Forming by locally varying vaporizing actuators

• Applicant: Professor Dr.-Ing. A. Erman Tekkaya
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 391967465

Vaporizing Foil Actuator Forming (VFAF) is a relatively young and flexible high speed manufacturing process. A rapid current discharge of a capacitor bank across an aluminum foil makes the material vaporize (bursting) and thus act as a disposable expanding actuator, so that a nearby sheet metal can be formed impulsively. Within the first project phase, two main goals were achieved: A process modeling approach has been established to improve the multi-physical understanding of the process. First, the electrical energy deposition until the burst point is modeled. From that, initial values are inferred for a subsequent mechanical forming simulation. In addition, this modeling chain was used for the development and testing of a predictive process design concept which takes into account part-individual optimization aspects. This way, for the first time, a part having distinct forming heights was realized by employing different actuators in parallel. The main goal of the second project phase is to enhance the VFAF process by increasing its flexibility. This may be achieved by purposefully making use of the dynamic characteristic of the process to reduce the dependence on geometry-specific, massive solid dies. The basic idea is to determine the final form of a part only through a thin tool shell backed by a shear thickening fluid (STF). The STF, in turn, almost instantaneously acts like a solid body when the actuator-accelerated blank impacts the die and thus the STF. The liquid-solid transition includes an advantageous damping behavior. Considering other part geometries, the STF can simply be filled into another tool shell, making it a resource-saving tool material. The functionality and critical physical mechanisms of the novel tool concept are to be investigated thoroughly both experimentally as well as numerically, and design criteria are to be derived. Finally, the knowledge of the first and second project phase are transferred to showcase the potential of the gained flexibility by manufacturing a freeform surface application part. For this, the range of materials of the project is enlarged by selecting a sheet made of titanium. The influence of cutting operations before or after the forming on the geometric quality of the VFAF part is also analyzed in this regard.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr.-Ing. Till Clausmeyer