Influence of the multi-axial Bauschinger effet in cold forging

• Applicant: Professor Dr.-Ing. A. Erman Tekkaya
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 418815343

• Final Report Year: 2023

Final Report Abstract

The numerical prediction of product properties such as residual stresses, damage and strain hardening, which are influenced by the forming, has become increasingly important in the recent years. A utilization of the altered component properties could significantly increase the resource and energy efficiency of cold forming processes as well as the performance of the manufactured products. In order to predict and exploit these changes in properties via FE-simulations, it is necessary to model the material’s behavior accurately. The anisotropic hardening behavior is currently only rarely taken into account in the field of cold forging, which means that it is not possible to predict the component performance sufficiently. As part of the project, typical materials for cold forging were characterized with regard to their anisotropic hardening behavior at large strains. The experimental data was used to develop constitutive models with the aim of modelling all relevant hardening phenomena. The Yoshida-Uemori multi-surface model was adapted and applied to increase the prediction accuracy of cold-forming simulations significantly. When using the hardening model in simulations of various cold forming processes, it was shown that the yield stress, residual stresses and process forces are strongly influenced by strain path reversals which is not considered in up-to-date forming simulations.

Publications

• Flow curves up to high strains considering load reversal and damage. International Journal of Material Forming, 12(6), 955-972.
  Hering, Oliver; Kolpak, Felix & Tekkaya, A. Erman
  
• Forming-induced anisotropy of product properties in cold extrusion. In: Proceedings of the METEC and 4th European Steel Technology and Application Days 2019, Düsseldorf, Germany.
  Kolpak, F., Dahnke, C. & Tekkaya, A. E.
  
• High Strain Flow Curves by Mechanical Tests on Specimens Pre-strained by Forward Rod Extrusion. In: Proceedings of the 52nd ICFG Plenary Meeting 2019, Donostia-San Sebastian, Spain.
  Hering, O., Kolpak, F., Dahnke, C. & Tekkaya, A. E.
  
• Vorrichtung und Verfahren zur Durchführung von Stauchversuchen an Probenkörpern zur Charakterisierung von Werkstoffen sowie entsprechender Probenkörper, DE 10 2019 001 442 (02.03.2019)
  Kolpak, F., Hering, O. & Tekkaya, A. E.
  
• Consequences of large strain anisotropic work-hardening in cold forging. International Journal of Material Forming 14, S. 1463-1481.
  Kolpak, F., Hering, O. & Tekkaya, A. E.
  
• Large strain flow curves of sheet metals by sheet extrusion. CIRP Annals, 70(1), 247-250.
  Kolpak, Felix; Traphöner, Heinrich; Hering, Oliver & Tekkaya, A. Erman