Collaborative Research Center/Transregio 188 „Damage Controlled Forming Processes“
German Research Foundation (DFG)
Prof. Dr.-Ing. Dr.-Ing. E.h. A. E. Tekkaya
Dr.-Ing. Frauke Maevus
The Collaborative Research Center TRR 188 is concerned with research on the damage mechanisms during forming and their effects on product properties. It is generally known that every metal material contains damage, e.g. in the form of casting pores and non-metallic inclusions, and every plastic deformation causes additional damage, e.g. in the form of pore growth. It is not yet known how the damage can be specifically influenced in the forming process and from which critical damage margin on a failure of the component is to be expected. However, this knowledge is necessary in order to fully exploit the potential of modern material concepts and forming processes and to reduce the component weight to a minimum without sacrificing safety. Therefore, the long-term goal of TRR 188, scheduled to run for twelve years, is to develop new methods and technologies for the control and quantitative prediction of the damage evolution as well as the targeted adjustment of the damage states with regard to the best possible component performance. Based on the guiding principle “damage is not a failure”, the aim is to ensure that production-induced damage, including its implications, is taken into account as a target variable in component and process design in the same way as other production-induced properties. This makes it possible for the first time not only to guarantee the formability of the components, but also the properties and functional safety of the components during the use phase.
Process chain bulk forming in TRR 188
The primary subject of the first funding period, which is currently under way, is to develop a fundamental physical understanding of initiation and development of damage in the forming process beyond the hypotheses generally used today. This is done using the example of representative process chains for bulk and sheet metal forming in three project areas with different focuses. In project area A “Process Technology” forming processes and their influence in production process chains are investigated from a technological point of view. The focus is on researching the relationships between the forming processes, the load paths, and the resulting damage development. On the basis of these findings, an analysis and evaluation of the influence of damage on the component properties is carried out. Subsequently, technological approaches for the targeted influencing and control of the damage development are derived, which are to be converted into modified or newly designed forming processes in the second funding phase. Project area B “Characterization” identifies and assesses the forming-induced damage mechanisms. The characterization takes place successively on the starting material, in the forming process, and on the finished formed component in order to be able to monitor the damage development over the complete process chain. Measuring methods and testing strategies for a qualitative and quantitative description of damage on various length scales are being developed. Important aspects are, on the one hand, the efficiency of the characterization methods with regard to time and effort and, on the other hand, a consistent approach for the application of the methods in order to ensure the comparability of the results.
Process chain sheet metal forming in TRR 188
The project area C “Modeling” deals with basic model approaches for the description of damage in sheet metal and bar material on various length scales and, building on this, recovery processes for the reduction of material damage. In detail, these are an anisotropic macroscopic material model, a coupled model of hardening, softening, and damage for hot forming, a crystal plasticity model as well as a damage model for service conditions and an approach for optimization problems. The development and verification of the approaches is carried out in close cooperation with the projects of the other two project areas. The coordination of the exchange is the task of the scientific service project “Model Integration”. Further cross-sectional topics are investigated across projects and project areas by means of three working groups.
The projects are jointly carried out by scientists from TU Dortmund University (Coordinating University) and RWTH Aachen University. Specifically, 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 in Dortmund are involved as well as the Chair of Numerical Methods and Information Processing from the Faculty of Architecture and Civil Engineering. At RWTH Aachen University, the participating institutes are the Metal Forming Institute (IBF), the Steel Institute (IEHK), and the Institute of Physical Metallurgy and Metal Physics (IMM) from the Faculty of Georesources and Materials Technology as well as the Laboratory for Machine Tools (WZL) from the Faculty of Mechanical Engineering and the Central Facility for Electron Microscopy (GFE). In addition,
there is the Chair of Mechanical Design and Manufacturing at BTU Cottbus-Senftenberg and the non-university Max-Planck-Institut für Eisenforschung GmbH (MPIE) in Dusseldorf.
The interdisciplinary consortium of production engineering, materials science, materials testing technology, and mechanics is supported by an industrial advisory board. The industrial advisory board advises the TRR 188 and discusses current R&D results with the researchers. The research association receives important impulses for further research activities by the experiences and suggestions from industrial practice. Members of the industrial advisory board are material and semi-finished product manufacturers, component manufacturers, technicians from sheet metal and bulk forming, component users as well as companies from the field of software and measurement technology.
In addition, first research results of the TRR 188 were presented and discussed at scientific and industry-related symposia in the national and international environment. These included ICTP, ECCM, IDDRG, ESAFORM, GAMM, MSEC, various DVM working group meetings and, not least, the 1st Industrial Colloquium organized by TRR 188 in November 2018 in Dortmund.