Abstract:

Abstract:In order to extract the effect characteristic parameters （smoke screen width， smoke screen height， smoke screen coverage area， masking time） and motion characteristic parameters （vertical and horizontal diffusion speed） from measured infrared smoke screens and， the layout of the test site for field measurement of infrared smoke screens was designed. The infrared thermal imager was used to collect the video data of the explosion and diffusion process of the infrared smoke bomb in 112 secs， and the five-frame difference method was used to segment and extract the infrared smoke screen from the video sequence of the infrared thermal imager， then the effect characteristic parameter area and motion characteristic parameter area of the infrared smoke screen were obtained. According to the geometric relationship of the site layout， the test results have been corrected for wind direction. The pixel points of the infrared smoke screen image were used as the basic unit that the actual smoke screen height and width values represented by each pixel in each frame of the video sequence were solved， and then the effect characteristic parameters and motion characteristic parameters of the infrared smoke screen were obtained. It was verified by the analysis of actually measured infrared smoke screen videos that this method can quickly extract the characteristic parameters of infrared smoke screen. At the moment of explosion， the width， height， and area of the smoke screen rapidly increase to 4.7 m， 5.2 m， and 24.2 m²， respectively， and the front diffusion speeds along the wind direction reached 126 m∙s^-1 horizontally and 146.3 m∙s^-1 vertically.， It has highly practical application value for the research on infrared smoke screens， including the correction of diffusion simulation equation， the combat effectiveness evaluation， and on the combat operation.

Abstract:Aiming at the problem of the irreversible deformation mechanism caused by thermal cycling in PBX-9502 （a type of TATB based polymer bonded explosive）， a three-phase microstructure model and an extended finite element method （XFEM） are used to establish a calculation model. The model takes into account the anisotropy of the TATB grains， the local differences in the thermodynamic properties of the bonding agent and its interface. Using the established model， the phenomenon and mechanism of irreversible deformation caused by thermal cycling of PBX-9502 are numerically analyzed. The results show that due to the severe anisotropy of TATB grains in PBX-9502 and the differences in the thermodynamic properties of TATB grains and binders， PBX-9502 specimens have internal deformation and stress concentration during thermal cycling. Resulting in the destruction of the bonding agent and the debonding of the interface and other internal damage to the material， which in turn led to the irreversible deformation of the PBX-9502 specimen under thermal cycling. At the end of the calculation， the axial strain of the PBX-9502 specimen reached 0.2%.

Abstract:In order to ensure the safety of field mixed emulsion explosive， dynamic extrusion was used to simulate the charging process of explosive. The stability of field mixed emulsion explosive prepared at different rotating speed was studied by laser particle sizer， microscope， water-soluble ammonium nitrate precipitation test and digital viscometer. The experimental results show that crystallization instability in the emulsion matrix will occur in some extent under dynamic extrusion when the particle size is larger than 5 μm.After 10 times of dynamic extrusion， the amount of ammonium nitrate released from the emulsion matrix is 5.14 times of that before extrusion， the viscosity increases by 43%， and the W/O structure has been completely destroyed.When the particle size is smaller than 5 μm， the dynamic extrusion resistance of emulsion matrix is improved，after 10 times of dynamic extrusion， the particle size of emulsion matrix increased by 2.16 times， the amount of ammonium nitrate released from the emulsion matrix is only 2.14 times of that before compression， the viscosity increased by 10%， and the microstructure remained stable.The dynamic extrusion process will accelerate the crystallization instability of matrix， change the physicochemical properties， reduce the performance of emulsion explosive， and is not conducive to the loading process. In production practice， it is necessary to reasonably control the particle size D≤5 μm.

Abstract:The crystal habit of explosives significantly affects their physicochemical properties， application mode and effect. A novel strategy to fabricate the flower spherical 2，6-diamino-3，5-dinitropyrazine-1-oxide （LLM-105） crystals based on solvent-antisolvent method was developed by introducing 1-ethyl-3-methylimidazole acetate （EmimOAc） ionic liquid as the additives， DMSO as the solvent and ethyl acetate as the antisolvent. The results show that the EmimOAc ionic liquid is a crucial factor to modify the crystal morphology of LLM-105. Long needle-like LLM-105 crystals were produced in the absence of EmimOAc. In contrast， flower spherical LLM-105 crystals were obtained in the presence of EmimOAc. In addition， the EmimOAc significantly enhanced the solubility of LLM-105 in DMSO. Meanwhile， ¹H NMR experiments were conducted to understand the intermolecular hydrogen bonds between LLM-105 and the ionic liquid molecules. Furthermore， the flower spherical LLM-105 crystals exhibit excellent thermal stability and safety properties. The DSC/TG results show that the thermal stability of the flower spherical crystals is comparable to that of the long needle crystals. The impact sensitivity was tested according to GJB-772A-1997 method， while the impulse initiation voltage was tested by slapper detonator. Results indicate that for the flower spherical crystal， the characteristic drop height is 22 cm higher than that of the needle crystal， and the impact sensitivity is significantly lower than that of the needle crystal but equivalent to that of the submicron crystal. The impulse initiation voltage of the flower spherical crystals is lower than that of submicron crystals， suggesting that the flower spherical crystals have better initiation performance and high potential for application in primary explosives. This ionic liquid induced crystallization provides a new idea for tuning the crystal habit of LLM-105， as well as a new method for modifying the crystal habits of other organic explosive crystals.

Abstract:In order to acquire the mechanical properties and constitutive relations of Zr-based amorphous reactive material under dynamic loading， the specimens were made by pressure infiltration casting， and the dynamic compression experiments under loading with different stain rates were conducted with the split Hopkinson bar （SHPB） test system. The stress-strain curves were acquired under different strain rates of 300-1600 s^-1， and a high-speed camera was used to record the fracture and energy output process of the specimens under different strain rates. Results show that the Zr-based amorphous reactive material belongs to brittle materials that no yielding stage exists in stress-strain curves. With the increase of strain rates from 947 s^-1 to 1587 s^-1， the compressive strength of materials increases from 2.71 GPa to 2.78 GPa with a small increase of 2.6%， while the fracture strain decreases from 0.032 to 0.028 with a decrease of 12.5%. The degree of fracture and reaction of the specimen is more evident with higher strain rate and the strain softening phenomenon occurred during the fracture of materials. According to experimental data， a one-dimensional elasto-brittle constitutive model with damage was fitted for the Zr-based amorphous reactive material before the fracture failure of specimens.

Abstract:A 1，3，5-trinitrobenzene /1，4-dinitroimidazole （TNB/1，4-DNI） cocrystal explosive was prepared by solvent evaporation. The crystal structure was characterized by single crystal X-ray diffraction analysis. Results shows that the cocrystal crystallizes in the orthorhombic space group P2₁2₁2₁ with crystal parameters of a = 6.4068（5） Å，b = 10.4569（8） Å， c = 20.7164（17） Å， α = β = γ = 90°， ρ = 1.776 g·cm^-3， Z = 4. The differential scanning calorimetry （DSC） was used to analyze the thermal properties of the TNB/1，4-DNI cocrystal explosive. The melting point is 84.4 ℃， which is significantly lower than that of both TNB （123.5 ℃） and 1，4-DNI （91 ℃）. The TNB/1，4-DNI cocrystal explosive can be re-formed into pure cocrystal explosive after melting and cooling. The detonation velocity and pressure of TNB/1，4-DNI cocrystal explosive were also calculated to be 7704 m·s^-1 and 26.08 GPa by the empirical nitrogen equivalent equations， which are significantly higher than those of the commonly used melt-cast explosive TNT. Therefore， TNB/1，4-DNI cocrystal explosive could be used as a new type of melt-cast explosive.

Abstract:Numerical simulation was carried out to study the reaction evolution of explosive charge under weak stimulation and the effect of confinement conditions on its explosion reaction. Based on the multi-media arbitrary Lagrangian-Eulerian method and fluid-structure coupling technique， the numerical simulation of the reaction evolution growth of constrained charge and its interaction with the shell after local ignition were realized. In order to simulate the process from slow burning to violent explosion， a phenomenological model of explosion evolution growth was established. Based on the central ignition experiment of the strongly constrained spherical charge， a series of simulations were conducted and the influence of confinement conditions on the reaction pressure growth process of PBX-2 explosive was analyzed. The results show that the peak value of reaction pressure increases with the increase of shell strength or thickness. When the thickness of the steel shell increases from 5 mm to 20 mm， the peak value of the pressure increases from 163 MPa to 1357 MPa， and the process of pressure increase varies greatly. However， with the fracture and disintegration of the shell， the transformation from explosion to detonation of the explosive charge is restrained.

Abstract:In order to investigate the influence of the pitch angular velocity on the penetration trajectory of projectile penetrating into multi-layered target， a large amount of experimental and simulation from literature was analyzed. In the paper， LS-DYNA finite element software was used to simulate the projectile penetrating into multi-layered slabs with or without considering the pith angle velocity. Data obtained in the simulations， like the paper studied the pith angle， landing time， landing speed， landing offset， angle of attack，landing angle， fuse overloading and etc.， were compared with the experimental results. The results show that the numerical simulation was agreed well with the corresponding experimental data， when the pitch was taken into consideration. The influences of pitch with different values and directions on the trajectory of projectile penetration into multi-layered reinforced concrete slabs were analyzed. It shows that， under the same value， the positive pith angular velocity had a greater influence than the negative one. Secondly， in order to ensure that the projectile explode in the target building， the value and direction of the pith angular velocity of the projectile must be controlled between -627°·s^-1 and 427°·s^-1.

Abstract:In this work， the auto-ignition behaviors of FOX-7/NC/NG powder were investigated by using rapid compression machine （RCM） under a high temperature environment. High speed images and pressure evolutions were used to record the responses of FOX-7/NC/NG samples under high temperature and pressure conditions. Results show that the samples were not able to ignite at 3.0 MPa and 598.1 K， with the heating rate of about 1.2×10⁴ K·s^-1. With the temperature increasing to 913.1 K （the heating rate is about 2.5×10⁴ K·s^-1）， the auto-ignition was observed. In addition， the validated tests of FOX-7/NC/NG samples were conducted. Results show that the experiment has a good repeatability. The uncertainties of ignition delay times （IDT_I） and burning duration are less than 20% and 5%， respectively. Lastly， the auto-ignition behaviors of FOX-7/NC/NG samples were studied at different thermal loading rates. It was found that the higher thermal loading rate， the faster ignition and the shorter burning duration.

Abstract:In order to study the laser radiation effect on Octogen （HMX） crystal， various technical methods were used to characterize the microstructure evolution of HMX crystal under 360 nm ultraviolet laser. By optical microscope， the process from accumulation of defects to cracking under laser irradiation was observed in HMX crystals. In-situ Raman spectroscopy demonstrated that the absorption of UV photons would stimulate HMX molecules， causing the ring vibration. In-situ wide-angle X-ray scattering （WAXS）， single crystal X-ray diffraction （SCXRD） and in-situ small-angle X-ray scattering （SAXS） were also adopted to study the crystal changes and defects evolution of HMX under UV laser irradiation. It is found that phase transformation does not happen but some new defects generate in HMX. The in-situ SAXS results show that the pores in HMX increase continuously after 1170 minutes of laser irradiation and a bimodal distribution exists in the region ranging from 10 to 20 nm and 30 to 40 nm， respectively. During the laser irradiation process， small pores in HMX keep accumulating and gradually merge into larger pores. Due to the accumulation of defects， the microcosmic pores extend into micro-cracks， and then expand into macro-cracks.

Abstract:High tension bonds or high-energy bonds are important elements in the formation of disruptive energetic materials， but it"s hard to form and easy to break，. Their construction has always been a difficult problemin the field of chemistry and energetic materials. By using the unique internal space of molecular cages to “assist” the construction of such chemical bonds provides a feasible route for related research， and has been put into practice. This review summarized “confinement effect”， weak interaction， electron transport and other characteristics of molecular cages. It is discussed that it can prevent oxygen oxidation of P₄ and other high-tension materials， stabilize aryl pentazoles and other high active substances， reactants such as NaN₃ to accelerate the reaction， change the reaction path. The roles of molecular cages in these processes， such as “firewall”， “stabilizer”， “accelerator”， “channel remover” and others， were reviewed， which provided references for the preparation of novel energetic compounds such as TdN₄ and the study of controllable energy release . At the same time， it also points out the key direction of future research： design and synthesis of new and efficient molecular cages. developing good characterization methods and means of molecular cage complex. Enhance the composite and release of multi-environment responsive molecular cages and energetic materials.