Electrically driven plasma via vaporization of metallic conductors: A tool for impulse metal working

Abstract

Forming, cutting and welding of metal by impulse has significant advantages, in that short time scales change the fundamental nature of the forming process and short duration impulses can enable much lighter and more agile equipment because large static forces do not need to be resisted. Impulse forming is most commonly executed using electromagnetic forming. However, the application of electromagnetic forming is limited at high energies and large numbers of operations by the availability of long-lived electromagnetic coils (or actuators, as they are sometimes referred to). Low-cost, disposable actuators have been suggested as one method to counteract this issue. Here we propose the use of low-cost foils or wires that are intentionally vaporized by a pulsed electric current, in order to create an intense mechanical impulse. Applications including cutting, forming, and dimensional calibration are demonstrated and discussed. The available literature that could provide design guidance is reviewed. A simple cutting and welding experiment using a vaporizing aluminum foil is demonstrated. Further experiments study the expansion of simple copper tubes using the impulse developed from copper and aluminum wires that are vaporized using capacitor bank discharge with nominal charged voltages between 3.4 and 6.7kV, and peak currents between 60 and 150kA delivered with rise times on the order of 20μs. This gives some guidance on how forming operations may be designed and, opens possible areas for further research.