Numerical-experimental method development for superplastic hydroforming processes of titanium hollow sections

• Applicants: Professor Dr.-Ing. Frank Walther; Dr.-Ing. Sven Winter
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 550647906

The main objective is to develop, test and validate a numerical-experimental and materials science-based design methodology for super plastic hydroforming (SPF-HF) processes and to demonstrate its transferability to near-industrial geometries. Titanium alloys are difficult to form at room temperature due to their microstructure (hcp packed lattice structure of the α-phase) and the resulting mechanical properties, such as limited formability, high tensile strength, and high elastic modulus. Therefore, quasi-static high-temperature slow-strain rate tensile and torsion tests supplemented with high-temperature slow-strain rate pipe burst tests and material analysis will establish the basis of a material model. The key point, however, is the numerical design and experimental validation of a strain rate-constant internal pressure-time curves matched to the component geometry and microstructure, which is the most important process parameter in the SPF-IHF process. In comparison to the internal pressure-time curves for IHF processes, which exhibit a constant pressure build-up rate. This method is intended to determine component-specific strain-rate-controlled pressure curves that prevent the local exceeding of strain-rate maxima in the material or component beyond the super plastic range. As a result, super plastic material properties and maximum necking-free forming degrees can be ensured throughout the entire process. The process design method to be developed should consider the wrought product and process-specific influencing factors on the forming process, such as production-related texture, microstructure and hardening, through adapted testing and evaluation strategies.

• DFG Programme: Research Grants