Abstract
A pyrotechnic device that consists of a donor/acceptor pair separated by a gap or a bulkhead relies on the shock attenuation characteristics of the gap material and the shock sensitivity of the donor and acceptor explosives. In this study, a miniaturized exploding foil initiator, based on high pulsed electrical power generator, was designed to launch a micro Kapton® flyer for impact initiation of a high explosive in order to understand its performance characteristics. Here, the explosive substance was replaced with a witness plate because the flyer poses various flight motions of rotation, bend, and fragmentation due to its extreme thinness. By using a Velocity Interferometer System for Any Reflector and ANSYS Explicit Dynamics, the averaged velocity of a flyer is measured, which then allows for the calculation of the shock pressure and the duration imparted to the explosive for an initiation. Subsequently, the relationship between the flyer velocity, the amplitude, and the width of impact loading can be used to assess the performance of the designed exploding foil initiator of a micro pyro-mechanical device.
Highlights
By using a Velocity Interferometer System for Any Reflector and ANSYS Explicit Dynamics, the averaged velocity of a flyer is measured, which allows for the calculation of the shock pressure and the duration imparted to the explosive for an initiation
Velocity Interferometer System for Any Reflector (VISAR)9 measurement was conducted to obtain the impact velocity of a flyer; the impact velocity is in principle the most significant parameter of exploding foil initiator (EFI) performance
Since the same impact pressure is loaded on both sides of the target and flyer from the momentum conservation, the flyer velocity can be obtained from a mirror image of a flyer Hugoniot intersecting with a target Hugoniot at the impact pressure, which is measured by VISAR in an ideally planar condition without any edge effects
Summary
A detonator is a primary initiator unit that ensures reliable triggering of an explosive train of which the sequence of events culminates in the detonation of sensitive high explosives in a variety of applications. Traditionally, the explosive train requires a physical barrier or misalignment between the primary and secondary explosives to avoid the inherent hazard of accidental discharging during handling and transport. an exploding foil initiator (EFI), known as a slapper detonator, simplifies the design of the explosive train by eliminating the mechanical assemblies usually used for safety when using explosives, because it can directly initiate secondary explosives by the impact of a flyer at a desired velocity. Since the EFI development from the mid 1970s,4 the performance map of the EFI detonator and the burst current density have been investigated in order to optimize the explosive system. studies on explosive initiation by a micro EFI and optical detonator have been continuously performed to devise micro energetic actuators.. An exploding foil initiator (EFI), known as a slapper detonator, simplifies the design of the explosive train by eliminating the mechanical assemblies usually used for safety when using explosives, because it can directly initiate secondary explosives by the impact of a flyer at a desired velocity.. Velocity Interferometer System for Any Reflector (VISAR) measurement was conducted to obtain the impact velocity of a flyer; the impact velocity is in principle the most significant parameter of EFI performance. In order to overcome this difficulty, numerical analysis based on the finite element method is performed in an inverse approach to determine the initial pressure at zero thickness of a target. Small-scale flyer and the ensuing shock pressure are investigated to determine the performance of the current EFI system.
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