Impact Mechanism of Micro-defects in the Exploding Foil Bridge Region on Energy Conversion Efficiency During Ignition
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摘要:为量化爆炸箔桥区微缺陷对其发火性能的影响，本文基于COMSOL Multiphysics构建了电热耦合三维有限元模型，系统对比了理想桥箔与含盲孔、通孔缺陷桥箔在0.22 μF/1 500 V放电回路中的瞬态温升及能量转换规律。结果表明：无缺陷桥箔通电后四角因电流密度集中率先升温，100 ns内桥区中心温度达1 400 K，桥区整体均匀熔化；含缺陷桥箔中，盲孔或通孔导致局部电流密度畸变，形成低温电流盲区，未熔金属碎片随射流飞散，能量转换效率显著降低（极端情况下相对降幅>21.7%）；缺陷尺寸效应呈现临界尺寸阈值，通孔直径>50 μm或盲孔深度>3 μm时，临界效应显著。当通孔直径>50 μm时，桥区平均温升起点提前3 ns，爆发时间缩短33 ns；盲孔深度>3 μm时，电流盲区范围扩大，能量转换效率相对降幅大于8%。本研究首次建立了爆炸箔微缺陷容限的定量判据，为高可靠性火工品制造工艺优化提供理论支撑。
Abstract:To quantitatively evaluate the influence of micro-defects( blind holes or through-holes) in the bridge region of exploding foil initiators (EFI), a three-dimensional electro-thermal coupled finite element model was established using COMSOL Multiphysics. Transient temperature rise and energy utilization were compared between defect-free and defective copper bridge foils under a 0.22 μF / 1 500 V discharge circuit. Results show that: for defect-free foils, the four corners heat first , and the centre reaches 1 400 K within 100 ns, leading to uniform melting; In defective foils, micro-holes distort local current density, forming low- temperature “current blind zones”; Unmelted metal fragments are ejected with the plasma jet, significantly reducing energy conversion efficiency (up to 21.7 % relative decrease in extreme cases). A critical size threshold is identified: when the through-hole diameter exceeds 50 μm or the blind-hole depth exceeds 3 μm, the threshold effect becomes pronounced. Specifically, for through-holes > 50 μm, the average temperature rise onset advances by 3 ns and the burst time is shortened by 33 ns; for blind-holes > 3 μm the current blind zone expands, and the relative decrease in energy conversion efficiency exceeds 8 %. This study establishes quantitative defect-tolerance criteria for EFI micro-defects for the first time, providing theoretical support for optimizing the manufacturing process of highly reliable pyrotechnic devices.
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