FOX-7和RDX基含铝炸药的冲击起爆特性

为研究FOX-7和RDX基含铝炸药的冲击起爆特性,对其进行了冲击波感度试验和冲击起爆试验,结合冲击波在铝隔板中的衰减特性,确定了FOX-7和RDX基含铝炸药的临界隔板值和临界起爆压力,并通过锰铜压阻传感器记录了起爆至稳定爆轰过程压力历程的变化。结果表明,以Φ40mm×50mm的JH-14为主发装药时,FOX-7和RDX基含铝炸药临界隔板值分别为37.51和34.51mm,对应的临界起爆压力为10.91和11.94GPa;起爆压力为11.58GPa时,FOX-7炸药的到爆轰距离为25.49~30.46mm,稳定爆轰后的爆轰压力为27.68GPa,爆轰速度为8 063m/s;起爆压力为14.18GPa时,RDX基含铝炸药的到爆轰距离为17.27~23.53mm,稳定爆轰后的爆轰压力为17.16GPa,爆轰速度为6 261m/s。     

Polyvinylidene Fluoride (PVDF) Gauges for Measurement of Output Pressure of Small Ordnance Devices

Polyvinylidene Fluoride (PVDF) gauges are thin (25 μm) pressure transducers capable of measuring shock pressures up to at least 25 GPa with nanosecond time resolution for impact‐loading conditions. In this work the application of PVDF gauges for measurement of the output pressure from small ordnance devices was investigated. Gauge assembly, firing fixtures, and data acquisition and analysis are described in detail. The gauges were used to record the pressure from impact of flyers accelerated by exploding bridgewire detonators and detonation cord endtips. Consistent peak pressures with standard deviations typically <10% were obtained. The measured pressures were within 10–30% of the pressures calculated from the velocities of the flyers. The peak pressure correlated with the explosive density of endtips prepared with different explosive loading pressures. These results confirmed that PVDF gauges produced by the Bauer process yield consistent results useful for characterizing the output of small ordnance devices.     

Effect of Scale and Confinement on Gap Tests for Liquid Explosives

The factors influencing initiation of detonation in gap tests for liquid explosives are investigated experimentally. A calibrated donor charge (nitromethane) and PMMA attenuator disk arrangement are used to transmit shocks of known strength (2–10 GPa) into a test explosive of nitromethane sensitized with 5% diethylenetriamine. The test explosive is contained in capsules of different wall materials (PVC, Teflon, aluminum), and the dimensions of the charges vary from 25 mm to 100 mm in diameter. For the small‐scale charges, the presence of the confining wall of the test capsule is seen to have a pronounced effect on the detonation initiation. Certain wall materials (PVC, Teflon) exhibit a multi‐valued critical gap thickness, meaning that a weaker shock may result in initiation while a stronger shock does not. The effect of the wall materials could not be correlated with their acoustic or shock impedance, and the only way to eliminate these effects was to make the diameter of the test charge larger than the donor charge. When the size of the donor charge was increased, the critical pressure required for initiation decreased. These results could be correlated to “ideal” shock initiation experiments that use flyer plates as shock sources assuming that lateral rarefactions quench detonation initiation if they reach the central axis of the charge before the onset of detonation is complete.     

Effects of Aluminum Particle Size on the Detonation Pressure of TNT/Al

To better understand the influence of the aluminum particle size on the detonation pressure of TNT/Al, electrical conductivity experiment and detonation pressure experiment were performed in this study. Four types of TNT/Al were considered, in which the particle size of aluminum was 50 nm, 100 nm, 1.50 μm, and 9.79 μm, respectively. The combustion process of Al in TNT/Al was detected by electrical conductivity experiment, and the detonation pressures of TNT/Al were measured by using the manganin pressure sensors. According to the experimental results, the Chapman Jouguet (CJ) pressure of the explosive containing nano‐sized aluminum is higher than the explosive containing micron‐sized aluminum powder because of the combustion of nano‐sized aluminum in the detonation reaction zone. In addition, a smaller aluminum particle size in TNT/Al is associated with a slower detonation pressure attenuation. This study gives a clearer picture of how aluminum particle size contributes to detonation pressure on timescales from 0 to 0.82 μs.     

Effect of Al/O Ratio on the Detonation Performance and Underwater Explosion of HMX‐based Aluminized Explosives

The performance of detonation and underwater explosion (UNDEX) of a six‐formula HMX‐based aluminized explosive was examined by detonation and UNDEX experiments. The detonation pressures, detonation velocities, and detonation heat of HMX‐based aluminized explosive were measured. The reliability between the experimental results and those calculated by an empirical formula and the KHT code was verfied. UNDEX experiments were carried out on the propagation of a shock wave and a bubble pulse of a 1 kg cylindrical HMX‐based aluminized explosive underwater at a depth of 4.7 m. Based on the experimental results of the shock wave, the coefficients of similarity law equation for the peak pressure and attenuation time constant of shock wave were in acceptable agreement. The bubble motion during UNDEX was simulated using MSC.DYTRAN software, and the radius time curves of bubbles were determined. The effect of the aluminum/oxygen ratio on the performance of the detonation and UNDEX for an HMX‐based aluminized explosive was discussed.     

Time Resolved Pressure Measurement of the Initiation in Gap Test Experiments

Time resolved measurement of shock pressures in high explosives is possible with inexpensive composite carbon resistors. These resistors are embedded plane to the surface of a Plexiglas slab fixed at the end of the explosive. This configuration was used with gap test experiments with a 10 g donor charge. No initiation delay is measured in Seismoplast I (plastic PETN) up to a gap height of 10 mm PMMA (Plexiglas) due to the time resolution of the measuring system. From 10 mm to 22.5 mm gap height distances for detonation development up to 25 mm are found. For even greater gap heights a shock wave with decreasing amplitude occurs. The detonation development can be explained by the measured structure of the shock waves. Behind a first shock front with nearly constant pressure a second front propagates with increasing pressure which at last catches up with the first and then the pressure increases further up to the Chapman-Jouguet pressure of 160 kbar. At a gap height of 25 mm a stationary shock wave configuration with amplitudes of 20 kbar and 30 kbar was observed.     

A Simple and Rapid Evaluation of Explosive Performance – The Disc Acceleration Experiment

It is crucial in the development of a new explosive to obtain an evaluation of performance early in the process when the availability of material is limited. Evaluation requires dynamic measurements of detonation velocity, pressure, and expansion energy – typically in separate experiments that require large amounts of material, time, and expense. There is also a need for evaluation of the total available thermodynamic energy. The dynamic evaluations, in particular, have been a major hindrance to development of new explosives. The new experimental testing method to be described here requires small charges and obtains accurate measurement of all three of the detonation performance characteristics in a single test. The design, a Disc Acceleration eXperiment (DAX), provides an initial condition of steady detonation and a charge‐geometry amenable to 2D hydrodynamic simulations. The velocity history of a metal disk attached to the end of the explosive charge is measured with Photonic Doppler Velocimetry (PDV). This disc velocity data is analyzed to give both CJ pressure and expansion energy. The detonation velocity is obtained with probes along the charge length. The experiments and subsequent analyses are concentrated on LX‐16, a known PETN based explosive, for the purpose of establishing the accuracy of the method and to provide a standard for comparison with other explosives. We present details of the experimental design and also detonation velocity and PDV results from a number of experiments. The total available internal energy for the explosive was obtained from published detonation calorimetry measurements by Ornellas [1], and from thermodynamic equilibrium calculations. An equation‐of‐state (EOS) for LX‐16 was derived from hydrodynamic simulations of thin plate‐push velocity‐time data. We will show a successful comparison with a previously published Jones‐Wilkins‐Lee (JWL) EOS for PETN by Green and Lee [2–4].     

Predicting Detonation Performance of CHNOFCl and Aluminized Explosives

A new “hand‐calculated” method is introduced for prediction of detonation pressure of explosive and mixture of explosives with general formula CHNOFClAl. Suitable decomposition paths are used to estimate heat of detonation and detonation pressure. These decomposition paths are based on the distribution of oxygen atoms between carbon and hydrogen atoms as well as the degree of oxidation of aluminum. For CHNOFCl explosives, it is shown that the predicted detonation pressures with the new method are more reliable with respect to one of the best available empirical methods for loading densities greater than or equal 0.8 g cm⁻³. Since aluminized explosives have non‐ideal behavior, the new method does not require using full or partial oxidation of aluminum, which is usually required by a computer code. The predicted results of the new model also provide more reliable results than outputs of complex computer code with the BKWS equation of state.     

The Critical Energy of Direct Initiation in Liquid Fuel‐Air and Liquid Fuel‐RDX Powder‐Air Mixtures in a Vertical Detonation Tube

Multiphase cloud detonation is an important but complex process, which has not been fully understood yet. Direct experimental data about the critical initiation energy (CIE) and pressure/velocity revolution of high explosive powder‐based multiphase cloud detonation is not available in the literature. In this paper, propylene oxide (PO), petroleum ether (PE), isopropyl nitrate (IPN), and a mixture of PE/IPN were individually dispersed to form a cloud in a 200 mm×5400 mm vertical detonation tube. Subsequently, this cloud was directly ignited by a high explosive. The critical initiation energy of various mist/air mixtures was measured by the up and down method. Meanwhile, the pressure history was recorded by six sensors along the detonation tube. RDX powder was added to the system and sprayed simultaneously with the liquid fuel to form a three‐phase gas‐liquid‐solid explosive cloud. The detonation pressure and velocity of all three‐phase cases significantly increased while the corresponding critical initiation energy decreased compared to the liquid‐air analogs. The CIE data were found to have a “U”‐shaped curve relationship to the fuel‐air ratio in two‐ and three‐phase systems, the minimum is always on the fuel‐rich side.     

聚黑-14C的传爆装置冲击起爆实验及数值模拟

基于聚黑(JH)-14C传爆药的小隔板试验方法及结果,建立了小隔板试验有限元模型并进行了模拟计算,确定了密度为1.65g/cm~3时JH-14C的Lee-Tarver参数。以RDX-8701为主发药柱,对实际装药条件下JH-14C的传爆装置进行了冲击起爆实验,得到了钢鉴定块的凹坑深度。根据小隔板试验确定的JH-14C传爆药Lee-Tarver参数,建立了全尺寸的冲击起爆实验有限元模型,并对比分析了模拟结果与实验结果,通过改变导爆药柱顶部的钢隔板厚度,确定了JH-14C的传爆装置发生冲击起爆的临界钢隔板厚度。结果表明,冲击起爆实验中钢鉴定块的凹坑深度约为2.1mm,模拟计算结果与实验结果基本吻合;JH-14C的传爆装置冲击起爆的临界钢隔板厚度在4~5mm。     

Evaluation of the James Initiation Criterion in the 21 mm and 50 mm PMMA Gap Test

The gap test has been used for several decades as a measure for the shock sensitivity of high explosives. Normally the axial pressure in the gap is used as the necessary initiation pressure of a high explosive for a shock to detonation transition. But it has been shown in the past that the pressure in the gap is not a suitable measure for shock sensitivity and other criteria like the James criterion in terms of critical energy fluence and critical specific kinetic energy should be used. To evaluate the James criterion in the 21 mm and 50 mm polymethylmethacrylate (PMMA) gap test numerical simulations are conducted. To validate the simulations a 21 mm water gap test is simulated and compared to experimental results, where the axial pressure calibration can be reproduced with high accuracy. With the results from the simulation of the 21 mm and 50 mm gap test it is shown that at the same maximum axial pressure the energy fluence is higher in the 50 mm gap test. This explains to some extent the higher initiation pressures observed in smaller gap tests. The James criterion is derived and it is shown that the two gap tests probe very different regions in the energy fluence vs. specific kinetic energy plane. The results can be used as a calibration for the gap tests and are intended to improve the comparability of gap test results among each other and with different initiation experiments like flyer or heavy fragment impact testing.     

Shock Initiation of the CL‐20‐Based Explosive C‐1 Measured with Embedded Electromagnetic Particle Velocity Gauges

Hexanitrohexaazaisowurtzitane (CL‐20) is a high‐energy material with high shock sensitivity. The evolution of shock into the detonation of CL‐20 deserves academic attention and research. An embedded electromagnetic particle velocity gauge was used to study the shock initiation of detonation in a pressed solid explosive formulation, C‐1, containing 94 wt‐% epsilon phase CL‐20 and 6 wt‐% fluororubber (FPM). In conventional experiments, the magnetic field was generated using a pair of electromagnets with a complex structure and operation. A new device was designed to solve complex problems. This device comprised NdFeB magnets, pole shoes and magnetic yokes; using this technique, a uniform magnetic field could be created. A series of shock initiation experiments on high‐explosive C‐1 was performed, and the explosive samples were initiated at different intensity input shocks by an explosive driven flyer plate. In situ magnetic particle velocity gauges were utilized to detail the growth from an input shock to detonation, and the attenuation of particle velocity in unreacted C‐1 was also obtained in low‐intensity shock initiation experiments. Hugoniot data for C‐1 in the form of shock velocity D vs. particle velocity Up were obtained. A simulation model for shock initiation of C‐1 was established, and the particle velocity data from several experiments were used to determine the parameters required for the unreacted equation of state and ignition and growth reactive flow model for C‐1. These coefficients were then applied in the calculation of the initial shock pressure−distance to detonation relationship (Pop‐plot) for the explosive. Based on the results of experiments and simulations, the shock sensitivity characteristic of C‐1 was described.     

Initiation of a Porous Explosive by Overdriven Gas Detonation Products

This paper reports results of experiments on initiation and development of detonation in cylindrical charges of a porous explosive by overdriven detonation products of a gas mixture C₂H₂ + 2.5 O₂. Explosive charges with a bulk density of about 1 g/cm³ in fragile shells were studied. For PETN and RDX charges, the critical initial pressure of the gas mixture at which detonation initiation still occurs is determined and the pressures acting immediately on the charge are given. For PETN, critical initial pressures and initiation delays were measured for the first time for charges with particles of various diameters. The obtained dependence characterizes the following abnormal property of porous charges: there is an optimum particle size for which the explosive sensitivity is maximal. Streak records of selfluminosity for typical initiation modes are given. Mass velocity profiles in initiation waves at different depth of the charge are obtained using an electromagnetic procedure.     

The Role of Aluminum in the Detonation and Post‐Detonation Expansion of Selected Cast HMX‐Based Explosives

In order to improve understanding of how aluminum contributes in non‐ideal explosive mixtures, cast‐cured formulations have been analyzed in a series of cylinder tests and plate‐pushing experiments. This study describes the contribution of 15 % aluminum (median size of 3.2 μm) vs. lithium fluoride (an inert substitute for aluminum; <5 μm) in cast‐cured HMX formulations in different temporal regimes. Small cylinder tests were performed to analyze the detonation and wall velocities (1–20 μs) for these formulations. Near‐field blast effects of 58 mm diameter spherical charges were measured at 152 mm and 254 mm using steel plate acceleration. Pressure measurements at 1.52 m gave information about free‐field pressure at several milliseconds. While the observed detonation velocities for all formulations were within uncertainty, significantly higher cylinder wall velocities, plate velocities, and pressures were observed for the aluminum formulations at ≥2 μs. Additionally, hydrocode calculations were performed to determine how non‐ideal behavior affected the plate test results. Collectively, this work gives a clearer picture of how aluminum contributes to detonation on timescales from 1 μs to about 2 ms, and how the post‐detonation energy release contributes to wall velocities and blast effects. The experiments indicate that significant aluminum reactions occur after the CJ plane, and continue to contribute to expansion at late times.     

Shock Compression and Initiation of LX-10

LX-10 is a high energy density solid explosive consisting of 94.5% octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and 5.5% Viton A Binder pressed to 1.865 g/cm³ (98.4% of theoretical maximum density). In this paper the shock compression and initiation of chemical reaction in LX-10 by sustained shock pressures of 0.4 to 3 GPa are studied experimentally using embedded pressure and particle velocity gauges. The resulting pressure and particle velocity histories are evaluated theoretically using the ignition and growth reactive flow computer model of shock initiation and detonation. Manganin resistance and polyvinylidene fluoride (PVF₂) ferroelectric pressure gauges are both employed in the low pressure (0.4 – 0.7 GPa) shock compression experiments. Multiple manganin pressure and multiple electromagnetic foil particle velocity gauges measure the growth of reaction at various positions in LX-10 shocked to 1 – 3 GPa. The reactive flow modeling results imply that less than one percent of the LX-10 shocked to 0.4 – 0.7 GPa reacts in fifteen microseconds. For the higher pressure experiments, the ignition and growth model accurately calculates the pressure and/or particle velocity buildup in LX-10 as the reaction grows toward detonation. The LX-10 calculations are compared to those for the well-calibrated explosive PBX-9404, which contains 94% HMX and a reactive binder. Since it has the inert binder Viton A and better mechanical properties than PBX-9404, LX-10 is demonstrated to be significantly less reactive than PBX-9404 at these shock pressures. Therefore LX-10 is safer than PBX-9404 in many hazard and vulnerability scenarios to which solid explosives may be subjected.     

Effect of initial air pressure on the detonation activity of an explosive aerosuspension

The effect of air pressure (0.01–0.3 MPa) on the detonatability of an aerosuspension of secondary explosive particles at a low mean volume density of the explosive (0.14–1.28 mg/cm³) is experimentally studied. The structure and basic parameters of detonation depending on the explosive density and initial gas pressure are determined, and the mechanism of low-velocity detonation propagation in explosive aerosuspensions is revealed. The lower concentration limits of detonation at different initial gas pressures are found.     

Performance Properties of Commercial Explosives

The aquarium test is a proven means of obtaining nonidial performance property data for commercial blasting agents. Optical data on the detonation velocity, shock wave in water, and expansion rate of the pipe enclosing the detonation products (in combination with the equilibrium thermodynamic chemistry code BKW) give the C-J state and degree of chemical reaction at the detonation front, as well as information on additional chemical reaction that occurs as the detonation products expand. Specific explosive systems that are studied are ammonium nitrate-fuel oil mixture (ANFO), aluminized ANFO, flaked trinitrotoluene (TNT), and several other commercial products in 10-cm-diam and 20-cm-diam pipes of Plexiglas and clay. Experimental shock pressure data are obtained with lithium niobate transducers placed in the water surrounding the explosive charge. These data show that the addition of ∼ 100-μm aluminum particles to ANFO significantly increases the initial peak shock pressure delivered to the surrounding medium. Peak shock pressures in the water, calculated from the shock-wave orientation, are also useful in comparing performance properties of various commercial explosives.     

Particle Size Modification of Thermally Stable Secondary Explosives for IM Applications

As well as improving the survivability of weapons and platforms, insensitive munitions (IM) reduce both casualty rates and mission losses. Their use also leads to improved safety during storage and transportation. For a munition to fulfil IM criteria, each of its energetic sub‐sections must be IM compliant. The initiator and explosive train are the most critical of these sub‐systems as their safety and reliability are of paramount importance if the weapon is to be suitable for service use, yet they are generally the most difficult part of a weapon to protect from inadvertent initiation. As part of an ongoing study into initiation methods suitable for use in IM systems, an investigation into the behaviour of energetic materials when impacted by laser‐driven flyers was performed. Laser‐based detonators exhibit increased safety characteristics over conventional initiation methods as they can be based on insensitive secondary explosives rather than sensitive primary explosives. Also, they are less susceptible to accidental initiation due to an external hazard threat. Single pulses from a high‐powered Q‐switched Nd:YAG laser were used to launch flyers from substrate‐backed aluminium films to velocities up to 6 km s⁻¹ across a short stand‐off to impact explosive targets. Several novel energetic materials have been selected for investigation as potential candidates for inclusion within flyer‐based initiation systems and explosive train applications. The materials are of interest due to their increased thermal stability and power output over conventional explosives currently in service. Attempts were made to increase the flyer responsiveness of the materials by tuning their particle size using ultrasound. The effect of particle size on the initiation threshold energy was investigated for three materials.     

Optical Measurement of Peak Air Shock Pressures Following Explosions

High speed video and streak camera imaging are used to measure peak pressures for explosions of spherical charges of the high explosive C‐4 (92 % trimethylenetrinitramine, C₃H₆N₆O₆). The technique measures the velocity of the air shock produced by the detonation of the explosive charges, converts this velocity to a Mach number, and uses the Mach number to determine a peak shock pressure. Peak pressure measurements are reported from a few millimeters to approximately one meter from the charge surface. Optical peak pressure measurements are compared to peak pressures measured using piezoelectric pressure transducers, and to peak pressure measurements estimated using the blast computer code CONWEP. A discussion of accuracy of peak pressures determined optically is provided.     

Experiments and Modeling for Biocidal Effects of Explosives

This paper reports an experimental and modelling study of the biocidal effect of an energetic mixture which is detonated in a closed chamber containing an initial spore distribution. The resulting spore neutralization efficiency is recorded as a function of measured detonation and combustion performance. We also report the results of a range of numerical modelling studies carried out to aid the interpretation of these experiments and to guide future developments. We find that the current energetic mixture (aluminum powder which is shock dispersed by detonation of a central high explosive core) gives variable combustion efficiency. The Al powder ignites on impact with the walls. In the modelling we match the recorded quasi‐static pressures in each experiment and compare predicted spore neutralization with measured values. Using a critical spore temperature for neutralization of 670 K gives a good match to the experiments. We report how neutralization efficiency varies with changes to this temperature. The coupled experimental and modelling approach allows us to suggest requirements for future biocidal energetic materials.