Abstract:To study the drop safety problem of a certain type of ship board solid rocket motor, the numerical simulation and analysis for the multi angle drop process at drop height of 37.5 m of solid motor were carried out by using ANSYS/LS-DYNA finite element analysis software. The verified test for drop test of real motor was performed. The results show that the dangerous angle at the same drop height is 78°, the temperature rise of charge in the motor calculated by ignition and growth model is less than 5 K, and the ignition reaction does not happen. The contact position of motor tail with collision surface is relatively dangerous. The stress and strain values of shell and internal charge are large, which may generate fracture failure. Through the drop test of solid rocket motor, it is found that the tail of motor has a fracture damage, but the ignition or explosion reaction do not occur. Data information collected from the test is consistent with the results of finite element analysis. The rationality of the calculation method is verified.

Abstract:To establish a failure criterion for hydroxyl-terminated polybutadiene(HTPB)propellant which considers the effect of temperature and strain rate. The time-temperature shift factor of HTPB propellant was obtained by stress relaxation tests at different temperatures(233.15, 253.15, 273.15, 293.15, 323.15, 343.15 K)of HTPB propellant. Based on cumulative damage theory and linear viscoelastic theory, a failure criterion of propellant with time-temperature shift factor α_T was established. The damage parameters of failure criterion were obtained by combining the uniaxial tensile test data at different temperatures and different strain rates. The failure criterion was used to predict the damage evolution characteristics and critical failure time of propellant material at different temperatures and strain rates. Compared with the experimental results, it is found that the relative error predicted by the failure criterion is less than 20%, indicating that the failure criterion can predict the failure condition of HTPB propellant in the range of low temperature 233.15-273.15 K at tensile speed of 2-500 mm·min^-1 and in the range of high temperature 293.15-343.15 K at tensile speed of 0.5-100 mm·min^-1.

Abstract:To accurately predict the storage life of hydroxyl-terminated polybutadiene(HTPB)coating in solid rocket motor, accelerated aging tests at 50, 60, 70 ℃ and 80 ℃ were carried out. Logarithmic model, power function model and exponential model were used to study the maximum elongation of HTPB coating with storage time. Kooij equation was regarded as the aging model, and the storage life of HTPB coating at normal temperature was predicted. Results show that the power function model with α = 0.4 can describe the variation law of maximum elongation with time. The apparent activation energy of the aging reaction obtained is 29 kJ   mol^-1 approximately, which is far less than 60 kJ   mol^-1, revealing that the aging reaction during 50 ℃ to 80 ℃ is easy to occur. Taking the maximum elongation decrease of 50% as the failure criterion, the storage life of the estimated HTPB coating at normal temperature is 15.62 years, which can meet the aging performance requirements of the coating.

Abstract:To improve the combustion and mechanical properties of ammonium perchlorate(AP)/composite modified double base(CMDB)propellant prepared by the solvent-extrusion method, the effects of carbon nanotubes(CNTs)on the thermal decomposition performances of the main components of AP/CMDB propellant and the microstructure of AP/CMDB propellant were studied by differential scanning calorimetry (DSC) and scanning electronic microscope(SEM). The burning rate and impact strength of AP/CMDB propellants with CNTs of mass fraction as 0.1%, 0.3% and 0.5% were tested. Results show that CNTs can effectively catalyze the thermal decomposition of AP, and make the low temperature decomposition peak of AP disappear, and the peak temperature of high temperature decomposition of AP shift 39.9 ℃ downwards, but it has little effect on the thermal decomposition of double base components NC and NG. CNTs can improve the microstructure of AP/CMDB propellant. There are no obvious micro cracks in the AP/CMDB propellant with the addition of 0.5% CNTs. CNTs can effectively improve the combustion and mechanical properties of AP / CMDB propellant. With increasing the content of CNTs the burning rate increases, the pressure exponent decreases, and the impact strength increases of the propellant. For AP/CMDB propellant with 0.5% CNTs, the burning rate at 10 MPa is 61.19 mm·s^-1, the pressure exponent between 10 MPa and 22 MPa is 0.51 and the impact strength is 5.55 kJ·m^-2 at -40 ℃.

Abstract:The triblock copolyether of hydroxyl-terminated polyallyl glycidyl ether (PAGE)/polytetrahydrofunan /PAGE (PAGE-PTMEG-PAGE)was synthesized via. the cationic ring-opening polymerization, using polytetrahydrofunan ether glycol (PTMEG)as initiator, boron-trifuoride ethylether complex(BF₃·OEt₂)as catalyst, allyl glycidyl ether(AGE)as monomer. The structure and properties of the copolyether were characterized by IR, ¹H NMR, ¹³C NMR, GPC and DSC. Results indicate that the chain segment ratio of PTMEG and PAGE in the synthesized copolyether is basically consistent with the feed ratio, the relative molecular mass of the copolyether is controllable and the molecular mass distribution is relatively narrow. The glass transition temperature of the copolyether is -80.3 ℃, the viscosity is1.94 Pa·s, The tensile strength and elongation at break at room temperature of elastomer film obtained after curing with tetramethyl-p-phenylnitril oxide(TTNO)are 1.2 MPa and 83%, respectively.

Abstract:Using 2-methylimidazole as raw material and dibromo methane as a bridging reagent, a bis-cationic energetic compound, 3, 3′-methylene-bis (2-methyl-1-nitroxyethylimidazolium)dinitrate(3)was synthesized via. methylene-bridging, quaternization, and nitration reactions. Then a series of bis-cationic energetic salts were obtained via the metathesis reactions of compound 3 with negative ions of picrate, dinitramide, 3, 5-dinitro-1, 2, 4-triazolate, and 5-nitrotetrazolate as anions. All the synthesized energetic salts were analyzed and characterized by ultraviolet visible spectrum(UV-Vis), infrared spectrum(IR), mass spectrum(MS), nuclear magnetic resonance(NMR), elemental analysis, and thermogravimetric analysis(TGA). The detonation peformance of the synthesized bis-cationic energetic salts, such as detonation velocity and detonation pressure, were estimated by Kamlet-Jacobs equation. Results show that the bis-cationic energetic salts have a good thermal stability, their decomposition temperatures are above 169 oC and their thermal decomposition peak temperatures are close to 200 ℃ for the first decomposition stage.The bis-cationic energetic salts apart from 5-nitrotetrazolate bis-cationic energetic salt have a better thermal stability than the corresponding mono-cationic imidazolium energetic salts. At the same time, all the bis- cationic energetic salts have a higher melting point than the corresponding mono-cationic energetic salts. Some bis-cationic imidazolium energetic salts have a higher density than the corresponding mono-cationic energetic salts. The detonation velocities and detonation pressures of 3, 3′-methylene-bis (2-methyl-1-nitroxyethylimidazolium)- di (3, 5-dinitro-1, 2, 4-triazolate)and 3, 3′-methylene- bis(2-methyl-1-nitroxyethylimidazolium)-di (5-nitrotetrazolate)are between those of 2, 4, 6-trinitrotoluene(TNT)and 1, 3, 5-trinitroperhydro-1, 3, 5-triazine(RDX), showing better detonation performances.

Abstract:To solve the flammable and combustible problem of discarded isopropyl nitrate, the hydrolysis of isopropyl nitrate was catalyzed by sodium hydroxide. The hydrolysis effect of isopropyl nitrate was detected by coupling gas chromatograph and mass spectrometer(GC/MS). Effects of reaction temperature, reactant ratio, catalyst dosage and reaction time on the conversion rate of isopropyl nitrate were discussed by orthogonal test. Results reveal that, the gas phase hydrolysis of isopropyl nitrate under high temperature and high pressure can greatly increase the hydrolysis rate constant and accelerate the hydrolysis reaction. The optimum process conditions for hydrolysis of isopropyl nitrate are determined as follows:reaction temperature 140 ℃, V(isopropyl nitrate):V(water) =1:3, n(isopropyl nitrate):n(sodium hydroxide) =1:1.1, reaction time 30 min. The hydrolysis conversion rate of isopropyl nitrate can reach 99% and the hydrolysis is more thorough. The yield of isopropyl alcohol is 70%-80%.

Abstract:To improve the mechanical property of 2, 4-dinitroanisole(DNAN)/RDX melt-cast explosives, the effect of functional additives, N-methyl -4-nitroaniline(MNA), Tween 60, tris-(β-chloroethyl)fosfat(CEF)and cellulose acetate butyrate(CAB) on the interfacial binding energy was simulated by molecular dynamics. The powder contact angle method and platinum plate method were used to measure the contact angle and surface tension, and the simulation results were verified by calculating the adhesion work. The experiments of adhesion work were verified from macroscopic and microscopic scales by Brazilian experiments and scanning electron microscopy(SEM), respectively. Results show that the order of change ability of functional additives on DNAN/ RDX interfacial binding energy from high to low is CAB>CEF>Tween 60>MNA, and the experimental results agree well with the numerical simulation ones. Functional additives, CAB, CEF, Tween 60 and MNA can make the tensile strength of DNAN/RDX explosive increase by 58.37%, 47.85%, 29.71% and 5.83%, respectively. With the increase of adhesion work, the fracture mode of grain is changed from transgranular/intergranular mixed fracture to pure transgranular fracture.

Abstract:To simulate the mechanical properties of polymer bonded explosives(PBXs)from the meso-scale, the concept of gradation of Monte Carlo method was introduced into the PBX model of high volume fraction. A generating method of Voronoi polygon particles which can consider the distribution of graded particles was formed by combining the Voronoi polygon particle generation algorithm. A PBX meso structure model considering gradation and volume fraction of 94% and above was established through the treatment of particle modification, shrinking, corner cutting and smoothing etc. At the same time, the model can maintain periodic continuity at the boundary. The uniaxial compression simulation for PBX meso model of three groups under different gradation condition was performed by numerical manifold method(NMM). The equivalent elastic modulus obtained from NMM simulation was compared with the experimental results in literature. The reasons of deviation occurred between the simulation results and the experimental ones were analyzed, and the rationality of the PBX meso structure model generation method was discussed. Results show that the equivalent modulus of PBX increases with the increase of volume fraction, and the higher the volume fraction is, the faster the growth rate is. At the same time, when the volume fraction is below 30% and higher than 85%, the effect of the particle gradation on the equivalent modulus is smaller, but when 30%≤volume fraction≤85%, the effect of the particle gradation on the equivalent modulus is significant.

Abstract:Compared with the traditional die pressing, the isostatic warm compaction is a better way to obtain dense and homogeneous polymer bonded explosive(PBX). To provide a meso-level structure basis for the study of precise physical properties of PBX, three dimensional mesoscopic structure of the cylindrical sample formed by 2, 4, 6-triamino-1, 3, 5-trinitrobenzene(TATB) granules under isostatic warm pressing was studied by X-ray microtomography(X-μCT). The results reveal that TATB granules are still intact after warm pressing, and typically have polyhedral morphologies. There are high density layers between neighboring granules, and the maximum contact number of which is 12. An analysis of CT images shows that the axial size distributions of the compacted granules remain unchanged, whereas a decreasing trend of the radial density and pressure along the axial direction is observed. The CT values dispersion of different slices is larger than 1.15%, but the bulk density tends to be homogeneous. By analyzing the internal force chain distribution, we found an isotropic compression characteristic of compacted TATB granules under isostatic warm compaction. The particle contact number is counted based on mesoscopic particle contact angle, from which the morphology and arrangement of compacted particles have been confirmed to be isotropic, while the local particles subjected to shear-compression loading could also be detected.

Abstract:To verify the feasibility of detecting the internal stress of polymer bonded explosive(PBX)by laser ultrasonic technology, a new and high efficiency nondestructive testing method for internal stress state of PBX simulation material based on laser ultrasonic skimming surface longitudinal wave was established. An experimental platform of on-line laser ultrasonic nondestructive testing used for PBX simulation specimen stress was built. The longitudinal wave signal of laser ultrasonic skimming surface was measured under different loading conditions. Results show that when the PBX simulation specimen is subjected to stresses above 1MPa, the velocity of sound changes obviously when the propagation direction of ultrasonic skimming surface longitudinal wave is parallel to the stress direction. The relation between the relative change quantity of sound velocity and the stress increases approximately linearly. With the increase of stress, the sound velocity of ultrasonic skimming surface longitudinal wave increases. The feasibility of detecting the internal stress state of PBX simulation material by laser ultrasonic skimming surface longitudinal wave is preliminarily verified.

Abstract:To improve the manufacturing efficiency and product consistency of exploding foil initiators, a kind of integrated ex- ploding foil energy conversion unit based on the flexible printing circuit(also called FPC or soft board)manufacturing process was designed and fabricated, and the basic performances of the integrated energy conversion unit, such as electrical explosion performance, driving flyer capability and initiating hexanitrostilbene(HNS-Ⅳ)capability were studied. In the experiment, the voltage curve at two ends of exploding foil was measured by a high-voltage probe. The current curve of discharge circuit was measured by Rogowski coil. The velocity history curve of flyer driven by electrical explosion process was measured by means of Photonic Doppler Velocimetry(PDV). Results show that the peak current of discharge circuit and burst current of bridge foil linearly increase with the increasing of voltage at two ends of capacitor, in which, the burst current increases from 2080 A to 2680 A. The burst time of bridge foil linearly decreases with the increasing of voltage at two ends of capacitor, from 232 ns to 156 ns. With charging voltage increasing, the flyer velocity increases continuously from 4056 m ·s^-1 to 4589 m ·s^-1, and standard deviation value of the velocity is between 38 and 48. The exploding foil energy conversion unit can reliably initiate HNS-Ⅳ explosive when the current peak of discharge circuit is about 2.04 kA, which is lower than that of energy conversion unit fabricated by traditional manufacturing process(2.340 kA).

Abstract:Nitropyrazole and its derivatives have high heat of formation, good thermal stability and detonation performances, which have broad application prospects in the field of energetic materials. Their research progress in recent years is briefly reviewed from the aspects of synthesis, properties and applications of nitropyrazole and its derivatives, and the development direction and trend of the research on the synthesis of nitropyrazole and its derivatives are combed. Several important directions in the future research are pointed out:considering that ones have need to explore and find new synthetic routes and optimize their technological conditions, shorten reaction steps, improve reaction efficiency, and realize high-quality, large-scale and stabilization preparation of nitropyrazole compounds, and to further explore the green environmental protection and recyclable high-efficiency rearrangement reagents, extraction agents and recrystallization media, strengthen the comprehensive research on the basic properties of MTNP and 3, 4-DNP, carry out the research on their volume shrinkage characteristics and safety properties after melting and solidification, comprehensively evaluate the feasibility of their application in fused cast explosives, and further expand their application research in high energy insensitive explosives.

Abstract:

Abstract:

Abstract: