Development of a procedure for the determination of flow curves by explicit pointwise inverse modelling

• Applicant: Dr.-Ing. Emad Scharifi, since 7/2024
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing ; Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 393221806

In the second phase of the project, a previously developed algorithm for inverse flow curve determination will be applied to other material characterization methods as well as adapted and optimized accordingly. Instead of the usual iterative parameter optimization of analytical flow curve descriptions, the algorithm calculates individual data points in terms of the flow stress and the strain during a single simulation. This eliminates the need for an analytical flow curve description, which means that the inverse flow curve determination can also take into account effects such as Lüders strain, Portevin-Le-Chatelier effect or the occurrence of multiple recrystallization cycles, which is almost impossible up to now. The determination of the individual data points during the calculation of the simulation model is performed by iteratively adjusting the data point until the deviation between the simulated force and the corresponding experimental value is minimized. This procedure was initially implemented and validated in the first project phase for almost frictionless cylinder compression tests. The overall goal in the second phase is to extend the algorithm in order to prepare for broad practical application. On the one hand, flow curves based on hot flat tensile tests up to failure in a forming dilatometer and torsion tests up to strains > 2 on a torsion plastometer will be considered. The first test allows reliably determining flow curves with high maximum elongation at relevant stress states for relevant processes of hot sheet forming, e.g. press hardening. The latter tests allow the determination of flow curves for bulk metal forming, e.g. forging. On the other hand, the algorithm is to be enabled to use the increased information content from inhomogeneous experiments for the efficient and precise characterization of multiple flow curves. This requires the development of an appropriate methodology for the determination of several flow curves from only one inhomogeneous test. Finally, the quality of the determined flow curves will be investigated in near-industrial demonstrator tests, such as a hot-gas bulge test, by using the determined flow curves in simulations of the demonstrator tests and subsequently analysing the deviation between measured and simulated force.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr.-Ing. Gerhard Hirt, until 6/2024