Experimental and Numerical Analysis of the Influence of Burst Pressure Distribution on Rapid Free Sheet Forming by Vaporizing Foil Actuators

Abstract

Vaporizing Foil Actuators (VFA) can be employed as an innovative, extremely fast sheet metal forming method. An ultimate goal in forming technologies is generally to be flexible and rely on as few part-specific tools as possible. Therefore, various realizable VFA pressure distributions were investigated with a focus on the free forming result. Fundamental experiments including laser-based dynamic velocity measurements were conducted to discuss some key forming characteristics of the process. To compare more complex pressure distributions in a well-defined way, a numerical model was built. The strain rate dependency of the blank material was identified experimentally and incorporated in the model. It is shown that there are some VFA free forming capabilities in terms of creating certain part shapes, but only to a limited degree because relevant inertial forces can be present in regions where displacements would actually be either undesirable or wanted. Potential solutions to this are given at the end.

Part-optimized forming by spatially distributed vaporizing foil actuators

“…The derived data was implemented experimentally using the setup platform and pulse generator described in Hahn et al [10] respectively in Hahn and Tekkaya [11,12]. The main differences were that the waterjet-cut aluminum foils were arranged in parallel in this work for the first time, and that a sealed closed die was used.…”

“…The optimization task is to be performed on the basis of a finite element (FE) model for the dynamic forming simulation. For this, the model of Hahn and Tekkaya [11] is utilized. It is built in Abaqus/Explicit and mainly contains: the sheet blank using volume elements, the strain-and strain rate-dependent flow curve of the material (in this case the isotropic Zerilli-Armstrong equation for DC01 steel), the part-specific die with a clamping, and a flexible load definition.…”

“…From preliminary numerical and experimental investigations, which include i.a. laser-based velocity measurements [11,12], the upper bound t dLim from Eq. 4 was found to be ca.…”

“…Beside the consequences of the missing elastomer in the FE model, a second potential reason for deviations between experiment and simulation is the used flow curve. The rate-dependence of DC01 was approximated and extrapolated by the Zerilli-Armstrong equation, supported by four different characterization tests at strain rates ranging from 2•10 −3 to 1.9•10 4 s −1 [11]. The flow curve fitting posed inaccuracies of up to 10%, while the accuracy at other process-relevant rates stays unknown.…”

“…There is no established overall modeling and simulation procedure for VFAF yet. In ongoing research, Hahn et al [10] and Hahn and Tekkaya [11,12] suggest basically two 'modeling levels':…”