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@PHDTHESIS{Helm:854339,
author = {Helm, Johanna Gisela Margarete},
othercontributors = {Gillner, Arnold and Reisgen, Uwe},
title = {{P}rozessstabilität und {P}rozesseffizienz beim
{L}aserstrahlfügen von hoch reflektiven
{K}upferwerkstoffen; 1. {A}uflage},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {Apprimus},
reportid = {RWTH-2022-09483},
isbn = {978-3-98555-112-5},
series = {Ergebnisse aus der Lasertechnik},
pages = {1 Online-Ressource : Illustrationen, Diagramme},
year = {2022},
note = {Druckausgabe: 2022. - Auch veröffentlicht auf dem
Publikationsserver der RWTH Aachen University; Dissertation,
RWTH Aachen University, 2022},
abstract = {The shift in energy conversion away from fossil fuels
towards solar and wind energy, as well as the transformation
of passenger and freight transport towards electric forms of
transportation, requires a large number of joining
compounds. Due to its electrical and thermal properties,
copper is the key element for this change. A reliable,
automatable, and efficient joining technology is needed to
realize the electrical connections. Laser beam welding meets
all requirements in this respect and has become established
in recent years, especially in battery module production.
Industrial laser beam sources used for joining metals emit
radiation in the wavelength range of one micrometer. The
reflectance of copper for these beam sources is over 90
$\%,$ so that only a small part of the irradiated energy is
absorbed in the component and affects the stability of the
joining process. In addition, the high thermal conductivity
makes it difficult to form a stable vapor capillary, so that
process efficiency is reduced. Process stability and process
efficiency in the welding of copper materials depend on the
interaction between light and material. Absorption and the
degree of coupling play a key role here, as they directly
determine the proportion of the irradiated energy that is
used for the welding process. The absorption depends on the
laser wavelength, the temperature, the thermal conductivity
and the condition or nature of the technical surface. The
degree of coupling, which in turn describes the ratio of
absorbed to irradiated energy during the process and thus
also when multiple reflections occur, is additionally
dependent on the process control. Increasing the absorption
and the degree of coupling thus leads to a higher proportion
of absorbed energy being available in the workpiece for the
formation of melt, thus increasing the efficiency. In this
work, the surface of copper is modified by laser structuring
and by a thermal furnace process. During the subsequent
laser beam welding process, the degree of coupling is
recorded by a high temporal resolution measurement. By
determining the melt volume, the process efficiency of the
joining process on modified surfaces can be compared with a
reference process. The approach presented here enables a
significant increase in process efficiency and thus
demonstrates the possibility of saving energy in the
production process while simultaneously stabilizing the
process flow.},
cin = {418710},
ddc = {620},
cid = {$I:(DE-82)418710_20140620$},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
doi = {10.18154/RWTH-2022-09483},
url = {https://publications.rwth-aachen.de/record/854339},
}
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