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@PHDTHESIS{Wang:1009589,
author = {Wang, Shuhan},
othercontributors = {Hirt, Gerhard and Korte-Kerzel, Sandra},
title = {{E}ntwicklung einer {M}ethodik zur {K}ontrolle der
{S}chädigungsentwicklung beim {K}aliberwalzen; 1.
{A}uflage},
volume = {218},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {Institut für Bildsame Formgebung der
Rheinisch-Westfälischen Technischen Hochschule},
reportid = {RWTH-2025-03555},
isbn = {978-3-95886-543-3},
series = {Umformtechnische Schriften},
pages = {1 Online-Ressource : Illustrationen},
year = {2025},
note = {Druckausgabe: 2025. - Auch veröffentlicht auf dem
Publikationsserver der RWTH Aachen University; Dissertation,
RWTH Aachen University, 2024},
abstract = {Today, sustainability and the reduction of emissions are of
the utmost priority. the principle of lightweight
construction proves to be crucial for industrial
manufacturing, especially in the production of metallic
components. This work examines the role of ductile damage in
forming processes, an aspect that has often been overlooked
in the past but offers great potential for improving the
performance and durability of components. Particular
attention is paid to caliber rolling, a hot forming process
for producing long products, which, despite its flexibility
and potential for damage control, has so far received little
attention in this regard. The central question of this work
is how the development of damage can be influenced through
targeted process design in caliber rolling, thereby
producing components with optimized mechanical properties.
Utilizing Finite-Element Analysis, a method was developed
with the goal of consciously influencing the development of
damage by adjusting the process parameters. Specifically,
the steel type 16MnCrS5 and a caliber sequence of
round-oval-round with defined starting and ending diameters
were chosen. The starting point of the investigation was a
practice-oriented reference calibration with four rolling
passes. For a targeted influence on the evolution of
micro-damages, it was first necessary to understand how the
load path (stress triaxiality and Lode parameter) can be
modified by adjusting the process parameters. A detailed
parameter study identified the axis ratio of the oval
caliber and the area reduction as key factors in controlling
the load path. An additional numerical investigation
determined the possibilities for varying these parameters
without negatively impacting the caliber filling. This
procedure ensures that only calibers that do not exhibit
filling errors are selected for the design of new processes.
Another important step for the controlled process design was
the establishment of a reliable method for predicting damage
evolution. Through the comparison and evaluation of existing
damage models, a modified GTN model accounting for dynamic
recrystallization was selected. This model, developed
specifically for hot forming, enabled a qualitative
prediction of damage development along the selected caliber
sequence. The distribution and reduction of damage at the
end of the process compared to the start of the process in
the reference calibration could be qualitatively predicted
with this model. Based on the findings regarding the
variation of the load path and damage prediction, two
additional processes with the round-oval-round caliber
sequence were developed. For each, a load path was chosen
that was considered critical for one and advantageous for
the other in terms of damage. The validated damage model
confirmed the expected variations in damage distribution for
these new processes. However, despite significant variation
of the load path in all processes, the damage prediction
showed only moderate damages at the end of the process. An
extended process design using a different caliber sequence
revealed that damages induced by factors such as intense
edge cooling could be significantly reduced in the further
forming process. These results suggested that besides the
load path, there are other significant factors affecting
damage development in caliber rolling. The subsequent model
experiments with the torsion plastometer suggested that
thermally activated processes, such as recrystallization,
can significantly influence the microstructure during hot
forming, depending on the load path. These processes have
the potential to overcome the impact of damage on the
component's performance. Based on these insights, it can be
concluded that an increase in component performance cannot
be achieved solely by adjusting the load path in hot
forming. Two additional factors have been identified for
future advancements in damage control during caliber
rolling: the consideration of microstructure development in
hot forming and the detailed examination of damage
mechanisms influenced by thermal processes such as
recrystallization. Developing specific damage models for hot
forming and selecting process-optimizing parameters to
achieve a damage-resistant microstructure are essential.
These approaches allow for comprehensive utilization of the
lightweight construction potential through an optimized
forming process design.},
cin = {523410 / 520000},
ddc = {620},
cid = {$I:(DE-82)523410_20140620$ / $I:(DE-82)520000_20140620$},
pnm = {DFG project G:(GEPRIS)278868966 - TRR 188:
Schädigungskontrollierte Umformprozesse (278868966)},
pid = {G:(GEPRIS)278868966},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
doi = {10.18154/RWTH-2025-03555},
url = {https://publications.rwth-aachen.de/record/1009589},
}
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