Abstract:

Abstract:The battlefield environment of modern war is becoming more and more complicated. The ammunition is facing severe mechanical, heat and electromagnetic environment, which demands higher safety. The concept of insensitive munitions (IMs) was proposed by the United States in the 1980s regarding the severe enviroments. With the implementation of insensitive ammunition program, the catastrophic accidents due to ammunition explosions were significantly reduced. Furthmore, the concept of robust munitions (RMs) was proposed by the Chinese Academy of Engineering Physics in 2013. RMs are the ammunitions that can not only meet the requirements of damage efficiency, but also with high safety in the actual combat stimulus, better environmental adaptability in full-life profile. According to the safety performance, RMs can be divided into three levels, one star, two stars and three stars. One star RMs are equivalent to insensitive ammunition. RMs development involves many scientific, technical and engineering aspects and needs to be handled systemically.

Abstract:To further reveal the effect of cocrystallizing and mixing on the sensitivity, mechanical properties and thermal decomposition mechanism of hexanitrohexaazaowuetzitane (CL-20)/1, 3-dinitrobenzene (DNB) energetic material from molecular level, the sensitivity, binding energy and mechanical properties of CL-20, DNB, CL-20/DNB cocrystal and CL-20/DNB mixture were simulated and calculated using molecular dynamics (MD) simulation method under the condition of COMPASS stress force field. Their thermal decomposition mechanisms were studied under the condition of ReaxFF/lg force field. Results show that the cocrystallizing and mixing can reduce the sensitivity of CL-20, increase that of DNB, but the cocrystallizing effect is more obvious. Compared with the mixture structure, the cocrystallizing structure is more stable. Cocrystallizing and mixing can change the mechanical properties of the system, reduce the stiffness, increase the flexibility and safety of CL-20 system, but mixing makes the mechanical properties of the system deteriorate. The strong effect between cocrystal molecules can promote the thermal decomposition of the components in the system. NO₂, N₂, NO, H₂O, HONO, HON and CO₂ are the main products of cocrystallizing and mixed systems. Considering that compared with mixing, co-crystallization is a mor effective modification way for energetic materials. which can provide theoretical guidance for the formulation design of energetic materials.

Abstract:In order to predict the crystal density of all-nitrogen materials accurately, the 'specific' molecular force field of all-nitrogen materials was established based on the quantum chemistry calculation method. The crystal densities of twenty kinds of all-nitrogen molecules were calculated by predicting the crystal packing structure. Results show that the crystal densities for five kinds of all-nitrogen molecules with cage type including N₄(T_d), N₆(D_3h), N₈(O_h), N₁₀(D_5h), and N₁₂(D_6h) are 1.81, 2.08, 2.47, 2.46 g·cm^-3 and 2.57 g·cm^-3, respectively. As the number of nitrogen atoms increases, the change in crystal densities of all-nitrogen molecules with cage type is different from the progressive trend in literatures, but at N₈(O_h), there is a mutation, which reflects the specific force field parameters.

Abstract:To investigate the problem about effect of formulations and extrusion process of nitroguanidine gun propellant on the extrusion molding size, the mathematical model and boundary conditions of extrusion process for nitroguanidine gun propellant with different formulations were established. The distribution siteration of shear rate field, pressure field and velocity field in different flow process under the condition of different formulations were simulated, calculated and obtained by the finite element method. The results show tha the actual outer diameter of 8.03 mm and simulation size of 8.38 mm of the propellant is basically the same, its error is 4.36%.The error of outer web size (7.89%), inner web size (3.10%), pore size (9.26%) and center pore size (5.36%) etc parameters is within 10%.

Abstract:To describe the crack tip failure zone of polymer bonded explosive (PBX), modeⅠcrack tip failure zone of PBX were studied based on the Mohr-Coulomb, Twin-shear and Drucker-Prager strength criterion. The expressions describing the crack tip failure zone of the tension-compression asymmetry for PBX were obtained. Results show that the Drucker-Prager strength criterion takes into account the factors such as tension-compression strength ratio, average stress and deviatoric stress, the solving crack tip failure zone is the biggest. The tension-compression ratio of the material has a significant effect on the crack tip failure zone, the smaller the tension-compression ratio, the more serious the tension-compression asymmetry of materialis, the greater the crack tip failure zone. The temperature has great influence on the mechanical properties of PBX materials, and the crack tip failure zone at 60 ℃ is significantly larger than that at 20 ℃.

Abstract:Peridynamics is a recently developed meshfree method with many aspects needing to be further studied, such as viscoelasticity, plasticity and the coupling of elasticity, plasticity and viscosity. The analytical ability for considering viscoelastic behavior of peridynamics is developed. The theoretical basis, modeling procedure and numerical scheme of peridynamics are first reviewed. Then the expressions of creep compliance under different stresses and the peridynamic creep response functions are deduced combing time-stress equivalence principle of nonlinear viscoelastic materials and utilizing Burgers viscoelastic model. In this manner, the peridynamic creep simulation method which can be applied to polymer bonded explosives is established. The creep behavior of PBX9502 is then simulated using this method, which indicates a good conformity with experiment results. The established method can be applied to analyze creep behavior of polymer bonded explosives under different temperatures and different stresses.

Abstract:An energetic coordination polymer, [Pb (BTO)(H₂O)]_n (BTO=1H,1′H-5, 5′-bistetrazole-1, 1′-diolate) was synthesized by a simple one-step solvothermal method using Pb (NO₃)₂ and H₂BTO·2H₂O as raw materials. The target compound was characterized by single-crystal X-ray diffraction, Fourier transform infrared (FT-IR) spectra and elemental analysis. The thermal decomposition process of the energetic coordination polymer was studied by differential thermal analysis (DTA), differential scanning calorimetry (DSC) and thermogravimetry-derivative thermogravimetry (TG-DTG). Its kinetic parameters of thermal decomposition (activation energy E_K、E_O and pre-exponential factor A) were calculated by Kissinger′s method and Ozawa′s method. Its characteristic drop height of impact sensitivity (H₅₀) was determined by WL-1 type impact sensitivity test instrument. The compound was explored as additive to promote thermal decomposition of ammonium perchlorate (AP) by DTA. Results show that the crystal belongs to monoclinic, its space group isC2/c with crysta parameters of a=14.342(3) Å, b=6.5757(12) Å, c=8.4715(16) Å, V=683.3(2) ų, D_c=3.823 g·cm^-3, Z=4. Its thermal decomposition temperature on DSC curve at 5 K·min^-1 is 582.2 K, there are three mass loss stages on TG curve with a main mass loss between 543.9 K and 599.5 K, the mass of the final residue is 44.60%.E_K=211.67 kJ·mol^-1, E_O=210.64 kJ·mol^-1, ln (A/s^-1)=18.594, H₅₀=7.6 cm, revealing that it has better thermal stability and appropriate sennsitivity. When the addition amount of the coordination polymer is 10 wt%, the high temperature decomposition peak of AP is decreased by 40.1 K, the intense degree of the thermal decomposition reaction is also greatly improved, showing that it has good catalytic performance to AP.

Abstract:In order to make the explosive charged in explosion network meet the charge uniformity, low detonation velocity dispersion requirement and at the same time achieve the high detonation velocity, high security, explosion detonation in groove of small size, 3, 4-dinitrofurazanfuro xan (DNTF) and HMX were chosen as the main explosive, GAP as the binder polymer, together with the other additives. A kind of booster formula was successful designed suitable for network booster and it was charged into the explosion network of microsize. The particle size and morphology of the DNTF and HMX was characterized by scanning electron microscopy (SEM). X-ray diffraction (XRD) was utilized to test the crystal. The booster charging surface were tested and observed by SEM and the detonation performance, impact sensitivity, shock sensitivity and detonation velocity were tested afterwards. The results showed that when the solid content was of 85%, the viscosity of the booster slurry can meet the requirements of charging process. After curing process the surface of booster was smooth with uniform particle distribution. The crystal of the two kinds of explosives was not changed and the density of booster charging in the groove was up to more than 1.6 g·cm^-3 (92% of theoretical density). Under this density of booster charging, the critical dimension of linear detonation is 0.6 mm×0.6 mm, the detonation velocity in 0.8 mm×0.8 mm groove was 7558 m·s^-1 and the velocity range was 29 m·s^-1. The impact sensitivity of the DNTF/HMX based booster explosive characteristic height (H₅₀) was 45.2 cm (5.0 kg hammer), the thickness of small scale gap was 8.74 mm in the shock sensitivity test.

Abstract:To study the influence of high temperature on the front curvature rate effect for insensitive high explosives, steady-state detonation velocities and wave shapes were obtained for TATB Based Insensitive High Explosives (IHEs) with three different diameters at the temperature 60 ℃ by using high speed streak camera technique and electric foil velocimetry. Results show that steady-state detonation velocities increase almost linearly with the diameter of TATB based IHEs at the temperature 60 ℃. For each charge diameter, steady-state detonation waves propagated slower and the wave shapes become much curved as the initial temperature increases. The D_n(κ) parameters of TATB based IHEs at the temperature 60 ℃ were obtained numerically using the genetic arithmetic method for DSD. By using these D_n(κ) parameters, the detonation propagation behaviors of TATB based IHEs at the temperature 60 ℃ were simulated with the DSD model. The numerical results agree well with the experimental ones.

Abstract:To deeply understand the combustion and propulsion mechanism in liquid propellant electrothermal chemical gun, an experiment device was designed.The expansion process of injecting the pulsed plasma jet into the liquid medium was observed by a high-speed video system. The changes in axial displacement and volume of Taylor cavity formed by the interaction of plasma jet and liquid medium were measured. The quantitative expansion law for the change in Taylor cavity volume with time was obtained. The effects of liquid chamber boundary shape, discharge voltage and nozzle diameter on the pulsed plasma jet expansion were discussed. Results show that the non smooth intefacer with wrinkles in junction of two-phase due to the turbulent mixing is formed. There is an obvious oscillation phenomenon in the expansion process of Taylor cavity. The stepped-wall structure factor decreases from 0.6 to 0.4, the axial displacement first peak and the volume first peak increase by 16.6% and 12.4%, respectively. The discharge voltage decreases from 3000 V to 2100 V, the axial displacement first peak and the volume first peak reduce by 36.1% and 60.7%, respectively. The nozzle diameter decreases from 2 mm to 1.5 mm, the axial displacement first peak and the volume first peak reduce by 27.2% and 56.7%, respectively.

Abstract:In order to assess the quality of nano-TATB, a simple and rapid method for the determination of Cl^- and SO₄^2- in the absorbent liquid by oxygen flask combustion-ionic chromatogram was developed to monitor the trace component of TATB. Na₂CO₃ solution with a concentration of 4.7 mmol·mL^-1 was used as an eluate on an anion separation column of the model Metrosep A Supp 7 and conductivity detection. The method detection limits (MDL) of Cl^- and SO₄^2- were 0.0025 μg·mL^-1 and 0.0032 μg·mL^-1 respectively, under the optimized condition. The linear ranges of Cl^- and SO₄^2- were (500~3000) μg·L^-1 and (100~2500) μg·L^-1 respectively, and the correlation coefficients were all greater than 0.9990. The recoveries of the two analytes were 96.30%-103.73% and 97.23%-100.91% with the relative standard deviations (RSD, n=6) of 1.65%, 2.28%. The method has the advantage of simple operation, reagent-free and pollution-free, and can meet the quantitative analysis requirements of sulfur and chlorinous in nano-TATB.

Abstract:The reaction kinetic parameters have an important guiding significance for the prepolymerization of acrolein-pentaerythritol resin. Online IR method was used to study the prepolymerization reaction kinetics of acrolein-pentaerythritol resin. When the reaction temperature was 338.15, 348.15 K and 358.15 K, and the dosage of diethyl sulfate (DES) as catalyst was 2% and 4% respectively, by monitoring the change in concentration of functional group =CH₂ in the reaction system, the kinetic equation of the polymerization reaction was obtained by calculation and the mechanical property of cured product was studied. The results show that the reaction is a second-order reaction, but the apprent reaction rate and reaction activation energy in the early stage and late stage for the reaction have a large difference. When the dosage of DES is 2%, the apparent activation energy in the early stage and late stage of the reaction is 36.5 kJ·mol^-1 and 49.6 kJ·mol^-1 respectively. When the dosage of DES is 4%, the apparent activation energy in the early stage and late stage of the reaction is 61.0 kJ·mol^-1 and 69.1 kJ·mol^-1 respectively. When the dosage of DES is 2% and 4%, the effect of dosage of DES on the mechanical property of cured product is not obvious. The reaction temperature on the mechanical property of cured product has a remarkable influence, when the dosage of DES is 2% and 4%, the maximum tensile strength appeared at 338.15 K is 41.99 MPa and 41.17 MPa, respectively, the maximum elongation at break appeared at 358.15 K is 8.47% and 7.27%, respectively.

Abstract:To improve the energy of a kind of single base propellant (nitrocellulose/2, 4-dinitrotoluen/dibutyl phthalate/diphenylamine, NC/DNT/DBP/DPA), cyclotrimethylenetrinitramine (RDX) with different contents (5%, 10%, 15% and 20%) and different particle sizes (0.2 μm, 3.7 μm, 7.6 μm and 100.0 μm) were added into this single base propellant, and then the modified single base propellants containing RDX were prepared and obtained. The effect of content and particle size of RDX on the combustion performances of these modified single base propellants was studied by closed bomb experiments. The results show that: when the RDX particle size is 7.6 μm, with increasing the content of RDX, the burning rate of the modified single base propellant first decreases and then increases, and has a minimum value when the content of RDX is in the vicinity of 10%; the average values of the burning rate pressure exponent of modified single base propellants are all greater than 1 in the pressure range of 50-p_dpm MPa (p_dpm is the corresponding pressure when dp/dt reaches its maximum value); when the content of RDX is 5%, the burning rate of modified single base propellant decreases with decreasing the particle size of RDX, and in the pressure range of 50-p_dpm MPa, the average values of the burning rate pressure exponents of modified single base propellants with 0.2 μm and 3.7 μm RDX are both less than 1, while the mean values of the burning rate pressure exponent of modified single base propellants with 7.6 μm and 100.0 μm RDX are both greater than 1.

Abstract:To study the effect of sensitizing methods on the detonation performances of MgH₂-based hydrogen storage emulsion explosives, the underwater explosion and brisance testing experiments of two kinds of hydrogen storage emulsion explosives were carried out. With the help of experimental data and theoretical analysis, the relationships between the work capability and brisance of MgH₂-based hydrogen storage emulsion explosives were studied and the theory of using the specific impulse to express the brisance of explosive was adjusted. The results show that in the physical and chemical sensitization of MgH₂-based hydrogen storage emulsion explosives, MgH₂ powders play the roles of energetic additive and chemical foaming agents, respectively. Compared with the chemical sensitization, the specific shock wave energy, specific bubble energy and total energy of the physical sensitization of MgH₂-based hydrogen storage emulsion explosives are decreased by 11.98%, 5.38% and 8.66%, respectively, but its brisance (lead block compression value) is increased by 5.15 mm, which means that sensitizing methods have significant impact on the work capability and brisance of MgH₂-based hydrogen storage emulsion explosives.

Abstract:Fine structure characteristic of 2, 4, 6-triamino-1, 3, 5-trinitrobenzene (TATB) molding powder was investigated by using X-ray sub-micron tomography. Three dimensional reconstruction images have been generated, from which obvious and quantifiable pores, vortex ring layers, dense surfaces and high density impurities can be observed inside the granules. It was revealed that the coagulated vortex rings with a smaller size have a tendency to possess elliptical shapes, with the ratio of the minor to major axes of the ellipses close to 0.7 and the vortex dissipation to be stable. The formation of dense surfaces was mainly attributed to the spread of vortex. TATB molding powder may experience strongly rotating turbulence, as deduced from the fact that high density impurities located near the surface of the granules. The configuration and distribution of the interior pores were affected by the mode of turbulent flow during the granulation process.

Abstract:

Abstract:

Abstract: