System modeling and simulation of flyer acceleration and explosive detonation in exploding foil initiator

Abstract

In this theoretical study on an exploding foil initiator (EFI), the sequential events in an EFI system were numerically modeled and investigated from metallic bridge burst by ohmic heating and flyer acceleration by plasma expansion to explosive detonation by high-speed flyer impact. The EFI system modeling employed mass, momentum, and energy conservation coupled with the resistance-inductance-capacitance circuit equation of the initiation circuit and plasma property calculations of highly dense metallic plasma as well as a semi-empirical detonation model. The aim was to predict transient bridge behavior, flyer velocity, and detonation initiation threshold. Through comparisons and verifications with measured data from several existing EFI firing tests, the present system model was shown to predict bridge burst and flyer velocity very well. The numerical results indicated two different thresholds of charging voltage for flyer creation out of plastic film and impact detonation of explosive charge to be quite consistent with the measurements. The system behaviors in three different ranges of charging voltage were discussed in terms of discrete nature of this high-voltage explosive charge initiator.