@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{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} } @book{PasternakStapelfeldLaunertetal., author = {Pasternak, Hartmut and Stapelfeld, Christoph and Launert, Benjamin and Michailov, Vesselin and Doynov, Nikolay}, title = {Ermittlung der Tragf{\"a}higkeit neuartiger st{\"a}hlerner Schalenbauwerke unter realit{\"a}tsnaher Ber{\"u}cksichtigung des Schweißverzugs}, publisher = {Forschungsvereinigung Stahlanwendung e. V.}, address = {D{\"u}sseldorf}, isbn = {978-3-946885-89-4}, pages = {227}, language = {de} } @misc{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} }