Measurement-Based Prediction of Inductive Ignition Risk Boundaries for Bridgewire Electro-Explosive Devices Under Transient Magnetic Fields.

Predicting the ignition risk of bridgewire electro-explosive devices (EEDs) under transient magnetic fields requires linking the local magnetic field history to the inductive response of the associated closed loop and the thermal response of the bridgewire-charge system. In this study, a measurement-grounded framework was developed by combining transient field measurement with a three-dimensional electromagnetic-thermal model. A custom inductive probe with a manufacturer-specified equivalent magnetic flux area of Ap = 12,029 mm2 was used to obtain the local magnetic field rate history (dB/dt). In bench tests, the induced-voltage histories of closed loops with different measured areas were reconstructed from the probe signal using the loop-to-probe area ratio and used as inputs to the bridgewire-charge model. Three measured transient magnetic field waveforms were used to evaluate the predicted ignition boundaries. For Waveform I, the experimental and predicted critical-area intervals were (772, 824] and (804.2, 907.9] mm2, respectively. For Waveforms II and III, the experimental interval (542, 583] mm2 lay within the predicted interval (530.9, 615.8] mm2. The evaluated framework was further applied to the projectile-fixed magnetic field history of a five-stage coilgun, yielding a predicted critical equivalent loop radius interval of (14, 15] mm. The results demonstrate that inductive ignition risk depends on closed-loop magnetic flux coupling and the complete transient excitation history rather than on peak magnetic flux density or peak dB/dt alone. The proposed method establishes a quantitative link among local transient magnetic field measurement, installed loop magnetic flux coupling, and device-level ignition risk boundaries, providing a practical framework for electromagnetic safety assessment of projectile-borne EEDs under complex transient magnetic field environments.