Detonation Parameters Research Articles

Characterization and response of three TNT equivalent materials in subsurface explosions

AbstractEnergetic compositions utilized for inducing seismic responses are often referred to in terms of their TNT equivalent, a metric which is often misused because observations of interest are not often understood with respect to explosive characteristics. In this investigation, we characterize three energetic compositions used to elicit seismic responses in a highly instrumented testbed to further our understanding of subsurface TNT equivalence. Three different energetic sources are prepared and studied for their fidelity to thermochemically predicted detonation behavior. We present effects of subsurface detonation on subsurface rock and seismic emission as a function of energetic source material within the testbed. Field experiments were conducted using a single thermochemical yield of 5 kg using diverse sources consisting of nitromethane, ammonal, and PBXN‐5 (an HMX based plastic bonded explosive) mixtures at the Energetic Materials Research and Testing Center in Socorro, New Mexico. Relative performance of energy density‐related detonation parameters, such as detonation velocity and pressure, affect the observed response in the subsurface. Most notable, equal thermochemical yields described in terms of TNT equivalence do not correlate to equal thermochemical effects in the subsurface.

Experimental and Numerical Study of Pulse Detonation Engine with Ethylene as a Fuel

This paper presents an insight on the study of transient, compressible, intermittent pulsed detonation engine with one-step overall reaction model to reduce the computational complexity in detonation simulations. Investigations are done on flow field conditions developing inside the tube with the usage of irreversible one-step chemical reactions for detonations. In the present simulations one and two-dimensional axisymmetric tubes are considered for the investigation. Studies are also performed with different grid sizes which influence the prediction of Von-Neumann spike, CJ Pressure and detonation velocity. Numerical studies are conducted using 66mm diameter tube and compared with the literature values. The simulation result from the single-step reaction model agrees well with the previous published literature of multi-step reaction models. The present studies shows that one-step overall reaction model is sufficient to predict the flow properties with reasonable accuracy. Experiments are conducted in a 25mm dia. tube with Ethylene/Air mixtures. The reactants are premixed and injected into the detonation tube using solenoid valves. The equivalence ratio of the fuel/oxidizer mixture and the length of the detonation tube are varied to understand their effects on detonation parameters. Finally the results from the present numerical study are compared and validated using NASA CEA and experiments.

Preparation of Primary Explosive by Self-assembly of Combustible and Oxidizing Agents under Acid.

In order to further explore the effect of ligands on the performance of primary explosives and gain a deeper understanding of the coordination mechanism, we designed furan-2-carbohydrazide (FRCA), a ligand, by using oxygen-containing heterocycles and carbohydrazide. Then, FRCA and Cu(ClO4)2 were used to synthesize coordination compounds [Cu(FRCA)2(H2O)(ClO4)2]·CH3OH (ECCs-1·CH3OH) and Cu(FRCA)2(H2O)(ClO4)2 (ECCs-1). The structure of the ECCs-1 was confirmed by single-crystal X-ray diffraction, IR and EA characterization. Further experiments on ECCs-1 show that ECCs-1 has good thermal stability, but is sensitive to mechanical stimuli (impact sensitivity = IS = 8 J, friction sensitivity = FS = 20 N). The predicted value of the detonation parameter is DEXPLO5 = 6.6 km s-1, PEXPLO5 = 18.8 GPa, but the ignition test, laser test, and lead plate detonation experiment show that ECCs-1 has excellent detonation performance, which is very worthy of attention.

Molecular dynamics simulation of CL20/DNDAP cocrystal-based PBXs.

CL-20/DNDAP cocrystal is a promising new type of explosive with exceptional energy density and detonation parameters. However, compared to TATB, FOX-7 and other insensitive explosives, it still has higher sensitivity. In order to decrease the sensitivity of CL20/DNDAP cocrystal explosive, in this article, a CL20/DNDAP cocrystal model was established, and six different types of polymers, including butadiene rubber (BR), ethylene-vinyl acetate copolymer (EVA), polyethylene glycol (PEG), hydroxyl-terminated polybutadiene (HTPB), fluoropolymer (F2603), and polyvinylidene difluoride (PVDF), were added to the three cleaved surfaces of (1 0 0), (0 1 0) and (0 0 1) to obtain polymer-bonded explosives (PBXs). Predict the effects of different polymers on the stability, trigger bond length, mechanical properties, and detonation performance of PBXs. Among the six PBX models, CL-20/DNDAP/PEG model exhibited the highest binding energy and the lowest trigger bond length, indicating that CL-20/DNDAP/PEG model had the best stability, compatibility, and the least sensitivity. Furthermore, although the CL-20/DNDAP/F2603 model demonstrated superior detonation capabilities, it should be noted that this model displayed low levels of compatibility. Overall, CL-20/DNDAP/PEG model exhibited the superior comprehensive properties, thereby demonstrating that PEG is a more suitable binder option for PBXs based on the CL20/DNDAP cocrystal. The properties of CL-20/DNDAP cocrystal-based PBXs were predicted by molecular dynamics (MD) method under Materials Studio software. The MD simulation time step was set at 1fs and the total MD simulation time was 2ns. The Isothermal-isobaric (NPT) ensemble was used for the 2ns of MD simulation. The COMPASS force field was used, and the temperature was set at 295K.

Incorporating of BCHMX in traditional plastic explosives

cis-1,3,4,6-tetranitro-octahydroimidazo-[4,5-d]imidazole (BCHMX) was investigated as an energetic filler with three different plastic explosives based on three matrices: C4 matrix, semtex10 matrix and EPX matrix. The original plastic explosives, composition C4 including RDX (1,3,5-trinitro-1,3,5-triazinane), Semtex 10 explosive based on PETN (pentaerythritoltetranitrate) and plastic RDX-silicone were included for comparison. Sensitivity and performance parameters were studied. Differential thermal analysis (DTA) was investigated to determine the thermal behavior. The sensitivities to friction and impact were evaluated and the explosive characteristics were determined by measuring the detonation velocity and determining the performance by the ballistic mortar test. The detonation parameters were also calculated for all samples using EXPLO5 code. By comparing the results obtained experimentally or by calculation, it is clear that the application of BCHMX in the used plastic matrices increases the performance and detonation characteristics in comparison with the original plastic explosives. Regarding to the results of sensitivity, thermal stability and performance tests, replacing PETN explosive by BCHMX in semtex matrices seems to form promising plastic explosive and needs further studies. On the other side, the performance of BCHMX-C4 is higher than that of composition C4.

Theoretical study on structure and properties of borate ester energetic compounds

The potential advantages of energetic boron esters in the application of energetic materials were analyzed. Based on the synthesis feasibility analysis, 10 kinds of tetrazolium energetic boron esters were designed. The geometric structure, density, enthalpy of formation and impact sensitivity of 10 energetic boron esters were calculated by using density functional theory. The detonation parameters were calculated by using Explo5 program. The results show that the density of 10 compounds is between 1.74 ~ 2.18g/cm3, the detonation velocity distribution range is 7675.92 ~ 9209.45km/s, and the detonation pressure distribution range is 26.75 ~ 36.18Gpa. Among them, tris (5-difluoroaminotetrazole) borate has the best energetic properties and has a good application prospect in propellant bonding agent and pyrotechnic agent.

Review of Evaluation Methods of Underwater Explosion Power of Explosives

Reasonable evaluation of underwater explosion power of explosives is very important for underwater warhead design and other tasks. This paper summarizes the typical experiments of underwater explosion power evaluation, discusses the power characterization methods involved in the tests, and focuses on the explosion bulge test of plate structure and its corresponding dimensionless deflection characterization means. Based on the existing research results, it is proposed to establish a standardized effect target evaluation method, strengthen the research on the relationship between work parameters, explosive detonation parameters and load parameters, and apply the dimensionless deflection method in explosion expansion test to the characterization of underwater explosion power.

Detonation behaviors in stoichiometric CH4-H2-O2 under different initial pressures conditions

In this study, the detonation behaviors (i.e., detonation limit, detonation overpressure, mean velocity, velocity deficit, and cell sizes) of CH4-H2-O2 mixtures in a small-bore tube at different initial pressures (ranging from 6 kPa to 300 kPa) were investigated. Mixtures with different proportions of H2 in the total fuel (0, 10%, 20%, 25%, 30%, 50%, 75%, 100%) were tested. Steady one-dimensional ZND calculations are used to obtain detonation parameters such as induction zone length, stability parameters, and cell sizes. Results indicate that increasing the hydrogen fraction decreases the detonation limit. The addition of hydrogen can reduce velocity deficit, especially near the detonation limit pressure. Velocity deficits were found to be within 3.5% when the initial pressure higher than 50 kPa. Higher initial pressure may result in the mean detonation velocity surpassing the theoretical CJ velocity. The detonation overpressure increases with the initial pressure and decreases with hydrogen fraction. The influence of initial pressure on cell sizes weakens as hydrogen fraction increases. Besides, the induction zone length and stability parameter decrease as hydrogen fraction increases Notably, the stability parameter of mixtures with different hydrogen fractions shows different trends as the initial pressure increases. A linear relationship between actual measured cell sizes and induction zone length is given as λ = 24.56Δi for hydrogen-methane-oxygen mixtures with the initial pressure range of 100 to 300 kPa. If experimental measurement error is considered, the prediction of the Ng model has reasonable accuracy.

Research on the quasi-isentropic driving model of aluminized explosives in the detonation wave propagation direction

Taking CL-20 (Hexanitrohexaazaisowurtzitane)-based aluminized explosives with high gurney energy as the research object, this research experimentally investigates the work capability of different aluminized explosive formulations when driving metal flyer plates in the denotation wave propagation direction. The research results showed that the formulations with 43 μm aluminum (Al) powder particles (The particle sizes of Al powder were in the range of 2∼43 μm) exhibited the optimal performance in driving flyer plates along the denotation wave propagation direction. Compared to the formulations with Al powder 13 μm, the formulations with Al powder 2 μm delivered better performance in accelerating metal flyer plates in the early stage, which, however, turned to be poor in the later stage. The CL-20-based explosives containing 25% Al far under-performed those containing 15% Al. Based on the proposed quasi-isentropic hypothesis, relevant isentropy theories, and the functional relationship between detonation parameters and entropy as well as Al reaction degree, the characteristic lines of aluminized explosives in accelerating flyer plates were theoretically studied, a quasi-isentropic theoretical model for the aluminized explosive driving the flyer plate was built and the calculation methods for the variations of flyer plate velocity, Al reaction degree, and detonation product parameters with time and axial positions were developed. The theoretical model built is verified by the experimental results of the CL-20-based aluminized explosive driving flyer plate. It was found that the model built could accurately calculate the variations of flyer plate velocity and Al reaction degree over time. In addition, how physical parameters including detonation product pressure and temperature varied with time and axial positions was identified. The action time of the positive pressure after the detonation of aluminized explosives was found prolonged and the downtrend of the temperature was slowed down and even reversed to a slight rise due to the aftereffect reaction between the Al powder and the detonation products.

Theoretical Prediction on Properties of 3,4-Bisnitrofurazanfuroxan (DNTF) Crystal and its Polymer Bonded Explosives (PBXs) Through Molecular Dynamics (MD) Simulation

3,4-Bisnitrofurazanfuroxan (DNTF) is a typical high energy density compound (HEDC), it has high crystal density and detonation parameters, but also high mechanical sensitivity. To decrease its mechanical sensitivity, the DNTF based polymer bonded explosives (PBXs) was designed. The pure DNTF crystal and PBXs models were established. The stability, sensitivity, detonation performance and mechanical properties of DNTF crystal and PBXs models were predicted. Results show that PBXs models containing fluorine rubber (F2311) and fluorine resin (F2314) have higher binding energy, meaning that DNTF/F2311 and DNTF/F2314 is relatively more stable. PBXs models have higher value of cohesive energy density (CED) than pure DNTF crystal, DNTF/F2311 and DNTF/F2314 have the highest value of CED, implying that the sensitivity of PBXs is effectively decreased, DNTF/F2311 and DNTF/F2314 is more insensitive. PBXs have lower crystal density and detonation parameters than DNTF, the energy density is declined, DNTF/F2314 has higher energetic performance than other PBXs. Compared with pure DNTF crystal, engineering moduli (tensile modulus, shear modulus, bulk modulus) of PBXs models are obviously decreased, but Cauchy pressure is increased, implying that the mechanical properties of PBXs is superior to pure DNTF component, the PBXs containing F2311 or F2314 have more preferable mechanical properties. Consequently, DNTF/F2311 and DNTF/F2314 have the best comprehensive properties and is more attractive among the designed PBXs, indicating that F2311 and F2314 are more advantageous and promising in ameliorating properties of DNTF. The properties of DNTF crystal and PBXs models were predicted through molecular dynamics (MD) method under Materials Studio 7.0 package. The MD simulation was performed with isothermal-constant volume (NVT) ensemble, and the force field was chosen as COMPASS force field. The temperature was set as 295K, the time step was 1fs and the total MD simulation time was 2ns.

Effect of Al/O ratio on underwater explosion energy characteristics of CL‐20‐based aluminized explosives

AbstractTo study the underwater explosion energy characteristics of CL‐20‐based aluminized explosives with different Al/O ratio, underwater detonation parameters of explosives, including the shock wave peak pressure, the decay time, the bubble pulsation period, the shock wave energy and the bubble energy at 1 m, were measured by a series of underwater explosion experiments. The calculation model of CL‐20‐based aluminized explosive in the pool was established by using Ansys LS‐DYNA software and was calculated the shock wave energy and bubble pulsation period. The results showed that Al/O ratio significantly changed the energy output structure of CL‐20‐based aluminized explosives. With increasing Al/O ratio, the proportion of shock wave energy in the total energy decreased, while the proportion of bubble energy increased. When Al/O ratio was 0.35, the shock wave peak pressure and shock wave energy of the explosive were the largest, and when the ratio was 0.6, the bubble period and total energy reach their maximum; when the ratio was 0.94, the bubble energy and the bubble pulsation reached the maximum. The experimental values are in good agreement with the simulation results, and the model can be used to estimate the underwater detonation parameters of CL‐20‐based aluminized explosives with different Al/O ratio.

Energetic derivatives of 3,3′,5,5′-tetranitro-4,4′-bipyrazole (TNBPz): Synthesis, characterization and properties

3,3‘,5,5‘-Tetranitro-4,4‘-bipyrazole monohydrate (TNBPz, 1⋅H2O) is an excellent precursor for the synthesis of new energetic materials (2–12). Several nitrogen-rich salts (e.g. guanidinium, aminoguanidinium, hydrazinium, ammonium and hydroxylammonium) were prepared from 1⋅H2O by neutralization reactions. In addition, the N-methylation and N-amination of compound TNBPz was investigated and is reported. All new synthesized energetic materials were fully characterized by NMR (1H, 13C, 14N, and 15N) spectroscopy, infrared spectroscopy, differential thermal analysis (DTA) and elemental analysis. Compounds 2, 4–8 and 10 were characterized with single crystal X-ray diffraction. The heats of formation for compounds 2, 4–6, 8, 11 and 12 were calculated using the atomization method based on CBS-4 M enthalpies. Several detonation parameters, such as detonation pressure, velocity and energy, were calculated by using the X-ray densities and the calculated standard molar enthalpies of formation. The sensitivities of all energetic materials toward external stimuli were tested according to the BAM standards. In addition, the toxicity toward vibrio fischeri bacteria of few energetic salts (3 and 4) is reported.

A shockwave calculation method for aluminized explosive of deep water explosion based on the Kirkwood‐Bethe model

AbstractTo calculate the shockwave propagation of deep water explosions for different explosives quickly and accurately, a calculation method, based on the Kirkwood‐Bethe theory, was proposed. At the same time, an underwater explosion experiment of the aluminized explosive was carried out in the pressure vessel under high hydrostatic pressure. Then, the calculated results and experimental results were compared for peak pressure, impulse and energy flux density. The results indicated that the proposed method can quickly and accurately determine the shockwave propagation of deep water explosions for the aluminized explosives, with satisfactory agreement with experimental data. Using the proposed method, the shockwave of aluminized explosive under the conditions of different charge weight, different depth and different distance were calculated, the propagation laws of peak pressure, impulse and energy flux density with depth and distance were obtained. The calculation method proposed could be used to calculate shockwave propagation for any kind of explosive, if only knows the parameters of detonation and JWL equation of state.

Searching for the analogues of 1,1-dinitro-2,2-diamino ethylene (FOX-7) by high-throughput computation and machine learning

1,1-dinitro-2,2-diamino ethylene (FOX-7) is typically representative of low sensitivity and high energy compound. In this work, analogues of FOX-7 are screened using a combined method of high-throughput computation (HTC) and machine learning (ML). The molecules are generated with typical unsaturated hydrocarbons backbones and random combination of substituents -H, -NH2 and -NO2, then HTC is performed based on 200 sample molecules. ML models are established based on the HTC results, with detonation parameters predicted using the most accurate model of extreme gradient boosting (XGB). Finally, stability of the filtered high energy molecules are confirmed by quantum chemistry calculations, and besides FOX-7, 8 more energetic molecules with high energy as well as high stability (detonation velocity ≥ 8841.1 m/s, detonation pressure ≥ 34.6 GPa and stability parameter bond dissociation energy ≥ 201.7 kJ/mol) are achieved. This work has shown the efficiency of HTC and ML methods in searching new target molecules.

Evaluation of Energetic and Detonation Parameters of Nitrohydrazine

Evaluation of Energetic and Detonation Parameters of Nitrohydrazine

The predictions of RoseBoom2.2© without the input of any data received from experiments or composite methods

ABSTRACT Recent studies with the new program RoseBoom© claim it can predict reliable detonation parameters only based on the structural formula, without the need of a heat of formation or density obtained using a different method. In this study, it was investigated how big the impact on the calculated detonation parameters is, when one uses the density and heat of formation predicted by RoseBoom2.2© vs. densities and the heat of formations published with the corresponding molecules. A range of traditionally used models in terms of the sensitivity to the accuracy to the input values is tested. Furthermore, it proofs the need to agree on one software for predicting the performance of energetic materials, starting with the input of values of energetic materials. Additionally, it puts further trust into the predictions by RoseBoom© and raises awareness of the uncertainty of published performance values.

Designing and property prediction of a novel three-component CL-20/HMX/TNAD energetic cocrystal explosive by MD method.

Cocrystallization technology can effectively regulate crystal structure, alter packing mode, and improve physicochemical performances of energetic materials at molecule level. CL-20/HMX cocrystal explosive has high energy density than HMX, but it also exhibits high mechanical sensitivity. To decrease the sensitivity and improve the properties of CL-20/HMX energetic cocrystal, the three-component energetic cocrystal CL-20/HMX/TNAD was designed. The properties of CL-20, CL-20/HMX, and CL-20/HMX/TNAD cocrystal models were predicted. The results show that CL-20/HMX/TNAD cocrystal models have better mechanical properties than CL-20/HMX cocrystal model, implying that the mechanical properties can be effectively improved. The binding energy of CL-20/HMX/TNAD cocrystal models is higher than CL-20/HMX cocrystal model, indicating that the three-component energetic cocrystal is more stable, and the cocrystal model with the ratio 3:4:1 is predicted to be the most stable phase. CL-20/HMX/TNAD cocrystal models have higher value of trigger bond energy than pure CL-20 and CL-20/HMX cocrystal models, meaning that the three-component energetic cocrystal is more insensitive. The crystal density and detonation parameters of CL-20/HMX and CL-20/HMX/TNAD cocrystal models are lower than CL-20, illustrating that the energy density is declined. The CL-20/HMX/TNAD cocrystal has higher energy density than RDX and can be regarded as a potential high energy explosive. This paper was performed with molecular dynamics (MD) method with the software of Materials Studio 7.0 under COMPASS force field. The MD simulation was performed under isothermal-isobaric (NPT) ensemble, the temperature and pressure was 295K and 0.0001 GPa, respectively.

Process and performance of DAAF microspheres prepared by continuous integration from synthesis to spherical coating based on microfluidic system

In order to improve the energy output consistency of 3, 3′-diamino-4, 4′-azoxyfurazan (DAAF) in the new insensitive booster and the safety and efficiency in the preparation process, a continuous preparation system of DAAF from synthesis to spherical coating was designed and established in this paper, which combined ultrasonic micromixing reaction with microdroplet globular template. In the rapid micromixing stage, the microfluidic mixing technology with ultrasonic was used to synergistically strengthen the uniform and rapid mass transfer mixing reaction between raw materials to ensure the uniformity of DAAF particle nucleation-growth, and to prepare high-quality DAAF crystals with uniform structure and morphology and concentrated particle size distribution. In the microdroplet globular template stage, the microfluidic droplet technology was used to form a droplet globular template with uniform size under the shear action of the continuous phase of the dispersed phase solution containing DAAF particles and binder. The size of the droplet template was controlled by adjusting the flow rate ratio between the continuous phase and the dispersed phase. In the droplet globular template, with the diffusion of the solvent in the dispersed phase droplets, the binder precipitates to coat the DAAF into a ball, forming a DAAF microsphere with high sphericity, narrow particle size distribution and good monodispersity. The problem of discontinuity and DAAF particle suspension in the process was solved, and the coating theory under this process was studied. DAAF was coated with different binder formulations of fluororubber (F2604), nitrocellulose (NC) and NC/glycidyl azide polymer (GAP), and the process verification and evaluation of the system were carried out. The balling effects of large, medium and small droplet templates under different binder formulations were studied. The scanning electron microscope (SEM) results show that the three droplet templates under the three binder formulations exhibit good balling effect and narrow particle size distribution. The DAAF microspheres were characterized by powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermo-gravimetric (TG) and sensitivity analyzer. The results showed that the crystal structure of DAAF did not change during the process, and the prepared DAAF microspheres had lower decomposition temperature and lower mechanical sensitivity than raw DAAF. The results of detonation parameters show that the coating of DAAF by using the above three binder formulations will not greatly reduce the energy output of DAAF, and has comparable detonation performance to raw DAAF. This study proves an efficient and safe continuous system from synthesis to spherical coating modification of explosives, which provides a new way for the continuous, safe and efficient preparation of spherical explosives.

Spreading Effect of Enhanced Blast in Explosives and Propellants

We performed tests on one of our propellants to determine its TNT equivalence. In such tests we detonate a charge of explosive at one end of a propellant cylindrical sample. We use two types of diagnostics: 1) to determine the propellant energy release rate, we wrap it with a thin aluminum shell, and measure the radial velocity of the shell along the propellant sample with velocity interferometers (PDV); and 2) we use commercial blast gauges at a distance of about 10m from the test sample, to determine the blast effect of the propellant (after deducting the blast effect of the driving explosive). We expected the two types of diagnostics to agree with one another, but this has not been the case. From the velocity gauges we see that only the part of the propellant which is near the explosive has fully reacted, and that the extent of this part depends on the size and configuration of the driving explosive. But from the blast diagnostics it seems, that as if the whole propellant has reacted. We’ve seen some sporadic indications in the literature to such an enhanced blast effect from propellants [1-5]. We refer here to such an enhanced blast effect as a spreading effect. We claim, that when a reacting propellant (or explosive) is spread out in space (without changing its total energy release upon reacting), the blast effect at a given distance is enhanced substantially compared to the same energy yield without spreading. In our tests, the relative amount of reacted propellant decreases substantially with distance from the initiating explosive, but because it does not react in a continuous fashion, there is a spreading effect, that enhances the level of air blast substantially. To demonstrate the action of the spreading effect, we make 1D simulations of outgoing detonations of an HB (H=HMX, B=Binder) explosive in spherical symmetry. For different runs we dilute the explosive with the binder to various extents, from W=1 (pure explosive) to W=0.01 (1% explosive). For each such formulation we compute the detonation parameters using our in-house chemical equilibrium code (not presented here). For each formulation we adjust the explosive radius so that the total detonation energy stays the same. For all runs we monitor the rigid boundary reflected pressure (pr) of the created blast wave in air, at a radial distance of 12m. We get that as W decreases below 0.5, the total amount of HMX decreases below 6% of the amount for pure HMX, but pr increases by about 12% relative to that of pure HMX. We attribute this enhanced blast effect to the spreading of the explosive, while keeping the amount of energy released unchanged (spreading effect).

Evaluation of Energy and Detonation Parameters of Nitrohydrazine

Evaluation of Energy and Detonation Parameters of Nitrohydrazine