Abstract:To explore promising energetic molecular species with huge energy release and significant kinetic stability, the singlet and triplet potential energy surface of nitrogen-rich compound PN₃ were constructed at the CCSD(T)/aug-cc-pVTZ//M06-2X/6-31+G(d,p) level.The computations performed identified 13 isomers and 21 transition states. The ground state isomer was the chain-like triplet PNNN(C_s). The kinetic stability of PN₃ was further evaluated by studying the dissociation, isomerization as well as the Born-Oppenheimer molecular dynamic (BOMD) simulations at the B3LYP/6-31+G(d) level. The results indicated that the chain-like triplet PNNN(C_s) and the tetrahedral-like singlet PN₃(C_3v) are both kinetically stable.

Abstract:In order to investigate the micro-crystalline structural morphology in Melt-cast explosive and improve the quality of explosive column, the CAFE module of ProCAST casting simulation software was used to simulate the internal crystalline structure of TNT melt-cast explosive. Using cellular automata in CAFE module, the shape and size of grain in column under different technological conditions and TNT nucleation parameters were predicted. The improvement measures of grain refinement process were obtained by adjusting the nucleation undercooling degree, pouring temperature and cooling rate of melt. The results show that with the decrease of melt nucleation undercooling, the equiaxed grain area in the column gradually increases, and the average grain size decreases to 458.5 μm from 715.5 μm; with the decrease of melt surface nucleation undercooling, the grain morphology inside the column does not change significantly, and the average grain size increases to 719.2 μm from 715.5 μm; with the decrease of melt pouring temperature, the equiaxed grain area in the column gradually increases, and the average grain size decreases to 729.2 μm from 1114.5 μm; with the decrease of cooling rate, the central equiaxed grain area gradually enlarges, the outer equiaxed grain area gradually disappears, and the average grain size increases to 1149.1 μm from 719.4 μm. After process optimization, the column is composed of fine equiaxed grains with an average grain size of 516.9 μm, the size distribution is concentrated, and the micro-quality of the grain is greatly improved.

Abstract:To investigate the thermal safety of modular charge, based on the chemical reaction mechanism of combustible cartridge material and single-base propellant, a two-dimensional unsteady state cook-off model of modular charge was established. The fast cook-off response characteristics of modular charge were analyzed at the external heating rates of 1-10 K·min^-1. The results show that the initial ignition position of modular charges is all in single-base propellant on the left and right sides near the inner wall surface of combustible cartridge material, and the ignition zones are two circular response zones. With increasing the heating rate, the circular response zone will move from the inside of single-base propellant to the inner wall of combustible cartridge material, but the change in external heating rates has little effect on the ignition position of modular charge. At the heating rates of 1, 6 K·min^-1 and 10 K·min^-1, the temperatures occurring the cook-off response of single-base propellant are 458.2, 453.9 K and 455.7 K, respectively, which are basically consistent with the ignition temperatures (443-463 K) measured by experiments. The change in external heating rate has little effect on the ignition temperature occurring the cook-off response of modular charge, but the ignition time occurring the cook-off response of modular charge reveals an exponential decay with increasing the heating rate.

Abstract:To research the dissolution characteristics of Hexogen (RDX) in ethyl acetate–water binary system, the solubility of RDX at temperatures ranging from 298.15 to 338.15 K was measured The experimental data were fitted using Apelblat equation, CNIBS/R-K model and Jouyban-Acree equation. The standard enthalpy of dissolution, entropy of dissolution and Gibbs free energy were calculated. To study the dissolution mechanism, the solubility parameters of RDX in ethyl acetate-water binary mixed solvent were calculated by molecular dynamics simulation method. Results show that the solubility of RDX increases with the increase of temperature and water content. The fitting values of empirical equation are basically consistent with the experimental ones. The experimental solubility data, model parameters, thermodynamic properties and solubility parameters provide basic data and models for the recovery process of RDX and HMX.

Abstract:To apply the high pressure water jet technology to the engineering practice of waste ammunition treatment project, the process of breaking explosives by high pressure water jet was studied by the numerical simulation method. A finite element calculation model with high pressure water jet velocity as the input parameter was set up. The Lagrange algorithm and SPH（Smoothed Particle Hydrodynamics）algorithm were used to solve the problem by DYNA solver. The safety for the process of breaking explosives by high pressure water jet was studied through the analysis of pressure, temperature and reaction degree of explosive, and the effectiveness for the process of breaking explosives by high pressure water jet was analyzed through the number analysis of failure unit. Results show that when the velocity of high pressure water jet is lower than 800 m·s^-1, the high pressure water jet can be used to break the charge of waste ammunition explosive, and ensure the safety of the breaking process. When the velocity of high pressure water jet is 150~350 m·s^-1, the large cross-section breaking can be performed more effectively; when the velocity of high pressure water jet is 400~800 m·s^-1, the small cross-section breaking can be realized efficiently.

Abstract:To improve the mechanical properties of nitrocellulose (NC), a cellulose mixed ester modified with double groups of nitrate and acetate groups-cellulose nitrate-acetate mixed ester (CNA) adhesive was prepared through the chemical modification of esterifying cellulose using nitric acid and acetic acid. The elemental content, solubility in acetone, ethyl acetate, dichloromethane, etc., thermal properties, and compatibility of CNA were characterized by elemental analyses (EA), dynamic mechanical thermal analysis (DMTA), thermogravimetry (TG), differential scanning calorimetry (DSC), etc.. The detonation velocity, heat of detonation and plate mark of CNA-bonded explosives were measured. Results show that the nitrogen contents of two kinds of CNAs prepared are 4.27% and 8.16%, respectively. The introduction of acetate groups increases the solubility of cellulose mixed esters and improves the flexibility of molecular chains. The thermal stability of CNA with larger acetate-group-content (1.28) is increased by 6 ℃ to 13 ℃ compared with that of NC. The compatibility between CNA and most energetic materials is good. CNA is used as a binder for press-packed mixed explosives. CNA-bonded explosives have higher energy performance than fluororubber-bonded explosives.

Abstract:To study the effect of mass fraction of hydroxyl-terminated polybutadiene (HTPB) system and temperature on the mechanical properties of paraffin/HTPB fuels, seven kinds of paraffin/HTPB tensile specimens with different formulations were prepared, and the unidirectional tensile experiments were carried out by an universal materials testing machine at a tensile rate of 10 mm·min^-1. The variation law of maximum tensile strength, elongation at break and the initial elasticity modulus of the fuel were analyzed. Results show that the fracture elongation of fuel increases with the increase of mass fraction of HTPB system, while the maximum tensile strength and the initial elasticity modulus decrease. When ambient temperature approachs the melting point of 58 ℃ for paraffin, the maximum tensile strength and initial elasticity modulus of the fuel increase with increasing the mass fraction of HTPB. The maximum tensile strength of fuel increases gradually with decreasing the temperature. In which, when the temperature decreases from 20 ℃ to -40 ℃, the maximum tensile strength of H20 fuel increases from 1.189 MPa to 2.150 MPa. The paraffin /HTPB fuel of HTPB system as matrix and paraffin as filler has mutual block acting force on the interface between its matrix and filler, which can increase the mechanical performance of the fuel.

Abstract:To study the quasi-static compression response behavior of polymer bonded explosive (PBX) under different end face friction conditions, a typical casting PBX explosive was selected as the research object, and the quasi-static compression tests were carried out under three kinds of end face friction conditions； molybdenum disulfide lubrication, dry friction, and grease lubrication. The load-displacement curves were measured by using electronic universal material testing machine. Based on the isotropic elastic theory, the friction mechanism of the end face was preliminarily discussed by the energy conservation method. Results show that the static failure strain is closely related to the friction coefficient. Under the same friction conditions, the material with viscoelastic properties, high Poisson′s ratio, great axial strain and small length-diameter ratio has an obvious end face friction effect in the static compression test.

Abstract:Taking 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)-based high polymer bonded explosive (PBX) material as research object, the quasi-static uniaxial tension and compression tests were carried out at -40-75 ℃, and the stress-strain relationship data at 17 preset temperature points were obtained. Setting temperature and strain as independent variables, stress as dependent variable, the stress-strain relationship under the tension and compression conditions was described based on support vector machine (SVM) algorithm, and the error analysis of the constructed relationship was carried out. The results show that the tensile strength and compressive strength of the materials deteriorate with increasing the temperature in the temperature range of -40-75 ℃ and the non-linearity of stress-strain curve and asymmetry of tension compression change obviously. Meanwhile, a set of parameters based on SVM algorithm is used to realize the description of the tensile and compressive strain-strain relationship of TATB-based PBX at different temperatures, which solves the problem that the model parameters often change with temperature. The average absolute percentage error of the constructed relationship is not more than 7.77%, and the correlation coefficients are all greater than 0.998, showing a good applicability.

Abstract:A capacitor discharge unit (CDU), consisting of domestic Metal-Oxide-Semiconductor（MOS） controlled thyristor (MCT) and high-voltage ceramic capacitor, was designed and prepared in order to study the discharge characteristics of CDU. The volume of the CDU is 40 mm(L)×25 mm (W)×8 mm(H). The CDU circuit inductance is about 10 nH, and the resistance is about 100 mΩ. The R-L-C zero input response equation of CDU circuit was analyzed, and was verified by the experiment of short-circuit discharge of CDU load. It is found that the key parameters of CDU, such as the peak current, rise time of peak current and discharge time of high-voltage capacitor all increase with the increase in capacitance value; the peak current increases with the increase of discharge voltage, and the peak current rise time remains constant. The function efficiency of CDU was verified by micro-chip exploding foil initiator(Cu bridge foil 35 mΩ) and boron-potassium nitrate pellet(B/1.50 μm, pressing density/1.57 g·cm^-3), under the condition of 0.36 μF/1.20 kV, the measured peak current of circuit is 2.032 kA, the voltage at both ends of the bridge foil is 0.9273 kV, the delay time between peak current and voltage is 32.4 ns, the burst time is 168.2 ns, and the burst point power is 1.490 MW, and the CDU can reliably ignite BPN pellet by flyer impact. Results show that the CDU based on the domestic MCT and high voltage ceramic capacitors is basically suitable for high-current pulsed initiating devices such as exploding foil initiator, but its comprehensive performance still needs to be improved.

Abstract:To realize high safety and intelligent control of ordnance initiation system, an addressable initiation network system based on RS485 bus was designed by means of bus networks topological structure and protocol coding addressing. The design of integrate energy conversion element of smart initiator embedded in “identity address” and its safety, system data interaction protocol and working mechanism were emphatically studied. The feasibility and safety of the system addressing control were tested and verified. Results show that the system can realize the multi-mode addressing control initiation of 255 smart initiators. The multi-point synchronous initiation has good synchronization, and the system has the characteristics of intellectualization and high safety.

Abstract:Small⁃angle scattering (SAS) is a useful technique to characterize the complex multi⁃scale microstructure of polymer bonded explosives (PBX). In this review the experimental methods, data analysis models and selected applications of SAS for PBX research are presented. First, the in⁃situ temperature, tensile and compressive loading methods suitable for PBX are discussed. Second, the commonly used models such as Guinier, interface, polydisperse particles, hard sphere interaction, and fractal are summarized and their applicability to PBX research are described. Third, research progress on mechanical and thermal damage, binder microstructure, sensitivity, and denotation carbon product analysis over the last 20 years using small⁃angle X⁃ray and neutron scattering techniques are summarized. Finally, the advantages of SAS for PBX research are summarized. In addition to the quantitative research of internal multi⁃phase interfaces and multi⁃scale voids in PBX, the review points to the continued development of ultra⁃small⁃angle scattering (USANS) technique, in⁃situ mechanical⁃thermal coupling loading of PBX, and data analysis software.

Abstract:

Abstract:

Abstract: