Abstract:To guide the detonating sequence design of the flyer driven by the impingement detonator, the numerical simulation method was used to calculate and obtain the velocity and shape of the flyer wih different materials(Stainless steel, titanium alloy, aluminum), different thickness(0.1-0.5 mm)and different diameter(3, 4 mm and 5 mm)driven by hexanitrostilbene-Ⅳ (HNS-Ⅳ)explosive. The calculation results show that at the same thickness, the velocity of the aluminum flyer is the highest, the velocity of the titanium alloy flyer is second, the velocity of the stainless steel flyer is the lowest, which is relative to their densities. For the same material, with increasing the thickness of flyer, the flyer velocity decreases gradually and tends to an extreme value. After detonation shearing of flyer with different diameter, the effective diameters of the fliers are reduced, in which, the effective diameters of Φ4 mm and Φ5 mm flyers are the same as those of 3.6 mm and 3.4 mm, respectively, and the Φ3 mm flyer is the smallest, only 2.8 mm. Under the action of detonation wave, HNS-Ⅳ explosive drives titanium alloy flyer with different diameter and 0.10 mm thickness, and the Φ4 mm and Φ5 mm flyers are slightly spherical, and the shape of Φ3 mm flyer is more flat. It is considered that the shock wave reflection drive is the main reason of its flat shape.

Abstract:Based on the cylindrical smoking device, the Truegrid simulation software was used to establish a cylindrical shell mesh model with a"V"groove. The simulation model of the smoking device was established by Autodyn software, and the variation law of the detonation pressure during the initial cloud explosion and dispersion process of the smoke screen was numerically simulated. With the help of the piecewise linear interpolation function provided by MATLAB, the pressure as a known quantity was introduced into the explosion dispersion theory model, and the model was numerically calculated by the Euler method. Field test experiments were carried out, and experimental data were obtained using camera method and image processing technology. The results show that the time occurring the first stage of explosion dispersion is from 0 to 8.9×10^-6 s, and the maximum radius of the initial smoke cloud increases by 3 to 4 times that of the original. In the second stage of the explosion dispersion, the maximum radius of the initial smoke cloud increases to about 3 m. Based on the mixed simulation of Truegrid and Autodyn and combined method with the theory of explosion dispersion theory, the calculation error of the maximum radius of the initial smoke cloud is reduced by 3%~8% compared with the traditional theoretical method of solving the explosion dispersion model by numerical integration alone. The maximum radius of the initial smoke cloud is closer to the experimental result than the single theoretical model method. The convergence of calculation model of the Euler method is better than that of the fourth-order Runge-Kutta method.

Abstract:To investigate the effect of hexogen(RDX)dopants produced during the preparation of octogen(HMX)on properties of HMX, four kinds of HMX models of doping rate as 4.17%, 8.33%, 12.50% and 16.67% were established. Molecular dynamic method was used to calculate the interaction energy of trigger bond, cohesive energy density, solubility parameter, detonation parameters and mechanical parameters of different models, and the results were compared with the related properties of pure HMX. Results show that RDX doping defect leads to the decrease of interaction energy of trigger bond and cohesive energy density, and the reduction amplitude is 9.53-36.36 kJ·mol^-1, 0.028-0.135 kJ·cm^-3, respectively. The difference between the solubility parameters of HMX explosives and F₂₃₁₁ decreases with the influence of RDX doping defect, and the reduction amplitude is 0.51-2.32. The decrease amplitude of density, detonation velocity, and detonation pressure are 1.12% -5.59%, 0.84% -4.19% and 2.27% -11.14%, respectively. The heat of detonation rises slightly, which is almost negligible.The RDX doping defect also leads to the decrease of elastic modulus, bulk modulus, and shear modulus of HMX, but Cauchy pressure, as well as the ratio of bulk modulus to shear modulus rises. The changes range is 1.04-3.63 GPa, 0.58-1.73 GPa, 0.42-1.45 GPa, 0.35-2.69 GPa, and 0.11-0.64, respectively. It reveals that with the increase of the concentration of RDX doping defects, the safety and detonation performance of HMX explosives decrease, the mechanical properties become worse, and the compatibility with F₂₃₁₁ becomes better.

Abstract:To research the effect of crystal defect on the stability, sensitivity and detonation performance of hexanitrohexaazaisowurtzitane(CL-20) /nitroguanidine(NQ)cocrystal explosive, the"perfect"and defective(adulteration, vacancy and dislocation)CL-20/NQ cocrystal explosive models were established. Molecular dynamics method was applied to predict the properties of various models. The binding energy, trigger bond length distribution, bonding diatomic interaction energy, cohesive energy density and detonation parameters of different models were got and compared. The results show that compared with the"perfect"crystal, the decreasing ampliture of binding energy of defective crystal is 4.29%-24.33%, indicating that the intermolecular interaction energy is weakened and the stability is decreased. The increasing ampliture of trigger bond length of defective crystal is 0.78%-6.04%, while the decreasing ampliture of bonding diatomic interaction energy is 2.86%-20.03% and the decreasing ampliture of cohesive energy density is 2.46%-12.72%, indicating that the sensitivity of explosive is increased and safety is worsened. Owing to the influence of crystal defect, the decreasing ampliture of density, detonation velocity and detonation pressure of explosive is 0.58%-7.57%, 0.43%-5.99%, and 1.19%-15.31%, respectively, indicating that the energy density and power are decreased. Therefore, crystal defect has a negative effect on the stability, sensitivity and energetic characteristics of CL-20/NQ cocrystal explosive, among them, the effect of vacancy defect on the performance of explosive is more significant.

Abstract:Polymer bonded explosive(PBX)formulations were successfully prepared in the laboratory scale containing 1, 1-diamino-2, 2-dinitroethene(FOX-7)and hexogen(RDX)as brisant high explosives and different binder types of polyurethane(PU) based on glycidyl azide polymer(GAP) and hydroxyl-terminated polybutadiene(HTPB) as an energetic and inert polymeric binder respectively. Casting technique was used for the preparation of different PBX formulations based on FOX-7/RDX and PU (GAP/HTPB)with 14% binder. The sensitivity to different initial impulses and performance characteristics of the explosive and lethal zone of the tested controlled fragmentation warhead by the fragmentation warhead assessment test(arena test)were studied, in which the arena test was carried out with a controlled fragmentation warhead made from Ck45 steel, with dimensions (100 mm length, 30 mm outer diameter and 3 mm thickness) . Results show that PBXGF4 has lower sensitivity to impact and heat than those of PBXGR4 by 188.4% and 3.2% respectively. Its friction sensitivity is the same as that of PBXGR4. It has better performance, in which detonation velocity increases by 2.1% and brisance increases by 0.5% when compared with those of PBXGR4. It was concluded that PBXGF4 which based on FOX-7 bonded with PU /GAP matrix has good characteristics as PBX, specially in the sensitivity to impact and can be applied for replacing PBXs based on RDX in the advanced PBXs for low sensitive frag

Abstract:A composite sample of CL-20 and dihydroxylammonium 5, 5'-bistetrazole-1, 1'-diolate(TKX-50, HATO)was prepared by in-situ crystallization method in aqueous suspension of CL-20 using 1, 1'-dihydroxy-5, 5'-bitetrazole(H₂DHBT)and hydroxylamine aqueous solution as raw material through neutralization reaction. The morphology and structure of the composite were characterized by scanning electron microscope(SEM), Fourier transform infrared spectroscopy(FT-IR), nuclear magnetic resonance(NMR)and X-ray diffraction(XRD). The effect of different processing conditions on the morphology of the composite was studied. Thermal property was analyzed using DSC. Its impact and friction sensitivity were measured with GJB772A-1997 method. Its detonation velocity was calculated using Urizar 's formula. Results show that the technological conditions for obtaining CL-20/HATO composite sample with uniform adhesion are:reaction temperature 90 ℃, reaction time 10 min and dropping rate 60 mL·min^-1 of NH₂OH aqueous solution. The crystal form of CL-20 in prepared CL-20/HATO composite sample does not change. The mass ratio of CL-20 and HATO in CL-20/HATO composite obtained by quantitative carbon spectroscopy is m(CL-20) :m(HATO) =55:45. The temperature of thermal decomposition of the complete is 238.3 ℃ and 250.7 ℃. Its characteristic drop height is 44.7 cm, the probability of impact explosion is 52% and the probability of friction explosion is 76%. Theoretical detonation velocity of the composite sample is 9516 m·s^-1.

Abstract:To seek forasymmetric 1, 2, 4, 5-tetrazine energetic compounds with good properties, 3-(p-nitrobenzyl methylene)-6-(3, 5-dimethylpyrazol-1-yl)hydrazone-s-tetrazine(DPHX) and 3-(m-dintrobenzyl methylene)-6-(3, 5-dimethylpyrazol-1-yl) hydrazone-s-tetrazine (DMHT) were synthesized, and their single crystals were cultrivate and their structures were characterized by EA, IR and X-ray single crystal diffraction. The thermal decomposition behaviorand thermal decomposition kinetics of DPHX and DMHT were studied by differential scanning calorimeter(DSC). Their apparent activation energies were calculated by Kissinger's method. The thermal safety of DPHX and DMHT was studied by the results of thermal decomposition kinetics. Results show that both of them are monoclinic with space group P2₁/c. The apparent activation energies of the two compounds are 176.20 and 229.29 kJ·mol^-1, respectively. The self-accelerating decomposition temperature (T_SADT), thermal ignition temperature (T_be) and critical temperature of thermal explosion(T_bp) are 191.83, 206.20℃ and 213.78 ℃ for DPHX, respectively, and T_SADT=203.91 ℃, T_be=212.24 ℃, T_bp=218.34 ℃ for DMHT, respectively. Therefore, DMHT is more stable than DPHX and has higher thermal safety.

Abstract:Dihydrazinium 3-dinitromethyl-4-nitraminofurazan (compound 6) was prepared via five steps of reaction using 3-amino-4-chloroximinofurazan as raw material. Its structure was characterized and determined by nuclear magnetic resonance (¹H spectrum and ¹³C spectrum), infrared spectroscopy, element analysis, and X-ray single crystal diffraction. Results show that the crystal belongs to monoclinic system with space group P2₁/n and unit cell parameters of a=3.7236(4) Å, b=14.3867(18) Å, c=20.386(2) Å, β=92.432(5)°, V=1091.1(2) ų, Z=4, D_c =1.815 g cm^-3. A large number of hydrogen bonds exist between cations and anions in the crystal, which is conducive to the improvement of molecular stability. The addition of hydrazine results in the cleavage of the C—N bond in N, N'-methylene-3-nitroamino-4-dinitromethylfurazan (compound 5) and the formation of compound 6. The enthalpy of formation of compound 6 calculated by Gaussian 09 is 291.7 kJ·mol^-1 and the crystal density at 298 K calculated by empirical formula is 1.782 g·cm^-3, the detonation velocity(D) and detonation pressure (p) of compound 6 calculated by EXPLO 5 are 9032 m·s^-1 and 35.9 GPa, respectively, which are superior than those (D=8848 m·s^-1, p=34.8 GPa) of RDX. The impact sensitivity of compound 6 determined by standard BAM method is 4 J and the friction sensitivity is 76 N.

Abstract:To obtain the change of thermal stress in the slow cook-off test of explosive charge, a set of thermal stress testing device was designed.The change curves of the thermal stress with temperature of octogen(HMX) based aluminized explosive charge under the closed confinement condition were obtained.Through adjusting the volume ratio of inert coating layer and charge, and changing the rising rate of thermal stress in the slow cook-off process, the critical response temperature of cook-off bomb and the intensity of response under three working conditions were researched.The difference of change rate of thermal stress, the whose process can be divided into six stages.Its influencing factors is thermal expansion, porosity decrease, HMX crystal transformation, slow decomposition of HMX, partial small molecule gas leakage, and accelerated decomposition of HMX in the order.When the temperature rises to 208 ℃, the thermal stress reaches 9.2 MPa and the charge is ignited immediately.Increasing the silicone rubber coating layer with greater thermal expansion on the charge surface of cook-off bomb, can make the growth rate of the thermal stress of charge accelerate and the critical ignition temperature of charge reduce, but the drastic degree of the response of charge does not change.

Abstract:Graphene oxide (GO)was prepared by Hummers method using flake graphite as raw material, and reduced grapheneoxide (rGO) was obtained by further thermal reduction.The apparent morphology of the material before and after reduction was observed by scanning electron microscope.The change of oxygen-containing functional groups on the surface of the two graphene derivative sheets was analyzed and compared by infrared spectroscopy.The thermal diffusivity and resistivity of B/KNO₃ ignition powder with different ratios of rGO were measured.According to the national military standard GJB5891-2006, the characteristic drop height, the critical ignition voltage, and the 50% firing energy of the boron-based ignition powder with different ratios of rGO were tested.Results show that after adding 1%-5% rGO, the thermal conductivity of ignition powder increases from 0.573 W·(m·K)^-1 to 0.620 W·(m·K)^-1, the resistivity of ignition powder decreases from the insulator to 1.11×10 5 Ω·cm, the characteristic drop height of ignition powder increases from 42.3 cm to 59.0 cm, and the critical ignition voltage increases from 5 kV to 25 kV, revealing that a small amount of rGO can significantly improve the impact sensitivity and electrostatic sensitivity of the ignition powder, and rGO has potential application value in the safety regulation of compound energetic materials.

Abstract:To reveal the coating mechanism of fluorine rubber(F2604) on nano-aluminum powder(n-Al), by using electrostatic spray technology, the composite particles with different content of F2604 were prepared in different solvents (ethyl acetate and acetone).The morphology of the composite particles was characterized by scanning electron microscope (SEM).The influence of solution parameters on the micro-morphology of nano-Al/F2604 composite particles was studied by means of experiment and molecular dynamics simulation.Results show that acetone as a solvent can make the composite particles more uniform and regular in morphology.When the content of fluorine rubber is less than 13%, the particle diameter increases with increasing the proportion of fluorine rubber.When the content of fluorine rubber continues to increase, the particle size distribution of composite particles becomes uneven.The shape is irregular and obvious spinning phenomenon is appeared.The diffusion coefficient of fluorine rubber in the solvent is one of the important factors affecting the molecular chain morphology when coating nano-aluminum powder using fluorine rubber, thus the principle of "large diffusion coefficient of fluorine rubber" should be followed when selecting solvents.The unit binding energy between fluorine rubber and nano-aluminum powder is mainly composed of electrostatic interaction energy (75%-93%) and van der Waals interaction energy(6%-22%).The effect of fluorine rubber content on the micro-morphology of composite particles is affected by intermolecular electrostatic interaction.

Abstract:To explore the damage evolution behavior of polymer bonded explosive (PBX) under uniaxial compression, the in-situ investigation of PBX substitute material in the uniaxial compression process was carried out by computed tomography (CT).In-situ CT images of the specimen under different loads were obtained.The mean gray value variations of the specimen in loading process were obtained through analyzing the gray value of CT images.Internal three-dimensional displacement field and strain field of the specimen were obtained using the digital volume correlation (DVC) method.Combined with the digital image correlation (DIC) method and the gray analysis of the specimen surface, the strain distribution and surface crack growth process of PBX substitute material in loading process were clarified.Results show that at the initial loading stage before the damage occurred, the mean gray value of CT image is almost constant.With the increase of load, the micro-damage may occur inside the specimen and the mean gray value of CT image decreases slightly.At the later loading stage, the damage accumulates rapidly and the mean gray value of CT images decreases sharply.The mean gray value of CT image can be considered as an important index to reveal the micro-damage change of material with resolution higher than CT technique, and internal strain field of the specimen and change of the surface gray value can be used to characterize the accumulation process of material damage during loading.

Abstract:The thermal decomposition properties of 5, 5'-bis(2, 4, 6-trinitrophenyl)-2, 2'-bi(1, 3, 4-oxadiazole) (TKX-55) at normal pressure(0.1 MPa)and high pressure (5.0 MPa) were studied by differential scanning calorimetry (DSC) and thermogravimetric analusis (TG).The thermal decomposition kinetic parameters of TKX-55 at normal pressure were calculated by Kissinger's method and Ozawa's method and compared with those of hexanitrostilbene (HNS) to study the correlation between molecular structure and its properties.Results show that compared with normal pressure state, the shape of exothermal peak of thermal decomposition behavior of TKX-55 under high pressure is sharper.Under the high pressure environment (5.0 MPa), TKX-55 still maintains high thermal stability.The initial decomposition temperature is 355.69 ℃, which is about 35 ℃ higher than the initial decomposition temperature of HNS.With increasing the heating rate, the decomposition peak temperature of TKX-55 and HNS is shifted to high temperature, and the decomposition peak temperature of TKX-55 at different heating rates is obviously higher than that of HNS.The decomposition.activation energy of TKX-55 obtained by integral isoconversional non-linear method (NL-INT method) is 233.71 kJ·mol^-1 and the decomposition.activation energy of HNS is 197.87 kJ·mol^-1.The decomposition activation energy of TKX-55 is obviously higher than HNS, indicating that TKX-55 has more excellent thermal stability than HNS.

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