Abstract:

Abstract:

Abstract:In order to improve the safety and ignition ability of Ni-Cr thin film igniter, a new Ni-Cr@Al/CuO insensitive energetic element was fabricated by combining Al/CuO energetic thin film with Ni-Cr thin film bridge by magnetron sputtering. The Ni-Cr@Al/CuO insensitive energetic element can be used both as the energy transducer element and as the simplest electrical ignition elements. It simplified the point fire transmission sequence and adapt to the development needs of ammunition miniaturization. The safety of Ni-Cr@Al/CuO was tested at the loading condition of 1A1W5min, and its electric ignition sensitivity and ignition capability were tested. The results show that the 50 ms critical ignition current of the insensitive nucleus Ni-Cr igniter is 3.08 A, 99.9% firing current is 3.18 A, 0.1% firing current is 2.98 A. Under the same conditions, Ni-Cr@Al/CuO insensitive energetic element can ignite B/KNO₃, besides, it can achieve 1mm gap ignition, while Ni-Cr thin film igniter can not successfully ignite B/KNO_3.

Abstract:The constitutive relationship of polymer bonded explosive (PBX) including damage is one of the key fundamental issues of the safety research of PBX. To study the damage constitutive relationship of PBX explosive, it is necessary to accurately acquire and understand the dynamic mechanical response of PBX explosive.. Therefore, in allusion to the SHPB tests on PBX, it is particularly discussed that the influence of loading ways on the mechanical response of PBX. Through different shapers, loading wave length, and repeated loading, the influences of different loading ways on the mechanical response including damage of PBX have been analyzed, and a series of stress-strain curves were obtained. The ultimate damage morphology of recycled samples was observed by scanning electron microscopy, and the damage development process of PBX explosive under dynamic uniaxial compression and its performance in stress-strain relationship were analyzed.. Results show that loading with brass shaper leads to large strain acceleration and still has an impact on PBX, resulting in additional damage. The failure of specimens subjected to dynamic uniaxial compression is characterized by multiple transgranular fracture or even fragmentation of crystals. The constitutive relationship considering damage can be described by the nucleation, stable growth, and unstable propagation through crystals of micro-cracks.

Abstract:In order to investigate the characteristics of crack penetration in explosive bulk driven by burning products, and deepen the mechanism understanding on the process of high intensity reaction induced by burning products entering into cracks and forming convective burning under accidental ignition. The penetration of cracks in a HMX-based PBX (with a content of 95% for HMX) under thermal initiation at the preformed gap was photographed by the high-speed camera. Experimental results reveal that, due to the strong meso-heterogeneity of polymer bonded explosive (PBX), different samples of the same kind of explosive have different meso-structures, which results in the difference of crack propagation paths (which may propagate in a straight line or deflect)., Velocities of the crack penetration are nearly the same under same confinement and same pre-load stress. The average crack penetration velocity is about 146.7 m·s^-1 in the experimental condition of this research.

Abstract:Visco-SCRAM model was applied to study on the influence of the initial crack on Octogen (HMX)-based polymer bonded explosive (PBX) ignition under low velocity impact. By means of the simulation of the standard low impact Steven test, the influence of the initial crack length and its distribution on the temperature rise and the hotspot formation was analyzed. The simulation results demonstrate that as the increment of the initial crack length, the friction work between the surfaces of the micro-cracks is strengthened, which brought in high temperature rise and further the hotspot is formed more easily. When the initial crack length is increased from 1mm to 3mm, the ignition impact threshold velocity is reduced from 45 m∙s^-1 to 38 m∙s^-1. Considering the heterogeneous initial crack, during the low velocity impact, the temperature rise region is obviously changed. Moreover, the hotspot formation is beneficial of the heterogeneous initial crack, and further it resulted in the reduction of the ignition impact threshold velocity. When the distribution of the initial crack follows the uniform distribution U(0.8, 1.2), the ignition impact threshold velocity is 36 m∙s^-1. When the distribution of the initial crack follows the normal distribution N(1, 0.115), the ignition impact threshold velocity is 31 m∙s^-1.

Abstract:To study the effect of inert sugar particles on the non-shock ignition mechanism of two kinds of single compounds octogen(HMX) and hexogen(RDX), the processes of undergoing the crushing, melting, sputtering, igniting and combustion of HMX and RDX single compound containing inert particles were captured by a drop weight impact device equipped with anoptical observation system. Results show that the ignition is easy to occur around the sugar particle in the cases of HMX fine particle and RDX powder containing sugar. The combustion will propagate outward along the periphery of the sugar particle, and intense sputtering phenomena occur before the combustion reaction. In the HMX particle with sugar, the ignition occurs in the solid phase. In the RDX powder explosive with sugar, the explosive near the sugar particle enters into the melting state firstly, then the melting region expands gradually, and the ignition points are easy to appear in the molten liquid phase of RDX at the edge of the sugar particle. The ignition frequency of HMX and RDX with one or three sugar particles respectively was compared. Results show that the cases of three sugar particles are more likely to cause the ignition of explosives, because the more fragments are produced after crushing, which interact strongly with HMX or RDX single compound, and may lead the hot spots to form in multiple locations, and the combustion reaction will be more intense than that of the cases of single sugar particle.Finally, the upper and lower limit analysis shows that the addition of sugar particles can inhibit the ignition of HMX fine particles and promote the ignition of RDX powder explosive.