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Abstract:To improve the damage ability of integral multiple explosively formed projectiles (MEFP), the effect of configuration parameters of charge on projectile formation was studied using LS-DYNA code.Results show that the charge spacing has great effect on the shape and the radial dispersion angle of surrounding projectile. With increasing the charge spacing, the velocity of integral MEFP and the length-diameter ratio of central projectile change in small ranges, but the shape of surrounding projectile changes from rods to ball shape gradually. The trail of surrounding projectile decreases gradually and the flight stability of projectile enhances. With increasing the charge spacing, the radial dispersion angle of surrounding projectile decrease gradually. With increasing the length-diameter ratio of charge, the velocity and length-diameter ratio of central projectile increase significantly and the penetration performance enhances. The shape of surrounding projectile changes from ball to rods shape gradually. The trail of surrounding projectile increases gradually and the flight stability of projectile decreases. With increasing the length-diameter ratio of charge, the radial dispersion angle of surrounding projectile increases firstly and then decreases, so selecting a suitable length-diameter ratio of charge could improve the damage effect based on definite aim.

Abstract:Aiming at the application problem of different liner materials in the multimode warhead, the effects of performance parameters of the liner materials on the forming of dual mode damage elements, explosively formed penetrator (EFP) and jetting projectile charge (JPC) were studied. Based on the Johnson-Cook′s constitutive model, the single variable method was used to change the material parameter values. The influence of material characteristic parameters on the forming of dual mode damage elements was simulated and calculated by ANSYS/LS-DYNA software. X-ray imaging verification test of three kinds of liner materials, aluminum, iron and copper was performed. Results show that the tip velocity and length-diameter ratio of dual mode damage elements, EFP and JPC, are exponentially decreasing with the increase of yield stress, strain hardening coefficient, strain hardening exponent, temperature correlation coefficient and strain hardening exponent under quasi-state. The density has the greatest influence on the tip velocity of the EFP and JPC, and the yield stress and the hardening coefficient have the greatest influence on the length-diameter ratio of the EFP. The formula calculating the tip velocity and length-diameter ratio of the dual mode damage elements considering the influence of material properties were presented by fitting. The error between calculated results and experimental ones for tip velocity and length-diameter ratio of the dual mode damage elements, EFP and JPC formed by three kinds of liner materials, aluminum, iron and copper is less than 10%, revealing that the two results are in good agreement.

Abstract:To study the characteristics and laws of jet formation process of circular shaped charge of cutting inward, the tri-dimensional numerical simulation of shaped charge was done by ANSYS/LS-DYNA program. The jet formation photographs, jet velocity gradient distribution curve and time history curve of maximum jet velocity of typical moment(4, 10, 22, 25, 26, 44 μs)under different detonation form were obtained. Results show that detonation point number and its synchronicity have great influence on jet formation performance of circular shaped charge. When detonation forms are two points, four points and eight points symmetry synchronous initiation of the whole round, jet shape are "inside the runway and outside the oval", "both inside and outside the approximate square", and "inside the wheels and outside the approximate octagon ". respectively. The jet formation performance with the increase of detonation point number is gradually getting better, and finally close to the circular. When detonation form is two points, four points and eight points symmetry synchronous initiation of the whole round, the jet velocity variation law with time in the cross-sectional area is almost the same, and the moment of jet maximum velocity is 10 μs. Secondary collision phenomenon of jet head happens at the circular symmetric axis. This alters significantly the direction of the newly formed jet, and made the motion of the newly formed jet along with the direction of axis of the circle. The moment of secondary collision of jet is different with the difference of detonation form. The moment of secondary collision of jet advances gradually from 43 μs to 36 μs with the increase of detonation point number.

Abstract:To improve the impact reaction damage effectiveness of Al/PTFE/W fluoropolymer-matrix reactive materials (RMs), quasi-static compression experiments of Al/PTFE/W RMs were carried out. The effects of W content(0%, 30%, 65%), Al particle size(13, 45, 75 μm) and PTFE particle size (25, 160 μm) on the quasi-static mechanical properties of the RMs were analyzed. The impact energy release test of the RMs was performed by quasi-sealed reaction vessel, the impact reaction pressure and duration of energy release of the RMs in the range of 750-1200 m·s^-1 were measured. The influence of Al particle size and PTFE particle size on the impact reaction energy release characteristics was analyzed. Results show that when the contents of W are 0%, 30% and 65%, the failure strength of the RMs is 55.6, 64.8 and 22.8 MPa respectively, and the change in W content has little effect on the yield strength. When the size of Al particles decreases from 75 μm to 13 μm, the failure strength of the RMs increases from 64.7 MPa to 83.1 MPa, the range increases by 28.4%. Increasing the particle size of the PTFE matrix material can also effectively improve the failure strength of the reactive material. The initial reaction pressure threshold and the duration of energy release of the RMs are affected by the particle size and quasi-static compressive mechanical properties of the materials.

Abstract:To improve the comprehensive performance of polymer bonded explosives(PBXs), low sensitivity nano-HMX and micrometer HMX were applied to PBX by particle gradation. Four molding powders were prepared by solution-water slurry method and pressed into explosive cylinders. The surface microstructures of JO-1, JO-2, JO-3 and JO-4 sampls (coarse/micrometer/nano-HMX mass ratios with 100/0/0, 60/35/5, 60/30/10 and 60/25/15, respectively) were observed and the component contents, impact sensitivities, friction sensitivities, thermal decomposition characteristics, compression properties and detonation velocities were measured. Results show that JO-3 sample has the best properties. Compared to the JO-1 sample with single coarse HMX(d₅₀=100 μm), JO-3 sample has the smoother surface, and the impact sensitivity is reduced by 38.3%, the friction sensitivity is reduced by 22.7%, the self-ignition temperature is increased by 5.17 ℃, the compression strength is enhanced by 46%, and the detonation velocity is increased by 55 m·s^-1. The HMX based PBX comprehensive performance is improved significantly.

Abstract:To obtain a friendly green catalyst for aldol resin, the ionic liquid [HSO₃-pHim]HSO₄ was applied to cure aldol resin. The curing kinetics of aldol resin were studied by differential scanning calorimetry (DSC) method, and the mechanical properties of aldol resin based PBXs were studied by electronic universal testing machine. Results show that the average apparent activation energy, frequency factor and reaction order are 2.59 kJ·mol^-1, 994.61 s^-1 and 0.93, respectively. When the content of [HSO₃-pHim]HSO₄ is 0.9% and curing temperature is 30 ℃, the tensile strength, compression strength and elongation to fracture of PBX are 16 MPa, 41 MPa and 0.81%, respectively. Comparing to cured by diethyl sufate (DES), the compression modulus of the PBX cured by [HSO₃-pHim]HSO₄ decrease by 35%.

Abstract:In order to research the drag reduction and extend range characteristics of base bleed projectile, the three burning models were established for base bleed propellant with different burning rate, cladding propellant with variable burning rate and different cladding layer position of propellant for 155 mm base bleed projectile. The drag reduction and extend range characteristics of base bleed projectile were calculated and analyzed numerically by introducing the burning rate change coefficient. Results show that the burning rate change coefficient increases from 0.7 to 1.2, the working time of the base bleed reduces 27.08 s, the firing range reduces 1.16 km and the extend range rate increases 3.86%. The extend range rate is 32.33% by using the variable burning rate propellant, which the inner layer burning rate is higher than outer layer. The maximum firing range is 39.76 km by optimizing the propellant at 1/4 of the inner ring. Therefore, the drag reduction and extend range characteristics of base bleed projectile could be improved by optimizing the layer position and using variable burning rate of base bleed propellant.

Abstract:In order to understand the distribution characteristics of the muzzle temperature field for gun launched in different environments, numerical simulation and contrast analysis for 12.7 mm gun launched in air and underwater were carried out. With the FLUENT software, the numerical simulation was performed using User Defined Function (UDF) and dynamic grid technology. The numerical results show that when the gun is sealed and launched underwater, the velocity of projectile slows down just when it contacts water. At this time, the gunpowder gas after the projectile is slowed up and its temperature is raised, so that the initial injection temperature of the gas reaches 2653 K, which is 417 K higher than that in air (2236 K). Influenced by both the projectile movement and the gas-liquid interface, the Mach disk was formed at 70 μs after the projectile shot out. However, the Mach disk was initially formed at 200 μs after the projectile shot out for gun launched in air. Compared with the situation of gun launched in air, the shock core area formed by the underwater launch is significantly smaller, while the temperature of the core region is higher. Especially, the maximum temperature in the compressed wave is up to 3200K, which is 1500K higher than that in air. By fitting the curve of the Mach disk position with the time for the underwater launch, it is found that the variation of the Mach disk position follows the law of exponential change within 200μs after the projectile shot out.

Abstract:To investigate the effects of external electric field on sensitivity of HMX/MDNI, different external electric fields (-0.010-0.010 a.u.) were employed on M06-2X//B3LYP/6-311++G(d, p) level by quantum mechanics method. The intermolecular interaction, trigger bond energy, electron density topological, electron density shifts and electrostatic surface potential of complexes were considered with different external electric fields. It shows that trigger bond length is shorter and bond dissociation energy is larger with the increasing of external electric field along the positive direction, while the trend is opposite along the negative direction. The correlation coefficients for 3 complexes (by B3LYP) are 0.995, 0.977 and 0.982, respectively. Q_NO2are decreasing with the negative external electric fields, indicating the sensitivity is increasing. Electron density topological analysis shows that there are weak hydrogen bond interactions between HMX and MDNI with external electric fields. Electron density shifts analysis shows that positive external electric field strengthens the trigger bond. Electrostatic surface potential indicates that sensitivity of explosive is decreasing in the positive external electric field, while increasing in the negative direction.

Abstract:To cooperate the identification and evaluation of suspected hazardous materials for public security department, the national standards including "Guidelines for physical hazard testing of chemicals" and "GB/T13226-1991 lead plate test for industrial detonator" issued by country were systematically applied to the identification and evaluation of explosiveness test for hazardous materials. Among them, the UN gap test 1(a), Koenen test 1(b) and time/pressure test 1(c) were applied to identify whether the hazardous materials had explosiveness or not. The cap sensitivity test 5(a) was applied to determine the sensitivity of hazardous materials on strong mechanical stimulation. The lead plate test was applied to identify whether the electric detonator, safety fuse and flash detonator had explosiveness or not. With above-mentioned test methods, the identification and evaluation of combustibility or explosiveness for hazardous materials including ammonium nitrate (AN), ammonium perchlorate (AP), suspected black powder, fuse, suspected AN explosive, suspected electric detonator and flash detonator obtained from public security department were performed. Results show that the AN can not be initiated with industrial detonator, while the AP and AP/AN mixture have explosiveness and can be initiated with industrial detonator, the effectiveness of the identification and evaluation standard of the explosiveness test is verified. Whether or not suspected AN explosive has explosiveness can be identified using UN gap test 1(a). Whether or not suspected black powders and safety fuse have combustibility can be qualitatively identified using combustion test. Whether or not suspected electric and flash detonators have explosiveness can be identified using lead plate test.

Abstract:As an ignition and detonated source of weapon system, initiator was an important factor affecting the safety and reliability of weapon systems. From the perspective of insensitive energy conversion component design and selection of protection devices, the latest research development of electromagnetic compatibility design of initiator over the past few years was reviewed. Two methods for improving the immunity of EEDs to electromagnetic environment: adding the protection device to absorb or bypass the energy which coupled from the electromagnetic environment and designing low-firing energy insensitive initiator, were introduced. It was noted that modern microelectronics technology was an effective way to design and prepare the initiator which had advantages of electromagnetic compatibility, large scale preparation, high consistency and high reliability.

Abstract:In order to reduce the sensitivity of 2, 4, 6, 8, 10, 12-hexanitro-2, 4, 6, 8, 10, 12-hexaazaisowurtzitane (CL-20), CL-20/3, 5-dinitrobenzoic acid (DNBA) spherical composite was prepared by ultrasonic-assisted emulsion method under room temperature using ethyl acetate as solvent and gelatin as the surfactant. Its morphology and structure were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD) and Fourier transform infrared spectroscopy (FT-IR). In addition, the thermal decomposition performance were measured by differential scanning calorimetry (DSC). The impact sensitivity and friction sensitivity were tested by GJB772A-1997. Results show that the surface of the composite particles is smooth without obvious edges and the particle size is uniformly distributed with an average particle size of 6.7 μm. XRD and FT-IR tests indicate that there is a certain interaction between the two molecules, which may form a new spherical composite structure. Compared with the raw CL-20, the impact sensitivity and friction sensitivity of CL-20/DNBA spherical composite significantly decrease with the H₅₀ of CL-20/DNBA spherical composite increasing from 13 cm(raw CL-20) to 50.4 cm and the explosion probability decreasing from 100%(raw CL-20) to 65%. At the same time, the thermal decomposition performance was significantly different from that of raw CL-20. The exothermic peak was 20.3 ℃ ahead of raw CL-20.

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