Pressure generated by the electric explosion of metal foils

Journal of Materials Processing Technology

Weddeling

Taber

et al. 2016

Photonic Doppler velocimetry was applied to compare magnetic pulse welding and vaporizing foil actuator welding against each other in the form of lap joints made of 5000 series aluminum alloy sheets under identical experimental conditions which are: charging energies of the pulse generator, specimen geometry, initial distances between flyer and target plate. Impact velocities resulting from rapidly vaporizing aluminum foils were up to three times higher than those of purely electromagnetically accelerated flyer plates. No magnetic pulse welds were achieved, while every vaporizing foil experiment yielded a strong weld in that failure always occurred in the joining partners instead of in the weld seam during tensile tests. An analytical model to calculate the transient flyer velocity is presented and compared to the measurements. The average deviation between model and experiment is about 11 % with regard to the impact velocity. Hence, the model may be used for the process design of collision welds generated by vaporizing foil actuators.

Section: Verification Of the Analytical Model For Vfasupporting

confidence: 73%

Section: Fundamentals Of Vaporizing Foil Actuators (Vfa)mentioning

confidence: 97%

Vaporizing foil actuator welding as a competing technology to magnetic pulse welding

Journal of Materials Processing Technology

Weddeling

Taber

et al. 2016

“…For every burst pressure amplitude p b , a resistive energy deposition in the form of a burst energy density w b may be determined from the linear coupling relation p b (w b ) found by Grigoriev and Pavlenko [15]. This means that, besides all actuator widths b, lengths l, and positions from the mechanical optimization, all required energy depositions w b are already known for the second step in Fig.…”

Section: Electrical Realization Strategymentioning

confidence: 99%

Part-optimized forming by spatially distributed vaporizing foil actuators

Tekkaya

2021

Int J Mater Form

Electrically vaporizing foil actuators are employed as an innovative high speed sheet metal forming technology, which has the potential to lower tool costs. To reduce experimental try-outs, a predictive physics-based process design procedure is developed for the first time. It consists of a mathematical optimization utilizing numerical forming simulations followed by analytical computations for the forming-impulse generation through the rapid Joule heating of the foils. The proposed method is demonstrated for an exemplary steel sheet part. The resulting process design provides a part-specific impulse distribution, corresponding parallel actuator geometries, and the pulse generator’s charging energy, so that all process parameters are available before the first experiment. The experimental validation is then performed for the example part. Formed parts indicate that the introduced method yields a good starting point for actual testing, as it only requires adjustments in the form of a minor charging energy augmentation. This was expectable due to the conservative nature of the underlying modeling. The part geometry obtained with the most suitable charging energy is finally compared to the target geometry.

“…Moreover, one can make use of the pressure on both sides of the foil to form two sheets at the same time [8]. Grigoriev and Pavlenko [9] experimentally found the relatively universal Equation (1) to relate the specific electrical energy deposition w (MJ/kg) into the foil until the burst to the burst pressure amplitude p b (h b is the Metals 2020, 10, 845 2 of 12 latent heat of vaporization of a metal (MJ/kg)) after which a very fast quasi-exponential decay can be observed due to the rapid volume expansion of the actuator. Equation (1) clearly shows that the specific achievable resistive energy deposition determines the burst pressure p b , as h b is a material constant.…”

Section: Introductionmentioning

confidence: 99%

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

Tekkaya

2020

Metals

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.