Collaborative Research Center Transregio 188 – Damage Controlled Forming Processes
German Research Foundation (DFG)
Prof. Dr.-Ing. A. Erman Tekkaya
Dr.-Ing. Frauke Maevus
The research hypothesis of the Collaborative Research Center TRR 188 is that the damage caused by the forming process can be controlled and that the damage significantly influences the performance of the components. Accordingly, the overall goal of TRR 188 is to understand the mechanisms of material damage during forming to quantitatively predict the evolution of damage and to adjust damage states with regard to component performance. The guiding principle of TRR 188 “Damage is not a failure” means that ductile damage in forming technology is not only a measure of the distance to the failure limit (“formability”), but also has a decisive influence on the performance in the application (“usability”). Thus, the damage is a product property that is influenced by the forming technology used in component production.
The first phase of the Collaborative Research Center TRR 188, which started in 2017, ends this year. Therefore, we look back on years full of results and events, on the one hand, and, on the other hand, expectantly to the future of this project. The application for approval of the second phase with a renewed term of four years was submitted in July. In September, the first virtual assessment of a collaborative research center with the participation of the IUL took place. The German Research Foundation (DFG) has decided to continue funding the CRC/TRR188. Thus, research on the paradigm shift in forming technology can be continued until the end of 2024.
Scientists from TU Dortmund University (the spokesman university) and RWTH Aachen University carry out research in multiple subprojects. In Dortmund, the Institute of Forming Technology and Lightweight Components (IUL), the Institute of Mechanics (IM), and the Department of Materials Test Engineering (WPT) from the Faculty of Mechanical Engineering and the Chair of Structural Mechanics (BM) from the Faculty of Architecture and Civil Engineering are involved. At RWTH Aachen University, the Institute of Metal Forming (IBF), the Steel Institute (IEHK), and the Institute for Physical Metallurgy and Materials Physics (IMM) from the Faculty of Georesources and Materials Engineering as well as the Laboratory for Machine Tools and Production Engineering (WZL) from the Faculty of Mechanical Engineering and the Central Facility for Electron Microscopy (GFE) are part of TRR 188. Moreover, there is the Chair of Mechanical Design and Manufacturing at BTU Cottbus-Senftenberg and the non-university institute Max-Planck-Institut für Eisenforschung GmbH (MPIE) in Dusseldorf.
In the first funding period fundamental forming processes were investigated with regard to damage development and the resulting performance. For this purpose, an interdisciplinary consortium was formed, which is divided into the project areas characterization, technology, and modeling (see figure).
In project area A (Technology) damage in the forming process was controlled by adjusting the hydrostatic pressure via process parameters and modifications. Furthermore, it was shown that the damage significantly influences the performance. In project area B (Characterization) efficient methods for quantifying the damage and characterizing the damage mechanisms were developed using samples from project area A. In project area C (Modeling) damage modeling approaches from the micro- to the macroscale were developed and validated using experimental data from project areas A and B. The scientific service project prepared the developed damage models for finite element (FE) simulations and provided software tools for process simulation and parameter identification.
In this research center an interdisciplinary team has grown together, which has learned to speak a common language. Besides the regular meetings, the work on central cross-cutting issues in the four working groups “Efficient damage characterization”, “Performance”, “Validation”, and “Damage definition” contributed to this.
Despite these successes, some questions already mentioned in the first phase’s proposal, but also new open questions remain for the possible second funding period. Potential topics include the consideration of more complex component geometries and process sequences, the variation of the Lode angle parameter, and temperature-assisted forming or heat treatment.
Not only because of the proposal phase and the upcoming assessment, five plenary meetings were held this year, four of which were virtual. In March, the second industrial colloquium took place in Aachen. Nearly 70 national and international participants were provided insights into the latest developments in the field of damage-controlled forming processes in 13 lectures and an accompanying poster exhibition. Due to the corona virus, the lectures of the second industrial colloquium were also available online. The focus of the conference was on the characterization as well as the multiscale modeling of damage evolution.
In collaboration with the international researchers Pierre-Olivier Bouchard, Stefania Bruschi, and Cem Tasan, A. Erman Tekkaya as main author published the keynote paper “Damage in Metal Forming” in the CIRP Annals. In addition, 10 papers of TRR 188 were published in a special issue of “Production Engineering” on the topic “Damage Controlled Forming Processes”.