Abstract:The initial thermal decomposition pathways as well as some important products generating mechanism of hexanitrohexaazaisowurtzitane(CL-20) /1, 3-dinitrobenzene(DNB)cocrystal at high temperatures(2000, 2500 K and 3000 K) were studied by reactive molecular dynamics simulations using ReaxFF force field. Results show that with the increasing of temperature during the thermal-decomposition process, the time to balance and potential energy decrease, while the quantity of products increases. The simulation results show that all the CL-20 molecules decompose faster than that of DNB, and as the temperature rises, the decomposition rate of DNB increases significantly. According to the product identification analysis, the main thermal decomposition products are NO₂, NO, N₂, H₂O, HNO₃, HON, HONO and CO₂ for cocrystal. The major initial decomposition mechanism is the breaking of N—NO₂ in the CL-20 and C—NO₂ in the DNB, which contributes to the formation of NO₂. And then, the number of NO₂ increases to the peak rapidly and decreased subsequently. After the NO₂→ONO rearrangement, it participates in other reactions and eventually occur N₂, NO, HONO, HON, H₂O and so on. In addition, the simulation results indicate that carbon-containing clusters formed in the later stage of decomposition at 2500 K and 3000 K, which is a common phenomenon during the detonation of rich carbon-containing explosives.

Abstract:The ignition ability and radiant efficiency. performances for pyrotechnic composition are related to the velocity distribution of the burning particles in its flame. Experimental research on the distribution of burning particles of the pyrotechnic composition composed of potassium perchlorate, magnesium powder and nitrocellulose was performed by a high-speed camera (HSC) photography and the mathematical modeling of flow field was carried out according to the related algorithm. The tracking statistics of particles and the analysis of velocity vector to the continuous images obtained by HSC were carried out through the succession image processing methods.The motion trajectory of the burning particles was calculated by a grey value weighted centroid method and the mathematical model of of burning particle motion vector was established. Results show that under the influence of taking into account the gravity, buoyancy, drag force etc. conditions, the coordinate of burning reaction particle and the particle trajectory model of velocity can be established, and the regional distribution of the burning particles velocity is obtained. The model can reflect preferably the characteristic of trajectory of flame particle and the flame structure of pyrotechnic composition.

Abstract:To explore and compare the stability and mechanical properties of hexaazaisowurtzitane/polyvinyl alcohol (ε-CL-20/PVA) and ε-CL-20/PEG (poly(ethylene glycol)) composites on (001), (110) and (020) crystalline surfaces, molecular dynamics (MD) simulation was conducted for the ε-CL-20/PVA and ε-CL-20/PEG composites by COMPASS force field at room temperature under atmospheric pressure. The cohesive energy densities (CED), the binding energies (E_bind) and mechanical properties (tensile modulus E, shear modulus G, bulk modulus K, Poisson ratio ν and Cauchy pressure C₁₂-C₄₄) were obtained. Results show that the cohesive energy densities of ε-CL-20/PEG composites are greater than those of ε-CL-20/PVA composites, indicating that the stability of the former is superior to that of the latter. For the same composite, the order of CED is (020)>(001)>(110). For the same crystalline surface, the binding energy with PEG is greater than that with PVA. The order of binding energy is (001)>(110)>(020). According to Poisson′s ratios and K/G values, the elasticity and ductility of ε-CL-20/PEG composites are all better than those of ε-CL-20/PVA composites.

Abstract:Aiming at polymer bonded explosive (PBX) thick wall spherical shell structure in steady temperature field, a thermoelastic deformation analysis was launched and the failure damage status of the structure under the action of thermal stress was discussed. The temperature difference carrying capacity and first failure point position of thick wall spherical shell structure were analyzed by strength criterions including the maximum tensile stress criterion, von-Mises criterion, Mohr-coulomb criterion and Drucker-Prager criterion. The rule of the temperature difference carrying capacity of ordinary PBX structure was obtained via related structure shape and size parameters factors isolated by the dimensionless analysis. Results show that Drucker-Prager criterion is accurate to describe the failure damage status of PBX thick wall spherical shell structure. The failure damage status of PBX structure relates to the material characterization and structure size etc factors. Increasing the tensile strength of materials, decreasing the elastic modulus of materials and optimizing the structure size and shape can improve its temperature difference carrying capacity. The temperature difference carrying capacity of PBX structure at room temperature can be considered by tensile failure strain, improving the tensile failure strain of PBX structure can improve the temperature difference carrying capacity of PBX structure. The material properties of three kinds of PBX materials PBX9-A, PBX-E and PBX-C with same structure under thermal environment were compared, the temperature difference carrying capacity of PBX-A is 5.6 times that of PBX-C, and the temperature difference carrying capacity of PBX-E is 4.4 times that of PBX-C.

Abstract:Ternary Al-Mg-Zr alloy fuels with Mg content ranging from 5% to 30% were prepared by a close-coupled gas atomization. The phase composition, morphology and exothermic oxidation behavior of the alloy powders were characterized by X-ray diffraction, scanning electron microscope(SEM)/ energy dispersive spectrometer (EDS) and thermogravimetry-differential thermal analysis (TG-DTA) respectively and an oxidation reaction mechanism model was proposed to explain the intensive oxidation exothermic phenomenon. Results show that the alloy powders consist of Al, Al₃Mg₂, Al₃Zr and Al₁₂Mg₁₇ mainly, and the powder has good sphericity. With the increasing of Mg content, the oxidation reaction temperature of Al-Mg-Zr alloys decreases, the multi-step oxidation process gradually transforms into single step oxidation process and the energy releasing amount increases first and then decreases. The intensive exothermic oxidations of Al₇₈Mg₂₀Zr₂ and Al₇₃Mg₂₅Zr₂ powders occur at 945 ℃ and 938 ℃, respectively. The intensive oxidation reaction of Al₇₈Mg₂₀Zr₂ powder is relatively complete and the highest exothermic enthalpy of oxidation of the powder is 9798.8 μV·s·mg^-1.

Abstract:To investigate the effect rule of aluminum powder on the explosion field pressure and temperature of aluminized explosive in vacuum environment, the explosion field pressure and temperature of four kinds of aluminized explosives containing spherical aluminum powder with particle size of 4, 13 μm and 28 μm and slice aluminum powder with particle size of 130 μm were measured in a sealed explosion chamber. Results show that the significance of aluminum powder on the explosion field pressure of aluminized explosive reduces in the order of 13 μm spherical aluminum >4 μm spherical aluminum >28 μm spherical aluminum >130 μm slice aluminum and the effect of aluminum powder on the explosion field temperature of aluminized explosive raises in the order of 28 μm spherical aluminum >130 μm slice aluminum >4 μm spherical aluminum >13 μm spherical aluminum, revealing that the effect of aluminum powder on the explosion field pressure and temperature has no correlation with particle size of aluminum powder.

Abstract:To improve the thermal shock resistance of TATB-based polymer bonded explosive (PBX), TATB-based PBX was modified by styrene copolymer. The tensile mechanical properties and thermophysical properties of TATB-based PBX and its formulation modified by styrene copolymer were analyzed, and the thermal shock resistances of formulation before and after modification were compared. The thermal conductivity behaviors of TATB-based PBX and its styrene copolymer modified formulation were simulated by Agari series model. Results show that the addition of styrene copolymer with high glass transition temperature and high mechanical strength can improve the tensile strength and elastic modulus of TATB-based PBX and simultaneously reduce the linear expansion coefficient and thermal conductivity of TATB-based PBX. The results predicted by theoretical model are in good agreement with the experimental data. After the addition of styrene copolymer of mass fraction as 1%, the thermal stress resistance factor of TATB-based PBX at normal temperature increases from 10.72 W·m^-1 to 13.16 W·m^-1. With the increase of temperature, the thermal shock resistances of TATB-based PBXs decrease gradually. The thermal stress resistance factor of TATB-based PBX decreases significantly in the temperature range of glass transition from 323 K to 343 K. The addition of styrene copolymer can restrict decreasing extent of the thermal stress resistance factor of TATB-based PBX in the temperature range of 323 K to 343 K.

Abstract:The laser-monitoring observation method was used to measure the solubility of Octogen(HMX) in γ-butyrolactone. The relation of the solubility vs temperature were established according to Apelblat empirical equation by the linear least squares method. The effects of saturation temperature, stirring speed and cooling rate on metastable zone width were explored. The nucleation series effected by cooling rate and stirring speed were calculated based on the classical nucleation theory. The results show that in the crystallization process of HMX, the metastable zone width significantly broadens with the increase of saturation temperature and cooling rate and narrows with the increase of stirring speed. The nucleation series effected by colling rate and stirring speed are related to the saturation temperature. The nucleation series gradually become smaller with the increase of saturation temperature. Appropriate cooling crystallization conditions of HMX in γ-butyrolactone are the saturation temperature of 40 ℃, cooling rate of 0.1-0.2 ℃·min^-1 and stirring speed of 400 r·min^-1.

Abstract:The feasibility of Fe(Ⅲ) and Co(Ⅲ) energetic complexes of 2, 6-diamino-3, 5-dinitropyridine-1-oxide (ANPyO) as combustion catalysts was tested by closed bomb test and target lines experiment. Results show that the two complexes have obvious catalytic effects on the combustion of double-base gun propellants and triple-base gun propellants by increasing of the burning rate and decreasing of the pressure exponent by 2.97%-11.36%. The Fe(Ⅲ) complex has significant catalytic effects on the combustion of double-base propellants with the burning rate increasing by more than 20% in the pressure range of 10-20 MPa and the pressure index decresing by 25.30%-45.78% at 10, 14, 18, 20 MPa, respectively. While, the catalytic effect of Co(Ⅲ) complex on double-base propellant is not obvious.

Abstract:The surface cracks of explosive parts have important influence on its mechanical properties and detonation properties and can remove the surface cracks by machining margin, and the accuracy of crack depth is the key. Based on the basic principle of ultrasonic wave edge peak echo, a quantitative detection method of surface crack depth for HMX based polymer bonded explosive (PBX) was established. The simulation test blocks with different-depth cracks were designed and manufactured. The quantitative precision of crack depth of ultrasonic edge peak echo method was checked. A better experiment repeatability was found. The different value between measured depth and actual one is less than 1.0 mm. The detection results of crack depth of explosive obtained by ultrasonic testing and micro focus X-μCT imaging technique were compared. The crack height results have good consistency, indicating that the edge peak echo method for measuring crack depth is reliable. The ultrasonic testing error sources are analyzed. Results show that the crack depths detected by the edge peak echo method are close to actual crack depths, with the error within ±1.0 mm.

Abstract:To explore the hot-spot forming mechanism of heterogeneous solid explosives under the complicated impact environment, in the "hot-spot" model of one-dimensional viscoplastic holes collapse, different patterns of external forces, such as tension and compression were considered and the effects of temperature and damage on the mechanical performance of explosive were introduced. The "hot-spot" forming model of holes collapse for explosive was established. The movement regularity of holes under the complicated impact environment was simulated. The formation model of hot-spots of PBX9404 under two kinds of different external forces including continuous compression, and tension and compression alternate was compared and analyzed. Results show that under continuous compression action of greater than 400 MPa, the holes can produce hot spots, whereas under the alternating action of tension and compression of 250 MPa, the holes can produce hot spots. So the alternating action of tension and compression is easer to produce the hot spots.

Abstract:To explore the expansion characteristics of multiple wall combustion-gas jets which uniformly distributed along the circumferential direction under high temperature and high pressure in confined liquid working medium, the combustion gas generator and cylindrical filling liquid chamber were designed. The expansion processes of multiple wall jets were recorded by high-speed digital photographic system. The average axial displacements of multiple wall jets at different time were achieved by disposing the expansion sequence diagrams. It shows that the irregular interface induced by the Kelvin-Helmholtz instability exists in the entire jets expansion process. The effects of the number of orifices and the blasting injection pressure on expansion characteristics of multiple wall jets are discussed. The experimental results indicate that, as the number of orifices increase from four to eight, the axial expansion displacements of multiple jets decrease, at t=5 ms, the number of orifices increase from four to six, the axial expansion displacements decrease 8.3 percent, and it decrease 3.1 percent when the number of orifices increase from six to eight. The larger the blasting injection pressure, the greater the axial expansion velocity, the earlier jets get to the top of liquid filling chamber, at t=5 ms, the blasting injection pressure increase from 12 MPa to 20 MPa, the axial expansion velocity increase 20.1 percent, and it increase 19.9 percent when the blasting injection pressure increase from 20 MPa to 28 MPa.

Abstract:To study the effect rule of the type and size for polysilicon bridge on the ignition performance of Al/CuO energetic igniter, six kinds of energetic igniters with different shapes and sizes were prepared by integrating polysilicon with Al/CuO multilayer films and the firing sensitivities of four sizes and two bridges-a total of six kinds of igniters(S, M, Lr, Lv, Hr, Hv)were tested by employing the Neyer D-optimal sensitivity method. The critical electro-exploding voltages of the igniters were explored. The change rule in firing time with the excitation voltage was obtained. The ignition performances of polysilicon igniter and energetic igniter were comparatively studied by sensitivity test and ignition test. Results show that the sensitivity and firing time decrease with increasing the bridge film volume, and the V-type-angle bridge film helps to decrease the action time and energy needed for the action. The 50%-firing voltage of 8.70 V and standard deviation of 0.53 of the polysilicon igniters are higher than those of the energetic igniters (8.19 V, 0.14). Due to the energy release during chemical reaction of Al/CuO multilayer films, average firing time of 52.85 μs of the energetic igniters at 14 V is much lower than that of 109.12 μs of the polysilicon igniter at 14 V and this difference decreases with the increase of excitation energy.

Abstract:To study the explosive welding of metal plates with larger different melting point and strength, the experiment used aluminum plate with dimension of 5 mm×300 mm×300 mm and steel plate of dovetail groove with dimension of 28 mm×300 mm×300 mm were used as flyer plate and base plate, respectively. The explosive material used in explosive welding was an emulsion explosive which was in aluminum honeycomb panel. Explosive welding parameters were selected by theoretical formulas, which made the inner surface aluminum plate come into being metal jet, and the inner surface of steel plate merely form plastic deformation. Results show that aluminum plate and steel plate of dovetail groove are welded together relying on combined action of metallurgical bonding, and extraction and meshing of dovetail grooves, which can save more explosives than those of traditional aluminum-steel explosive welding by over 31%, and reduce the lower limit of explosive welding window of aluminum and steel clad plate. Interface of the explosive clad plate is combined closely, whose combined area is 141 percent bigger than that of traditional aluminum-steel explosive clad plate, and whose shear strength are higher than 79 MPa, then mechanical properties of the explosive cladding plate meet the requirements of bonding strength of aluminum alloy-steel clad plate.

Abstract:The dehydrogenation thermodynamics and kinetics of hydrogen-storage materials are critical for their applications in solid propellants. In this paper, the effects of nanosizing on dehydrogenation thermodynamics and kinetics of various categories of hydrogen-storage materials were systematically reviewed. It is revealed that the nanoscale chemical hydrogen-storage materials possess lower dehydrogenation temperatures and better dehydrogenation kinetics in comparison with their bulk counterparts, which is favorable for the full utilization of their hydrogen during the combustion of solid propellants. On the other hand, the nanoscale chemical-physical hydrogen-storage materials can be adopted as both hydrogen sources and combustion catalysts for propellants. In addition, it is believed that modifications in structural characteristics of nanoscale physical hydrogen-storage materials can enable them to dehydrogenate/hydrogenate fast at room temperature, illustrating their great potential as hydrogen sources for solid propellants. The key point for development of practical nanoscale hydrogen-storage materials as hydrogen sources for propellants is to determine the optimal thermodynamics and kinetics parameters for the applications, which are crucial for the design and preparation of nanoscale hydrogen-storage materials for propellants.

Abstract:The melting point is an important indicator determining the explosives can become the carrier for melt-cast explosives. To obtain the relationship between the molecular structure of explosives and the melting point, the relationship between the molecular structure and the melting point of nitro diazole compounds was investigated. Change relation of the melting point and the parent structure of explosive molecule, the number of substituting group and configuration was concluded and summarized. The regularity between the structure of energetic diazole compounds and the melting point was obtained. Seven types of explosives with low melting point were designed on the basis of pyrazole ring as the basic structural unit, of which the predicted melting point of five explosives is lower than 120 ℃. Results show that the predicted melting point of two kinds of energetic pyrazole compounds: 1-amino-3, 4, 5-trinitropyrazole and 1-methyl-3, 5-dinitropyrazolyl-4-methylnitramine is 112.7 ℃ and 86.5 ℃, respectively. Their detonation performances are better than those of TNT.

Abstract:Analysis conditions of 5, 5′-bistetrazole-1, 1 ′-dyhydroxy dihydrate(BTO)by high performance liquid chromatography (HPLC) were determined as follows:UV detection wavelength 213 nm, reversed phase column(SinoChrom ODS-BP, 4.6 mm×200 mm, 5 μm), binary mobile phase acetonitrile and water(volume ratio of 30/70) with flow rate of 1.0 mL·min^-1 at column temperature of 25 ℃. External standard method was used to analyze BTO standard solution. Results show that there is a good linearity between peak height(h) and concentration(c)from 0.12 mg·mL^-1 to 0.60 mg·mL^-1.The linear equation is h=573.78c-1.18 with linear correlation coefficient of 0.9998. The relative standard deviation is 0.48%-1.00% and the average recovery is 98.10%-100.64%, indicating that the method is accurate and sensitive and can be applied in the determination of BTO purity.

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