = {1}, issn = {2195-8572}, doi = {10.1515/mt-2020-0002}, pages = {17 -- 28}, language = {en} } @misc{ValkovKotlarskiOrmanovaetal., author = {Valkov, Stefan and Kotlarski, Georgi and Ormanova, Maria and Doynov, Nikolay and Ossenbrink, Ralf and Petrov, Peter and Michailov, Vesselin}, title = {Crystallography and Mechanical Properties of Wire Arc Additively Manufactured Al5356 Components}, series = {Comptes Rendus de L'Academie Bulgare des Sciences}, volume = {74}, journal = {Comptes Rendus de L'Academie Bulgare des Sciences}, number = {No. 6}, issn = {1310-1331}, doi = {10.7546/CRABS.2021.06.03}, pages = {820 -- 827}, abstract = {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.}, language = {en} } @misc{WasilewskiKaneneksDoynovetal., author = {Wasilewski, Eric and Kaneneks, Michael and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Laserstrahlschweißen - Verzugs- und Kaltrissminimierung durch simulationsbasierte Steuerung}, series = {DVD Congress 2020 : Große Schweißtechnische Tagung : DVS Campus : Vortr{\"a}ge der Online-Veranstaltungen vom 14. bis 18. September 2020}, journal = {DVD Congress 2020 : Große Schweißtechnische Tagung : DVS Campus : Vortr{\"a}ge der Online-Veranstaltungen vom 14. bis 18. September 2020}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-098-6}, pages = {9}, abstract = {Leichtbau und das Streben nach Ressourcen- und Energieeffizienz f{\"o}rdern in den letzten Jahren vermehrt den Einsatz hochfester St{\"a}hle. Das Laserstrahlschweißen dieser Werkstoffe wird in der industriellen Großserienferti-gung zur effizienten Herstellung hochpr{\"a}ziser Bauteile und Komponenten mit h{\"o}chsten Qualit{\"a}tsanforderungen eingesetzt. Die Vermeidung schweißbedingter Fehler wie Schweißverzug und Kaltrissbildung sind dabei von ent-scheidender Bedeutung. Konventionelle Anwendungen erf{\"u}llen diesen Anspruch derzeit bedingt durch sehr enge Prozesstoleranzen und die Auswahl unkritischer Werkstoffe, was die Potentiale der F{\"u}geverbindung begrenzt. Auf Basis von FE-Schweißprozesssimulationen konnten Konzepte entwickelt werden, welche eine Verzugs- und Riss-minderung durch aktive Steuerung des Laserschweißprozesses erm{\"o}glichen. Die zugrundeliegenden Modelle be-r{\"u}cksichtigen zum einen das schweißbedingte Temperaturfeld, Gef{\"u}geumwandlungen und Eigenspannungen f{\"u}r die Berechnung des Verzugs. Zudem wird die lokale Wasserstoffkonzentration berechnet und die Ergebnisse der Schweißprozesssimulation mittels eines Kaltrisstools bewertet, welches werkstoffspezifische Risskriterien enth{\"a}lt. Die F{\"a}higkeit das Verzugs- und Kaltrissverhalten abzubilden, er{\"o}ffnet die M{\"o}glichkeit zur Parametervariation. Aus den erhobenen Daten wurden Konzepte der aktiven Krafteinleitung mit einer dynamischen Werkst{\"u}ckeinspannung abgeleitet, die zu Verzugs- und Kaltrissminimierung f{\"u}hren und die Schweißbarkeit hochfester Werkstoffe f{\"o}rdern.}, language = {de} } @misc{JokischDoynovOssenbrinketal., author = {Jokisch, Torsten and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin and B{\"o}ttger, Bernd and Senger, Aleksej}, title = {Analysis of temperature field during electron beam welding of hot crack sensitive nickel base alloy}, series = {IEBW International Electron Beam Welding Conference: lectures of the 6th International Conference taking place online on 9 to 10 March 2021}, journal = {IEBW International Electron Beam Welding Conference: lectures of the 6th International Conference taking place online on 9 to 10 March 2021}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-133-4}, pages = {81 -- 87}, abstract = {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.}, language = {en} } @book{PasternakStapelfeldLaunertetal., author = {Pasternak, Hartmut and Stapelfeld, Christoph and Launert, Benjamin and Michailov, Vesselin and Doynov, Nikolay}, title = {Ermittlung der Tragf{\"a}higkeit neuartiger st{\"a}hlerner Schalenbauwerke unter realit{\"a}tsnaher Ber{\"u}cksichtigung des Schweißverzugs}, publisher = {Forschungsvereinigung Stahlanwendung e. V.}, address = {D{\"u}sseldorf}, isbn = {978-3-946885-89-4}, pages = {227}, language = {de} } @misc{PiottWerberSchleussetal., author = {Piott, Michael and Werber, Alexandra and Schleuss, Leander and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Numerical and experimental analysis of heat transfer in resistance spot welding process of aluminum alloy AA5182}, series = {International Journal of Advanced Manufacturing Technology}, volume = {Vol. 111}, journal = {International Journal of Advanced Manufacturing Technology}, number = {5-6}, issn = {0268-3768}, doi = {10.1007/s00170-020-06197-7}, pages = {1671 -- 1682}, abstract = {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.}, language = {en} } @misc{PiottWerberSchleussetal., author = {Piott, Michael and Werber, Alexandra and Schleuss, Leander and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {A study of the heat transfermechanism in resistance spot welding of aluminum alloys AA5182 and AA6014}, series = {International Journal of Advanced Manufacturing Technology}, volume = {Vol. 111}, journal = {International Journal of Advanced Manufacturing Technology}, issn = {0268-3768}, doi = {10.1007/s00170-020-05650-x}, pages = {263 -- 271}, abstract = {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.}, language = {en} }