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@PHDTHESIS{Hollatz:972480,
author = {Hollatz, Sören},
othercontributors = {Häfner, Constantin Leon and Reisgen, Uwe},
title = {{F}unktionsorientiertes {L}aserstrahl-{M}ikroschweißen von
{A}luminium-{K}upfer-{V}erbindungen mit örtlicher
{L}eistungsmodulation; 1. {A}uflage},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {Apprimus Verlag},
reportid = {RWTH-2023-10190},
series = {Ergebnisse aus der Lasertechnik},
pages = {1 Online-Ressource : Illustrationen},
year = {2023},
note = {Druckausgabe: 2023. - Auch veröffentlicht auf dem
Publikationsserver der RWTH Aachen University; Dissertation,
RWTH Aachen University, 2023},
abstract = {The increasing demand for battery cells to electrify
transportation requires the automated joining of highly
electrically conductive materials such as aluminum and
copper. These materials are part of common lithium-ion
battery cells in the form of foils. The electrical
connection of such cells to battery systems requires the
joining of dissimilar aluminum and copper. The main function
is the lossfreeconduction of the electrical current during
the whole lifetime of the product. Due to its good
automation capability and short process times, laserbeam
welding is a suitable process for the series production of
battery systems. The challenge in the melt-based joining of
aluminum and copper is the formation of brittle and hard
intermetallic phases. As a starting point for cracks, these
phases can damage the joint in the long term. Operating
influences such as vibrations, thermal or electrical stress
additionally shorten the lifetime. Industrial applications
therefore require precise knowledge of the quality of
thewelded joint and its long-term stability.Due to the
functional requirement, the contact resistance of the joint
is asuitable quantitative measure of weld seam quality. In
addition to thefundamentals of measuring electrical
resistances of welded joints, this work simulates the
current flow through the joint in order to optimize the
design and weld seam positioning. In the experimental
validation, the influence of a spatialpower modulation on
electrical and mechanical properties is investigated. In
this process, the feed motion of the laser beam is
superimposed with a circular oscillation. As a result, the
bond width of the welds is increased and non uniformities in
the seam cross-section of the lap joint due to the different
melting point and thermal conductivity can be compensated.
The intermixing of the two materials is visualized by
in-situ transmission experiments with synchrotron radiation.
For the analysis of the long-term stability, the welded
joints are dynamically, electrically and thermally loaded to
simulate the operating influences. In addition to the
development of a long-term stablewelding process of aluminum
and copper, this work investigates methods forin-process
monitoring of the welding penetration depth by using optical
coherence tomography and spectrometry. By combining a
function-oriented process development with suitable
monitoring, this work supports the industrial application of
laser beam welding of aluminum-copper joints.},
cin = {418710},
ddc = {620},
cid = {$I:(DE-82)418710_20140620$},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
doi = {10.18154/RWTH-2023-10190},
url = {https://publications.rwth-aachen.de/record/972480},
}
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