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Bielenin, Martin; Bergmann, Jean Pierre
Reparatur von Bauteilen aus Nickellegierungen. - In: Schweissen und Schneiden, ISSN 0036-7184, Bd. 69 (2017), 10, S. 712-718

Im Rahmen dieses Beitrags werden experimentelle Untersuchungen zur laserbasierten Reparatur von Turbinenschaufeln aus Nickelbasis-Superlegierungen mit drahtförmigen und γ'-ausscheidungshärtenden Schweißzusatzwerkstoffen vorgestellt. Durch den Einsatz einer pulsmodulierbaren Laserstrahlquelle kann die artgleiche Reparatur bei Raumtemperatur ohne das Auftreten von Heißrissen ausgeführt werden.



Nagel, Falk; Drechsel, Christine; Bergmann, Jean Pierre
Reduction of the spatter formation due to the use of superposition of two laser intensities. - In: Lasers in Manufacturing 2017, (2017), insges. 4 S.

New developments of laser system technology result in an increased power output at better beam quality. However, available laser power cannot always be transferred to increase the processing speed since imperfections such as the formation of spatter occurs, especially in the range of 5 m/min to 20 m/min for fiber and disk lasers. The appearance of spatter is strongly connected to the conditions in and around the capillary. This paper shows an experimental approach to reduce the spatter formation by using two laser spots. The experimental trails were executed with austenitic steel (1.4301) sheets using a high power disk laser and a diode laser. The modification of the resulting intensity reduces the loss of mass. High speed camera footage shows a different behavior of the weld pool due to the additional laser spot. Moreover, metallurgical cross-sections demonstrate the influence of the approach on the shape of the melt pool and the resulting weld seam.



Bielenin, Martin; Bergmann, Jean Pierre; Sieber, Philipp
Repair of nickel-based superalloys by pulsed Nd:YAG welding with wire feeding. - In: Lasers in Manufacturing 2017, (2017), insges. 5 S.

In this paper deposition of IN 625 filler wire on γ-hardened IN 738 superalloy with pulsed laser beam welding was investigated. High-speed observation was performed to examine the influence of the spatial and temporal alignment between the pulsed laser beam and the wire feeder on the material transition from the solid wire onto the substrate. The deposition process has shown to be extremely sensitive to the wire position and orientation relative to the melt pool. To obtain stable and repeatable welding conditions influence of the significant parameters, such as the wire feed rate, the energy input, and the traverse speed should be attentively considered. Significant improvements of the process stability could be achieved with the adjustment of the wire position in the negative z-direction. The preliminary results showed the potential of this approach as an alternative automated or partially automated repairing method for worn turbine components made of nickel-based superalloys.



Lohse, Martin; Hertel, Martin; Schricker, Klaus; Kohl, Marie-Luise; Füssel, Uwe; Bergmann, Jean Pierre
Der Einfluss von Laser und WIG-DC-EP-Oberflächenstrukturierung auf das Benetzungsverhalten und die Verbindungsfestigkeit von lasergefügten Stahl-Kunststoff-Leichtbauverbindungen für automobile Anwendungen. - In: DVS Congress 2017, (2017), S. 369-377

Hasieber, Michael; Bergmann, Jean Pierre
Strategien zur Werkzeugskalierung und Prozesskraftreduzierung beim Rührreibschweißen von Aluminiumlegierungen. - In: DVS Congress 2017, (2017), S. 113-118

Reimche, Maxim; Bergmann, Jean Pierre
Single item production within collaborative networks. - In: Engineering for a changing world, (2017), insges. 10 S.

http://nbn-resolving.de/urn:nbn:de:gbv:ilm1-2017iwk-106:1
Soltanzadeh, Hadi; Hildebrand, Jörg; Kraus, Matthias
A reliable modelling of thermal, microstructure, and stress in arc stud welding joints and effect on fatigue strength. - In: ce/papers, ISSN 2509-7075, Bd. 1 (2017), 2/3, S. 453-460

This paper presents numerical calculations of welding residual stresses and the evolution of microstructure in stud joints embedded in common structural steels S235 and S355. The study deals with a numerical transient thermal modelling of stud welding using the commercial software suite SYSWELD FE. Microstructure phase fraction of Martensite, Bainite and Ferrite-Pearlite are also calculated by trajectory tracking of the thermal profile on the CCT diagram for the weld region. Thermal loading from welding as non-moving heat source is further fed into the stress solver and welding residual stresses are computed. The computational stresses are validated by comparison with stresses of XRD experimental measurements. The aim of this paper is to specify the stress distributions regarding residual stresses from the manufacturing and welding processes as well as stress states due to operational loads, which can constitute the basis of fatigue analyses.



https://doi.org/10.1002/cepa.81
Nagel, Falk; Simon, Flaviu; Hildebrand, Jörg; Bergmann, Jean Pierre
Optimisation strategy for the laser beam welding of high-alloyed steels. - In: Welding and cutting, ISSN 1612-3433, Bd. 16 (2017), 4, S. 256-262

Bergmann, Jean Pierre; Bielenin, Martin; Herzog, Roland A.; Hildebrand, Jörg; Riedel, Ilka; Schricker, Klaus; Trunk, Carsten; Worthmann, Karl
Prevention of solidification cracking during pulsed laser beam welding. - Ilmenau : Technische Universität, Institut für Mathematik, 2017. - 1 Online-Ressource (7 Seiten). - (Preprint ; M17,09)

We present a mathematical model to describe laser beam welding based on the heat equation. Since the material coeff cients depend on the temperature, this leads to a quasi-linear parabolic partial differential equation. It is our goal to prevent solidif cation cracking. We address this problem by means of optimal control. It is the intensity prof le of the laser beam which acts as the control function. The main challenge is the formulation of a suitable objective function. In particular, high velocities of the solidif cation interface need to be properly penalized in order to deal with and avoid cracking phenomena.



https://www.db-thueringen.de/receive/dbt_mods_00032771