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1.
    
Detonating solid plastic bonded explosives (PBX) formulated with the insensitive molecule triaminotrinitrobenzene (TATB) exhibit measurable reaction zone lengths, curved shock fronts, and regions of failing chemical reaction at abrupt changes in the charge geometry. A recent set of “hockey puck” experiments measured the breakout times of diverging detonation waves at ambient temperature LX‐17 (92.5% TATB plus 7.5% Kel‐F binder) and the breakout times at the lower surfaces of 15 mm thick LX‐17 discs placed below the detonator‐booster plane. The LX‐17 detonation waves in these discs grow outward from the initial wave leaving regions of unreacted or partially reacted TATB in the corners of these charges. This new experimental data is accurately simulated for the first time using the Ignition and Growth reactive flow model for LX‐17, which is normalized to detonation reaction zone, failure diameter and diverging detonation data. A pressure‐cubed dependence for the main growth of reaction rate yields excellent agreement with experiment, while a pressure‐squared rate diverges too quickly and a pressure‐quadrupled rate diverges too slowly into the LX‐17 below the booster equatorial plane.  相似文献   

2.
    
After reconsidering the definition and characteristics of the Gurney energy, we explain some points related to the evaluation and practical use of this quantity. We correct a recently published relationship between the detonation velocity of an explosive and its Gurney energy at infinite expansion. Then, in the framework of cylinder tests, we indicate that the Gurney energy gives only a rough evaluation of experimental results; it can, however, be reasonably used to compare the ability of explosives to accelerate metals. Besides, the value γ=3 classically evoked for the polytropic gamma of the detonation products generally leads to significant errors in the evaluation of the Gurney energy at infinite expansion.  相似文献   

3.
    
The detonation velocity and performance were determined for four mixtures of triacetone triperoxide (3,3,6,6,9,9‐hexamethyl‐1,2,4,5,7,8‐hexoxonane, TATP), ammonium nitrate (AN) and water (W) by cylinder expansion tests. The composition of these mixtures varied in the following ranges: 21–31% TATP, 37–54% AN and 19–32% W. The obtained results were compared with those of powdery 2,4,6‐trinitrotoluene (TNT), AN‐fuel oil explosive (ANFO) and emulsion explosive. It was found that the tested TATP/AN/W mixtures represent typical non‐ideal explosives with relatively low critical diameter and with high sensitivity to initiation despite the high content of water due to the presence of the primary explosive (TATP). The detonation velocity is comparable to that of powdery TNT (at similar density). However, the acceleration ability is significantly lower than that of powdery TNT.  相似文献   

4.
    
We have applied thermal insults on LX‐04 at 185 °C and found that the material expanded significantly, resulting in a bulk density reduction of 12%. Subsequent detonation experiments (three cylinder tests) were conducted on the thermally damaged LX‐04 samples and pristine low‐density LX‐04 samples and the results showed that the fractions reacted were close to 1.0. The thermally damaged LX‐04 and pristine low‐density LX‐04 showed detonation velocities of 7.7–7.8 mm μs−1, significantly lower than that (8.5 mm μs−1) of pristine high‐density LX‐04. Detonation energy densities for the damaged LX‐04, low‐density pristine LX‐04, and hot cylinder shot of LX‐04 were 6.48, 6.62, and 6.58 kJ cm−3, respectively, lower than the detonation energy density of 8.11 kJ cm−3 for the high density pristine LX‐04. The break‐out curves for the detonation fronts showed that the damaged LX‐04 had longer edge lags than the high density pristine LX‐04, indicating that the damaged explosive is less ideal.  相似文献   

5.
    
A screening test was developed at Los Alamos National Laboratory [1] that can be used to decide if a newly synthesized/formulated explosive might warrant further development. The test consists of firing a rate‐stick composed of 12.7 mm diameter by 12.7 mm high pellets of different densities ordered from lowest to highest, initiated by a detonator at the low‐density end of the stick. This poly‐rho test yields detonation velocities over a range of densities using only the small amount of the explosive typically generated by the synthetic organic chemist at an early stage of the scale‐up process. The amount of material required is far less than that required for the typical rate‐stick series. This paper presents results on poly‐rho tests that were conducted on three explosives commonly used at Los Alamos National Laboratory, namely PBX 9501, PBX 9502 and PETN. The results are compared with empirical detonation‐theory predictions and existing explosive experimental data, with good agreement in all cases.  相似文献   

6.
    
In order to study the detonation velocity deficits of wound mild detonation cords, a physical model and a theoretical mathematical equation for detonation velocity deficits of wound mild detonation cords were established based on the detonation wave’s corner effects and delay time phenomenon by using non‐dimensional analysis method. Besides, a semi‐empirical formula for detonation velocity deficit of wound mild detonation cords in the same charge size was obtained through experiments and curve fitting. Both the theoretical mathematical equation and the semi‐empirical formula show that the detonation velocity deficit of wound mild detonation cords and the reciprocal of the curvature radius have an exponential relationship.  相似文献   

7.
    
A systematic overview of melt cast explosives is given. The research on melt cast explosives over several decades can be divided into three broad areas: (i) aromatic compounds with C CH3, N CH3, OCH3 C NO2, N NO2 and ONO2 groups, (ii) improved synthesis of compounds, which are currently used in formulations or which have shown promise for such use and (iii) the preparation of melt cast formulations with various compositions. Exudation, high volume change from liquid to solid, super cooling, irreversible growth, fragility and unpredictable sensitivity are the disadvantages of existing melt cast formulations.  相似文献   

8.
    
Reactive flow cylinder code runs on six explosives were made with rate constants varying from 0.03 to 70 μs−1. Six unconfined/steel sets of original ANFO and dynamite data are presented. A means of comparing confinement effects both at constant radius and at constant detonation velocity is presented. Calculations show two qualitatively different modes of behavior. For Us/Co≥1.2, where Us is the detonation velocity and Co the zero‐pressure sound speed in steel, we find a sharp shock wave in the metal. The shock passes through the steel and the outer wall has a velocity jump‐off. For Us/Co≤1.04, we find a pressure gradient that moves at the detonation velocity. A precursor pulse drives in the explosive ahead of the detonation front. The outer wall begins to move outward at the same time the shock arrives in the explosive, and the outer wall slowly and continuously increases in velocity. The Us/Co≥1.2 cylinders saturate in detonation velocity for thick walls but the Us/Co<<1.04 case does not. The unconfined cylinder shows an edge lag in the front that approximately equals the reaction zone length, but the highly confined detonation front is straight and contains no reaction zone information. The wall thickness divided by the reaction zone length yields a dimensionless wall thickness, which allows comparison of explosives with different detonation rates. Even so, a rate effect is found in the detonation velocities, which amounts to the inverse 0.15–0.5 power.  相似文献   

9.
    
A simplified method is shown, based on a semi‐empirical procedure, to estimate the detonation velocities of CHNO explosives at various loading densities. It is assumed that the product composition consists almost of CO, CO2, H2O and N2 for oxygen‐rich explosives. In addition solid carbon and H2 are also counted for an oxygen‐lean explosive. The approximate detonation temperature, as a second needed parameter, can be calculated from the total heat capacity of the detonation products and the heat of formation of the explosive by PM3 procedure. The detonation velocities of some well‐known CHNO explosives, calculated by the simple procedure, fit well with measured detonation velocities and the results from the well‐established BKW‐EOS computer code.  相似文献   

10.
    
The DFT‐B3LYP method, with basis set 6–31G*, is employed to optimize molecular geometries and electronic structures of eighteen nitramines. The averaged molar volume (V) and theoretical density (ρ) are estimated using the Monte‐Carlo method based on 0.001 electrons/bohr3 density space. Subsequently, the detonation velocity (D) and pressure (P) of the explosives are estimated by using the Kamlet‐Jacobs equation on the basis of the theoretical density and heat of formation (ΔfH), which is calculated using the PM3 method. The reliability of this theoretical method and results are tested by comparing the theoretical values of ρ and D with the experimental or referenced values. The theoretical values of D and P are compared with the experimental values of electric spark sensitivity (EES). It is found that for the compounds with metylenenitramine units ( CH2N(NO2) ) in their molecules (such as ORDX, AcAn and HMX) or with the better symmetrical cyclic nitramines but excluding metylenenitramine units (such as DNDC and TNAD), there is a excellent linear relationship between the square of detonation velocity (D2) or the logarithm of detonation pressure (lg P) and electric spark sensitivity (EES). This suggests that in the molecular design of energetic materials, such a theoretical approach can be used to predict their EES values, which have been proven to be difficult to predict quantitatively or to synthesize.  相似文献   

11.
    
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12.
    
The enthalpies of combustion (ΔcombH) of dinitrobiuret (DNB) and diaminotetrazolium nitrate (HDAT‐NO3) were determined experimentally using oxygen bomb calorimetry: ΔcombH(DNB)=5195±200 kJ kg−1, ΔcombH(HDAT‐NO3)=7900±300 kJ kg−1. The standard enthalpies of formation (ΔfH°) of DNB and HDAT‐NO3 were obtained on the basis of quantum chemical computations at the electron‐correlated ab initio MP2 (second order Møller‐Plesset perturbation theory) level of theory using a correlation consistent double‐zeta basis set (cc‐pVTZ): ΔfH°(DNB)=−353 kJ mol−1, −1 829 kJ kg−1; ΔfH°(HDAT‐NO3)=+254 kJ mol−1, +1 558 kJ kg−1. The detonation velocities (D) and detonation pressures (P) of DNB and HDAT‐NO3 were calculated using the empirical equations by Kamlet and Jacobs: D(DNB)=8.66 mm μs−1, P(DNB)=33.9 GPa, D(HDAT‐NO3)=8.77 mm μs−1, P(HDAT‐NO3)=33.3 GPa.  相似文献   

13.
    
Prilled/granulated ammonium nitrate is commonly used as a fertilizer and a basic ingredient of industrial explosives, especially of ANFO. One of the most important factors that affect the explosive properties of ANFO is the porosity of the prills/granules. This paper describes an attempt to manufacture ammonium nitrate prills of determined porosity in order to investigate its influence on the ANFO detonation velocity. A method of manufacturing porous ammonium nitrate prills with a high‐level of oil absorption (up to 20% by volume) was developed. The relations between porosity and granulometric distribution of ammonium nitrate prills versus the detonation velocity of ANFO were examined. It has been proved that the detonation velocity of ANFO increases significantly with higher porosity and smaller size of ammonium nitrate prills/granules. The influence of ANFO oxygen balance (researched by changing the content of fuel oil in the mixture) on detonation velocity has been determined for two kinds of ammonium nitrate prills–one with a low and another one with a high level of porosity.  相似文献   

14.
    
Various measurements under ambient conditions are presented for LX‐17. The size (diameter) effect has been measured with copper and Lucite confinement, where the failure radii are 4.0 and 6.5 mm, respectively. The air well corner‐turning has been measured with an LX‐07 booster, and the dead‐zone results are comparable to the previous TATB‐boosted work. Four double cylinders have been fired, and dead zones appear in all cases. The steel‐backed samples are faster than the Lucite‐backed samples by 0.6 μs. Bare LX‐07 and LX‐17 charges of 12.7 mm radius were fired with air gaps. Long acceptor regions were used to truly determine if detonation occurred or not. The LX‐07 booster crossed a 10 mm gap with a slight time delay. Steady‐state LX‐17 crossed a 3.5 mm gap but failed to cross a 4.0 mm gap. LX‐17 charge with a 12.7 mm radius run after the booster crossed a 1.5 mm gap but failed to cross a 2.5 mm gap. Timing delays were measured where the detonation crossed the gaps. The Tarantula model is introduced as embedded in reactive flow JWL++and Linked Cheetah V4, mostly at 4 zones mm−1. Tarantula has four pressure regions: off, initiation, failure, and detonation. The physical basis of the input parameters is considered.  相似文献   

15.
    
Pin and X‐ray corner turning data have been taken on ambient LX‐17 and PBX 9052, and the results are listed in tables as an aid to future modeling. The results have been modeled at 4 zones/mm with a reactive flow approach that varies the burn rate as a function of pressure. A single rate format is used to simulate failure and detonation in different pressure regimes. A pressure cut‐off must also be reached to initiate the burn. Corner turning and failure are modeled using an intermediate pressure rate region, and detonation occurs at high pressure. The TATB booster is also modeled using reactive flow, and X‐ray tomography is used to partition the ram‐pressed hemisphere into five different density regions. The model reasonably fits the bare corner turning experiment but predicts a smaller dead zone with steel confinement, in contradiction with experiment. The same model also calculates the confined and unconfined cylinder detonation velocities and predicts the failure of the unconfined cylinder at 3.75 mm radius. The PBX 9502 shows a smaller dead zone than LX‐17. An old experiment that showed a large apparent dead zone in Composition B was repeated with X‐ray transmission and no dead zone was seen. This confirms the idea that a variable burn rate is the key to modeling. The model also produces initiation delays, which are shorter than those found in time‐to‐detonation.  相似文献   

16.
    
We have performed a series of highly‐instrumented experiments examining corner‐turning of detonation. A TATB booster is inset 15 mm into LX‐17 (92.5% TATB, 7.5% kel‐F) so that the detonation must turn a right angle around an air well. An optical pin located at the edge of the TATB gives the start time of the corner‐turn. The breakout time on the side and back edges is measured with streak cameras. Three high‐resolution X‐ray images were taken on each experiment to examine the details of the detonation. We have concluded that the detonation cannot turn the corner and subsequently fails, but the shock wave continues to propagate in the unreacted explosive, leaving behind a dead zone. The detonation front farther out from the corner slowly turns and eventually reaches the air well edge 180° from its original direction. The dead zone is stable and persists 7.7 μs after the corner‐turn, although it has drifted into the original air well area. Our regular reactive flow computer models sometimes show temporary failure but they recover quickly and are unable to model the dead zones. We present a failure model that cuts off the reaction rate below certain detonation velocities and reproduces the qualitative features of the corner‐turning failure.  相似文献   

17.
    
It has been hypothesized that four parameters are solely responsible for a material's performance in a flammability scenario. This excludes effects of material physical integrity, i.e. melting, delamination, etc. They are (1) the critical heat flux below which piloted ignition cannot occur (CHF), (2) the ratio of heat of combustion to heat of gasification (HRP), (3) the thermal response parameter related to the thermal inertia and the ignition temperature (TRP), and (4) the available energy per unit area (AEP). The fire scenario controls the process by its initial heat flux and region of ignition. The hypothesis is applied to 54 tests of the ISO Room Corner Test to assess its validity. It is shown that these four parameters give good correlations in predicting the time to flashover and whether it occurs. In principle, different correlations could be developed for other scenarios of tests and fire configurations. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

18.
    
Density functional theory (DFT) calculations were performed for a series of polynitrobenzene derivatives. Some nitrobenzenes with amino groups attached were also investigated as a benchmark or as a precursor. Heats of formation (HOF) were evaluated. The isodesmic reactions used for the prediction of HOFs are of permutation type in terms of the substituents. The HOFs increase non‐additively with increasing number of nitro groups. The attachment of the amino groups to polynitrobenzenes dramatically decreases the HOF. The HOF of hexanitrobenzene (HNB) is 344.05 kJ mol−1 at the B3LYP/6‐311+G** level. This value is much larger than that of the widely used 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB), which engenders HNB a large chemical energy of detonation. The strengths of the group interactions were analyzed according to the disproportionation energy. The nearest‐neighbor interactions in polynitrobenzenes are in the range of 27.20–55.90 kJ mol−1. The energy barrier for the internal rotation of nitro group in nitrobenzene is 24.6 kJ mol−1. However, the energy barrier for the internal rotation of 2‐position nitro group of 1,2,3‐trinitrobenzene is as large as 216.3 kJ mol−1. The chemical energies of detonation for polynitrobenzenes with three or more nitro groups are over 6000 J g−1. Pentanitroaniline and HNB have good performances in terms of detonation velocity and pressure.  相似文献   

19.
    
A new detonation model that can simulate both high and low velocity detonations is established using the least action principle. The least action principle is valid for mechanics and thermodynamics associated with a detonation process. Therefore, the least action principle is valid in detonation science. In this model, thermodynamic equilibrium state is taken as the known final point of the detonation process. Thermodynamic potentials are analogous to mechanical ones, and the Lagrangian function in the detonation process is L=T−V. Under certain assumptions, the variation calculus of the Lagrangian function gives two solutions: the first one is a constant temperature solution, and the second one is the solution of an ordinary differential equation. A special solution of the ordinary differential equation is given.  相似文献   

20.
    
A modified Ignition & Growth model is used to calculate the detonation propagation and corner-turning of LX-17, based on the augmented model. The calculation results showed that the edges of dead zones are significantly smoothed, which is more physically realistic, as predicted by models such as CREST and WSD. In this work, a fifth-order WENO-JS scheme and a third-order Runge-Kutta method are used for space discretization and time integration respectively. Level set method is used for interface tracking, and RGFM (Real Ghost Fluid Method) is used for interface treatment.  相似文献   

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