Explosive Field Research Articles

Application of Molecular Electrostatic Potential Surface to Predict Supramolecular Synthons for RDX/Solvent Cocrystals

AbstractCocrystallization has attracted growing interests in the energetic field as it can tune properties by selecting and arranging existing molecules. Herein, the application of molecular electrostatic potential surface to predict supramolecular synthons for 1,3,5‐trinitro‐1,3,5‐triazinane (RDX)/solvent cocrystals is demonstrated. Six RDX/solvent supramolecular synthons are constructed and investigated by density functional theory. The results of Bader's atoms in molecules (AIM) and independent gradient model (IGM) indicate that unconventional CH···O type hydrogen bonds are the main intermolecular interactions between RDX and solvents. The thermodynamic properties are studied to assess the spontaneity of assembly reactions. The most stable packings for the supramolecular synthons of the RDX/solvents are predicted and they present lower sensitivity than RDX. The work may provide valuable insight for the rational design of RDX‐based cocrystals and promote the application of supramolecular chemistry in the field of explosives.

Observed airblast variability and model error from repeatable explosive field trials

Explosive field trials have been conducted to measure the peak incident pressure, impulse and time of positive phase duration following the detonation of 15 different masses of the Plastic Explosive No #4. A novel aspect of these field trials was the repeatability of tests. Eight pressure gauges collected data during each blast, and at each scaled distance. In all, 4 blasts were conducted for each scaled distance (i.e. up to 32 measurements recorded for each scaled distance) – 60 blasts were fired in total. Consequently, this repeatability of testing allowed the mean and variance of blast pressure–time histories to be quantified, with a view to better characterise the variability of a blast itself and model error variability. This article describes the explosive field trials, and the statistical analysis of blast load variability and model error for peak incident pressure, impulse and time of positive phase duration. It was found that the mean model error is close to unity with a coefficient of variation of up to 0.15 for pressure and 0.21 for impulse. The lognormal probability distribution best fits the model error data. The probabilistic models derived from these tests can be used for a variety of structural engineering applications, such as calculating reliability-based design load or partial safety factors for explosive blast loading, and estimating the probability of damage and casualties for infrastructure subject to explosive blast loading. This is illustrated for a terrorist explosive scenario involving a spherical free-air burst, where the damage modes of interest are breaching and spalling of a concrete slab. It was found that the variability of charge mass, range and model error have a significant effect on reliability-based design.

Численный анализ управляемой потери устойчивости пологих менисковых облицовок при высокоскоростном обжатии

Experimental and analytical research methods of losses of stability of meniscal form liners at their high-speed deformation, i.e., collapse, by products of detonation of explosive have limited opportunities. They are caused by the complicated nature of liner thickness change to control the operated loss of stability --- folding, high-speed deformations of liners, intensive drop of pressure acting on them and some other features. The paper introduces an approach to numerical three-dimensional modeling of collapse of meniscal form liners with variable thickness in the circumferential direction in the area of their periphery, the modeling being carried out by the finite element method in Lagrange coordinate system in LS-DYNA software package. The study also shows the main stages of implementing this approach and describes the key parameters of the materials models used, as well as the type of the final element and mechanism of adaptive updating of the computational grid. By the method of numerical simulation, we found the main regularities of liners collapse and folding of the afterbody of high speed elements formed during the collapse of the liners. The results of numerical calculations are confirmed by experimental data. The studies done are of interest to specialists involved in the analysis of the loss of stability of various structures under dynamic loads, as well as to specialists in the field of explosion and impact physics.

Compensation method for infrared temperature measurement of explosive fireball

The temperature of explosive fireball is an important index for measuring the performance of explosives. Considering the harsh environment in the explosion field, the acquisition of fireball temperature depends mainly on the radiation temperature measurement method. The content of research on radiation temperature measurement in the explosion field includes two main points, namely, (1) how to measure the fireball radiation energy accurately and (2) how to convert the measured radiation energy into fireball temperature accurately. Theoretical studies on infrared temperature measurement in the explosion field are scarce. No theory is suitable for modifying fireball temperatures measured by IR system.A temperature compensation formula is proposed based on geometrical optics and infrared radiation theory in this study to eliminate the measurement error of radiation energy caused by the test environment. The principle of the influence of distance and meteorological conditions on measurement accuracy is analyzed. After eliminating the temperature error, image gray level is introduced as an intermediate variable, and the temperature compensation relationship is derived based on error transfer theory. Subsequently, the correctness of the theory is verified through simulation experiments. The measured temperature of 3 Kg of HMX mixing powder is compensated for and corrected. Compared with the original data, the revised values are closer to the detonation temperature of 2000 °C.

Experimental study and numerical simulation on damage assessment of reinforced concrete beams

In order to study the dynamic response characteristics and damage effect of reinforced concrete beams in an adjacent physical field of explosion, in this study, three groups of nine 1:6 scale models of reinforced concrete beams are subjected to blast loads. All factors, such as the weight of explosive charge, distance from the model to the explosion center (including the contact explosion), and position of explosive charge are all considered. Thereafter, the pressures, displacements, accelerations, and strains are introduced at certain typically measured points to investigate the dynamic response characteristics as well as the local state of these models that have been subjected to the blast. And then, a monotonic loading test is conducted to assess the damage of these models. Finally, a series of numerical simulation analyses are conducted on the reinforced concrete beams that have been subjected to blast load. Results show that the damage index increases as the scaled distance decreases, and moreover, the models that have been subjected to the blasts from larger amount of explosive charges suffer extensive destruction; the models that have been exposed to the blasts from smaller amounts of explosive charges experience severe local damage. As the explosive charge is moved away from the mid-span to the beam column joints, the damage index in the reinforced concrete beam gradually decreases. The influence of different parameters (compressive strength of concrete, section size, longitudinal reinforcement ratio, and transverse reinforcement ratio) on the damage change law of reinforced concrete beams is different, and the failure mode of reinforced concrete beam is severely effected by the section sizes, particularly in the height of the beam. The results prove that the blast resistance of reinforced concrete beam is greatly affected by the column. Accordingly, the results of this study can be used as technological support and theoretical basis for engineering applications.

Effect of particle gradation of aluminum on the explosion field pressure and temperature of RDX-based explosives in vacuum and air atmosphere

Abstract To optimize the energy output and improve the energy utilization efficiency of an aluminized explosive, an explosion device was developed and used to investigate the detonation pressure and temperature of R1 (Al6) aluminum powder and the aluminum powder particle gradation of R2 (Al6+Al13), R3 (Al6+Al24) and R4 (Al6+Al flake) in a confined space. By using gas chromatography, quantitative analysis and calculations were carried out to analyze the gaseous detonation products. Finally, the reaction ratios of the aluminum powder and the explosion reaction equations were calculated. The results show that in a confined space, the quasi-static pressures and equilibrium temperature of the aluminum powder in air are higher than in vacuum. In vacuum, the quasi-static pressures and equilibrium temperatures of the samples in descending order are R1>R3>R4>R2 and R3>R4>R1>R2, respectively. In air, the quasi-static pressures and equilibrium temperatures of the samples in descending order are R1>R2>R4>R3 and R1>R4>R2>R3, respectively. R4 (Al6+Al flake) and R3 (Al6+Al24) have relatively higher temperatures after detonation, which shows that the particle gradation method can enhance the reaction energy output of aluminum during the initial reaction stage of the explosion and increase the reaction ratio by 10.6% and 8.0%, respectively. In air, the reaction ratio of Al6 aluminum powder can reach as high as 78.16%, and the reaction ratio is slightly reduced after particle gradation. Finally, the reaction equations of the explosives in vacuum and in air were calculated by quantitative analysis of the explosion products, which provides a powerful basis for the study of RDX-based explosive reactions.

Effects of Ti and Mg particles on combustion characteristics of boron–HTPB-based solid fuels for hybrid gas generator in ducted rocket applications

In the field of propellants and explosives, boron has been considered as an attractive fuel due to its calibre to produce high energy density. Therefore, boron as a fuel has great prospect for application in solid fuel ducted rocket (SFDR) with hydroxyl-terminated polybutadiene (HTPB) which is widely used solid fuel. Experimentally, it has been observed that ignition and combustion of boron is problematic due to boron oxide (B2O3) coating around active boron which inhibits its ignition/combustion. In the present study, titanium and magnesium have been used with boron-HTPB based solid fuel as burning promoters. Various combustion parameters have been evaluated for nine different fuel compositions. An opposed flow burner (OFB) system has been used for fuel evaluation with the help of gaseous oxygen (GOX) impingement where oxygen mass flux (Gox) is maintained between 20 and 57 kg/m2-s. Favorable result has been observed for boron-magnesium combinations as compared to boron-titanium. Around 18% enhancement in regression rate has been achieved for boron-magnesium-HTPB sample (at max. Mg %) compared to that of boron-HTPB sample. In all the boron-based samples, greenish appearance has been observed during combustion which corresponds to BO2 emission. Spectroscopy analysis confirmed the same. Burning events have been analysed using color and high-speed camera. Condensed combustion products (ejected from the burning surface) have been analysed by various material characterization techniques such as: FE-SEM, EDX, XRD, and TGA. Through TGA, the active residual boron content in the condensed product of magnesium-based sample is found to be 33%. This value is found to be the lowest among the tested fuel compositions. The present investigation has been mainly focused on the formulation of new composition of boron-based solid fuel having high energy density.

Experimental study on explosion process of flour deposits/air mixture in horizontal pipelines

Combustion and explosion of flour is a popular research topic in the field of dust explosion. In this study, combustion and explosion processes of a two-phase flow of wheat flour in a pipeline are investigated using a horizontal dust combustion explosion experimental pipeline system with a length of 5.5 m and diameter of 100 mm. Physical properties of flour dust dispersed under different aerodynamic conditions are compared experimentally. The average characteristic diameter of the intrinsic characteristic of wheat flour D50 was 36.80 μm; the suspension characteristics of dust particles in the pipeline under pneumatic action are also obtained. When the density of the flour in the pipe is 800 g/m3, the flame speed reaches a maximum of 289 m/s. When the quality of flour placed in the pipe continues to increase, after reaching 1000 g, the flame speed of the flour–air mixture explosion decreases.

ПРОСТРАНСТВЕННО-ВРЕМЕННОЙ АНАЛИЗ СЕЙСМИЧЕСКОГО ВОЛНОВОГО ПОЛЯ ОТ РАСПРЕДЕЛЕННОГО КАРЬЕРНОГО ВЗРЫВА

The article presents a space-time analysis of the seismic wave from a distributed career explosion. The method of direct measurement based on the dynamic model of the wave field is used to form an image of the seismic wave field in the field of quarry explosions. The efficiency of the proposed method is shown by the example of experimental seismic recording processing. The program "Nelumbo" is used to visualize the seismic field, which on the basis of experimental seismic records allows to form an image of the wave field in the space of the hemisphere, the center of which corresponds to the position of the seismometer (registration point). The algorithm of the program "Nelumbo" is based on the Huygens – Fresnel principle and Kirchhoff's theorem. The algorithm of the program allows to allocate from record of a seismic signal frames of a certain duration and to form the image of a wave field in space of a solid angle dimension π. This approach can be used as a tool to analyze the nature of the development of disturbances in the environment and the analysis of environmental risks in the production of blasting.

Experimental and numerical study of rubber concrete slabs with steel reinforcement under close-in blast loading

We conducted explosion field tests on rubber concrete slabs with steel reinforcement, including four kinds of concretes with different mix proportions of volume fractions of rubber particles (0%, 10%, 30%, and 50%, termed NC, RC10, RC30, and RC50, respectively). In addition, we compared the measured overpressure at the center of a slab with some empirical models to verify the accuracy our model. Field testing results showed that the tensile zone damage of rubber concrete slabs is smaller than that of normal concrete slabs under large explosive charges. Additionally, we validated a numerical simulation employing Multi-Material ALE and Lagrangian algorithms using the data from field experiments and employed it to further study the deformation process during the field test. Finally, we showed that rubber concrete slabs with steel reinforcements are practical structures for blast resistance, especially when subjected to a large energy detonation.

Zeeman spectroscopy as a method for determining the magnetic field distribution in self-magnetic-pinch diodes (invited).

In the self-magnetic-pinch diode, the electron beam, produced through explosive field emission, focuses on the anode surface due to its own magnetic field. This process results in dense plasma formation on the anode surface, consisting primarily of hydrocarbons. Direct measurements of the beam's current profile are necessary in order to understand the pinch dynamics and to determine x-ray source sizes, which should be minimized in radiographic applications. In this paper, the analysis of the C IV doublet (580.1 and 581.2 nm) line shapes will be discussed. The technique yields estimates of the electron density and electron temperature profiles, and the method can be highly beneficial in providing the current density distribution in such diodes.

Quantitative research on gas explosion inhibition by water mist.

Water mist as an effective explosion inhibitor has wide application prospect to prevent and reduce gas explosion hazard. The quantitative study of gas explosion inhibition with water mist provides the groundwork for the design of gas explosion suppression system. In this paper, the influence of the initial droplet sizes and spraying concentrations on explosion inhibition were numerically studied in a 2D numerical model. Under the initial spraying concentrations in the range of ∼1.5 kg/m3, the inhibition effect of water mist on the explosion overpressure was not significant. The inhibition effect of water mist was mainly reflected in the suppression of the explosion flame temperature. When the initial droplet sizes were in the range of 50-150 μm, the flame length was obviously reduced. But when the initial droplet sizes were less than 50 μm or more than 150 μm, the inhibition to reduce flame length begin to weaken. The results of this study provide the theoretical basis of the suppression technology for gas explosion.

Recent approaches in guar gum hydrogel synthesis for water purification

Guar gum based hydrogels have evoked great attention in research as well as in industry for exploring miscellaneous applications in the field of water purification, medicine, agriculture, explosives, cosmetics, textile, paper, and food to name a few. In this article, latest modifications for developing guar gum based hydrogels and composite materials for water purification application are extensively reviewed. Regenerative nature of Guar gum hydrogels makes it a better choice for treating wastewater as well as other value-added applications. Moreover, nonionic nature makes guar gum an acceptable material for further modifications. In this article, we also present a brief discussion on structure and properties of guar gum.

Influence of particle size distribution skewness on dust explosibility

It is well known that the particle size of dusts and powdered materials exerts a strong influence on the various phenomena involved in self-heating, ignition and explosion processes. However, it is not only the median diameter (D50) that has an influence, but also the entire particle size distribution. Nevertheless, in many cases, little importance is attached to reporting size data and only the D10, D50 and D90 percentiles of the cumulative distribution curve are given. In recent years, the polydispersity index has been proposed for characterising the particle size distribution of these materials. In the present study, data obtained in the literature have been analysed and compared to examine the effects of particle size distribution and provide guidance to researchers and practitioners in the field of dust explosions on how to report particle size distribution. This analysis indicated that the polydispersity index does not consistently correlate with explosion severity; therefore, polydispersity is not recommended for reporting particle size distribution. An alternative parameter, skewness, was analysed and the results obtained were promising, suggesting that this parameter could yield useful information about the particle size distribution curve in relation to explosion hazard characterisation.

Diameter Effect on the Propagation of Curved Detonation Waves in Micro‐Channel Charges Within a Strong Confinement

AbstractThe property of detonation wave propagation in micro‐channel charges is one of the most important research areas in the field of explosives. Based on DSD (Detonation Shock Dynamics) theory and a linear assumption for the streamline deflection angle, this paper proposes a theoretical model for curved detonation wave propagation in cylinder‐type micro‐channel charges within a strong confinement of metal tube. Further, dynamic control equations related to the detonation velocity and charge diameter are deduced, a numerical calculation method of detonation velocity and shock front shape is given, and propagation rules for detonation waves with different diameters are obtained. An experiment was designed to test the detonation velocities for micro‐channel charges with a booster explosive. The results closely agree with calculations, validating the propagation model of curved detonation waves. It was found that the detonation velocity loss and shock front curvature in the central axis decreased with increasing diameter in the calculation range. Moreover, the smaller the diameter, the greater the rate of change. It is also shown that the model is suitable for the prediction of diameter effects in micro‐channel charges, which is of significance for structural design and performance optimization in MEMS initiation systems.

Characteristics of a plasma flow field produced by a metal array bridge foil explosion

To improve the energy utilization efficiency of metal bridge foil explosion, and increase the function range of plasmas, array bridge foil explosion experiments with different structures were performed. A Schlieren photographic measurement system with a double-pulse laser source was used to observe the flow field of a bridge foil explosion. The evolution laws of plasmas and shock waves generated by array bridge foil explosions of different structures were analyzed and compared. A multi-phase flow calculation model was established to simulate the electrical exploding process of a metal bridge foil. The plasma equation of state was determined by considering the effect of the changing number of particles and Coulomb interaction on the pressure and internal energy. The ionization degree of the plasma was calculated via the Saha–Eggert equation assuming conditions of local thermal equilibrium. The exploding process of array bridge foils was simulated, and the superposition processes of plasma beams were analyzed. The variation and distribution laws of the density, temperature, pressure, and other important parameters were obtained. The results show that the array bridge foil has a larger plasma jet diameter than the single bridge foil for an equal total area of the bridge foil. We also found that the temperature, pressure, and density of the plasma jet’s center region sharply increase because of the superposition of plasma beams.

Onset of the Magnetic Explosion in Solar Polar Coronal X-Ray Jets

Abstract We follow up on the Sterling et al. discovery that nearly all polar coronal X-ray jets are made by an explosive eruption of a closed magnetic field carrying a miniature filament in its core. In the same X-ray and EUV movies used by Sterling et al., we examine the onset and growth of the driving magnetic explosion in 15 of the 20 jets that they studied. We find evidence that (1) in a large majority of polar X-ray jets, the runaway internal/tether-cutting reconnection under the erupting minifilament flux rope starts after both the minifilament’s rise and the spire-producing external/breakout reconnection have started; and (2) in a large minority, (a) before the eruption starts, there is a current sheet between the explosive closed field and the ambient open field, and (b) the eruption starts with breakout reconnection at that current sheet. The variety of event sequences in the eruptions supports the idea that the magnetic explosions that make polar X-ray jets work the same way as the much larger magnetic explosions that make a flare and coronal mass ejection (CME). That idea and recent observations indicating that magnetic flux cancellation is the fundamental process that builds the field in and around the pre-jet minifilament and triggers that field’s jet-driving explosion together suggest that flux cancellation inside the magnetic arcade that explodes in a flare/CME eruption is usually the fundamental process that builds the explosive field in the core of the arcade and triggers that field’s explosion.

The quantitative studies on gas explosion suppression by an inert rock dust deposit

The traditional defence against propagating gas explosions is the application of dry rock dust, but not much quantitative study on explosion suppression of rock dust has been made. Based on the theories of fluid dynamics and combustion, a simulated study on the propagation of premixed gas explosion suppressed by deposited inert rock dust layer is carried out. The characteristics of the explosion field (overpressure, temperature, flame speed and combustion rate) at different deposited rock dust amounts are investigated. The flame in the pipeline cannot be extinguished when the deposited rock dust amount is less than 12 kg/m3. The effects of suppressing gas explosion become weak when the deposited rock dust amount is greater than 45 kg/m3. The overpressure decreases with the increase of the deposited rock dust amounts in the range of 18–36 kg/m3 and the flame speed and the flame length show the same trends. When the deposited rock dust amount is 36 kg/m3, the overpressure can be reduced by 40%, the peak flame speed by 50%, and the flame length by 42% respectively, compared with those of the gas explosion of stoichiometric mixture. In this model, the effective raised dust concentrations to suppress explosion are 2.5–3.5 kg/m3.

Research on the Distribution of Unconfined Gas Cloud Explosion Field

To research the distribution of unconfined gas cloud explosion overpressure field and impulse field, build domed finite element model of combustible gas, use computational fluid dynamics, and get the numerical simulation of the methane–air gas explosion. The numerical calculation of overpressure fits the experimental result. The impulse field depends on the overpressure and time; the impulse at the gas cloud boundary is maximum. And the formulas of overpressure and impulse were calculated by data fitting.

Theoretical Calculation and Experimental Analysis on Initial Shock Pressure of Borehole Wall under Axial Decoupled Charge

This paper attempts to calculate the exact initial shock pressure of borehole wall induced by the blasting with axially decoupled charge. For this purpose, Starfield superposition was introduced considering the attenuation and superposition of blasting pressure, and the theoretical solution of initial borehole wall pressure was obtained for the upper and middle air‐decked charging structures. Then, the explosive pressure field around the borehole was measured by cement mortar models and a dynamic pressure test system, and the pressures at multiple measuring points were simulated with numerical models established by ANSYS/LS‐DYNA. The results show that the deviations between simulated and theoretical pressures are smaller than 10%, indicating the reliability of the theoretical formula derived by Starfield superposition. For the upper air‐decked charging structure, the initial shock pressure of the charging section followed a convex distribution, with the peak value near the charge centre. With the increase in the distance from the charging section, the borehole wall shock pressure in the air gap underwent a sharp decline initially before reaching a relatively constant level. The minimum pressure was observed at the hole collar. For the middle air‐decked charging structure, the pressures at both ends of the charging section obeyed a convex distribution, with the peak value near the charge centre. Finally, the author optimized air‐decked charging structure of periphery boreholes within Grade III surrounding rocks of Banjie tunnel, China, and proved the enhancement effect of the theoretical findings on smooth blasting. The research findings provide valuable references to the theoretical and experimental calculation of air column length and other key parameters of air‐deck blasting and shed new light on the charging structure determination of smooth blasting and blasting vibration control for the excavation of large‐section, deep mining roadways.