Hasil untuk "Explosives and pyrotechnics"

Chao HUANG, Weizheng XU, Fan ZENG et al.

Blasts near the water surface are one of the major threats to ships. Experiments were carried out to study the load characteristics of the shock wave on the water surface with TNT/RDX(40/60) explosives. Three typical scaled burst heights were used: contact burst, near-surface blast, and air blast. In the experiments, overpressures in air and water were obtained, and high-speed photographic was used to record the explosion images. A numerical simulation method based on a five-equation model was used to study further the explosion phenomenon and the loading characteristic of shock waves on the water surface. The numerical simulation results are in good agreement with the experimental results. The results show significant differences among contact bursts, near-surface blasts, and air blasts. In the contact burst, the detonation products drive the water surface directly, creating a hemispherical cavity, and the water at the edge of the cavity is squeezed upwards, forming a hollow water column. In the near-surface blast, the collision of the detonation products with the water surface is relatively weak, and the shock wave on the water surface mainly propagates outwards as Mach waves along the water surface. In the air blast, there are clear regular and irregular reflection zones of the shock wave on the water surface. Under the same yield conditions, the overpressure on the water surface of the contact burst is lower than that of the near-surface blast, but the pressure in the water is more stressful. Therefore, the water surface can no longer be considered a rigid plane. The formulas of overpressure and positive pressure duration of shock wave on the water surface within the range of 0.5～4.0 m/kg1/3 in the contact burst and the near-surface blast were obtained through data fitting, which provides a reference for shock wave loading calculation and analysis.

Yu GE, Quan WANG, Wenyan ZHU et al.

Renewable energy is addressing some of the key challenges facing global society today, and zero-carbon energy systems are the fundamental way to achieve carbon neutrality. Therefore, hydrogen and ammonia have gained great attention as zero-carbon energy sources. To further study the combustion characteristics of ammonia-hydrogen-air premixed gas flame inside and outside the duct, the influence of ammonia doped amount (φ) on the flame morphology and the evolution of pressure inside and outside the duct under stoichiometric ratio was explored with the help of high-speed photography and pressure sensor in the 2000-mm-long stainless steel duct with a 400-mm-long and 70-mm-wide observation window. The results show that φ significantly affects the pressure inside and outside the duct, and the time to reach the reverse flow phenomenon caused by the secondary explosion also increases. The pressure measuring point PS1 is set at 400 mm away from the explosion vent in the duct to collect data. The pressure curves in the duct under each working condition are presented as a three-peak structure, named p1, p2, and p3. The three pressure peaks are caused by the rupture of the explosion vent film, the gas venting in the duct, and the gas reverse generated by the secondary explosion outside the duct. The size of p1 depends on the tensile strength of the explosion venting membrane, and its amplitude is almost independent of the φ. p2 and p3 both increase with the increase of φ, and the p3 increase rate is the largest when φ is in 50%–65%. p2 changes from a single peak to a fluctuating pressure platform in the pressure curve diagram, and the time of the platform extends with the increase of φ. The pressure measurement point PS2 is set at the horizontal central axis, 500mm away from the explosion vent outside the duct, to collect data. And the peak pressure of the secondary explosion outside the duct (pout) decreases with the increase of the φ, and the time to reach pout increases. This study provides a theoretical basis for the utilization of ammonia and hydrogen energy.

Yun Shen, Jianbing Xu, Yinghua Ye

Initiating explosive devices are the primary energy and driving force of a weapon system, which can be excited by some form of external energy (mechanical, thermal or electrical) to produce chemical reactions such as combustion and explosion. With the development of micro-electro-mechanical system (MEMS) technology, initiating explosive devices based on MEMS technology have become a research hotspot in recent years. The energetic metallic bridge is a critical component in initiating explosive device based on MEMS technology, where MEMS technology integrates reactive multilayer films (RMFs) with metallic bridges to achieve energy amplification. In this review, the latest progress of metallic bridges and energetic metallic bridges is summarized from the aspects of types of metallic bridges, structures, preparation methods and reaction mechanism. The application of energetic metallic bridges based on two types of reactive multilayer films is mainly introduced. This article investigates the energy conversion models and principles governing various types of energetic metallic bridges under diverse excitation conditions. The analysis provides a theoretical foundation and technical support for the design and optimization of energetic metallic bridges across different ignition conditions. At the end of the review, an outlook and discussion on the development trends of energetic metallic bridges are presented.

Mianji Qiu, Baoyun Ye, Jiaxing Wang et al.

To investigate the reaction process between 3,3′-bis(aminomethyl)oxetane/tetrahydrofuran copolymer(PBT) binder and acetylenic curing agents, this study employed bis-propargyl-succinate (BPS) as the curing agent and tris(iodoacetate) trimethyl propane ester (TMP-N3) as the cross-linking agent. The curing reaction kinetics of PBT were analyzed using Fourier Transform Infrared Spectroscopy (FT-IR). The curing kinetic model was fitted by the Kamal model and the apparent activation energy (Ea) was calculated by Friedman's isoconversional method. The results indicated that the reactions of both PBT/BPS and PBT/BPS/TMP-N3 are autocatalytic in nature. It was observed that with an increase in the TMP-N3 content, the non-catalytic activation energy (Ea1) showed a decreasing trend, while the autocatalytic activation energy (Ea2) initially increased and then decreased. Additionally, as the curing progressed, the apparent activation energy (Ea) demonstrated an initial increase followed by a decrease. Detailed analysis of the curing kinetics at the molecular level shows that this is a combined effect of the viscosity change of the system, the diffusion of reactants, the autocatalytic effect and the interaction between molecular chains. Furthermore, the mechanical properties of elastomers in different systems were examined using a universal testing machine. The results show that as the TMP-N3 content increases, the mechanical properties of the elastomers initially improve and then decrease. Among these, In the tested samples, sample P-B-N20 shows the best mechanical properties. Compared with the P-B sample, the tensile strength increased by 33.6%, and the breaking elongation increased by 15.4%.

Teng WANG, Guang ZHENG, Yuxuan ZHENG et al.

The dynamic mechanical properties of deep rocks are critical to understanding geological processes and optimizing resource extraction. Accurately understanding the dynamic mechanical properties of deep rocks not only provides insights into the geological processes and evolution of the earth’s interior, but also offers a theoretical basis for the effective extraction of deep minerals and energy. In this study, the dynamic mechanical behavior of white sandstone from a coal mine was experimentally and numerically analyzed under uniaxial, biaxial, and triaxial stress conditions. Numerical simulations based on three constitutive models consisting of the Riedel-Hiermaier-Thoma (RHT) model, the Holmquist-Johnson-Cook (HJC) model, and the continuous surface cap model (CSCM), were validated by using experimental results from three-dimensional Hopkinson bar experiments. The results indicate that the shear failure damage of white sandstone specimens decreases with the increasing prestress, with triaxial stress conditions yielding significantly lower damage than uniaxial or biaxial conditions. Among the three models, the RHT constitutive model demonstrates the closest agreement with the experimental results in terms of stress waveforms, peak stress, peak strain, and damage degree. Compared with the experimental data, the RHT model exhibits a stress peak deviation ratio of 3.5% and 13.6% for the reflected wave under uniaxial and biaxial conditions, respectively, while the stress peak deviation ratio for the transmitted wave is the lowest. Additionally, the peak stress and strain values predicted by the RHT model are numerically closer to the experimental results. The damage state predicted by the RHT model also aligns well with the experimental observations: under uniaxial loading, the damage exhibits a U-shaped pattern, whereas the HJC model showed a larger V-shaped damage pattern and fracture, and the CSCM model displayed surface damage with a smaller affected area. In terms of energy absorption and dissipation, the simulation results based on the three constitutive models shows minimal differences. The incident, reflected, and transmitted energy values are nearly identical across all three models. In addition, the damage degree of the white sandstone specimens increases with the impact velocity. The damage simulation results of the three constitutive models also show an increasing trend with the impact velocity, while retaining the damage characteristics.

Bei LI, Haoshen YU, Bing HAN et al.

Understanding the generation, transformation, and dissipation mechanisms of energy in high-pressure tanks during fire scenarios is of critical significance for the consequence assessment of explosion accidents. This study investigates the differences in properties between high-pressure hydrogen storage tanks and nitrogen tanks under fire conditions through comparative experiments. Fire tests were conducted using 6.8L-30MPa type Ⅲ tanks. The results indicate that fire exposure can significantly impair the pressure-bearing capacity of the tanks. Specifically, the critical bursting pressure decreased from 125.1 MPa at room temperature to 46.8 MPa under fire conditions, representing a reduction of 62.6%. The explosion dynamics of hydrogen tanks were characterized by typical physical-chemical composite features. A fireball with a diameter of 9 m was formed during the explosion. The peak shockwave pressure measured at a distance of 2 m reached 882.47 kPa, with a positive pressure duration of 168.11 ms. In contrast, nitrogen tanks experienced only physical explosions, with a peak shockwave pressure of 59.42 kPa and a positive pressure duration of merely 2.17 ms. This study analyzed the energy conversion pathways during explosions of high-compressed gas tanks (H2 and N2) in open environments. A novel method for assessing the blast power of hydrogen storage cylinder explosions in unconfined spaces was developed. Initially, the physical explosion energy was calculated based on fundamental parameters such as critical burst pressure, nominal volume, and initial filling pressure of the high-pressure tanks. The applicability of five mechanical energy calculation models was compared. Subsequently, the mass of hydrogen was determined using the actual gas equation, and the total chemical explosion energy was derived by integrating the heat of combustion of hydrogen. Finally, considering the contributions of mechanical and chemical energy to the shock wave intensity, the total explosion energy was converted into shock wave energy using an open space energy correction factor. Quantitative analysis and error verification were conducted in conjunction with measured data. The findings of this research provide essential support for enhancing risk assessment of explosion accidents involving high-pressure hydrogen storage devices.

Jiashuai Wang, Bo Wu, Lingfeng Yang et al.

Thermites are widely used in propellants, explosives and ignition materials because of their high heat release rate and good combustion efficiency. Structural control over thermites to achieve improved performance leads to a promising research area. Among these, core-shell structured composites have attracted wide attention due to their excellent properties and close contact among components. Herein, core-shell structured α-AlH3/Fe2O3 thermites were prepared, which exhibit high heat-release and excellent combustion performance. At an equivalence ratio of 2.0, the core-shell structured α-AlH3/Fe2O3 has the most heat release (1213.8 J/g) and the lowest reaction activation energy (147.5 kJ/mol). The ignited combustion performance of α-AlH3/Fe2O3 was notably strengthened by the shorter ignition delay period (11 ms). Interestingly, the core-shell structured α-AlH3/Fe2O3 was less sensitive to electrostatic discharge, which suggests that the core-shell structured α-AlH3/Fe2O3 reaches the goal of high energy release and electrostatic safety. The core-shell thermite system with α-AlH3 as metal fuel could provide an efficient alternative to hunt for thermites with high reactivity.

Yi Wang, Xiao-lan Song, Chongwei An et al.

Randall L. Simpson

Agin P, Ashisha A Aloysius, Dhaneesh K John

Lead-based primary explosives are highly common in the military, mining and pyrotechnics. However, lead is non-biodegradable and poses a serious threat to the environment and living beings. Lead is a potent neurotoxin that causes organ damage and affects cognitive development in humans. It contaminates the air, water and soil, thereby affecting the flora and fauna through bioaccumulation and food chain contamination. It is also notorious for degrading soil fertility and biodiversity. The search for a greener alternative landed on nanostructured materials, fuelling considerable research in this domain. Although their large-scale manufacturing is challenging, these materials promise enhanced performance, safety and reliability over existing systems. The SFE method has been identified as a major breakthrough in facilitating mass-scale manufacturing of such explosive nanoparticles with decent productivity. Coating these nanoparticles with nanothermites resulted in a benign alternative with improved performance over traditional lead-based explosives, called NSTEX. This eliminates the risk of lead contamination while also improving the explosive performance. Despite the success of this system, stabilising these mixtures into operational systems has remained a challenge, hindering its application. A breakthrough in this aspect could be a significant step forward in greener and safer pyrotechnics for the future.

Andy Haverly, So Yeon Kim, Ju Li

Climate change is a rapidly accelerating problem that requires fast and large-scale carbon sequestration to prevent catastrophe. This paper proposes a novel approach to use explosives for large-scale carbon sequestration. Combining the long-practiced method of explosive mining with newer enhanced rock weathering techniques, we propose a faster, greener, and profitable method of large-scale carbon sequestration. This method is applicable for all explosives, including thermonuclear, and can be done safely with minimal anthropological and ecological impact. We estimate a cost of $0.68/ton of CO2 sequestered.

Jason Loiseau, Sebastian Rodriguez Rosero, Yaroslava Poroshyna et al.

The potential for reactive metal fuels to enhance the energetic output of high explosives has generated an enduring interest in the study of composite explosives. It has typically been demonstrated that added metal fuels can have little or even deleterious impact on the accelerating ability of composite military explosives relative to baseline performance. Often this has led to the assumption of limited reaction of the metal fuel over microsecond timescales. The widespread availability of Photonic Doppler Velocimetry has enabled time resolved measurement of accelerated confinement, ultimately demonstrating prompt reaction of metal fuels. Motivated by this observation, hydrocode modelling studies, and prior author's modifications of Taylor's tubular bomb model, we developed a differential equation form of Taylor's model in a manner where it is straightforward to add sources or phases. An afterburning version of the JWL equation of state was used to add energy to the gaseous products at a linear, time-dependent rate. The metal particles are assumed to remain in velocity equilibrium with the gaseous products and do not transfer heat or influence chemical composition. We focus exclusively on added aluminum as it remains the most ubiquitous choice of metal fuel. The model is initialized with a CJ state calculated from Cheetah 2.0 assuming the Al particles are inert in the detonation. JWL coefficients for the baseline explosive are also used. Qualitative agreement is observed between the model and previously published experiments.

Xinghe Jiang, Yuhang Li, Yuzhu Li et al.

Detecting concealed chemicals and explosives remains a critical challenge in global security. Terahertz time-domain spectroscopy (THz-TDS) offers a promising non-invasive and stand-off detection technique owing to its ability to penetrate optically opaque materials without causing ionization damage. While many chemicals exhibit distinct spectral features in the terahertz range, conventional terahertz-based detection methods often struggle in real-world environments, where variations in sample geometry, thickness, and packaging can lead to inconsistent spectral responses. In this study, we present a chemical imaging system that integrates THz-TDS with deep learning to enable accurate pixel-level identification and classification of different explosives. Operating in reflection mode and enhanced with plasmonic nanoantenna arrays, our THz-TDS system achieves a peak dynamic range of 96 dB and a detection bandwidth of 4.5 THz, supporting practical, stand-off operation. By analyzing individual time-domain pulses with deep neural networks, the system exhibits strong resilience to environmental variations and sample inconsistencies. Blind testing across eight chemicals, including pharmaceutical excipients and explosive compounds, resulted in an average classification accuracy of 99.42% at the pixel level. Notably, the system maintained an average accuracy of 88.83% when detecting explosives concealed under opaque paper coverings, demonstrating its robust generalization capability. These results highlight the potential of combining advanced terahertz spectroscopy with neural networks for highly sensitive and specific chemical and explosive detection in diverse and operationally relevant scenarios.

Vladimir V. Parakhin, Gennady A. Smirnov

In order to discover of high-energy materials with characteristics that surpass modern benchmarks, it is necessary to study the widest range of potential structures. The design of energetic compounds using high-nitrogen cage scaffolds provides new opportunities. One of the promising representatives of polycyclic multinitragen cages is the hexaazaisowurtzitane, since the most powerful explosive CL-20 is based on it. In recent years, the synthesis of CL-20 analogues has been actively developed. This review presents progress in the synthesis, performance and study of the structure-property relationship for energetic polynitro hexaazaisowurtzitanes over the past decade.

Jun Wang, Jie Chen, Wei Cao

Introducing additional oxidizers in aluminized explosives is an effective way to improve energy performance by enhancing the secondary combustion reaction. In this work, perfluorocarbon as oxidizer has been introduced into TATB/Al based energetic materials to improve combustion reaction and energy output performance. The uniform TATB/Al/perfluorocarbon composites are prepared through acoustic resonance mixed technology, and the energy and pressure output performance are fully studied in air blast and underwater explosion. A significantly exothermic peak derived from the reaction between fluorine and Al is observed between 540 ℃ and 580 ℃ for TATB/Al/perfluorocarbon. The heat of explosion of TATB/Al/perfluorocarbon is increased first and then decreased with F/Al ratio from 0 to 0.608. The highest heat of explosion is 6021 J/g for TATB/Al/perfluorocarbon with F/Al ratio of 0.274. Furthermore, the enhanced working capacity, the significantly enlarged fireball and relatively high overpressure are obtained for TATB/Al/perfluorocarbon. More importantly, the shock impulse and first bubble oscillation time of TATB/Al/perfluorocarbon have been increased by 23.2% and 21.18% during underwater explosion, respectively. The results further illustrate that adding perfluorocarbon is a feasible approach to enhance energy output due to combustion reaction between fluorine and Al, which can be applied in explosives and propellants.

Roberto Sanchirico, Valeria Di Sarli

The shelf life of energetic materials (EMs) (i.e., explosives, propellants, and pyrotechnics) is strictly linked to safety and functionality. Therefore, a priori knowledge of this parameter is of paramount importance. The standard method for predicting the shelf life of EMs, the so called multi temperature aging method, is tremendously time and money consuming. Specifically, it consists of massive isothermal accelerated aging tests at temperatures typically between 40 and 80°C for relatively long time periods (from months to years) with different aging time intervals, followed by analysis of the aging-induced changes. A subsequent kinetic analysis with Arrhenius evaluation provides the effective activation energy for calculating shelf life at lower storage temperatures. In this work, a much less time- and resource-intensive approach is presented as a possible alternative for the shelf life prediction of EMs. This approach is based on the kinetic analysis of decomposition data gathered by using thermal analysis techniques, which are usually operated under dynamic (i.e., non-isothermal) conditions and possess the advantage of a rapid reaction process, and requires accelerated aging tests only to validate the kinetics extracted from such data. Results from the literature to support this alternative approach are discussed, with particular emphasis on those obtained by the present authors.

Jianbing Xu, Jiangtao Zhang, Fuwei Li et al.

With the development of micro-spacecraft technology, micro-nano satellites have the advantages of small size, low power consumption, short development cycle, formation networking, etc., and can complete many complex space tasks at a lower cost. Micro-nano satellites require a micropropulsion system with the capability of performing precise total impulse and thrust to execute maneuvers, such as attitude control, orbital transfer, and gravitation compensation. In contrast to other micropropulsion systems, solid propellant microthrusters (SPM) arrays based on micro-electromechanical system (MEMS) technology possess a simple structure and quick response, which is a potential micropropulsion system. In recent years, many research groups have done a lot of research on SPM arrays. In this paper, the latest progress of SPM arrays is summarized from the aspects of structure design, propellant selection, bonding technology, ignition unit type and micro-thrust test, and some suggestions for the future development direction are given.

D.V. Khakimov, T.S. Pivina

The results of modeling the structure of compounds 2,4,7,9-tetranitrobenzo[c]cinnoline (1) and 1,2,3,4-tetrazino[5,6-f]pyridazino-1,2,3,4-tetrazine 1,3,7,9-tetra-N-oxides (2) containing a pyridazine core are presented. The structure in the gas phase was estimated by quantum chemistry methods (DFT, B3LYP), on the basis of which the Atom-Atom Potentials method was used to model crystal packings in 35 most common space symmetry groups, which made it possible to identify the optimal packings and structural classes corresponding to them. Some physicochemical properties of the compounds have been calculated. It has been determined that the compounds under consideration have a molecular-crystal density of 2 g/cm3 and a high enthalpy of formation, which indicates the prospects for their use as high-energy-density materials.

Dany Frem

The Gurney velocity is an important performance parameter that characterizes the metal pushing capability of conventional chemical explosives. Herein, this study proposes a mathematical model that aims to provide a simple and effective means by which the Gurney velocity of pure and mixed CHNO-based explosives can be accurately determined using as input information the volumetric heat of detonation, the parameter psi (Ψ) and an adjustable parameter (λ) that accounts for the type of the explosive being studied. The new model proved adequate for evaluating the Gurney velocity of sensitive and insensitive explosives of military interest, including melt-castable and plastic-bonded explosives (PBXs) and showed superior predicting performance compared to benchmark models. It is believed that the Gurney velocity obtained by the new method along with the Gurney-type equations would be very helpful for ordnance engineers for calculating the peak fragment deployment velocity from various warhead geometries, including omnidirectional and directed energy warheads for use in various weapons systems.

Weiqiang Pang, Xu Xia, Yu Zhao et al.

Burning rate catalysts (BRCs) are usually utilized to adjust the burning rates of solid rocket propellants (SRPs). Carbon nanotubes (CNTs), for their unique structure and properties, have been studied by several researchers worldwide with a wide range of applications. In this paper, several worthy CNTs-based materials and effects are described. Specifically, the influence of CNTs on the thermal behavior of energetic materials (EMs) are discussed, and we investigated the impact of CNTs/metal (metal oxide, MO) composites on the thermal degradation of EMs. Applications for SRPs and solid rocket nozzle motors might benefit from a focus on the examination of the burning rate, pressure exponent characteristics, and hazardous aspects. It was discovered that CNTs, as opposed to the comparable micro-sized additives, can modify the combustion behavior and speed up the burning of SRPs. Lastly, the difficulties encountered in implementing some of these applications are also examined in terms of manufacturing, processing, pricing, and potential future uses.