Hasil untuk "Explosives and pyrotechnics"

Yuantong ZHANG, Renshu YANG, Cheng CHEN et al.

Layered composite rock masses are widely found in mining, tunnel excavation, and slope stabilization engineering, representing a common geological structure in nature. Due to their formation conditions, the internal strength of layered composite rock masses often exhibits gradient variations. This study simulates layered composite rock masses using epoxy resin materials and employs a dynamic photoelasticity-digital image correlation integrated experimental system to conduct a visualized, detailed analysis of the propagation process of explosive stress waves in gradient media. To investigate the attenuation patterns and energy flux density evolution of explosive stress waves under both forward and reverse gradient conditions. By comparing the dynamic photoelastic stripe patterns, the study visually analyzes the transmission and reflection characteristics under different propagation paths, and uses digital image correlation to quantitatively assess the differences in the attenuation rates of explosive stress waves. The results indicate that the fringe order of the explosive stress wave remains unchanged in the forward propagation path, with significant reflection at the joint surface. In the reverse propagation path, the fringe order exhibits a decaying pattern, and the dynamic photoelastic fringes maintain good continuity at the joint surface. The explosive stress wave demonstrates better penetration in reverse gradient media. Changes in joints and materials within gradient media alter the rate of horizontal stress attenuation, with faster attenuation observed in positive gradient media. By introducing the Poynting vector to compare energy flux density, it was found that energy flux density decays faster in positive gradient materials at the same measurement points, and the propagation of explosive stress waves in positive gradient materials exhibits an energy-absorbing process.

Jiangzhou PENG, Liujuan PAN, Guangfa GAO et al.

To accurately predict the explosion power fields in buildings, solving the failure of traditional empirical formulas often failing to account for complex environmental factor due to their inability to account for complex environmental factors, and that of numerical simulations inefficient for large-scale urban scenarios and do not meet the needs of rapid damage assessment. Addressing this challenge, an innovative prediction model for explosion power fields based on graph neural networks (GNN) was constructed using an end-to-end strategy. This model enabled rapid and precise forecasting of three-dimensional physical fields, including peak overpressure, peak impulse, and shock-wave arrival times on building surfaces. Compared with numerical simulations, the proposed GNN model demonstrated excellent predictive performance: it achieved a mean square error of 0.97% for predicting surface overpressure parameters of single buildings with varying geometries, and an average prediction error of 3.17% for complex geometric buildings and building communities. When applied to real-world urban settings, the model maintains an average prediction error of 1.29%, completing individual physical field predictions in under 0.6 seconds—three to four orders of magnitude faster than numerical simulations. Furthermore, the model's high-precision predictions allow for the reconstruction of overpressure time history curves at any building surface location and the accurate assessment of structural damage. The proposed GNN model offers a novel approach for rapidly and accurately predicting explosion power fields in urban buildings during blast events. This advancement significantly enhances the capabilities for explosion damage assessment and anti-explosion design in ultra-large-scale complex engineering scenarios, providing substantial engineering value.

Oleksii Galganov, Andrii Ilienko

In this short note, we provide an explicit sufficient condition for non-explosion of Crump--Mode--Jagers branching processes with pure birth reproduction. It shows that the standard sufficient condition for explosion, namely the convergence of the series of reciprocals of the birth rates, is -- at least for rate sequences without excessive oscillations -- remarkably close to being necessary. At the same time, it is not necessary in full generality: we construct a counterexample which also yields a general preferential attachment tree without fitness with an infinite path and no vertices of infinite degree, thereby answering an open question previously raised in the literature.

Yuteng Cao, Tianyu Jiang, Ying Li et al.

With the constant development of energetic materials, numerous explosive molecules have been synthesized, some of which feature competitive performances. However, energetic materials are directly oriented to application requirements. Therefore, more emphasis is gradually placed on route simplification and cost reduction while designing novel energetic molecules. In this work, monocyclic energetic compound 2,4-diamino-6-hydrazineyl-5-nitropyrimidine (3) was successfully obtained. This compound exhibits an alternating “amino–nitro–hydrazino” arrangement, featuring strong intramolecular hydrogen-bonding interaction. With cheap raw material, the whole reaction comprised only two steps, and exhibited simple post processing, only filtration. This novel energetic molecule possesses excellent mechanical security (IS > 40 J, FS > 360 N), acceptable thermal stability (Td = 225 °C), and good detonation parameters (Dv = 8470 m/s, P = 24.9 GPa), indicating that compound 3 may act as a candidate of insensitive explosives.

Jianbing Xu, Jiangtao Zhang, Yinghua Ye et al.

Nano-reactive multilayer films consisting of alternating layers of the nano-aluminum and nano-metal oxide is a new type of nano thermite. These multilayer films can be stimulated by an external energy to promptly release stored chemical energy in a sudden emission of light and heat, which has high energy releasing rate and energy transforming efficiency since the scale of the composite components for nanoscale and the reaction mechanism based on the interaction between molecules. This multilayer composite film can be prepared by Complementary Metal-Oxide-Semiconductor (CMOS) compatible technology with magnetron sputtering, and can be integrated with circuit chips to construct micro-nano energetic devices. In this paper, the influence of processing parameters on the structure and properties of nano-reactive multilayer films is analyzed systematically. And the application of reactive multilayer films in micro igniter is also introduced. In addition, the application prospect and development direction of nano-reactive multilayer films in micro-nano energetic devices are prospected.

Yonghao ZHOU, Zhe YANG, Huan LIU et al.

The leakage of combustible gas could lead to serious explosion accidents, which could cause great damage to people’s lives and property. Explosion suppression technology can effectively reduce the consequences of the explosion accidents, which is an important part of combustible gas explosion safety protection technology. As the core component of explosion suppression device, the performance of the explosion suppressant can directly affect the reliability of explosion suppression system. The research results in the field of explosion suppression at home and abroad are focused on, and the explosion suppression powder and its inhibition mechanism are systematically summarized and analyzed. Based on the different compositions, the explosion suppressing powder is divided into one-component and compound materials. According to the difference of the suppressing mechanism, the one-component suppressing powder is divided into active powder and inert powder. Due to the synergetic effects of different substances, the development of the compound material is the research hotspot. In the literature review part, this paper follows the structure “General introduction of powder materials—Related experimental and theoretical research—Suppression mechanism summary”. The first part provides the general introduction of the material, including the origin, structure and property. The second part offers the summary of the related research result about the material. The third part focuses on the physical and chemical suppression mechanism of different material, which contributes to the deeper understanding of the suppression effect. Finally, the existing problems of the research at present is summarized and the development of the future research work is discussed. In addition, this article proposes to standardize the testing process, emphasizes the use of numerical simulation to guide the suppressing of material synthesis and reduce the blindness of research. The aim of this review is to provide scientific understanding and technical support for the development of high-efficiency explosion suppression technology.

Tomasz Otłowski, Maciej Zalas, Błażej Gierczyk

Abstract Homemade explosives become a significant challenge for forensic scientists and investigators. In addition to well-known materials such as acetone peroxide trimer, black powder, or lead azides, perpetrators often produce more exotic and less recognized Homemade Explosives (HMEs). Mixtures of hydrogen peroxide with liquid fuels are widely acknowledged as powerful explosives. Interestingly, similar explosive properties are found in mixtures of numerous solid materials with H2O2. Notably, powdered groceries, such as coffee, tea, grounded spices, and flour, are particularly interesting to pyrotechnics enthusiasts due to their easy production using accessible precursors, which do not attract the attention of security agencies. H2O2-based HMEs may become a dangerous component of improvised explosive devices for terrorists and ordinary offenders. For the four most powerful mixtures—HMEs based on coffee, tea, paprika, and turmeric—molecular markers useful for identification using the GC–MS technique have been proposed. Furthermore, the observed time-dependent changes in mixtures of H2O2 with these food products were studied and evaluated as a potential method for assessing the age of the evidence and reconstructing timelines of crimes. The paper also discusses the usefulness of FT-IR spectroscopy for identifying H2O2-based HMEs.

Slimane Bekhouche, Djalal Trache, Amir Abdelaziz et al.

The present work aims to study the effect of environmental hazards, namely, temperature and humidity, on the performance and sensitivity of tracer pyrotechnic composition. The experiments showed that the different pyrotechnic compositions, aged under different conditions, are prone to become more sensitive to impact and friction. It is also revealed that aging has a negative impact on luminous intensity for which the thermal aging declined the light intensity by 38.5%, while the moisture deteriorated it by 66%, compared to the pristine composition. The thermal analysis of the aged pyrotechnic compositions demonstrated a direct correlation between the heat of reactions and the magnesium content, the primary heat source, which decreases due to the formation of metal oxides (Mg(OH)2 and MgO) during the aging process. This investigation will certainly contribute to comprehensively understanding the degradation mechanism of tracer pyrotechnic compositions, and provide information on how the physical status of materials influences the luminosity, the sensitivity, and the heat of combustion reaction.

Ayush Koul, Aparna Ojha, Prenav Vimal et al.

Aluminum (Al) holds a pivotal role in augmenting the energetic potential of solid fuel formulations. Its incorporation can notably amplify the energy yield upon combustion. Nevertheless, challenges such as ignition delay and incomplete combustion have hindered its optimal utilization. In the context of hybrid rocket propulsion, where reignition and high regression rates are sought, a promising solution lies in harnessing the potential of metal-fluoropolymer combinations. This paper explores the influence of polytetrafluoroethylene (PTFE) and Viton fluoropolymer additives on the combustion and regression rates of hydroxyl‑terminated polybutadiene (HTPB)-based solid fuels loaded with nano-aluminum (nAl). To comprehensively address these objectives, binary composites of nAl-PTFE and nAl-Viton were prepared using high-energy ball-milling, and the resulting mixtures were incorporated into hydroxyl‑terminated polybutadiene (HTPB)-based fuel through a vacuum-casting technique. The ignition and combustion characteristics of the solid fuels, as well as the post-combustion products, were examined using an opposed flow burner setup to gain insights into their oxidation and combustion mechanisms. The findings demonstrate that the inclusion of PTFE and Viton in nAl has a positive impact on the ignition delay time, combustion behavior, and regression rates of the solid fuels. The HTPB-nAl-PTFE(S3) sample exhibited the shortest ignition delay time of 108 ms, outperforming the other tested samples (S1: 227 ms, S2: 182 ms, S4: 122 ms). Furthermore, the addition of nAl to pure HTPB resulted in an average regression rate of 0.3–0.6 mm/s for HTPB-nAl (S2), representing a two fold improvement compared to pure HTPB-based samples. Compared to the baseline HTPB fuel, HTPB-nAl-PTFE(S3) demonstrated a significant increase in regression rate by approximately 178%, while HTPB-nAl-Viton(S4) exhibited an increased regression rate of 122%. These results highlight the positive influence of fluoropolymers on combustion behavior, ultimately enhancing the overall performance of the fuel. Additionally, the study observed gas-phase reactions during the combustion process, including the reaction between nano-aluminum (nAl) and fluoride, the intermediate product of Al oxidation, and the decomposition products of fluoride. These reactions resulted in the faster fracture of the alumina (Al2O3) shell, leading to improved heat release and regression rate performance.

Xiaolan Song, Zhihong Yu, Kanghui Jia et al.

In light of the challenges posed by the low density, diminished energy levels, and shrinkage holes in the loading arise of the current cast-cured explosive liquid vehicle, TNT, the investigation of low-melting eutectic materials as potential substitutes for TNT has emerged as a focal point of research. By employing the solvent-nonsolvent method, the lowest eutectic mixture of TNBA(2,4,6-trinitro-3-bromoanisole)/MTNP(1-methyl-3,4,5-trinitropyrazole) was synthesized, distinguished by a moderate melting point and markedly elevated energy levels as compared to TNT. Comprehensive SEM, EDS, IR, XRD, and XPS analyses were conducted on the lowest eutectic mixture, substantiating the absence of any chemical interaction between TNBA and MTNP and affirming their exceptional compatibility. Moreover, an exploration into the thermal decomposition behavior and mechanism of the lowest eutectic mixture was undertaken, its mechanical sensitivity was tested, and its detonation performance was evaluated by EXPLO-5 software. The thermal decomposition parameters of the lowest eutectic mixture closely paralleled those of the precursor materials, with the thermal decomposition kinetics model function being identified as the Jander function. The impact sensitivity of the lowest eutectic was 48.1 cm and the friction sensitivity was 12%. Furthermore, the density of the lowest eutectic mixture surpassed 1.8 g/cm3, and its detonation velocity approached 8000 m/s, markedly surpassing the explosive performance of TNT.

Jialin Li, Fen Li, Zhao Xu et al.

Due to the high dispersion of solid powder, it is very easy to form a powder/gas hybrid system, which greatly increases the probability and severity of explosion accidents. The researchers both domestically and internationally have conducted extensive research on the hybrids explosion systems. This paper reviews the combustion characteristics, explosion mechanisms, and explosion prevention experiments of hybrids. Current research results on explosion prevention technology are organized, and the current challenges in experimental studies of hybrids explosions are summarized, providing references for future experimental studies.

Noam Soker

I examine recent theoretical studies and observations of the recent core-collapse supernova (CCSN) SN 20224ggi and find that the likely explanation for its dense, compact circumstellar material is an effervescent model, where parcels or streams of gas are uplifted by stellar convection and pulsation and fall back. The effervescent zone exists alongside the regular wind from the red supergiant (RSG) progenitor of SN 2024ggi. I find that an extended wind-acceleration zone encounters some difficulties in accounting for the required CSM mass. Recent modelling finds the explosion energy of SN 2024ggi to be >1e51 erg, and up to 2e51 erg. I examine this explosion energy against a recent study of the delayed neutrino explosion mechanism and find that this mechanism might have some difficulties in accounting for the required energy. This might suggest that the explosion was caused by the jittering jets explosion mechanism (JJEM). This adds to other recent pieces of evidence supporting the JJEM, particularly point-symmetric CCSN remnants.

Sangita Dutta, Prosenjit Kundu, Pitambar Khanra et al.

This study aims to develop a generalised concept that will enable double explosive transitions in the forward and backward directions or a combination thereof. We found two essential factors for generating such phase transitions: the use of higher-order (triadic) interactions and the partial adaptation of a global order parameter acting on the triadic coupling. A compromise between the two factors may result in a double explosive transition. To reinforce numerical observations, we employed the Ott--Antonsen ansatz. We observed that for a wide class of hypergraphs, combining two elements can result in a double explosive transition.

Cheng-yin Tu, Xiong Chen, Ying-kun Li et al.

Aluminum (Al) particles are commonly added to energetic materials including propellants, explosives and pyrotechnics to increase the overall energy density of the composite, but aluminum agglomeration on the combustion surface may lower the combustion efficiency of propellants, resulting in a loss in two-phase flow. Therefore, it is necessary to understand the agglomeration mechanism of aluminum particles on the combustion surface. In this paper, a high-pressure sealed combustion chamber is constructed, and high-speed camera is used to capture the whole process of aluminum accumulation, aggregation and agglomeration on the combustion surface, and the secondary agglomeration process near the combustion surface. The microscopic morphology and chemical composition of the condensed combustion products (CCPs) are then studied by using scanning electron microscopy coupled with energy dispersive (SEM-EDS) method. Results show that there are three main types of condensed combustion products: small smoke oxide particles oxidized by aluminum vapor, usually less than 1 μm; typical agglomerates formed by the combustion of aluminum agglomerates; carbonized agglomerates that are widely distributed, usually formed by irregular movements of aluminum agglomerates. The particle size of condensed combustion products is measured by laser particle size meter. As the pressure increases from 0.5 MPa to 1.0 MPa in nitrogen, the mass average particle size of aluminum agglomerates decreases by 49.7%. As the ambient gas is changed from 0.5 MPa nitrogen to 0.5 MPa air, the mass average particle size of aluminum agglomerates decreases by 67.3%. Results show that as the ambient pressure increases, the higher oxygen content can improve combustion efficiency and reduce the average agglomeration size of aluminum particles.

Clint Guymon, Ming Liu, Josephine Covino

Separation Distances are used throughout the world to protect people and assets from the potential hazardous effects from propellants, explosives, and pyrotechnics. The current separation distances for Hazard Division (HD) 1.3 substances and articles used in the United States, in some cases, may not adequately protect against the effects from heat flux and debris when those substances and articles are ignited in a confined structure. Multiple tests in such a confined scenario with HD 1.3 substances have shown that the heat flux and debris hazards could result in injury at distances beyond the current specified explosives safety separation distance (ESSD). Herein are the recommended ESSDs for confined as well as unconfined HD 1.3 articles and substances based on the analysis of hundreds of tests. Recommended ESSDs include a smaller value for unconfined quantities less than 145 kg and ESSDs that are consistent with NATO distances for confined substances and articles.

Ying Xiong, Panwang Zhou, Jianyong Liu et al.

Photo-induced decay may serve as a way to decompose energetic materials under some special conditions, and understanding the related mechanism is crucial to guide the determination of storage, transport and use conditions. In this work, we confirm the photo-induced intramolecular hydrogen transfer (HT) of 2,4,6-trinitrotoluene (TNT) by matrix-isolation infrared spectroscopy method; meanwhile, no backing of the H transferred isomer to the original TNT molecule is found when annealed and it exhibits an irreversible HT. With time-dependent density functional theory and state-averaged complete-active-space self-consistent-field calculations, we propose a photoisomerization path that occurs in the T1 state. This is because the H transferred isomer can readily back to the ground state (S0 state) by means of intersystem crossing (T1/S0), with a rather high energy barrier required to overcome for the reverse reaction to the original TNT molecule. Thereby, the irreversible HT when annealed is understandable.

Mengjie Zhang

In this paper, we prove that entropy degeneracy and entropy explosion happen in the flow constructed by Ohno. We also construct a flow which has the only one invariant and ergodic measure supporting at a fixed point. This flow is no entropy explosion.

Ruihua Zhang, Jihua Liu, Changhui He et al.

Studying the stress propagation and damage mechanism for the mechanical environment of the gun bore is an important way to popularize and apply the new propellant. Taking rosette 19-hole gun propellant as the research object, transverse drop hammer impact tests for the propellant under low temperature were carried out. Electron microscope tests for the propellant interface were conducted before and after the drop hammer tests. Then, a simulation mechanical model of the propellant was established by using the discrete element method with the rosette shape and 19 inner holes taken into consideration. And a simulation of the transverse drop hammer impact on the propellant was carried out. Research results show that the discrepancy between the simulation and test results of the maximum drop hammer force is 3.16%; the amplitude and pulse width of the drop hammer force-time curves and the fracture damage in the simulation and test studies are also in good agreement. The results reveal that the established simulation model is able to well describe the stress propagation and fracture process of the rosette 19-hole gun propellant under low temperature when affected by transverse drop hammer impact, providing an effective theoretical model basis for studying the damage mechanism of the new propellant.

Jiahao Dong, Suhang Chen, Hui Li et al.

In view of the volatile quality of 2,4,6-triazido-1,3,5-triazine (TAT) after melting, a special high-pressure hermetic crucible was used to analyze the compound's thermal decomposition behaviors. The complete exothermic decomposition process of TAT was obtained, and the extrapolated onset temperature, peak temperature, and decomposition enthalpy at a heating rate of 10.0 °C/min were measured as 195.1 °C, 221.4 °C and -3753.0 J/g, respectively. The hermetic thermal decomposition kinetic equation was thus obtained. The self-accelerating decomposition temperature and critical temperature of thermal explosion for TAT were 173.7 °C and 186.6 °C, respectively. The specific heat capacity of TAT was determined, and the molar heat capacity was 234.67 J/(mol · K) at 298.15 K. It can be observed that TAT possesses a high thermal decomposition temperature and a drastic heat release.