Extension of the forming limits in internal high-pressure hot forming through isothermal process conditions

• Applicant: Professor Dr.-Ing. A. Erman Tekkaya
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 553625186

In this research project, open questions regarding the thermal softening of the used materials, the geometry-dependent temperature distribution during forming and the requirements for geometry flexibility are to be investigated for the recently developed isothermal high-temperature pneumoforming process. Innovations based on the use of tubular semi-finished products currently exist only to a limited extent. For this reason, the above-mentioned process was developed in order to be able to transfer the advantages of press hardening to closed profiles under isothermal conditions. In this process, tubes are heated conductively and formed by means of internal pressure. Resistance heating is maintained during forming so that temperature loss is minimized. Quenching of the workpieces in the die is achieved by forced convection. For this purpose, a defined volume flow of the pressure medium flows through the component after forming. The feasibility of this method has already been demonstrated experimentally, although only doubly symmetrical cross-sections could be investigated at a temperature of 1000 °C. In this project, quantitative investigations of isothermal high-temperature pneumo-forming are carried out with regard to the following aspects: 1) Thermal softening during forming is characterized and incorporated into numeric process modeling. Potential strain-induced strain hardening is taken into account. 2) The parameter- and geometry-specific temperature distribution is predicted numerically. Inhomogeneous current density distributions as well as interactions between workpiece and tool are modeled. Quantitative correlations between the formed cross-sectional dimensions and resulting temperature differences are targeted. This allows the derivation of process windows. 3) An increase in geometry flexibility is intended through the use of actively forming tool segments. The additional active axis means that punches, for example, can be integrated into the process.

• DFG Programme: Research Grants
• Co-Investigator: Dr.-Ing. Heinrich Traphöner