The action-integral and energy to explode short gold wires in ambient air

Rae, Philip

doi:10.1063/5.0041067

Cited by 6 publications

(3 citation statements)

References 26 publications

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“…A standard commercial detonator header (RP-1, Teledyne RISI, www.teledynerisi.com) with an empty brass sleeve had thin layers of 0.88 g/cc either confectioners sugar or high specific surface area PETN pressed against the bridgewire using a precision die-set and press. Confectioners sugar has been previously shown to result in the same electrical signals at burst as PETN, but being a largely inert organic crystal as opposed to an organic energetic one, the compaction in the powder bed is a function of only the drive from bridge-burst [13]. In fact, in contrast to the highly exothermic process of reaction in PETN, the breakdown of sugar will be endothermic.…”

Section: Methodsmentioning

confidence: 99%

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The effects of electrically exploding gold bridgewires into inert and explosive powder beds

Rae

Rettinger

2021

Shock Waves

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The particle velocity created in beds of both low-density inert sugar and explosive PETN as a function of distance from an exploding bridgewire was measured using optical velocimetry and a silvered PMMA window. As expected, more violent bridge-bursts (from a greater-stored-energy capacitive discharge unit) resulted in greater particle velocities and a better supported compaction wave in sugar. In all cases, ramp waves, not shocks, were observed in the inert sugar. Large window velocities were observed for very powerful bursts (up to 270 m/s), but bursts required for stochastic detonator operation conditions resulted in sugar/PMMA window velocities of only 8–10 m/s 0.85 mm from the bridge location. In contrast, after a distance of only 0.65 mm, a building shock wave was observed in PETN under both threshold and reliable firing conditions. Subsequently a hot-spot-driven shock-to-detonation (SDT) process was observed prior to full detonation. The measured buildup process accounts for $$\approx $$ ≈ 66% of the so-called excess transit time (ETT) between the observed and theoretical total function time for the particular exploding-bridge-wire (EBW) detonator studied. The remainder must occur in the powerful output pellet region. In contrast to a common understanding, the ETT is found to be a weak function of the discharge energy. Thus, the operation of the detonator after a bridge-burst energy-to-powder reaction transition process is found to be hot-spot-driven SDT in both the low- and high-density pellets.

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Section: Methodsmentioning

confidence: 99%

“…The least-squares fitting form used is described in the text Distance From Bridge / mm Hard-Fire Shock Velocity Soft-Fire Shock Velocity Fig. 13 The corresponding VOD versus distance through the PETN powder bed from the fits presented in Fig. 12.…”

Section: Explosive Powder Studiesmentioning

confidence: 99%

The effects of electrically exploding gold bridgewires into inert and explosive powder beds

Rae

Rettinger

2021

Shock Waves

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“…The operability of an exploding bridgewire (EBW) detonator is defined as the ability of the initial pressing (IP), in contact with the EBW, to promptly shock initiate the output pellet (OP) after energy is delivered to the bridgewire that is commonly made from gold [1]. Joule heating causes the thin gold wire to rapidly melt, expand, and form an expanding plasma that subsequently collapses inward by magnetic forces [2].…”

Section: Introductionmentioning

confidence: 99%

A Liquid Stratification Model to Predict Failure in Thermally Damaged EBW Detonators

Hobbs

Coronel

2022

Propellants Explo Pyrotec

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In previous work, commercially available downward facing exploding bridgewire detonators (EBWs) were exposed to elevated temperatures. These detonators were then initiated using a firing set which discharged a high amplitude short duration electrical pulse into a thin gold bridgewire. Responses of the detonators were measured using photonic doppler velocimetry (PDV) and high-speed photography. A time delay of 2 μs between EBW initiation and first movement of an output flyer separated operable detonators from inoperable detonators or duds. In the current work, we propose a simple method to determine detonator operability from the calculated state of the detonator at the time the firing set is initiated. The failure criterion is based on the gap distance between the exploding bridgewire (EBW) and the adjacent initiating explosive within the detonator which is low-density pentaerythritol tetranitrate (PETN) that melts between 413-415 K (140-142 °C). The gap forms as PETN melts and flows to the bottom of the input pellet. Melting of PETN is modeled thermodynamically as an energy sink using a normal distribution spread over a temperature range between the onset temperature of 413 K and the ending temperature of 415 K. The extent of the melt is determined from the average temperature of the PETN. The PETN liquid is assumed to occupy the interstitial gas volume in the lower part of the input pellet. The vacated volume from the relocated liquid forms the gap between the EBW and the PETN. The remaining sandwiched layer consists of solid PETN particles and gas filling interstitial volume. We predict that a threshold gap between 17-27 μm separates properly functioning detonators from duds.

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Investigation of thermal damage in explosive bridgewire detonators via discrete element method simulations

Wolf,

Clemmer,

Hobbs

et al. 2024

Propellants Explo Pyrotec

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Exploding bridgewire (EBW) detonators are used to rapidly and reliably initiate energetic reactions by exploding a bridgewire via Joule heating. While the mechanisms of EBW detonators have been studied extensively in nominal conditions, comparatively few studies have addressed thermally damaged detonator operability. We present a mesoscale simulation study of thermal damage in a representative EBW detonator, using discrete element method (DEM) simulations that explicitly account for individual particles in the pressed explosive powder. We use a simplified model of melting, where solid spherical particles undergo uniform shrinking, and fluid dynamics are ignored. The subsequent settling of particles results in the formation of a gap between the solid powder and the bridgewire, which we study under different conditions. In particular, particle cohesion has a significant effect on gap formation and settling behavior, where sufficiently high cohesion leads to coalescence of particles into a free‐standing pellet. This behavior is qualitatively compared to experimental visualization data, and simulations are shown to capture several key changes in pellet shape. We derive a minimum and maximum limit on gap formation during melting using simple geometric arguments. In the absence of cohesion, results agree with the maximum gap size. With increasing cohesion, the gap size decreases, eventually saturating at the minimum limit. We present results for different combinations of interparticle cohesion and detonator orientations with respect to gravity, demonstrating the complex behavior of these systems and the potential for DEM simulations to capture a range of scenarios.

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The action-integral and energy to explode short gold wires in ambient air

Cited by 6 publications

References 26 publications

The effects of electrically exploding gold bridgewires into inert and explosive powder beds

The effects of electrically exploding gold bridgewires into inert and explosive powder beds

A Liquid Stratification Model to Predict Failure in Thermally Damaged EBW Detonators

Investigation of thermal damage in explosive bridgewire detonators via discrete element method simulations

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