强约束球形装药反应裂纹传播和反应烈度表征实验

炸药燃烧的高温高压气体产物可以进入基体裂纹中引发炸药表面热传导燃烧，形成所谓的对流燃烧。在一定约束条件下，不断上升的气体压力反过来又使炸药基体产生更多的裂纹，为对流燃烧提供更多的通道和燃烧表面积，快速生成大量产物气体导致高烈度反应现象的产生。本文中设计了一种新型强约束球形装药中心点火实验，针对一种HMX为基的PBX炸药，对高烈度反应条件下燃烧裂纹传播和反应增长过程进行了观测，实验中采用测得的反应压力和壳体速度历程对反应烈度进行了量化表征。在带窗口结构中，早期炸药中的燃烧裂纹不可见；中期燃烧裂纹扩展到药球表面时，先形成4条沿经线方向近似对称的主裂纹，随后环向贯通并扩展到整个药球表面；最后的剧烈反应造成强烈发光。上述反应演化经历低压增长阶段约为100 μs，之后伴随着壳体变形膨胀产生剧烈的反应，此时产物压力在约10 μs时间内超过1 GPa，并形成约20%相对于裸炸药爆轰的超压输出。在全钢结构中，20 mm厚的壳体膨胀速度最大可达到500 m/s，此时壳体完全破裂。

Propagation of reactive cracks and characterization of reaction violence in spherical charge under strong confinement

High temperature gaseous products of conductive burning on explosive surface can penetrate into preformed crack inside explosive bulk under high pressure to form so-called convective burning. The high rising gaseous products pressure resulting from the convective burning in turn will create cracks inside the explosive bulk, leading to the formation of new channels for convective reaction and the more reaction surfaces for burning. In this paper, a new experimental method is designed for a pressed HMX-based PBX, in which a highly confined spherical charge is ignited on center point via non-shock initiation. The propagation of such kind of reactive cracks inside is recorded and evaluated with the total reaction violence growth behavior characterized by reaction pressure and confinement wall velocity profile. In the experiment with a transparent window, the early stage evolution of crack inside explosive sphere is invisible and the crack system after the crack break through to the spherical surface shows a 4 fold symmetric crack pattern which is deduced to be related with outer layer confinement conjunction manner. The violence evolution experiences a sustaining low pressure growing rate stage for 100 μs. Then it is observed that a rapid burst pressure in about 10 μs is up to over 1 GPa during the confinement wall movement stage, which gives to a typical explosion outcome with ～20% of bare explosive detonation calculated by air blast over pressure. In the experiment with a 20 mm steel wall, the velocity of the wall has reached 500 m/s at the moment of confinement wall rupture.