用十字形超细药条离散群同步起爆实现超低比冲量加载

余弦分布载荷的化爆加载技术是高空核爆软X射线辐照下空间结构动态响应考核的主要手段。为适应新型空间飞行器结构考核的复杂构型、高同步性和低比冲量载荷设计要求,提出了一种用十字形超细药条离散群同步起爆实现超低比冲量加载的方法。实验结果验证表明：(1)所制作的十字形超细药条,最小截面尺寸为0.33 mm×0.5 mm,传爆性能稳定,并可通过直径0.5 mm的柔爆索直接起爆;(2)与相同布药密度的条状布药方式相比,布药空间均匀度提高了76.7%;(3)所采用的21点柔爆索同步起爆网络,起爆率达100%,起爆不同步性小于1μs。进一步建立了离散片炸药加载数值计算模型,分析了离散片炸药群同步起爆加载的比冲量空间分布和匀化规律,将匀化过程分为扩散段、叠加段和均匀段3个阶段;对比了方形、十字形、短条形3种形状药片阵列的比冲量演化过程,发现十字形药片所需匀化距离最短、均匀度最高,仅需约0.8倍布药间距即可使比冲量均匀度偏差降至10%以下。

Realization of ultra-low specific impulse loading by synchronous initiation of discrete group of cross ultra-fine explosive rods

The loading technology of cosine distributed load by chemical explosion is the main method for evaluating the dynamic response of space structures under the irradiation of high-altitude nuclear explosions with soft X-rays. A loading method of discretely-distributed sheet explosives synchronously detonated by a mild detonating fuse (MDF) network was proposed to meet the design requirements of complex configuration, high synchronicity and low specific impulse load in the structural assessment of new space vehicles. In terms of experimental study, the cross-shaped sheet explosive made by stacking explosive strips with a cross-sectional size of 0.33 mm×0.5 mm can be directly detonated by a mild detonating fuse with the diameter of 0.5 mm. Compared with strip distribution, the space uniformity of cross distribution is improved by 76.7%. A high-speed camera was used to record the shock wave luminescence during the detonation process. The results show that the detonation ratio of the 21-point MDF detonation network reaches 100%, and the detonation asynchrony is less than 1 μs. In terms of numerical simulation, a numerical model for the explosion of sheet explosives was established based on the multi-material arbitrary Lagrangian-Eulerian (ALE) algorithm. The numerical model has strong grid sensitivity, and the results by it tend to converge when the mesh size reaches 0.5 mm, with the deviation from the measured specific impulse results within 5%. Based on the numerically-simulated results, the following conclusions can be drawn. (1) Under the periodic discrete distribution condition, the peak specific impulse is determined by the surface density of the explosive, and the evolution process of the peak specific impulse is determined by the spacing. (2) The homogenization process of specific impulse can be divided into three stages: diffusion stage, superposition stage and uniform stage. The specific impulse is homogenized through free diffusion of shock wave in the diffusion stage, and through shock wave superposition and collision in the superposition stage, and finally enters the uniform stage with relatively uniform distribution. (3) The homogenization distance into the uniform stage required by the arrays of square and short rod explosives is about equal to the spacing of the explosives, while the arrays of cross explosives only need about 0.8 times the spacing, and the degree of homogenization in the uniform stage is higher, so the cross explosive has a greater advantage in the case of plane explosive loading. (4) The loading mode of synchronous initiation of discrete explosive group not only improves the load synchronization, but also improves the load uniformity, compared with the slip detonation loading of rod distributed charge. The structural response distortion caused by the excessive additional mass of rubber can also be avoided by using the air layer between the sheet explosives and the structure to homogenize the load.