@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} } @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{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} } @techreport{SchleussBrobeckOssenbrinketal., author = {Schleuß, Leander and Brobeck, Andreas F. W. and Ossenbrink, Ralf and Polzin, Ralf and Michailov, Vesselin}, title = {Rollennahtschweißen strukturierter Feinbleche}, publisher = {BTU, Lehrstuhl F{\"u}ge- und Schweißtechnik}, address = {Cottbus-Senftenberg}, pages = {XV, 154}, abstract = {Strukturierte Bleche besitzen eine dreidimensionale Struktur aus regelm{\"a}ßig angeordneten Versteifungselementen, welche die Steifigkeit der Bleche global erh{\"o}hen. Neben der Steifigkeitserh{\"o}hung besitzen strukturierte Bleche eine vergr{\"o}ßerte Oberfl{\"a}che, ein ver{\"a}ndertes akustisches Verhalten sowie ein ansprechendes Design als positive Merkmale. Mit der Qualifizierung des Rollennahtschweißens f{\"u}r verzugsarme, mediendichte Schweißn{\"a}hte erschließen sich neue wichtige industrielle Anwendungen f{\"u}r strukturierte Bleche und den daraus hergestellten mehrschaligen Bauelementen (zwei strukturierte Bleche im Parallelstoß) mit Hohlr{\"a}umen zwischen den Blechen. Innovative Produktentwicklungen in der W{\"a}rmetechnik, im Transportwesen und im Bauwesen k{\"o}nnen mit strukturierten Blechen f{\"u}r Rekuperatoren, L{\"u}ftungsanlagen, W{\"a}rmeboxen, chemische Apparate, temperierbare Beh{\"a}lter sowie Fußbodenheizungen, K{\"u}hlr{\"a}ume, Klimakammern, Fassadenelemente oder L{\"a}rmschutzw{\"a}nde umgesetzt werden. Derzeit steht dazu kein geeignetes F{\"u}geverfahren zur Verf{\"u}gung, welches alle Anforderungen erf{\"u}llt. Das Rollennahtschweißen eignet sich, strukturierte Bleche so zu f{\"u}gen, dass sie den Anforderungen der zuk{\"u}nftigen Einsatzbereiche entsprechen unter Erhalt der positiven Eigenschaften. In diesem Projekt wurden strukturierte Einzelbleche und der aus ihnen gefertigten mehrschaligen Bauelemente mit dem Rollennahtschweißen gef{\"u}gt. Zur Herstellung der mehrschaligen Bauelemente wurden Rollpunktn{\"a}hte genutzt, welche strukturerhaltend hergestellt wurden. Dazu sind neuartige Rollennahtelektroden entwickelt, gefertigt und erprobt worden. Die notwendigen Schweißparameter zum strukturerhaltenden Schweißen und zum Schweißen mit Verformung der Struktur wurden in schweißbereichsdiagrammen dokumentiert und die Verbindungseigenschaften durch Zugversuche und Metallografie qualifiziert. F{\"u}r die genannten Anwendungsbereiche wurden Dichtn{\"a}hte an den Randbereichen der Bleche hergestellt. Durch die {\"U}berpr{\"u}fung der Dichtheit, der Druck- und Korrosionsbest{\"a}ndigkeit wurden die mehrschaligen Bauelemente f{\"u}r m{\"o}gliche Anwender qualifiziert. F{\"u}r die durchgef{\"u}hrten Recherchen und Untersuchungen wurde ein wissenschaftlicher Mitarbeiter in Vollzeit besch{\"a}ftigt und durch eine studentische Hilfskraft, sowie einen Techniker unterst{\"u}tzt. Die geleistete Arbeit entspricht im vollen Umfang dem begutachteten und bewilligten Antrag und war f{\"u}r die Durchf{\"u}hrung des Vorhabens notwendig und angemessen.}, language = {de} } @inproceedings{OssenbrinkMichailov, author = {Ossenbrink, Ralf and Michailov, Vesselin}, title = {Simulation der Gef{\"u}geumwandlungen mit der STAAZ-Methode}, series = {23. CAD-FEM Users Meeting, 08.-10. November 2005, Bonn}, booktitle = {23. CAD-FEM Users Meeting, 08.-10. November 2005, Bonn}, publisher = {CAD-FEM GmbH}, address = {Grafing bei M{\"u}nchen}, language = {de} } @inproceedings{OssenbrinkMichailov, author = {Ossenbrink, Ralf and Michailov, Vesselin}, title = {Thermomechanical Numerical Simulation with the Maximum Temperature Austenisation Cooling Time Model (STAAZ)}, series = {Mathematical modelling of weld phenomena}, booktitle = {Mathematical modelling of weld phenomena}, editor = {Cerjak, Horst-Hannes}, publisher = {Verl. der Techn. Univ. Graz}, address = {Graz}, isbn = {978-3-902465-69-6}, language = {en} } @inproceedings{SchleussOssenbrinkMichailov, author = {Schleuß, Leander and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Widerstandspunktschweißen strukturierter Bleche - Schweißbereiche, Pr{\"u}fung, Anwendung}, language = {de} } @inproceedings{MichailovOssenbrinkStapelfeld, author = {Michailov, Vesselin and Ossenbrink, Ralf and Stapelfeld, Christoph}, title = {Anwendungsnahe Schweißsimulation komplexer Strukturen}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-87155-290-8}, language = {de} } @incollection{GrafSchleussOssenbrinketal., author = {Graf, K. and Schleuß, Leander and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Auswirkung von strukturierten F{\"u}gepartnern auf geklebte Verbindungen}, series = {Große Schweißtechnische Tagung 2011}, booktitle = {Große Schweißtechnische Tagung 2011}, publisher = {DVS-Verl.}, address = {D{\"u}sseldorf}, isbn = {978-3-87155-267-0}, pages = {472 -- 477}, language = {de} } @misc{MichailovDoynovStapelfeldetal., author = {Michailov, Vesselin and Doynov, Nikolay and Stapelfeld, Christoph and Ossenbrink, Ralf}, title = {Hybrid Model for Prediction of Welding Distortions in Large Structures}, series = {Journal of Frontiers of Materials Science}, volume = {5}, journal = {Journal of Frontiers of Materials Science}, number = {2}, issn = {2095-025X}, pages = {209 -- 215}, language = {en} } @misc{FritzscheOssenbrinkMichailov, author = {Fritzsche, Sebastian and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Experimental characterisation of structured sheet metals}, series = {Key Engineering Materials}, volume = {473}, journal = {Key Engineering Materials}, issn = {1013-9826}, pages = {404 -- 411}, language = {en} } @misc{DreibatiOssenbrinkDoynovetal., author = {Dreibati, Ossama and Ossenbrink, Ralf and Doynov, Nikolay and Michailov, Vesselin}, title = {Physical and numerical simulation of thermo-mechanical properties in the weld heat affected zone of an AlMgSi-alloy}, series = {Materials Science Forum}, volume = {706-709}, journal = {Materials Science Forum}, issn = {0255-5476}, pages = {1491 -- 1496}, language = {en} } @misc{MalikovOssenbrinkViehwegeretal., author = {Malikov, Viatcheslav and Ossenbrink, Ralf and Viehweger, Bernd and Michailov, Vesselin}, title = {Experimental investigation and analytical calculation of the bending force for air bending of structured sheet metals}, series = {Advanced Materials Research}, volume = {418-420}, journal = {Advanced Materials Research}, issn = {1022-6680}, pages = {1294 -- 1300}, language = {en} } @misc{KornienkoOssenbrinkMichailov, author = {Kornienko, Elena and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Corrosion properties of structured sheet metals in salt environment}, series = {Engineering Review}, volume = {31}, journal = {Engineering Review}, number = {2}, issn = {1330-9587}, pages = {97 -- 104}, language = {en} } @misc{MalikovOssenbrinkViehwegeretal., author = {Malikov, Viatcheslav and Ossenbrink, Ralf and Viehweger, Bernd and Michailov, Vesselin}, title = {Analytical and numerical calculation of the force and power requirements for air bending of structured sheet metals}, series = {Key Engineering Materials}, volume = {Vol. 473}, journal = {Key Engineering Materials}, issn = {1013-9826}, doi = {10.4028/www.scientific.net/KEM.473.602}, pages = {602 -- 609}, language = {en} } @inproceedings{MalikovOssenbrinkViehwegeretal., author = {Malikov, Viatcheslav and Ossenbrink, Ralf and Viehweger, Bernd and Michailov, Vesselin}, title = {FE-Simulation of deep drawing of structured sheet metals}, series = {New technologies and achievements in metallurgy and materials engineering, XIII International Scientific conference, a collective monograph}, booktitle = {New technologies and achievements in metallurgy and materials engineering, XIII International Scientific conference, a collective monograph}, isbn = {978-83-87745-74-5}, pages = {410 -- 413}, language = {en} } @book{MichailovDoynovOssenbrink, author = {Michailov, Vesselin and Doynov, Nikolay and Ossenbrink, Ralf}, title = {Sensibilit{\"a}tsanalyse der thermomechanischen FE-Schweißsimulation}, publisher = {Shaker}, address = {Aachen}, isbn = {978-3-8440-1016-9}, pages = {137}, language = {de} } @misc{GenchevDreibatiOssenbrinketal., author = {Genchev, Gancho Vladimirov and Dreibati, Ossama and Ossenbrink, Ralf and Doynov, Nikolay and Michailov, Vesselin}, title = {Physical and Numerical Simulation of the Heat-affected Zone of Multi-pass Welds}, series = {Materials Science Forum}, journal = {Materials Science Forum}, number = {Vol. 762}, issn = {0255-5476}, pages = {544 -- 550}, abstract = {The paper presents a numerical and experimental approach for the quantification of the thermo-mechanical properties in multi-pass weld's heat affected zone (HAZ) of low alloy steel "S355J2+N". First, the characteristic temperature cycles for multi-pass welds were identified by FE temperature field simulations of welding. Based on the identified temperature cycles, the microstructure in the HAZ has been physically simulated with the simulation and testing system Gleeble 3500 to investigate the influence of multi thermal exposure on the thermo-mechanical properties. Thus, the thermo-mechanical material properties including thermal strain and temperature dependent stress strain behaviour as function of peak temperatures and cooling rates have been determined. These material properties were used to calibrate a developed model for numerical prediction of the material properties of multi-pass weld HAZ.}, language = {en} } @incollection{GenchevOssenbrinkDoynovetal., author = {Genchev, Gancho Vladimirov and Ossenbrink, Ralf and Doynov, Nikolay and Michailov, Vesselin}, title = {Gef{\"u}geeigenschaften in der W{\"a}rmeeinflusszone von Mehrlagenschweißungen aus S355J2+N}, series = {Fortschritte in der Metallographie}, booktitle = {Fortschritte in der Metallographie}, editor = {Keßler, Olaf}, publisher = {Inventum}, address = {Bonn}, isbn = {978-3-88355-392-4}, pages = {167 -- 172}, language = {de} } @phdthesis{Ossenbrink, author = {Ossenbrink, Ralf}, title = {Thermomechanische Schweißsimulation unter Ber{\"u}cksichtigung von Gef{\"u}geumwandlungen}, publisher = {Shaker}, address = {Aachen}, isbn = {978-3-8322-8131-1}, pages = {152}, language = {de} } @incollection{OssenbrinkBrandMichailov, author = {Ossenbrink, Ralf and Brand, M. and Michailov, Vesselin}, title = {Numerische Simulation der Eigenspannungen und des Bauteilverzugs beim Schweißen mit Ber{\"u}cksichtigung des Umwandlungsverhaltens}, series = {Große Schweißtechnische Tagung, Schweissen und Schneiden, 2003}, booktitle = {Große Schweißtechnische Tagung, Schweissen und Schneiden, 2003}, publisher = {DVS-Verlag}, address = {D{\"u}sseldorf}, isbn = {3-87155-683-1}, pages = {279 -- 283}, language = {de} } @misc{ZhangDoynovWolfetal., author = {Zhang, Wei and Doynov, Nikolay and Wolf, Matthias and Dreibati, Ossama and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Investigation of the Thermal Shock Behavior of Ceramic Using a Combination of Experimental Testing and FE-Simulation Methods}, series = {Advanced engineering materials}, volume = {15}, journal = {Advanced engineering materials}, number = {6}, issn = {1527-2648}, doi = {10.1002/adem.201200241}, pages = {480 -- 484}, abstract = {Thermal shock behavior of ceramics plays a decisive role in their broad industrial applications. For enhanced understanding of damage and failure mechanism under thermal shock loading, in the present work, a combination of experimental testing and numerical simulation methods has been used. The thermal shock behavior of the alumina (99.7\%) disk samples has been investigated by using a plasma test stand: the bottom of the ceramic disks were locally heated in the center by plasma beam; during the heat treatment the temperature distribution at the top of the sample was recorded with a thermographic system. To characterize the thermal shock resistance, a thermomechanical simulation was subsequently carried out. It calculates the temperature and stress distribution within the ceramic disks. The calculated critical thermal tension stresses are reported, which led to the failure of the ceramic disks under thermal shock loading. The effect of the sample thickness on the temperature and stress distribution is presented. Compared with the experimental results the simulated results show excellent agreement. As conclusion, it is possible to determine the thermal shock behavior of ceramic materials by the combination of experimental testing and numerical simulation.}, language = {en} } @misc{KornienkoOssenbrinkMichailov, author = {Kornienko, Elena and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Corrosion resistance of zinc-coated structured sheet metals}, series = {Corrosion Science}, volume = {Vol. 69}, journal = {Corrosion Science}, issn = {0010-938X}, pages = {270 -- 280}, abstract = {The purpose of this study is to characterise the corrosion behaviour of zinc-coated sheet metals after a structuring process using the salt spray test. The investigated structured material is manufactured by hydroforming and has a periodic hexagonal geometry. The corrosion behaviour has been evaluated by estimating the development of the corrosion area and penetration depth. The results of the investigation show that the corrosion area is larger on the smooth sheet than on the structured sheet. The difference between the structured and smooth sheets is negligible with increasing exposure time. Furthermore, the reasons for the different corrosion behaviours are discussed.}, language = {en} } @incollection{OssenbrinkGenchevDoynov, author = {Ossenbrink, Ralf and Genchev, Gancho Vladimirov and Doynov, Nikolay}, title = {Simulation der Schweißeigenspannungen und des -verzuges unter Ber{\"u}cksichtigung der Gef{\"u}geumwandlungen mit dem STAAZ-Modell}, series = {Internationales Symposium Schweißtechnik - Verfahren, Werkstoffe, Simulation, Cottbus, 6. November 2013}, booktitle = {Internationales Symposium Schweißtechnik - Verfahren, Werkstoffe, Simulation, Cottbus, 6. November 2013}, editor = {Michailov, Vesselin}, publisher = {Shaker Verlag}, address = {Aachen}, isbn = {978-3-8440-2319-0}, pages = {149 -- 167}, abstract = {Die vorliegende Arbeit stellt das von Professor Michailov vorgeschlagene Spitzentemperatur-Austenitisierungs- Abk{\"u}hlzeit-Modell f{\"u}r die thermomechanische Schweißsimulation unter Ber{\"u}cksichtigung der Gef{\"u}geumwandlungen vor. Das Modell erfasst die f{\"u}r die Gef{\"u}geausbildung maßgebenden Temperaturzyklen durch seine drei so genannten STAAZ-Parameter: Spitzentemperatur, Austenitisierungs- und Abk{\"u}hlzeit. Die Korrelation dieser Temperaturzyklusparameter mit den thermomechanischen gef{\"u}geabh{\"a}ngigen Werkstoffeigenschaften erfolgt auf Grundlage einer empirischen Datenbasis. Mit der vorgenommenen Erweiterung zu Mehrmalig-(M-)STAAZ l{\"a}sst sich das aus einem vorgelagerten Temperaturzyklus entstandene Zwischengef{\"u}ge ber{\"u}cksichtigen.}, language = {de} } @misc{DreibatiOssenbrinkMichailov, author = {Dreibati, Ossama and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Quantification of cold cracking parameters of high strength steels by physical simulation under welding conditions}, series = {Quarterly journal of the Japan Welding Society}, volume = {31}, journal = {Quarterly journal of the Japan Welding Society}, number = {4}, issn = {0288-4771}, doi = {10.2207/qjjws.31.148s}, pages = {148 -- 152}, abstract = {Cold cracks in welds are the result of the formation of brittle microstructure as martensite in the presence of diffusible hydrogen as well as of tensile stresses. Cold cracks occur when the combination of cold crack influence parameters (CCIP) overcomes a critical limit. In this study, critical combinations of CCIP were identified with an enhanced test procedure under welding conditions. The test is based on the physical simulation technique of heat affected zone (HAZ) and it is carried out using the test and simulation center Gleeble 3500. Thereby, laboratory special specimens are charged with hydrogen from pure hydrogen atmosphere in the initial stage of the test. Rigidly restraint specimen section is subjected to different weld temperature cycles. Through the thermal exposure, the desired microstructure of HAZ is set in the test zone of the restraint specimen section. A plastic deformation takes place owing to the prevented expansion during heating and contraction of the specimen during cooling. Consequently, compressive or tensile reactions stresses arise in the deformed zone. Cracked specimen represents a critical combination of the CCIP. The quantitative cold crack criterion separates the cold crack susceptible combinations from those non susceptible.}, language = {en} } @misc{MichailovDreibatiOssenbrinketal., author = {Michailov, Vesselin and Dreibati, Ossama and Ossenbrink, Ralf and Schweizer, Frank}, title = {Rechnergest{\"u}tzte Vorhersage der Kaltrissneigung laserstrahlgeschweißter Bauteile aus hochfesten St{\"a}hlen - Teil 1}, series = {Schweißen und Schneiden : Fachzeitschrift f{\"u}r Schweißen und verwandte Verfahren}, volume = {65}, journal = {Schweißen und Schneiden : Fachzeitschrift f{\"u}r Schweißen und verwandte Verfahren}, number = {11}, issn = {0036-7184}, pages = {776 -- 781}, 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{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} } @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{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} } @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} } @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{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{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{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{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{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{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{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{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} } @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} } @misc{JokischDoynovOssenbrinketal., author = {Jokisch, Torsten and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Analysis of Local Strain Evolution during Electron Beam Welding of Hot Crack Sensitive Nickel Base Conventionally Cast Alloy 247 LC CC}, series = {Journal of Materials Engineering and Performance}, volume = {31}, journal = {Journal of Materials Engineering and Performance}, number = {9}, issn = {1544-1024}, doi = {10.1007/s11665-022-06660-4}, pages = {7009 -- 7017}, abstract = {Among different joining methods, the electron beam welding is recently applied for manufacturing of turbine components from temperature-resistant nickel-based conventionally cast Alloy 247 LC CC. However, the high tendency to hot cracking, in particular the formation of solidification cracks, remains a major challenge. Experiments indicate a significant reduction in hot cracks if the welding is performed outside the common welding parameter range. To understand these observations, a study of local thermo-mechanical conditions during electron beam welding of Alloy 247 samples was carried out using numerical simulations. The results were subsequently compared with reference test welds. For this purpose, a finite element model for coupled transient thermal and mechanical analysis was created and used. The work presents a comparative analysis of the evolution of strain components in brittle temperature range during cooling, considering the distribution and orientation of the cracks. Various relations between local strain kinetics and crack appearance, with notable influence of the plastic strain vector, were observed. Finally, the aspects of assessment of hot crack susceptibility with aid of thermo-mechanical welding simulation are discussed.}, language = {en} } @misc{HagenKlinkenbergOssenbrinketal., author = {Hagen, Christian and Klinkenberg, Franz-Josef and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Resistance spot welding of dissimilar material joints with a cold-gas-sprayed inlayer}, series = {The International Journal of Advanced Manufacturing Technology}, journal = {The International Journal of Advanced Manufacturing Technology}, issn = {1433-3015}, doi = {10.1007/s00170-023-11897-x}, pages = {12}, abstract = {In this publication, cold gas spraying (CGS) is investigated as an enabler for aluminum-steel joints. Using a powder-based coating process to adhere a steel layer to an aluminum substrate allows a steel component to be welded to the deposited layer by resistance spot welding. This method permits the metallurgical connection between similar materials to be separated, while mechanical bonding ensures the connection at the dissimilar aluminum-to-inlayer interface. A modification of the porous CGS layer, as well as the creation of the remelted zone in the aluminum, can be observed during the resistance spot welding process. Electron backscatter diffraction (EBSD) analyses show that the severely prestressed particles in the CGS coating recrystallize, which coincides with a decrease in defect density and hardness in the heat-affected zone. Microscopy of the aluminum substrate shows the creation of metallurgical pores as well as the expansion of pores attributed to the casting process. The rise in remelted aluminum hardness and decrease in the heat-affected zone of the CGS layer indicate the formation of a metallurgical notch.}, language = {en} } @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} } @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} } @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{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} }