h1

%0 Thesis
%A Wang, Shuhan
%T Entwicklung einer Methodik zur Kontrolle der Schädigungsentwicklung beim Kaliberwalzen; 1. Auflage
%V 218
%I RWTH Aachen University
%V Dissertation
%C Aachen
%M RWTH-2025-03555
%@ 978-3-95886-543-3
%B Umformtechnische Schriften
%P 1 Online-Ressource : Illustrationen
%D 2025
%Z Druckausgabe: 2025. - Auch veröffentlicht auf dem Publikationsserver der RWTH Aachen University
%Z Dissertation, RWTH Aachen University, 2024
%X 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.
%F PUB:(DE-HGF)11 ; PUB:(DE-HGF)3
%9 Dissertation / PhD ThesisBook
%R 10.18154/RWTH-2025-03555
%U https://publications.rwth-aachen.de/record/1009589