@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} } @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} } @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{MiahKloshekGonzalezCastanoetal., author = {Miah, Kamal Uddin Mohammad and Kloshek, Alexander and Gonz{\´a}lez-Casta{\~n}o, Miriam and Kehm, Christian and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Herstellen hocheffektiver Mikroreaktoren durch selektives Laserstrahlschmelzen}, series = {DVS Congress 2022, Große Schweißtechnische Tagung, DVS Campus ; Kurzfassungen der Vortr{\"a}ge der Veranstaltung in Koblenz vom 19. bis 21. September 2022 ; (Langfassungen der Beitr{\"a}ge auf USB-Karte)}, journal = {DVS Congress 2022, Große Schweißtechnische Tagung, DVS Campus ; Kurzfassungen der Vortr{\"a}ge der Veranstaltung in Koblenz vom 19. bis 21. September 2022 ; (Langfassungen der Beitr{\"a}ge auf USB-Karte)}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-189-1}, pages = {708 -- 713}, abstract = {Das pulverbasierte 3D-Metalldrucken erm{\"o}glicht die Fertigung von hochkomplexen Integralbauteilen, die als Tr{\"a}gerstruktur f{\"u}r Mikroreaktoren benutzt werden. Nach einer Beschichtung der Struktur mit einem Katalysatormaterial, k{\"o}nnen diese Mikroreaktoren h{\"o}chst effizient f{\"u}r die CO2-Methanisierung eingesetzt werden. Durch die additive Fertigung mit dem selektiven Laserstrahlschmelzen (SLM) wurden adaptierte dreidimensionale periodische Gitterstrukturen mit sehr geringen Wandst{\"a}rken hergestellt. Diese weisen ein sehr g{\"u}nstiges Verh{\"a}ltnis von Oberfl{\"a}che zu Volumen (TPMS - Triply periodic minimal surface) auf. Des Weiteren zeigen die TPMS-Strukturen vorteilhafte Str{\"o}mungseigenschaften, die sowohl f{\"u}r die Beschichtung mit dem Katalysator-Material als auch die Durchstr{\"o}mung mit den Reaktionsmedien im Betrieb essentiell sind. So ist es beispielsweise m{\"o}glich, durch die Variation der Dimension einer TPMS-Struktur die Oberfl{\"a}che pro Volumeneinheit, den hydraulischen Durchmesser des Reaktors und somit auch den Transportprozess des Fluids deutlich zu verbessern. Diese Faktoren erm{\"o}glichen eine effektivere Gas-Katalysator-Reaktion. Im Vergleich zu Mikroreaktorstrukturen aus den traditionellen Herstellungsverfahren liefern die additiv gefertigten Strukturen sowohl eine h{\"o}here CO2-Umwandlungsrate als auch eine CH4-Selektivit{\"a}t innerhalb des diffusionskontrollierten Bereichs.}, language = {de} } @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} } @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{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{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{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} } @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} } @inproceedings{SasseOssenbrinkMichailov, author = {Sasse, Ina and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Welding of structured sheet metals with high power fiber laser}, series = {Międzynarodowa Sesja Studencka, 30. Mai 2012, Częstochowa/Polen}, booktitle = {Międzynarodowa Sesja Studencka, 30. Mai 2012, Częstochowa/Polen}, address = {Częstochowa}, isbn = {978-83-87745-69-1}, pages = {285 -- 290}, language = {en} } @inproceedings{OssenbrinkDoynovMichailov, author = {Ossenbrink, Ralf and Doynov, Nikolay and Michailov, Vesselin}, title = {Welding simulation of aluminium to steel joints by means of arc welding Processes}, series = {10th International Scientific and Technical Conference, Advanced metal materials and technologies (AMMT'2013), June 25-29, Saint Petersburg, 2013}, booktitle = {10th International Scientific and Technical Conference, Advanced metal materials and technologies (AMMT'2013), June 25-29, Saint Petersburg, 2013}, publisher = {Izdat. Polytechn. Univ.}, address = {Saint Petersburg, Russia}, pages = {523 -- 528}, abstract = {The object of the present work is the introduction of a welding simulation approach for aluminium to steel welded joints which are realised by short-arc welding. The study is carried out with special emphasis on the simulation of temperature field by means of conduction solution, on the applicability of different metallurgical models as well as the aspects of the mechanical simulation of the residual welding stresses and distortions. As result an approved heat source model is suggested and the calibration parameters are presented. For the modelling of the microstructure and corresponding thermomechanical material properties in the heat affected zone different material models are validated. They are used to simulate the welding residual stresses and distortions. Furthermore, the welding simulation of a real component as well as a simulation study of different welding scenarios is presented.}, language = {en} } @inproceedings{GenchevDoynovOssenbrinketal., author = {Genchev, Gancho Vladimirov and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Simulation des Mehrlagenschweißens unter Ber{\"u}cksichtigung der Gef{\"u}geumwandlungen}, series = {Conference proceedings, 2012 - ANSYS Conference \& 30. CADFEM Users' Meeting, 24. - 26. Oktober 2012, Kassel}, booktitle = {Conference proceedings, 2012 - ANSYS Conference \& 30. CADFEM Users' Meeting, 24. - 26. Oktober 2012, Kassel}, publisher = {CADFEM GmbH}, address = {Grafing}, pages = {Art. 2.2.9}, abstract = {Der Konferenzvortrag stellt das entwickelte M-STAAZ Modell vor. Mit dem M-STAAZ l{\"a}sst sich in der FE-Simulation die {\"A}nderung der Werkstoffkennwerte bei mehrmaliger Temperaturbelastung wie in der WEZ von Mehrlagenschweißungen ber{\"u}cksichtigen.}, language = {de} } @inproceedings{GenchevOssenbrinkDoynovetal., author = {Genchev, Gancho Vladimirov and Ossenbrink, Ralf and Doynov, Nikolay and Michailov, Vesselin}, title = {Material Properties of the HAZ of Multi-Pass Welded Joints from low alloyed Steel}, series = {Junior Euromat 2012, Paperlist}, booktitle = {Junior Euromat 2012, Paperlist}, pages = {A297}, language = {en} } @inproceedings{GenchevDoynovOssenbrinketal., author = {Genchev, Gancho Vladimirov and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Bewertung der relevanten Einflussfaktoren auf die Gef{\"u}geumwandlungen und thermomechanischen Eigenschaften bei komplexen Temperaturbelastungen}, series = {ANSYS Conference \& 29. CADFEM Users' Meeting 2011, conference proceedings, 19. - 21. October 2011, Stuttgart, ICS}, booktitle = {ANSYS Conference \& 29. CADFEM Users' Meeting 2011, conference proceedings, 19. - 21. October 2011, Stuttgart, ICS}, publisher = {CADFEM GmbH}, address = {Grafing}, isbn = {3-937523-08-1}, abstract = {Der Vortrag stellt die Identifizierung und Bewertung der relevanten Einflussfaktoren auf die Gef{\"u}geumwandlungen und auf die thermomechanischen Werkstoffkennwerte bei komplexen Temperaturbelastungen vor. Dies erfolgt durch physikalische Simulation der Gef{\"u}ge in der WEZ von Mehrlagenschweißungen und Aufnahme von Dilatometerkurven und Spannungs-Dehnungskurven. Es wurden einflussarme Kombination von Temperaturzyklen und weitere mit starkem Einfluss auf die Gef{\"u}geumwandlung identifiziert. Hinweise zu den erforderlichen Werkstoffkennwerten f{\"u}r die numerische Schweißsimulation wurden gegeben.}, language = {de} } @inproceedings{OssenbrinkMichailov, author = {Ossenbrink, Ralf and Michailov, Vesselin}, title = {Vorhersage der H{\"a}rteverteilung beim Schweißen mit Hilfe der numerischen Simulation}, series = {Conference proceedings, 21st CAD-FEM Users' Meeting 2003, International Congress on FEM Technology, 12. - 14. November 2003, im Hotel Dorint Sanssouci Berlin, Potsdam}, booktitle = {Conference proceedings, 21st CAD-FEM Users' Meeting 2003, International Congress on FEM Technology, 12. - 14. November 2003, im Hotel Dorint Sanssouci Berlin, Potsdam}, publisher = {CAD-FEM GmbH}, address = {Grafing bei M{\"u}nchen}, isbn = {3-937523-00-6}, language = {de} } @inproceedings{SasseSchleussOssenbrinketal., author = {Sasse, Ina and Schleuß, Leander and Ossenbrink, Ralf and Michailov, Vesselin}, title = {F{\"u}gen strukturierter Bleche - Remote-Laserstrahlschweißen im Vergleich zum Widerstandspunktschweißen}, series = {DVS Congress 2013, Große Schweißtechnische Tagung, DVS-Studentenkongress}, booktitle = {DVS Congress 2013, Große Schweißtechnische Tagung, DVS-Studentenkongress}, publisher = {DVS-Verlag}, address = {D{\"u}sseldorf}, isbn = {978-3-87155-614-2}, pages = {98 -- 103}, language = {de} } @misc{BaenaMorenoGonzalezCastanoNavarrodeMigueletal., author = {Baena-Moreno, Francisco Manuel and Gonz{\´a}lez-Casta{\~n}o, Miriam and Navarro de Miguel, Juan Carlos and Miah, Kamal Uddin Mohammad and Ossenbrink, Ralf and Odriozola, Jos{\´e} Antonio and Arellano-Garcia, Harvey}, title = {Stepping toward Efficient Microreactors for CO2 Methanation: 3D Printed Gyroid Geometry}, series = {ACS Sustainable Chemistry \& Engineering}, volume = {9}, journal = {ACS Sustainable Chemistry \& Engineering}, number = {24}, issn = {2168-0485}, doi = {10.1021/acssuschemeng.1c01980}, pages = {8198 -- 8206}, abstract = {This work presents a comparative study towards the development of efficient micro-reactors based on 3D-printed structures. Thus, the study evaluates the influence of the metal substrate geometry on the performance of structured catalysts for the CO2 methanation reaction. For this purpose, 0.5\%Ru-15\%Ni/MgAl2O4 catalyst is wash coated over two different micro-monolithic metal substrates: a conventional parallel channel honeycomb structure and a novel 3D-printed structure with a complex gyroid geometry. The effect of the metal substrate geometry is analyzed for several CO2 sources including ideal flue gas atmospheres, the presence of residual CH4 and CO in the flue gas, as well as simulated biogas sources. The advantages of the gyroid-3D complex geometries over the honeycomb structures are shown for all evaluated conditions, providing at the best-case scenario a 14\% improvement of CO2 conversion. Moreover, this contribution shows that systematically tailoring geometrical features of structured catalysts becomes an effective strategy to achieve improved catalysts performances independent of the flue gas composition. By enhancing the transport processes and the gas-catalyst interactions, the employed gyroid 3D metal substrates enable boosted CO2 conversions and greater CH4 selectivity within diffusional controlled regimes.}, language = {en} } @misc{GonzalezCastanoBaenaMorenoNavarrodeMigueletal., author = {Gonz{\´a}lez-Casta{\~n}o, Miriam and Baena-Moreno, Francisco Manuel and Navarro de Miguel, Juan Carlos and Miah, Kamal Uddin Mohammad and Arroyo-Torralvo, F{\´a}tima and Ossenbrink, Ralf and Odriozola, Jos{\´e} Antonio and Benzinger, Walther and Hensel, Andreas and Wenka, Achim and Arellano-Garc{\´i}a, Harvey}, title = {3D-printed structured catalysts for CO2 methanation reaction: Advancing of gyroid-based geometries}, series = {Energy Conversion and Management}, volume = {258}, journal = {Energy Conversion and Management}, issn = {2590-1745}, doi = {10.1016/j.enconman.2022.115464}, pages = {8}, abstract = {This work investigates the CO2 methanation rate of structured catalysts by tuning the geometry of 3D-printed metal Fluid Guiding Elements (FGEs) structures based on periodically variable pseudo-gyroid geometries. The enhanced performance showed by the structured catalytic systems is mostly associated with the capability of the FGEs substrate geometries for efficient heat usages. Thus, variations on the channels diameter resulted in ca. 25\% greater CO2 conversions values at intermediate temperature ranges. The highest void fraction evidenced in the best performing catalyst (3D-1) favored the radial heat transfer and resulted in significantly enhanced catalytic activity, achieving close to equilibrium (75\%) conversions at 400 ◦C and 120 mL/min. For the 3D-1 catalyst, a mathematical model based on an experimental design was developed thus enabling the estimation of its behavior as a function of temperature, spatial velocity, hydrogen to carbon dioxide (H2/CO2) ratio, and inlet CO2 concentration. Its optimal operating conditions were established under 3 different scenarios: 1) no restrictions, 2) minimum H2:CO2 ratios, and 3) minimum temperatures and H2/CO2 ratio. For instance, for the lattest scenario, the best CO2 methanation conditions require operating at 431 ◦C, 200 mL/min, H2/CO2 = 3 M ratio, and inlet CO2 concentration = 10 \%.}, 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} } @inproceedings{OssenbrinkMichailovWohlfahrt, author = {Ossenbrink, Ralf and Michailov, Vesselin and Wohlfahrt, Helmut}, title = {Numerische Simulation der Eigenspannungen und des Bauteilverzugs beim Schweißen unter Ber{\"u}cksichtigung der zeitlichen und {\"o}rtlichen {\"A}nderung der Dehnrate}, series = {Internationale FEM-Technologietage, 20th CAD-FEM Users' Meeting, 9-11 Oktober 2002, Friedrichshafen}, booktitle = {Internationale FEM-Technologietage, 20th CAD-FEM Users' Meeting, 9-11 Oktober 2002, Friedrichshafen}, publisher = {CAD-FEM GmbH}, address = {Grafing bei M{\"u}nchen}, 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} } @misc{WasilewskiDoynovOssenbrinketal., author = {Wasilewski, Eric and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Investigations on the thermal conditions during laser beam welding of high-strength steel 100Cr6}, series = {Advances in Industrial and Manufacturing Engineering}, volume = {6}, journal = {Advances in Industrial and Manufacturing Engineering}, issn = {2666-9129}, doi = {10.1016/j.aime.2023.100118}, abstract = {This study examines the thermal conditions during laser beam welding of 100Cr6 high-strength steel using a TruDisk5000 disc laser with a continuous adjustable power range of 100-5000 W. Two parameter sets, characterized by laser power and welding speeds, were analyzed by thermal-metallurgical FE simulations to determine their impact on the thermal conditions during welding. The results show a significant shift in heat coupling, with conduction transitioning to deep penetration welding. As a result of the high welding speeds and reduced energy input, extremely high heating rates up to 2∙104 K s-1 (set A) respectively 4∙105 K s-1 (set B) occur. Both welds thus concern a range of temperature state values for which conventional Time-Temperature-Austenitization (TTA) diagrams are currently not defined, requiring calibration of the material models through general assumptions. Also, the change in energy input and welding speed causes significantly steep temperature gradients with a slope of approximately 5∙103 K mm-1 and strong drops in the temperature rates, particularly in the heat affected zone. The temperature cycles also show very different cooling rates for the respective parameter sets, although in both cases they are well below a cooling time t8/5 of 1 s, so that the phase transformation always leads to the formation of martensite. Since the investigated parameters are known to cause a loss of technological strength and conditionally result in cold cracks, these results will be used for further detailed experimental and numerical investigation of microstructure, hydrogen distribution, and stress-strain development at different restraint conditions.}, language = {en} } @misc{MeessAnasenzlOssenbrinketal., author = {Meeß, Joachim and Anasenzl, Manuel and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Influence of Particle Velocities on Adhesion Strength of Cold Spray Inner Diameter Coatings}, series = {Journal of Thermal Spray Technology}, volume = {31}, journal = {Journal of Thermal Spray Technology}, number = {7}, issn = {1544-1016}, doi = {10.1007/s11666-022-01439-4}, pages = {2025 -- 2038}, abstract = {Due to the recent developments of hardware components and the hereby resulting ability to increase process parameters, the application area of the cold gas spray technology is expanding quickly. The present research focuses on the influence of working gas pressure and working gas temperature on the adhesive strength of inner diameter coatings, which were produced with two different alloy steel powder variants. Gas pressure and gas temperature were varied in four different parameter sets. At first, the powder variants were examined for morphology and particle size distribution. Secondly, the influence of four different process parameters on the achievable particle velocity was measured. In addition, the arithmetical mean height (Sa) of the coating was measured in order to determine the effect of the four parameter sets on the achievable surface roughness. Furthermore, the impact of the process parameters on the steel particles' penetration depth into the aluminum substrate was examined. Finally, adhesion strength measurements of the inner diameter coatings were carried out. The results reveal that with rising process parameters, the particle velocity increases, and the achievable surface roughness is lowered. It was also shown that the penetration depth of the particles into the substrate increases with increasing particle velocity. In addition, this study demonstrated a dependence of the process parameters on the adhesion strength for inner diameter coatings.}, language = {en} } @misc{EvdokimovJasiewiczDoynovetal., author = {Evdokimov, Anton and Jasiewicz, Filip and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Simulation of surface heat treatment with inclined laser beam}, series = {Journal of Manufacturing Processes}, volume = {81}, journal = {Journal of Manufacturing Processes}, issn = {1526-6125}, doi = {10.1016/j.jmapro.2022.06.051}, pages = {107 -- 114}, abstract = {The beam inclination leads to a change in the laser spot size on the material surface. The higher the inclination, the larger the irradiated area and the lower the laser intensity. Moreover, if the material surface is outside of the beam focal plane, the intensity distribution profile becomes asymmetric. In this study, a heat source model, which calculates the intensity distribution on the workpiece surface as a function of beam parameters (beam waist, divergence half-angle) and process parameters (laser power, incidence angle, and distance to focal plane) was developed. The applicability of the heat source model was demonstrated by simulating 4 different laser hardening regimes. Once the heat efficiency coefficient had been calibrated the developed finite-element model allowed computation of temperatures while hardening with perpendicular laser beams as well as with inclined beams. The open-source software FEniCSx was used for the finite element computations. The mathematical formulation, required for performing temperature simulations with FEniCSx was briefly introduced.}, language = {en} } @misc{MeessAnasenzlOssenbrinketal., author = {Meeß, Joachim and Anasenzl, Manuel and Ossenbrink, Ralf and Michailov, Vesselin and Singh, Reeti and Kondas, Jan}, title = {Cold Gas Spray Inner Diameter Coatings and Their Properties}, series = {Journal of Thermal Spray Technology}, volume = {31}, journal = {Journal of Thermal Spray Technology}, issn = {1544-1016}, doi = {10.1007/s11666-022-01365-5}, pages = {1712 -- 1724}, abstract = {Due to recent developments, cold gas spraying technology can now be used to create inner diameter coatings for cylinder inner diameters > 70 mm. The present investigations focus on the process optimization and the specific properties of cold gas spray inner diameter coatings created with three different alloy steel powder variants. The cold gas spray coating properties were compared with the corresponding properties of coatings created with twin wire arc technology. The particle velocities and deposition efficiencies were measured with the aim of optimizing the process parameters. The most suitable process parameters were used to analyze the microstructure of the deposited coating in terms of porosity and interface quality. Furthermore, the hardness and adhesion strength properties of the coatings were measured. In addition, the different liners were honed, and the achievable surface roughness of each was determined. Finally, wear resistance was evaluated using ball-on-disk testing. The results reveal that with the maximum process parameters, the cold gas spray coating properties are comparable to the twin wire arc coating properties. Further investigations are necessary to determine whether cold gas spraying is a feasible alternative to the current series production process for cylinder surface coatings.}, language = {en} } @inproceedings{MalikovOssenbrinkViehwegeretal., author = {Malikov, Viatcheslav and Ossenbrink, Ralf and Viehweger, Bernd and Michailov, Vesselin}, title = {Flat hemming of structured sheet metals}, series = {Proceedings of International Conference on Innovative Technologies, IN-TECH, 01.09.2011 to 03.09.2011, Bratislava, Slovakia}, booktitle = {Proceedings of International Conference on Innovative Technologies, IN-TECH, 01.09.2011 to 03.09.2011, Bratislava, Slovakia}, language = {en} } @inproceedings{DreibatiOssenbrinkMichailov, author = {Dreibati, Ossama and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Hydrogen charging of high strength steel specimens and physical simulation of cold cracking under laser beam welding conditions}, series = {THERMEC 2011, International Conference on Processing \& Manufacturing of Advanced Materials, processing, fabrication, properties, applications, August 1 - 5, 2011, Quebec City, Canada, Vol. 2}, booktitle = {THERMEC 2011, International Conference on Processing \& Manufacturing of Advanced Materials, processing, fabrication, properties, applications, August 1 - 5, 2011, Quebec City, Canada, Vol. 2}, publisher = {TTP, Trans Tech Publ.}, address = {Durnten-Zurich [u.a.]}, isbn = {978-3-0-3785-303-0}, pages = {1391 -- 1396}, language = {en} } @inproceedings{SasseSchleussOssenbrinketal., author = {Sasse, Ina and Schleuß, Leander and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Cutting of structured sheet metals with high power fiber laser}, series = {Proceedings of International Conference on Innovative Technologies, IN-TECH, 01.09.2011 to 03.09.2011, Bratislava, Slovakia}, booktitle = {Proceedings of International Conference on Innovative Technologies, IN-TECH, 01.09.2011 to 03.09.2011, Bratislava, Slovakia}, pages = {485 -- 488}, language = {en} } @inproceedings{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 = {THERMEC 2011, International Conference on Processing \& Manufacturing of Advanced Materials, processing, fabrication, properties, applications, August 1 - 5, 2011, Quebec City, Canada, Vol. 2}, booktitle = {THERMEC 2011, International Conference on Processing \& Manufacturing of Advanced Materials, processing, fabrication, properties, applications, August 1 - 5, 2011, Quebec City, Canada, Vol. 2}, publisher = {TTP, Trans Tech Publ.}, address = {Durnten-Zurich [u.a.]}, pages = {1491 -- 1496}, language = {en} } @inproceedings{DreibatiZhangWolfetal., author = {Dreibati, Ossama and Zhang, Wei and Wolf, Matthias and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Thermo-mechanical properties of refractory ceramic for the numerical simulation of their thermo-shock behaviour}, language = {en} } @inproceedings{KornienkoOssenbrinkMichailov, author = {Kornienko, Elena and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Investigation of corrosion behaviour of structured sheet metals by salt spray test}, series = {Proceedings of International Conference on Innovative Technologies, IN-TECH, 01.09.2011 to 03.09.2011, Bratislava, Slovakia}, booktitle = {Proceedings of International Conference on Innovative Technologies, IN-TECH, 01.09.2011 to 03.09.2011, Bratislava, Slovakia}, pages = {308 -- 311}, language = {en} } @inproceedings{OssenbrinkMichailov, author = {Ossenbrink, Ralf and Michailov, Vesselin}, title = {Schweißtechnische FE-Simultaion mit Gef{\"u}geumwandlungen}, language = {de} } @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} } @inproceedings{DoynovOssenbrinkMichailov, author = {Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Verbesserte Verzugsvorhersage beim Laserstrahlschweißen durch Implementierung eines Prozessmodells}, series = {Schweißen und Schneiden 2006, Vortr{\"a}ge der gleichnamigen Großen Schweißtechnischen Tagung in Aachen vom 20. bis 22. September 2006}, booktitle = {Schweißen und Schneiden 2006, Vortr{\"a}ge der gleichnamigen Großen Schweißtechnischen Tagung in Aachen vom 20. bis 22. September 2006}, publisher = {DVS-Verl.}, address = {D{\"u}sseldorf}, isbn = {978-3-87155-699-9}, language = {de} } @inproceedings{DoynovOssenbrinkSchmidtetal., author = {Doynov, Nikolay and Ossenbrink, Ralf and Schmidt, J. and Michailov, Vesselin}, title = {Utilization of Weld Pool Models in Thermal-Mechanical Simulations}, series = {Mathematical modelling of weld phenomena 8}, booktitle = {Mathematical modelling of weld phenomena 8}, publisher = {Verl. der Techn. Univ. Graz}, address = {Graz}, isbn = {978-3-902465-69-6}, language = {en} } @inproceedings{OssenbrinkDoynovMichailov, author = {Ossenbrink, Ralf and Doynov, Nikolay and Michailov, Vesselin}, title = {FE-Simulation des Schweißens}, language = {de} } @inproceedings{DoynovOssenbrinkKlosheketal., author = {Doynov, Nikolay and Ossenbrink, Ralf and Kloshek, Alexander and Michailov, Vesselin}, title = {Simulation of the Welding Distortions in Large Welded Structures}, language = {en} } @inproceedings{NauroschatOssenbrinkMichailov, author = {Nauroschat, C. and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Ermittlung von lokalen Bauteileigenschaften durch physikalische Simulation des Schweißens}, series = {Fortschritte in der Metallographie, Vortragstexte der 42. Metallographie-Tagung, 17. - 19. September 2008 in Jena}, booktitle = {Fortschritte in der Metallographie, Vortragstexte der 42. Metallographie-Tagung, 17. - 19. September 2008 in Jena}, publisher = {MAT-INFO}, address = {Frankfurt am Main [u.a.]}, isbn = {3-88355-370-0}, pages = {227 -- 232}, language = {de} } @inproceedings{PfennigKloshekOssenbrinketal., author = {Pfennig, T. and Kloshek, Alexander and Ossenbrink, Ralf and Doynov, Nikolay and Michailov, Vesselin}, title = {Experimentelle und numerische Untersuchungen von Al-Stahl-Mischverbindungen}, series = {Die Verbindungs-Spezialisten 2009, Vortr{\"a}ge der Veranstaltung in Essen vom 14. bis 19. September 2009}, booktitle = {Die Verbindungs-Spezialisten 2009, Vortr{\"a}ge der Veranstaltung in Essen vom 14. bis 19. September 2009}, isbn = {978-3-87155-584-8}, pages = {236 -- 240}, language = {de} } @misc{KarkhinHomichOssenbrinketal., author = {Karkhin, Victor A. and Homich, P. N. and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Experimentellgest{\"u}tztes Berechnungsverfahren zur Ermittlung des Temperaturfeldes beim Laserstrahlschweißen}, series = {Zeitschrift "Schweißproduktion"}, journal = {Zeitschrift "Schweißproduktion"}, pages = {13 -- 17}, language = {de} } @incollection{MichailovDoynovPfennigetal., author = {Michailov, Vesselin and Doynov, Nikolay and Pfennig, T. and Degen, M. and Ossenbrink, Ralf}, title = {Simulationsgest{\"u}tzte Entwicklung einer Aluminium-Stahl-Schweißkontruktion eines Slicermessers f{\"u}r die Lebensmittelverarbeitung}, series = {Große Schweißtechnische Tagung 2011}, booktitle = {Große Schweißtechnische Tagung 2011}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-87155-267-0}, pages = {428 -- 433}, 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{MalikovOssenbrinkViehwegeretal., author = {Malikov, Viatcheslav and Ossenbrink, Ralf and Viehweger, Bernd and Michailov, Vesselin}, title = {Investigation of air bending of structured sheet metals by multistage FE simulation}, series = {The International Journal of Advanced Manufacturing Technology}, volume = {63}, journal = {The International Journal of Advanced Manufacturing Technology}, number = {5-8}, issn = {1433-3015}, doi = {10.1007/s00170-012-3927-4}, pages = {449 -- 455}, language = {en} } @misc{SasseSchleussOssenbrinketal., author = {Sasse, Ina and Schleuß, Leander and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Joining of structured sheet metals - Remote laser beam welding in comparison with resistance spot welding}, series = {Welding and Cutting}, volume = {13}, journal = {Welding and Cutting}, number = {1}, pages = {43 -- 47}, abstract = {One main problem of thin-walled, large-area sheet components for lightweight construction solutions is the inadequate stiffness. One approach for a solution is provided by structured sheet metals which have an increased flexural stiffness due to three-dimensionally incorporated structures. The areas of application of the structured sheet metals (e.g. in subassemblies in automobile, rail vehicle and tank construction) necessitate adapted welding technologies. Since few systematic investigations have been conducted on structured sheet metals in the field of joining technology until now, there is a lack of knowledge about the further processing of these sheets by means of welding technology. The aims of the presented investigations are to make it possible to utilise these modern semi-finished products industrially using remote laser beam welding and to compare this with resistance spot welding. Both are important joining processes in the areas of applications interesting for structured sheet metals and thus constitute key technologies for industrial utilisation. Resistance spot welding has already been qualified for utilisation on structured sheet metals [1]. In addition, investigations were conducted into the remote laser beam welding of structured and flat sheets. These investigations encompass the possibilities of joining structured and flat joining members by means of remote laser beam welding as well as the assessment of the joint strength in tensile shear and peel tests. Thereafter, the results of the investigations are compared with the resistance spot welding of structured sheet metals and specific application recommendations are derived.}, language = {en} } @article{OssenbrinkMichailovWohlfahrt, author = {Ossenbrink, Ralf and Michailov, Vesselin and Wohlfahrt, Helmut}, title = {Numerical simulation of welding stresses and distortions under consideration of temporal and local changes of strain rate}, 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} } @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{KotlarskiOrmanovaNikitinetal., author = {Kotlarski, Georgi and Ormanova, Maria and Nikitin, Alexander and Morozova, Iuliia and Ossenbrink, Ralf and Michailov, Vesselin and Doynov, Nikolay and Valkov, Stefan}, title = {Structure Formation and Mechanical Properties of Wire Arc Additively Manufactured Al4043 (AlSi5) Components}, series = {Metals}, volume = {14}, journal = {Metals}, number = {2}, issn = {2075-4701}, doi = {10.3390/met14020183}, abstract = {In the current paper, the correlation between the physical size of additively built wire arc specimens and their structure and properties is studied. For the purpose of this work, two oval shaped specimens of different lengths were manufactured under the same technological conditions. The specimens have a length of 200 mm and 400 mm and will be referred to as L200 and L400. The microstructure of the samples was studied using X-ray diffraction analysis (XRD), optical microscopy, and scanning electron microscopy (SEM). The microhardness, yield strength (YS), and ultimate tensile strength (UTS) were determined and their correlation with the technological conditions of specimen build-up was clarified. The results of the carried out experiments indicated that the crystallographic structure of both specimens is similar. The scanning electron microscopy images show a higher concentration of irregularly shaped micro-pores formed near the edge of the αAl grains in the structure of the L400 specimen compared to the L200 one. An increase in the size of the αAl solid solution grains in the case of the L200 specimen towards its top section was noticed using optical microscopy. A slightly lower magnitude change was noticed concerning the L400 specimen. The increase in the size of the aluminum crystals was determined to be the increasing interpass temperature. Due to the much smaller thermal dissipation capacity of the smaller specimen, the interpass temperature of the same increased faster compared to the larger specimen. All of the above-mentioned factors led to a decrease in the microhardness of the specimens at higher stages of build-up. Since the specimens were deposited using similar layer deposition conditions, the resultant YS and UTS data are also highly comparable.}, language = {en} } @misc{KotlarskiOrmanovaNikitinetal., author = {Kotlarski, Georgi and Ormanova, Maria and Nikitin, Alexander and Morozova, Iuliia and Ossenbrink, Ralf and Michailov, Vesselin and Doynov, Nikolay and Valkov, Stefan}, title = {Microstructural and Mechanical Properties of CAP-WAAM Single-Track Al5356 Specimens of Differing Scale}, series = {Materials}, volume = {12}, journal = {Materials}, number = {1}, issn = {2075-1702}, doi = {10.3390/machines12010072}, abstract = {The mass production of metallic components requires high agility in the working process conditioned by the necessity of building details of different shapes and sizes. Changing the size of the components theoretically influences the thermal dissipation capability of the same, which could lead to a change in their structure and mechanical properties. This is particularly important when aluminum alloys are concerned. For this reason, two Al5356 single-track specimens were built using the same technological conditions of layer deposition by varying only their geometrical size. In all cases, the specimens were wire and arc additively manufactured (WAAM) using a process based on gas metal arc welding (GMAW) in the cold arc pulse mode (CAP). The structure of both specimens was studied and defects along their surfaces were detected in the form of micro-pores and micro-cracks. A high concentration of undissolved Mg particles was also detected, along with some standalone Si particles. Uniformity in the build-up process was achieved, which led to the formation of nearly identical structures in the specimens. Subsequently, the resultant mechanical properties were also highly comparable. This indicates that the geometry-related variation in thermal conditions has an insignificant influence on the component's structure and properties.}, language = {en} }