Explosive Field Research Articles

Research on thermal protection of piezoelectric pressure sensor for shock wave pressure measurement in explosion field

PurposeThe purpose of this study is to clarify the mechanism of ambient and transient temperature effects on piezoelectric pressure sensors, and to propose corresponding compensation measures. The temperature of the explosion field has a significant influence on the piezoelectric sensor used to measure the shock wave pressure. For accurate shock wave pressure measurement, based on the actual piezoelectric pressure sensors used in the explosion field, the effects of ambient and transient temperatures on the sensor should be studied.Design/methodology/approachThe compensation method of the ambient temperature is discussed according to the sensor size and material. The theoretical analysis method of the transient temperature is proposed. For the transient temperature conduction problem of the sensor, the finite element simulation method of structure-temperature coupling is used to solve the temperature distribution of the sensor and the change in the contact force on the quartz crystal surface under the step and triangle temperatures. The simulation results are highly consistent with the theory.FindingsBased on the analysis results, a transient temperature control method is proposed, in which 0.5 mm thick lubricating silicone grease is applied to the sensor diaphragm, and 0.2 mm thick fiberglass cloth is wrapped around the sensor side. Simulation experiments are carried out to verify the feasibility of the control method, and the results show that the control method effectively suppresses the output of the thermal parasitic.Originality/valueThe above thermal protection methods can effectively improve the measurement accuracy of shock wave pressure and provide technical support for the evaluation of the power of explosion damage.

Explosion and vented explosion behaviors of low-concentration gas in large-scale pipes

The extraction, transmission, and use of low-concentration gas in coal mines are often challenged by potential accidents due to proximity to the combustion and explosion concentration limit. Water sealing of fire barriers and explosion venting devices guarantee the safe transmission of low-concentration gas. The propagation and venting of gas explosion under different concentrations are experimentally investigated in a DN500 mm pipe explosion propagation test system. The water sealing of fire barrier vented explosion field evolution of methane-air mixture at the stoichiometric concentration (9.5 vol%) is examined through Fluent numerical simulation to reveal the water sealing of fire barrier further vented explosion pattern of gas transmission pipelines under low concentrations. The explosion overpressure and flame propagation of low-concentration gas in pipes are observed and correlated. Based on their coupling relationship, the design basis for the installation location of the explosion venting device is derived. The vented explosion characteristics of low-concentration gas during pipe transmission are summarized, proving that this explosion venting technique enhances both the explosion venting device and explosion parameters. Our observations and analysis can offer useful clues to underground gas explosion and prevention in coal mines.

Spatial variability of explosive blast loading and its effect on damage risks to reinforced concrete buildings

Explosive blast loading is subject to inherent variabilities due to complex interactions between chemical reactions, air particles, fireball and shockwave. Explosive field trials have quantified this variability, and described herein is the probabilistic characterisation of spatial variability of airblast for pressure and impulse. In other words, pressure–time measurements from adjacent (close) gauges are not identical, but correlated based on the distance between adjacent gauges. The degree of correlation is moderate if distance between adjacent gauges is small (i.e., angle between gauges is small where each gauge has the same radial standoff from the charge), and reduces to a weak correlation for gauges spaced much further apart. The effect of spatial variability of airblast on damage and collapse risks is investigated for a 10 storey reinforced concrete building subject to a vehicle borne improvised explosive device (VBIED) attack, and the accidental detonation of explosive ordnance (EO). The structural reliability analysis considered load redistribution for failed columns, dead and live loading variabilities, and blast loading and resistance model errors. It was found that allowing for the spatial variability of airblast decreased progressive collapse probabilities by up to 65% when compared to the case of fully correlated airblast. Designing against progressive collapse using either a threat dependent design or the Alternate Path method reduced damage risks by over 90%, and in many cases by over 99%.

On the question of the criminal legal concept of an explosive device

The subject of the study is problematic issues related to the concept of the subject of the crime under Article 222.1 of the Criminal Code of the Russian Federation, namely, an explosive device, and with the assessment of the degree of public danger of objects that have the design features of explosive devices, but are not legally such. To resolve the issue of the relevance of the subject to the subject of Article 222.1 of the Criminal Code of the Russian Federation, as a rule, an explosive examination is appointed, however, expert terminology is based on special knowledge in the field of forensic explosives and differs somewhat from legal. The purpose of the work is a detailed study of these inconsistencies in the concepts of an explosive device, an assessment of the degree of public danger of a number of objects that are not explosive devices, but contain an explosive charge and have other design features of explosive devices. In the course of the study, methods of observation, comparison, analysis of expert practice, current legislation and scientific literature were applied. The novelty of the research lies in the study of the concept of an explosive device both from a legislative point of view and from the point of view of forensic explosives. According to the results of the study, the necessity of changing the legislative approach to the concept of an explosive device, and revaluation of the degree of public danger of imitation and pyrotechnic devices is argued. Recommendations have been developed to bring the measures of the criminal law fight against illegal trafficking of explosives and explosive devices in line with modern requirements. The results of the work can be used both in the judicial interpretation of the subject of the crime provided for in Article 222.1 of the Criminal Code of the Russian Federation, and directly by the law enforcement officer when evaluating the conclusions of the explosive expertise.

Research on damage effect of penetration and explosion integration based on volume filling method

It is difficult to distinguish the damage effects of penetration and explosion loads in the test of projectile penetration and explosion integration. At present, there is no mature method to simulate the whole process of projectile penetration and dynamic explosion integration. To solve this problem, a numerical simulation method of projectile penetration and explosion integration based on the volume filling method is proposed, the explosive material is generated by volume filling in the background grid (ALE), and given the same initial velocity as the cartridge case. The fluid-structure coupling algorithm is set to restrict the cooperative deformation and movement of the cartridge case and the explosive, the static or dynamic explosion occurred after the cartridge case and the explosive penetrate the target medium synchronously. The empirical formula is used to verify the model of the inert projectile penetration process, and the numerical simulation of the whole process of penetration and dynamic explosion integration and penetration and static explosion integration is completed. The change rule of the medium internal pressure field, surface crater, and crater depth are given, and the damage effects of penetration and explosion loads in the process of penetration and explosion integration are quantitatively analyzed. The results show that: when the penetration and dynamic explosion integration, the non-dissipated penetration wave field in the target medium will be superimposed with the explosion shock wave field, and the pressure peak is higher than that of the single explosion wave field of charge static explosion after penetration, but it is not obvious; When the penetration and dynamic explosion integration, the dynamic explosive effect of the explosive makes the explosion shock wave field in the medium present an irregular spherical distribution, which has an influence that can not be ignored. When the target velocity is fixed, the later the initiation time is, the smaller the surface crater is and the greater the crater depth is; In the case of fixed initiation depth, the greater the target velocity, the smaller the surface crater, and the greater the crater depth.

High-pressure new phases of V–N compounds

The high-pressure diagram of V–N compounds is enriched by proposed seven new stable high-pressure phases. The P-1-VN4 with the armchair N-rich structure may be quenched to ambient conditions. The formed N–N covalent bond plays an important role for the structural stability of N-chain. The charge transfer results in a V–N ionic bond interaction, which further improves the stability of N-chain structure. The P-1-VN4, P4mnc-VN8, and Immm-VN10 with the outstanding detonation properties have potential application in explosive field.

Failure analysis of gas explosion load based on structural impact failure characteristics

The purpose of this study is to obtain the peak of the gas explosion load which is affected by many factors and is not easy to determine. Explosion peak is a key factor in the time-load curve of the explosion field. In this paper, the static and dynamic modal analysis method of gas explosion fracture of reinforced concrete prefabricated slabs is used to obtain the static fracture, maximum reflective pressure applied and peak dynamic load of prefabricated plates. In the actual explosion study, all three prefabricated plates broke at one-third, and the peak dynamic load was 6.743 times the span buckling load in the plate. The analysis also shows that when plastic hinges appear at one-half, the above ratio is 3 times. The calculated peak is within the pressure range of the explosion test. The Baker model is used to fit the explosion time-load curve. This function is applied to the dynamic analysis of the finite element analysis of the explosion plate, and the failure of the plate is more consistent with the explosion case site. The median value of the explode field load time-load equation with the curve function can be applied to the rapid evaluation of post-explosion structure.

Resistant ecologies

AbstractIn South Lebanon, war is lived as landscape, environment, milieu. Those pursuing life in such quarters do what they can to make‐live, and their lifelines are often as vitalizing as they are deadly: tobacco farmers ally themselves with what they call a “bitter crop” that flourishes in an arid war zone, while pastoralists walk in explosive fields with their mine‐evading goats. These multispecies alliances flourish because they can survive the deadly infrastructures of war. Dwelling alongside two steadfast families in the borderlands of South Lebanon, this ethnography of life in war moves away from tropes of trauma to grasp a militarized world from within the lived terrain of its operations. Neither green‐tinged utopia nor total devastation, these resistant ecologies make being possible in an insistently deadly region. Thinking life from disastrous war zones forces anthropological theory to reckon with harsh ethnographic realities while bringing to light unsung alliances of hope for life ongoing.

Analysis on research trends with dust explosions by bibliometric approach

Highly destructive combustible dust explosions, which is prone to cause secondary explosion, has been a concern in industrial processes. To understand the current development and status of research on dust explosions, 1276 publications related to dust explosions from 1998 to 2021 were indexed through the Web of Science Core Collection database. CiteSpace and VOSviewer were used to visualize and analyze the collected literature information. The number of articles related to dust explosions has increased from 12 in 1998 to 191 in 2021. China, the United States, and Canada are the major contributors in this field. Dalhousie University, Beijing Institute of Technology, and Dalian University of Technology are at the core of dust explosion research. Wei Gao, Paul Amyotte, and Chi-Min Shu are the most prolific researchers. Journal of Loss Prevention in the Process Industries, Powder Technology, and Process Safety and Environmental Protection are the major sources of publications related to dust explosions. The research topic of dust explosions mainly evolves into four aspects: explosion characteristics and influencing factors, research media, explosion suppression, and numerical simulation. New research hotspots have appeared related to gas–dust hybrid mixtures, nanomaterials, and powder suppressants. The results can help researchers in the dust explosion field to quickly determine the research frontier and the overall situation.

Effect of magnetic field on alkane gas explosions

Magnetic field has excellent development potential in the field of explosion. The authors found the suppression effect of magnetic fields on alkane gas explosions. In this paper, the effects of magnetic field on the maximum explosion pressure, rate of pressure rise, and flame propagation velocity of alkane gas have been investigated experimentally. The crucial free radicals and elementary reactions in the process of alkane gas explosions were simulated by CHEMKIN-PRO. The explosion mechanism of alkane gas under a magnetic field was revealed by a comprehensive analysis of experimental and simulation results combined with the gradient magnetic field force. The experimental results show that the magnetic field significantly reduces the maximum explosion pressure, rate of pressure rise, and flame propagation velocity of alkane gas, thus weakening the gas explosion intensity. Compared with methane and propane, the inhibitory effect of magnetic fields on ethane explosions is more substantial. In addition, from the variation law of explosion pressure and flame propagation velocity, which concluded that the magnetic field not only inhibits the propagation of shock waves, but also significantly the propagation of the light waves. Simulation results show that ·OH plays a more dominant role in the explosion of ethane than methane and propane. The magnetic field changes the trajectory of key free radicals such as ·H, ·O and ·OH by applying a gradient magnetic field force, which increases the collision between free radicals and the wall of the reaction vessel, produces the wall effect, and reduces the collision probability between free radicals. Thus, the explosion of alkane gas was inhibited. The equation for the gradient magnetic field force further demonstrates that the magnetic field has the most excellent effect on ·OH, thus presenting that the magnetic field has a more significant inhibitory effect on ethane explosions than methane and propane.

Synthesis of CuII and CdII Metal-Organic Frameworks Based on 4,5-Bis(1-hydroxytetrazol-5-yl)-1,2,3-triazole and Their Effects as the Catalyst in Ammonium Perchlorate Thermal Decomposition.

Two new three-dimensional (3D) energetic metal-organic frameworks (EMOFs), namely, [Cu(OBTT)(NC2H8)2]n (1) and [Cd3(OBTT)2(H2O)2]n·4H2O (2), where H3OBTT = 4,5-bis(1-hydroxytetrazol-5-yl)-1,2,3-triazole, were prepared, and their structures were characterized by single-crystal X-ray diffraction analysis, which revealed that the EMOFs feature a rigid 3D framework architecture. The possibility of these two EMOFs as potential catalysts for the thermal decomposition of ammonium perchlorate (AP) was investigated. The results show that they have significant catalytic activity, up to reducing the peak temperature of AP decomposition from 704.0 to 613.6 K and contracting the decomposition temperature range from 451 to 320 K, which is almost one-third less than the decomposition temperature range of pure AP. The Kissinger and Ozawa-Doyle methods were used to calculate the kinetic parameters of the thermal decomposition of pure and mixed AP samples. The experimental results suggest that compound 1 has potential applications in the field of explosives and propellants. All properties suggest that compound 1 can be used as a potential catalyst.

Influence of Ground Impedance on Explosive Shock Wave Test Accuracy

Different propagation media have different effects on explosion shock wave attenuation during the propagation process. Studying the attenuation effect of dielectric impedance on shock wave pressure is of great significance to accurately measure shock wave pressure and evaluate the ammunition damage power. This study analyzes the measured shock wave overpressure peak data of TNT bare charge (60 kg) on soil, sand soil, and concrete grounds. Dimensional analysis was used to establish the medium impedance expressed by material densityρ, burst center distancer, equivalent TNT quality ω, and impedance coefficient η. Based on this, the mapping relationship between the propagation medium impedance coefficientηand the shock wave overpressure peak value was established. The test data were analyzed, and the results showed that in the same explosive environment, different ground propagation media had different impedance effects on the shock wave pressure, which is specifically expressed as ηsoil>ηsandsoil>ηconcrete; the modified calculation model of shock wave pressure established using material impedance coefficient has a fitting accuracy of 93.39% to the measured data, which can well represent the attenuation law between different ground propagation media and shock wave overpressure peak. This provides a theoretical basis and method for obtaining shock wave pressure data in explosion field and verifying validity of the test data.

Effect of particle size polydispersity on the minimum ignition temperature of PMMA dust clouds

For minimum ignition temperature (MIT) values, the variation is not significant for blends with the same median particle size (D 50 ) but varying polydispersity (σ D ) However, the contribution of small particles to the ignition sensitivity in a G-G furnace should not be discarded due to small changes in MIT values. The ignition delay times and ignition probability are additional parameters that can be obtained by MIT testing. These are useful for further exploring the effect of polydisperse powders on explosion taking place in a G-G furnace. When studying the ignitability of dust clouds from a risk assessment perspective, the kurtosis and σ D should not be considered primary parameters for describing the particle size distribution of polydisperse dust. Compared to σ D and kurtosis, skewness (Sk g ) and Sauter mean diameter (D 3,2 ) provide a more accurate description of polydisperse dust particle size distributions because they are more correlated with the ignition delay time and ignition probability. • The MIT parameter is not very sensitive to polydisperse dust clouds with the same D 50. • Ignition delay times and the ignition probability are additional parameters that can be obtained by MIT testing. • The ignition probability escalation interval of PMMA is given (50–60 °C). • D 3,2 and skewness have a high potential for application in the field of dust explosions.

Evolution of the Reaction Front Shape and Structure on Flame Acceleration and Deflagration-to-Detonation Transition

Flame acceleration (FA) and the deflagration-to-detonation transition (DDT) are among the most interesting and exciting phenomena in the field of combustion and explosion of gases. From both practical and theoretical points of view, it is important to understand the basic laws governing these phenomena as well as the physical and/or chemical mechanisms and features of the process. High-speed flame-front photography during the deflagration of a premixed gas mixture in a long smooth tube with transparent walls was performed. A stoichiometric mixture of acetylene with oxygen diluted with argon by 25% is used. The experiments are carried out in a transparent cylindrical tube with an inner diameter of 60 mm and a length of 6 meters. The evolution of the structure and shape of the flame front from the moment of initiation of deflagration by a weak ignition source to the formation of a detonation wave is determined. Four characteristic phases of the propagation process are distinguished: at the first stage, the flame accelerates, then slows down, followed by flame propagation at an almost constant speed, and finally repeated acceleration, during which detonation is formed. It is shown how the dynamics of the process changes with a change in the initial pressure of the mixture. The most interesting and poorly studied stage of the DDT, the stage of intensive reacceleration, during which the flame abruptly changes shape, is described in detail.

Research on the Temperature Field of Unconfined Gas Cloud Explosion

Hemispherical finite element model of combustible gas was created by Fluent software to simulate the gas cloud explosion. The temperature field of unconfined gas cloud explosion was studied by data fitting. The result shows that, each monitoring point experienced four stages: rose to peak temperature; dropped to a high temperature quickly; maintained in this high temperature and lasted some time; declined slowly. Double fold line model can fit the curves of temperature change, and get the temperature-time functions finally.

An image processing method for an explosion field fireball based on edge recursion

To overcome the limitations caused by the complex fireball geometry in an explosion field and the smoke interference of fireball contours, a pre-processing strategy for fireball images in an explosion field, combining threshold segmentation, rectangular filtering, nearest-neighbor clustering and morphological processing, as well as an edge-recursive fireball image segmentation algorithm based on the polar coordinate system, is proposed. The overlap rate was used to compare and evaluate the segmentation effect of the proposed method and traditional image-processing methods on the measured explosion fireball image. The results demonstrate that the edge-recursive fireball image segmentation algorithm based on the polar coordinate system is excellent for identifying fireball image segmentation and fireball damage contour recognition under different smoke-obscured conditions in an explosion field, thereby facilitating the accurate recognition and measurement of the fireball image and contour under a smoke plume. This method improves the accuracy of measuring explosive fireball damage power and provides a method for effectively extracting the distribution information of explosive fireball damage.

Study on the characteristics of blast loads due to two simultaneous detonated charges in real air

Most studies about the air blast loads due to a single explosion have been widely reported based on the assumption that the air is an ideal gas. However, this assumption is not applicable for investigating the blast load due to multiple charge explosions in a realistic environment. In this paper, according to the existing data, the mathematical relationship between the specific internal energy and adiabatic index under high pressure is determined, and a new equation of state(EOS) for the real gas is derived. Then, the new EOS is implemented in LS-DYNA to simulate the reflected procedure of blast waves near the ground, and the average errors of overpressure and positive impulse are less than 10% and 21%, respectively. Finally, the validated model is used to investigate the effects of the total charge weight, scaled distance, and distance between the charges on the characteristics of the blast load due to two simultaneous detonated charges. Numerical simulation results show that under the condition of real gas, the total mass and distances between charges will heavily affect the starting and optimal positions of overpressure and impulse enhancement, which lays a foundation for characterizing the closed flow field of multiple charge explosions.

STUDY ON THE REASONABLE SPACING OF FLAT CHARGE IN THE FORM OF LONG AND PARALLEL CYLINDRICAL CHARGES FOR BREAKING ROCK

In practice, the flat charge is often used in the form of a group of long cylindrical charge set parallel and equidistant from each other and lying in the same plane. However, until now, the theory of the rock-destroying effect of flat charge has only mentioned flat charge as a flat plate explosive. Therefore, on the basis of the hydrodynamic theory of the destructive effect of a single charge, we have established a computational model, built a calculation program based on the Matlab programming language. Surveys of the explosive energy field of a group of long cylindrical charge set parallel and lying in the same plane were carried out when the relative distance parameter between the charges was changed. The results have shown that the reasonable range of the relative distance parameter between the corresponding charges receives the best destruction performance and also depends on the rock characteristics. The more stable the rock is, the smaller the reasonable distance between the long cylindrical charges is, and vice versa. The reasonable distance between long cylindrical charges is 10 to 15 times the blasting hole diameter when blasting in an endless rocky environment and 23 to 27 times the blasting hole diameter when smoldered blasting in claystone in water.

A transient heat flux sensor based on the transverse Seebeck effect of single crystal Bi2Te3

A novel transient heat flux sensor (THFS) was developed to measure the heat flux of an explosive driven shock tube. The working principle of the THFS is based on the transverse Seebeck effect (TSE) of a single crystal Bi2Te3. The sensor has a rise time of 51 μs and sensitivity of up to 69.8 μV/(kW/m2), with no signal amplifier required for the transient high heat flux test. This sensor allows for highly time-resolved measurements of heat flux in the explosion field, thereby supporting the study of the thermal damage effect of an explosion.

Study the Damage Effects of Different Laser Pulses on the Pyrotechnic Bridge

lasers are used more and more widely in daily life, medicine and aerospace fields, which promoted the development of all kinds of laser and laser technology. With the continuous breakthroughs in the research field, the application of high power lasers is also more extensive. When the frequency doubling light is emitted from the laser, different wavelengths will act on the separation film simultaneously. Therefore, it is necessary to investigate the damage of optical thin films by laser of single wavelength or multiple wavelengths. The film was irradiated repeatedly by laser aiming, and the damage radius and damage morphology were studied under the action of 1064nm laser and 532nm laser alone and together, as well as the primary and secondary relationship of the damage induced by the two wavelengths. Then, the distribution of explosive damage temperature field was analyzed by simulation. It is concluded that the damage radius at 532nm is larger than that at 1064nm, and the damage depth is deeper. When the two pulses work together, 532nm laser plays a dominant role in the damage process. This study is helpful to better understand the damage mechanism of bridge film and provide reference for the preparation of damage-resistant explosive bridge and laser ignition.