Analysis of the geometrical deviations of long forged components under consideration of the influence of variable stress states on the transformation induced plastic strain behaviour

• Applicant: Professor Dr.-Ing. Bernd-Arno Behrens
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 511687873

The aim of the proposed research project is the numerical analysis of the occurring distortion in multi-stage process chains for the production of long forged components under consideration of the mechanical, thermal and metallurgical material properties. Hot forging is a widely used process for the production of complex high-performance components. However, the geometrical deviations that occur are challenging both in process as well as in component design. Particularly in multi-stage hot forging processes, the workpiece is subjected to diverse and locally varying thermal and mechanical loads. In interaction with occurring phase transformations, it can lead to locally varying residual stresses and ultimately distortion in the finished component. The design process is therefore often iterative, which results in a high expenditure of time and resources in the form of testing tools or tool revisions. At this point, the use of numerical simulations offers a huge potential to analyse possible causes of distortion at an early point in the development process. As a result, distortions and costly manual reworking can be reduced by means of an adapted process control. However, a prerequisite for the use of numerical simulation with regard to a realistic representation of the distortion in hot forging processes is to describe the manifold and interdependent thermal, mechanical and metallurgical effects by means of suitable material models. For this purpose, the material model developed is to be transferred and extended to an industrially relevant multi-stage forging process chain for the manufacture of long components. For this purpose, a practice-oriented multi-stage demonstration process will be defined and implemented in collaboration with the application partner. In order to include all thermal, mechanical and metallurgical effects that may occur, the workpiece and tool material used will be characterised in detail. A detailed experimental analysis of the demonstration process in cooperation with the application partner provides a wide range of data regarding temperatures and their distributions as well as transfer times. Furthermore, components are removed and geometrically measured after individual process stages. Thus, the created database provides boundary conditions for the numerical process simulation and also serves to validate the developed material model. For the holistic illustration, a linked simulation model of the demonstrator process is built and validated. Finally, the validated model is used for the numerical analysis of distortion in multi-stage hot forging processes. Based on the knowledge gained, suggestions recommended courses of actionand measures for the process stages can be identified in order to actively compensate the distortion within the process and minimize time-consuming reworking.

• DFG Programme: Research Grants (Transfer Project)
• Application Partner: Schöneweiss & Co GmbH
• Co-Investigator: Dr.-Ing. Kai Brunotte