Abstract:To improve the ignition reliability of firearm firing-ignition systems， the Lagrangian-Eulerian fluid-structure coupling method （ALE） was used to establish the ignition model of the firing-ignition systems， and a parametric simulation platform was built. The pressure start time was used as the ignition output performance characteristic parameter to establish the ignition reliability proxy model of the firearm firing-ignition system. The reliability of the firing-ignition systems under the influence of changes in structure and assembly parameters was simulated and studied. At the same time， based on small-caliber rifle firing-ignition system， an ignition system simulation test device was designed， and experimental research on the ignition performance and reliability of the ignition system was carried out to verify the ignition model. The results show that the error between the calculation results of the firearm firing-ignition reliability analysis model and the experimental results is 0.72%， indicating that the model has good accuracy. The influence rule of the average change of each factor on the system reliability is as follows： striking pin protrusion> locking gap> fire table head diameter> primer shell thickness> primer loading depth> firing pin head diameter. The standard deviation change has little impact on system reliability. This study provides theoretical and technical guidance for the reliability design of firearm firing-ignition systems.

Abstract:To develop a high-performance burning rate catalyst for solid propellant， an iron-loaded carbon nanotube material （Fe@CNTs） was synthesized by high-temperature pyrolysis of the caged precursor. The elemental composition， microscopic morphology， phase structure， specific surface area， and catalytic decomposition performance of Fe@CNTs were investigated by scanning electron microscope-energy dispersive spectrometer （SEM-EDS）， transmission electron microscopy （TEM）， X-ray diffraction （XRD）， X-ray photoelectron spectroscopy （XPS）， Fourier transform infrared spectroscopy （FTIR）， nitrogen sorption isotherm measurement （BET）， differential scanning calorimeter （DSC）， and thermogravimetry-mass spectrometry （TG-MS）. The results show that， Fe@CNTs is an iron-loaded carbon nanotube material with a high specific surface area， which can reduce the exothermic peak temperatures of octogen （HMX）， dihydroxylammonium 5，5′-bistetrazole-1，1′-diolate （TKX-50）， 1，1-diamino-2，2-dinitroethylene （FOX-7）， hexogeon （RDX）， and hexanitrohexaazaisowurtzitane （CL-20） by 1.8 ℃， 40.4 ℃， 4.9 ℃， 6 ℃， and 8.8 ℃， respectively， when the addition amount of this material is 6%. The calculations of thermal decomposition kinetics based on the Kissinger-Ozawa model show that the apparent activation energies of 6%Fe@CNTs/HMX and 6%Fe@CNTs/TKX-50 decrease by 96.9-97.1 kJ·mol^-1 and 11.2-11.9 kJ·mol^-1， respectively. Theoretical calculations of thermodynamic and thermal safety parameters indicate that HMX and TKX-50 are still in a thermodynamically stable state after adding Fe@CNTs. Based on the results of TG-MS， the possible catalytic mechanism of Fe@CNTs on HMX and TKX-50 is further proposed.

Abstract:In recent years， molecular perovskite energetic materials have emerged as a kind of new-concept energetic materials， offering a new approach to design practicable single explosives for different applications by rational assembling diverse ionic components. Ammonium chlorate （NH₄ClO₃） is commonly used as an oxidizer benefiting from its high oxidizing ability， but its high hygroscopicity greatly limits its application. By mixing sodium chlorate， aqueous ammonia， and triethylenediamine （dabco）， then acidizing the aqueous solution， we have obtained a new molecular perovskite energetic material， （H₂dabco）（NH₄）（ClO₃）₃（DAC-4）. X-ray single-crystal diffraction analysis revealed that DAC-4 possesses an ABX₃-type perovskite structure belonging to the cubic space group Pmm with a crystallographic density of 1.86 g·cm^-3. DAC-4 exhibits exceptional theoretical detonation performances， with detonation heat， velocity， and pressure of 4.91 kJ·g^-1， 8.43 km·s^-1， and 32.6 GPa， respectively. DTA showed that DAC-4 has a decomposition peak temperature of 106 ℃， higher than that of ammonium chlorate （75 ℃）. Moisture absorption experiments demonstrate that DAC-4 remains nearly non-hygroscopic after being stored for near 2 month at relative humidity below 86%， the weight of DAC-4 only increases by 0.18%， much lower than that of ammonium chlorate （30%）.

Abstract:The solidification process of melt-cast explosive is a significant step during its research and manufacture. solidification， and related charge quality play a key role in the detonation performance and safety of explosives. Based on domestic and foreign research works， the development of solidification techniques of the melt-cast explosive is systematically summarized from three aspects： finite element simulation， solidification process and on-line detection methods. The application of the finite element simulation in flow -temperature-stress field simulation during casting and solidification process of the melt-cast explosive is reviewed. The formation of defects during the solidification process and the effects of different techniques on solidification are elucidated. Furthermore， the application of on-line detection of temperature， stress-strain， viscosity， and internal structure in the high-quality precision forming techniques of melt-cast explosive is discussed. The development of numerical simulation， solidification process optimization and on-line detection technique in melt-cast explosive can provide vital theoretical and technical guidance for the design and development of the solidification equipments and the quality improvement of solidified charges. In the future， the improvement of the charge and solidification technique requires further development and application in aspects such as model construction of equipment-material， safety of process equipment， precise control of process conditions， real-time information monitoring， on-line detection and adaptive regulation.

Abstract:In order to explore the propagation patterns and characteristics of methane vapor cloud combustion waves in tunnels， the CE/SE （space-time conservation element and solution element） method in LS-DYNA software was employed to establish a pre-mixed explosion model of methane and air in the tunnel， which was validated through experimental data. In this paper， typical combustion waveforms of methane vapor cloud with a concentration 9.5% in different test positions were demonstrated by numerical simulation. The propagation and evolution law of overpressure and temperature was analyzed. The injury effects of overpressure and thermal radiation on human in tunnel were investigated. It was revealed that the combustion pressure wave along the tunnel can be divided into four stages： free expansion， reflection dissipation， wall acceleration， and Mach propagation. The pressure variation presented three characteristics： wall impact rise， reflective decay， and stable propagation. The pressure wave presented a sort of periodical reflection propagation mode radially， while the intensity was declining according to the consumption of methane. The temperature field evolved symmetrically from the ignition point to the tunnel entrance and the peak temperature decayed rapidly along the path. The temperature field radiated from the ignition point to the bottom of the tunnel， leading to a gradual convergence of in a certain section and decreased slowly over time. For the injury effects caused by a combination of combustion overpressure and thermal radiation， the fatal distance was 13.51m， the severe injury distance was 13.51~23.51m， the moderate injury distance was 23.51-160 m while the concentration of methane vapor cloud was 5%. For the methane vapor cloud with a concentration 6.5%， those distances were 16.46 m， 16.46~45.36 m and 45.36~160 m respectively. As for a concentration 9.5%， the fetal distance was 20.58m and the severe injury distance was 20.58~160m.

Abstract:To investigate the combustion characteristics of ternary active metal fuels Al/B/Mg （ABM） and Al/B/MgH₂ （ABM-H）， the heat of combustion and minimum ignition energy were studied by using an oxygen bomb calorimeter and a Hartmann tube， respectively. The sub-transient process of flame propagation and the spatiotemporal distribution characteristics of temperature fields were determined by using a high-speed camera system and a high-speed infrared camera system. The results indicate that the calorific values of ABM and ABM-H are 34.1 and 32.2 MJ·kg^-1， respectively， exhibiting increases of 14.4% and 8.1% over pure Al （29.8 MJ·kg^-1）. The minimum ignition energies of ABM， ABM-H， and Al are 160-170， 100-110， and 20-30 mJ， respectively. Compared to pure Al， the combustion duration of ABM and ABM-H increase by 65.5%， 34.5% and the peak flame propagation velocities increase by 12.6%， 23.0%， respectively， at a mass concentration of 625 g·m^-3. At a mass concentration of 500 g·m^-3， ABM-H and ABM exhibit the largest peak flame propagation velocities by 45.05， 38.7 m·s^-1， and the maximum temperatures peak of flame surface by 1856， 1717 ℃， respectively， where ABM-H shows a 7.6% improvement on temperatures peak of flame surface and a faster heating-rate compared to ABM. It suggests that the ABM and ABM-H formulations significantly reduce the explosion risk of the dust/air mixture， and significantly improving the combustion performance. ABM demonstrates superior thermal effects in calorific value and duration of combustion， whereas ABM-H exhibits higher reactivity in terms of minimum ignition energy， flame propagation speed， and temperature rise rate.

Abstract:To study the characteristics of after-effect parameters of shaped charge jet penetrating finite thickness steel target， the experiments on small shaped charge jet formation and penetration on finite thickness plate with after-effect target were carried out. The numerical simulation on the process of shaped charge jet penetrating finite thickness target plate was carried out by ANSYS/LS-DYNA finite software. The influence of target plate thickness， standoff and after-effect material density on the after-effect parameters of shaped charge jet penetration was analyzed， including the residual jet tip diameter d， tip velocity v and after-effect initiation ability v²d. The results show that with the increase of target thickness， the after-effect initiation ability v²d shows a linear attenuation trend， and around 16% of the initial initiation parameter is lost for every 20 mm increase in thickness. In the range of standoff that the jet keeps continuous， with the increase of standoff， the after-effect initiation ability v²d first increases and then decreases， and its stagnation point appears at the standoff of 8 times the shaped charge diameter. In the range of common explosive density， with the increase of after-effect material density ρ， the attenuation rate of after-effect initiation ability v²d first decreases and then increases. At the same time， there is a stagnation point in the v²d-ρ curve. The peak value of v²d is distributed between ρ=1.6-1.8 g·cm^-3， and the stagnation point position moves to the right with the increase of penetration time.

Abstract:Herein， we develop a new method to prepare the ammonium dinitramide/pyrazine-1， 4-dioxide （ADN/PDO） cocrystal， which is highly efficient and environmental-friendly due to utilizing the reaction crystallization with pure water as the solvent， and also comprehensively characterized its performance.. The morphology and structure of the cocrystal were characterized by optical microscopy （OP）， powder X-ray diffraction （PXRD）， and single crystal X-ray diffraction （SXRD）， respectively. In detail， the ADN/PDO cocrystal was prismatic and formed by the combination of ADN and PDO molecules at a molar ratio of 2∶1. Moreover， the ADN/PDO cocrystal belongs to the monoclinic crystal system with a space group of P2₁/c， owning a theoretical density of 1.779 g·cm^-3 at room temperature. Furthermore， through the differential scanning calorimetric （DSC） measurement， it turned out that the melting point of the prepared ADN/PDO cocrystal is 113.3 ℃， which is 21.3 ℃ higher than that of ADN， and the decomposition temperature is slightly higher than that of ADN， demonstrating good thermal stability of the prepared ADN/PDO cocrystal. Then， the hygroscopicity of the prepared cocrystal， measured by the weight increment method， is significantly low at only 2.6%， while that of ADN is at 45%. In addition， calculated by the NASA CEA， the theoretical specific impulse of the cocrystal reaches 277.9 s while that of ADN is 197.5 s， demonstrating the high energy performance of the cocrystal. In conclusion， the reported method based on the reaction crystallization successfully enables the efficient production of a high-energy， low-hygroscopic ADN/PDO cocrystal， thereby facilitating the further assessment of its application performance.

Abstract:In order to study the influence of explosive crystal particle size on mechanical properties and interfacial enhancement of polymer bonded explosive （PBX）， HMX-based PBXs were prepared by using four kinds of HMX with different particle sizes （160 μm，60 μm，25 μm and 150 nm） as main explosive. The fluorine resin and neutral polymeric bonding agent were used as binder and interface enhancement agent， respectively. The compressive stress-strain test and Brazilian test were performed to obtain the compressive and tensile mechanical properties of 8 types of PBXs at room temperature （20 ℃） and high temperature （60 ℃）， respectively. The storage modulus and mechanical loss factor were obtained using the three-point bending mode of dynamic mechanical analysis. The cross-sections of PBXs were characterized by scanning electron microscopy. Results show that both the compressive and tensile mechanical strength of explosive increase with the decreasing of HMX particle size， in which the nano-HMX based PBX （PBX-nano） shows the highest strength. The compressive strength and tensile strength of PBX-nano are 61.3 MPa and 5.7 MPa， increasing by 73.1% and 63.5% from PBX-L， respectively. By adding the bonding agent， the compressive mechanical strength and tensile mechanical strength for all the PBXs are significantly improved， especially the PBX-nano. The tensile strength of PBX-nano-M at 20 ℃ and 60 ℃ are up to 10.4 MPa and 5.8 MPa， which are 82.6% and 101.4% higher than that of PBX-nano， respectively. When the average particle size of HMX decreases from 100 μm to 100 nm， the greater the fracture energy required for interface debonding/damage and even fracture of explosive， the greater the increase in tensile mechanical strength.

Abstract:This study presents a method for rapidly estimating energy density based on the energy difference of chemical bonds， along with a technique for promptly evaluating cage structural stability by integrating Laplacian bond order and the bond dissociation energy of molecular fragments. By exhaustively constructing all nitrogen-rich frameworks derived from Noradamantane and its 435 nitro derivatives， the study applied the aforementioned computational methods to screen molecular structures with high energy density and stability. The reliability of the screening results was confirmed through quantum chemical energy calculations and transition state reaction barrier calculations. Two nitro compounds exhibiting both high energy density and structural stability were identified， with theoretical maximum values of detonation heat， detonation velocity， detonation pressure， and metal acceleration capability reaching 7.77 kJ·g^-1， 10.1 km·s^-1， 47 GPa， and 1.14 times the metal acceleration capability of HMX， respectively， and with structural decomposition reaction barriers ≥96 kJ·mol^-1. The rapid screening method for energy density and stability of energetic molecules established in this study can provide theoretical guidance for the future design of high-energy stable energetic molecules.