Hasil untuk "Explosives and pyrotechnics"

Tianhao LIU, Nan JIANG, Chuanbo ZHOU et al.

To investigate the protective effect of ground concrete cushion layers on buried pipelines used for water transmission, field rockfall impact tests were conducted by pre-burying multi-section bell-and-spigot concrete pipelines and casting in-situ concrete cushions on the ground. Combined with the DH8302 dynamic strain testing system, the spatial distribution characteristics of dynamic strain in the pipeline body and the variation law of earth pressure at the bell-and-spigot joints were analyzed. The LS-DYNA numerical simulation software was used to establish a detailed model of the rockfall impact test, and the reliability of the numerical model was verified by comparing simulation results with test results. By increasing the impact energy of rockfalls, the failure characteristics of buried bell-and-spigot concrete pipelines were studied. The influence mechanism of concrete cushion parameters (thickness and strength) on the protective effect was further analyzed by varying these parameters. The results show that under the condition of a burial depth of 2 m, unstable crack propagation in the pipeline body is more likely to cause leakage of bell-and-spigot concrete pipelines under rockfall impact. The peak tensile strain in the pipeline body decreases nonlinearly with the increase of cushion thickness and strength. The cushion thickness must exceed a critical value (15 cm) to significantly dissipate energy, and there is an optimal strength range (C30−C35). Excessive strength enhancement will reduce protective efficiency. Cushion thickness accounts for 74% of the protective effect contribution, indicating that the design principle of “geometry prior to material” should be followed. It is recommended to use a concrete cushion with a strength of C30−C35 and a thickness large than 0.2 m, which can significantly reduce the risk of pipeline impact damage and provide a quantitative design basis for pipeline protection in mountainous areas.

Chen ZHANG, Fei GAO, Rui HE et al.

In order to investigate the dynamic mechanical properties of ultra-high performance concrete (UHPC) under coupled high-temperature and explosive impact effects, a 75 mm-diameter high-temperature split Hopkinson pressure bar (SHPB) apparatus was employed. Uniaxial compression tests were conducted on C140 UHPC specimens in the temperatures ranging from 25 ℃ to 600 ℃ and the strain rate ranging from 90 s−1 to 200 s−1. A systematic analysis was performed on the strength, strain, toughness, stress-strain relationship, and failure modes of the material under the combined condition of high temperature and impact loading. The influence of temperature and strain rate on the dynamic mechanical properties was revealed, and the yield surface of the Holmquist-Johnson-Cook (HJC) constitutive model was modified by incorporating thermal effects. The results indicate that UHPC exhibits a significant strain rate strengthening effect under high-temperature dynamic compression, while elevated temperatures simultaneously degrade its mechanical properties. The evolution of material strain capacity and toughness stems from the synergistic interaction between thermal and strain rate effects. At identical temperatures, increased strain rates exacerbate the damage of UHPC. When temperatures exceed 400 ℃, matrix degradation and steel fiber oxidation cause the material to exhibit overall brittle failure characteristics; however, its local core region remains integrity and retains notable residual load-bearing capacity. The modified HJC yield surface is suitable for describing the dynamic mechanical behavior of this material under coupled high-temperature and impact conditions. These findings provide theoretical foundations and data support for the safety design and evaluation of military and civil protective engineering.

Shujian YAO, Yanjing WANG, Yikai CHEN et al.

Against the backdrop of rising global terrorism and industrial accidents, research on infrastructure safety under blast impact has become critically urgent. As a pivotal approach for investigating dynamic responses and damage characteristics of materials and structures subjected to explosive loading, the equivalent blast-loading techniques, which show safe, efficient, and accurate, have emerged as both a research frontier and challenge. This review synthesizes advancements in equivalent blast-loading techniques for far-field explosion simulation, encompassing explosive-driven shock tubes, high-pressure gas-driven shock tubes, drop-weight impact testing machines, and hydraulically-actuated simulators. While each technique exhibits distinct advantages and limitations in simulating blast shockwaves, all strive to establish controlled and secure experimental environments that reproduce high-velocity air flow fields and pressure waves generated by explosions. Through comparative assessment, their performance in load replication fidelity, applicability, and operational efficiency are elucidated, alongside discussions on implementation challenges and potential. Finally, a novel blast simulation technique leveraging liquid-gas phase-transition-driven expansion is introduced and the follow-up research directions are prospected.

Mohammed Dourari, Ahmed Fouzi Tarchoun, Djalal Trache et al.

This study investigate the catalytic behavior of activated carbon-supported metal oxides on the thermal decomposition of a double-base propellant comprising nitrocellulose (NC) and diethylene glycol dinitrate (DEGDN). Three metal oxides (MxOy: CoO, CuO, Fe2O3), successfully grafted onto activated carbon (AC), are thoroughly characterized with Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). These latter were introduced into energetic NC-DEGDN formulation to assess their catalytic activity. The thermal characterization using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) provided valuable insights into the thermal properties and reactivity of the NC/DEGDN/AC-MxOy composites. Experimental results revealed that while the different AC-MxOy additives had a minimal effect on the peak decomposition temperature of NC/DEGDN, they resulted in a significant increase in both the reaction enthalpy and the density of the composites. Isoconversional kinetic studies showed that the incorporation of AC-MxOy reduced the apparent activation energy of the NC/DEGDN composite by up to 35%, with ACCoO showing the highest catalytic efficiency. These findings highlight the potential of AC-MxOy additives to enhance the performance of the double-base solid propellants and provide a basis for future research in this area.

Valery P. Sinditskii, Sergey P. Smirnov, Anastasia D. Smirnova et al.

The kinetics and mechanism of thermal decomposition of high-energy 3,4,5-trinitro-1H-pyrazole (TNP) and 1-methyl-3,4,5-trinitro-1H-pyrazole (MTNP) and the combustion behaviour of these compounds were investigated. The thermal stability of the nitropyrazoles was determined using both differential scanning calorimetry and an isothermal manometric method. The experiments demonstrated that the isomerisation step of the nitro group, previously hypothesised to play a significant role in the TNP decomposition process, does not have a substantial impact. Based on the burning rate experiments and thermocouple measurements, the decomposition kinetics of TNP and MTNP were obtained over a wide temperature range. The kinetic parameters of TNP and MTNP decomposition (activation energies of 155.4 kJ/mol and 164.2 kJ/mol and log (A, s-1) values of 13.06 and 14.00, respectively) were found to be more indicative of the nitro group detachment reaction than the intramolecular oxidation of carbon by oxygen of the nitro group. The leading combustion reaction occurs in the molten layer at the boiling point and its rate is consistent with the kinetics of the initial stages of TNP and MTNP decomposition. The temperature dependence of the vapour pressure of the trinitropyrazole derivatives was determined. The kinetic data obtained were used to make thermal safety predictions for the trinitropyrazole derivatives.

Nikhil S Prakash, Akhil G, Amjith L R

Anticipating a doubling in global air travel demand by 2040, the present work underscores the need for innovation in aviation propulsion systems. This study presents the design and analysis of tubular combustors for lower Mach numbers in Turbo-Ramjet engines, utilizing input parameters derived from automotive turbochargers. The combustion chamber design is based on thermodynamic analysis, incorporating empirical data for optimal configuration. Three-dimensional simulations were conducted using CATIA V5 and ANSYS 2018 software to model and analyze three geometric configurations of chamber. Various configurations, including those with and without cooling holes and swirl vanes, were used to analyze fluid dynamics and combustion behavior. Velocity and temperature profiles were assessed at specific positions along the combustor, notably at x = 73 mm, x = 138 mm, and x = 195 mm. Simulation results indicate that MODEL 1, without cooling holes, exhibited non-uniform combustion with a peak surface temperature. MODEL 2 showed poor flame stabilization due to the absence of a swirl vane. MODEL 3, achieved optimal performance, with a peak temperature of 2241 K and outlet temperature reduction near the walls to approximately 1124 K and with shortest ignition delay of 40 mm. These findings, supported by graphical results, highlight MODEL 3′s suitability for efficient combustor design and performance optimization.

M. Ben Ali, M. El Hazzat, M. Flayou et al.

The management of sewage sludge (SS) is a significant global environmental challenge. Thermochemical conversion methods like incineration, pyrolysis, and gasification offer a way to reduce SS volumes and recover energy, yet their complexity requires a deep understanding of SS reactivity and conversion product properties for effective use and scale-up. This study investigates the non-isothermal combustion kinetics of SS, identifying six reaction stages through deconvolution analysis. Kinetic parameters were estimated using the isoconversional method for each pseudo-component, specifically the Kissinger-Akahira-Sunose (KAS) and Ozawa-Flynn-Wall (OFW) methods were utilized to determine activation energies, while the master plot method identified nth order kinetics (Fn) with n < 1 as the dominant reaction mechanism. The found activation energies were ranging from 71.57 kJ/mol to 267.91 kJ, and the pre-exponential factors from 2.35 × 103 min⁻¹ to 2.35 × 1017 min⁻1. Further thermodynamic assessments provided insights into enthalpy (ΔH = 65.62 to 261.69 kJ/mol), entropy (ΔS = -192.31 J/(mol·K) to 71.68 J/(mol·K)) and Gibbs free energy (ΔG = 149.19 kJ/mol to 208.00 kJ/mol) for the pseudo-components, contributing to a comprehensive kinetic and thermodynamic profile of SS combustion.

Hongli WANG, Zelin ZENG, Xingya SU et al.

With the increasing speed of trains, the impacts of mechanical shock, arc heat, and Joule heat on the high-speed railway catenary system have become increasingly significant. The coupling effect of high temperature and impact load has emerged as a key limiting factor for the safe operation of the pantograph-catenary system. This study focuses on copper-magnesium alloy materials used in the catenary system to address the challenges of dynamic impact and friction-induced heat generation in high-speed railways. To investigate the mechanical properties of the high-speed railway pantograph-catenary system under service conditions such as dynamic impact and frictional temperature rise, a DF14.205D electronic universal testing machine and a split Hopkinson pressure bar were employed. The uniaxial compression mechanical properties of the copper-magnesium alloy in the catenary were tested over a strain rate range of 0.001 s−1 to 3000 s−1 and a temperature range of 293 K to 873 K. The strain-rate effect and temperature sensitivity of the stress-strain response were carefully analyzed. The study also revealed the compression deformation mechanism and the evolution law of the alloy’s microstructure under the combined influence of strain rate and temperature. Furthermore, a dynamic constitutive model was established to accurately describe the plastic flow behavior of the material. The findings indicate that during compression, the copper-magnesium alloy materials exhibit significant strain-rate strengthening and temperature softening effects. These effects result from the combined action of work hardening, strain rate, and temperature softening. When the temperature exceeds 473 K, temperature softening becomes the dominant factor in material deformation, and the elevated temperature can stimulate dynamic recovery and dynamic recrystallization processes. The modified Johnson-Cook model was found to be capable of accurately predicting the plastic flow stress-strain response. These research outcomes provide valuable guidance and references for the safety design and evaluation of the high-speed train pantograph-catenary system during its service.

Yan Zhang, Jianhua Yi, Xiao Xie et al.

The ignition characteristics of nano-aluminum (nano-Al) in oxygen and steam environments were numerically studied in this work. A detailed kinetic mechanism of nano-Al combustion was developed, and the effects of initial reaction temperature, ignition pressure, the phase of reactant, and the ratio of O2 and H2O in the oxidizer on the oxidation performance of aluminum (Al) were analyzed in detail. Numerical results show that increasing the initial temperature promotes the ignition of liquid-phase Al, while the promotion is not significant for gas-phase Al ignition. The oxidation of liquid-phase Al is significantly slower than that of gas-phase Al, and the phase transition reaction of liquid-phase Al exhibits a typical endothermic process, which results in a temperature drop before ignition. The increase of initial reaction pressure can accelerate the consumption of both liquid-phase Al and gas-phase Al in the ignition process. The oxidizability of O2 is much larger than that of H2O, and the oxidation of Al becomes slower by adding H2O in the oxidizer. The rate of production (ROP) was performed to deeply realize the reaction pathways of Al consumption and main products formation. The reaction Al + O2 = AlO + O is the key reaction pathway in the Al-O2 ignition process, while the reaction Al + H2O = AlOH + O plays a more important role in the Al-H2O ignition process. In the all ignition cases, Al2O2 is a key intermediate species since it is the main precursor of gaseous Al2O3, and liquid-phase Al2O3 formed by the phase transition reaction of gaseous Al2O3 is the dominant final product.

R. Madhumitha, Srinibas Karmakar

Boron, a high-energy metalloid has been recognized as a potential secondary energy source for liquid hydrocarbon fuel to power volume-limited propulsion devices such as ramjet and scramjet. The higher volumetric and gravimetric energetic content makes boron a more suitable candidate than other energetic particles. The stability of the particle is one of the significant drawbacks of adopting metal particles in liquid fuel, which gel fuels can overshoot. Though several works have been published on metalized and non-metalized gel fuels, studies focusing on boron-loaded gel fuels are scarce. The present work comprehensively reviews recent advancements and challenges in adopting boron-loaded gel fuel for practical ramjet and scramjet propulsion devices. It mainly encompasses the formulation of boron-loaded gel fuel, rheological behavior and its influencing factors, single droplet combustion characteristic, spray characteristics, spray combustion characteristics, and the effect of boron-loaded gel fuel on the performance of practical ramjet and scramjet combustors.

Takashiro Akitsu, Yuji Takiguchi, Shintaro Suda et al.

Perchlorate compounds are well-known for their explosive and hazardous nature. Considering previously reported perchlorate crystals of salen-type manganese (III) complexes, our study aimed to identify the specific molecular/crystal structure responsible for their explosive properties. Employing deep learning, we conducted an analysis of the Hirschfeld surface for salen-type metal complexes within a crystal structure database. The results indicate that the salen-type complex site lacks distinctive structural features, attributing its explosive potential to the chemical bonding of the perchlorate ion and the surrounding intermolecular interactions.

Harshit Shukla, Gurunadh Velidi

Over the past few years, there has been a growing recognition of the importance of multi-spacecraft missions for a variety of purposes, including Earth observation, navigation, guidance, climate monitoring, and environmental monitoring. The trend amongst agencies is to favour constellations of smaller satellites, which can aggregate data from various sources, rather than relying on larger satellites. The numerous benefits of multi-spacecraft formation flying missions have led to an increasingly growing interest to explore its propulsion technologies, i.e., micro propulsion. Thoroughly characterising and studying the behaviour of the energetic materials is essential to ensure the safe and effective use of these micro-thrusters. Through the optimisation of micro-thruster design, the current research aims to generate outcomes that can be utilised to enhance the design and optimisation processes. Consequently, this will facilitate the widespread utilisation of micro-thrusters in multi-spacecraft missions. To optimise the performance of pyrotechnic micro-electromechanical systems, an efficient heater design, appropriate base material, channel dimensions, and electrical resistance must be considered based on available power and heat transfer requirements. A unique firing and monitoring test setup has been developed to produce a current-time plot for the device. Additionally, different micro-heater configurations, including spiral, loop, and meander types, were designed for the igniter. Experimental observations indicate that the spiral micro-heater design resulted in the lowest ignition delay and produced highly reliable combustion. The proposed microthruster design demonstrated efficient combustion and yielded promising results when tested with energetic materials such as Zirconium Potassium Perchlorate (ZPP) and Boron Potassium Perchlorate (BPN).

Błażej Gierczyk, Maciej Zalas, Tomasz Otłowski

Metal-containing compounds form a large and rapidly expanding group of high-energy materials. Many compounds in this class attract the attention of non-professionals, who may attempt the illegal production of explosives. Several of these substances have been commercially available and pose significant danger if used by terrorists or for criminal purposes. Others are experimental compounds, kinds of curiosities, often created by pyrotechnics enthusiasts, which can present serious risks to both the creators and their immediate surroundings. The internet hosts a vast amount of information, including recipes and discussions on forums, private websites, social media, and more. This paper aims to review the variety of metal-containing explosives and discuss their appeal and potential accessibility to unauthorized individuals.

Prawal P.K. Agarwal, Themis Matsoukas

The limited use of boron (B) in energetic applications is due to the presence of a native oxide layer on its surface, which acts as a thermodynamic barrier and adds to the dead weight that does not contribute to the oxidation energy release. To extract maximum energy from B oxidation, its native oxide must be chemically reduced or modified. In this paper, we report the synthesis of a new energetic material via solid-state reactions, a composite of boron (B), aluminum (Al), and magnesium (Mg), which we call BAM. We use Al and Mg to induce cyclic thermite reactions in parallel to metal oxidation: Al and Mg reduce B2O3 to form B and oxides of Al and Mg, while Mg reduces Al2O3 to form MgO along with Al, which further reduces B2O3. The result is a material that registers higher energy release than its constituents. Specifically, BAM composites show enhanced gravimetric heat release by 40% and improved oxidation by 25% than B alone under identical conditions. The sequence and synergy of oxidation and thermite reactions are illustrated by integrating XRD with thermal analysis in the air for different exothermic peaks and temperature stages. The results demonstrate that the proper selection of metallic additives can enhance the oxidation and energetic performance of B.

Yu Shang, Lin-ying Sun, Zi-ming Ye et al.

Research on the structural responses to thermal stimuli for crystalline energetic materials is crucial to their practical applications. DAP-4 is a metal-free molecular perovskite high-energetic material attracting increasing attentions on its application potential as heat-resistant explosive. In order to reveal its structural responses to thermal stimuli, herein we investigated the structural phase transitions and thermal expansion of DAP-4 by DSC, single-crystal X-ray diffraction, and variable-temperature capillary powder X-ray diffraction. The results show that DAP-4 undergoes two-step reversible phase transitions at 300.4/298.9 K and 548.4/547.7 K, respectively, which are caused by two-step order-disorder transition of the molecular components during a heating/cooling cycle. The axial and the volumetric expansion coefficients of DAP-4 are estimated based on the temperature-dependent cell parameters obtained by Pawley refinement in a large temperature range of 173–353 K, and they are close to those estimated for β-HMX. Notably, although a volume change of 0.77% occur in the near-room-temperature phase transition, all the crystalline phases of DAP-4 possess cubic structures with isotropic expansibility, rather than the commonly-observed anisotropic one in the most of known energetic crystals, which may be propitious to reduce the adverse effect of its volume change on the formulation design.

Dieter Vollath

The application of nanosized metallic particles as additive to propellants for rockets is at the laboratory and research level and except for burning rate modifiers not yet common for industrial applications. However, sometimes it is difficult to interpret experimentally determined particle size distribution functions of these metallic additions. It is the aim of this paper to give some support in answering questions posed by the interpretation of these experimental data. Properties of nanoparticles differ from those of conventional particles significantly. These different properties become apparent if one looks at particle size distributions stemming from different methods of synthesis and possibly the following aggregation processes. To understand these processes, it is necessary to describe the mechanisms causing size distributions and aggregation processes. This paper describes the influence of synthesis methods – especially looking at gas phase processes – and the thermodynamics rules governing aggregation processes. Understanding these processes, helps to interpret particle size distributions determined experimentally.

Xiong Yang, Kai Zhao, Xuan Tian et al.

Exploring new composite explosives based on 1,1-diamino-2,2-dinitroethylene (FOX-7) is significant in the field of insensitive high explosives (IHE). Despite having good detonation performance compared to RDX, FOX-7 has not been successfully applied in the preparations of aluminized explosives due to the poor explosion heat values. In this paper, the explosion heat and detonation velocity of FOX-7-based aluminized explosives were studied systematically. The experiment results showed that the explosion heat of FOX-7-based aluminized explosives are significantly lower than that of RDX-based ones, especially when the content of aluminum powder exceeds 30%. To solve this problem, a simple but effective method of adding RDX to FOX-7-based aluminized explosives was developed, leading to a huge growth of explosion heat values. Finally, in order to compare the safety performance with RDX-based aluminized explosives, the low vulnerability of the FOX-7/RDX-based aluminized explosives formulation was investigated by fast cook-off, sympathetic detonation and 12.7 mm bullet impact tests. The results showed that the safety performance of FOX-7/RDX-based aluminized explosives is better than that of RDX-based aluminized explosives, proving that good low vulnerability is kept with the addition of RDX into FOX-7-based aluminized explosives.

Han-yue Deng, Liang Wang, Duo Tang et al.

Laser ignition has been widely studied, and is regarded as a potential initiation technique in pyrotechnics owing to its simple ignition sequence, good safety, high ignition consistency, and strong anti-electromagnetic interference ability. One of the most important requirements for the practical application of laser ignition is the reduction of ignition energy, which requires both good light absorption and good photothermal properties of energetic materials or additives in energetic materials. Therefore, in this review, the recent progress of different photothermal materials and their laser-induced performances have been summarized. First, an overview of optical ignition, especially laser ignition, including the main categories, mechanisms, advantages, and applications, was introduced. Then, different photothermal materials, including carbon-based materials, composite materials, explosives, and gaseous mixtures, were summarized, and their photothermal performances were listed and compared. Finally, the strategies and challenges of designing photothermal materials with optimized performance were discussed, which can provide suggestions for the choice of photothermal energetic materials and can provide primary guidance for the design and fabrication of the same for laser ignition applications.

Adam Okninski, Wioleta Kopacz, Damian Kaniewski et al.

This paper presents the status of developments worldwide regarding use of hybrid rocket motors for space transportation. Historical roots are presented and reasons for revisiting hybrid technology after a few decades of limited interest are examined. Modern developments in sounding rockets, reusable suborbital systems and launch vehicles are discussed with particular focus on propellant technology. Various propellant combinations include use of liquid oxygen, hydrogen peroxide, nitrous oxide and nitrous oxide-oxygen mixtures as oxidizers. Different fuels are considered, taking into account performance, as well as inter alia obtainable regression rates. Results of preliminary calculations for vehicles using different propellant combinations are presented and analysed. This is compared with proposed configurations of hybrid rockets worldwide. Unresolved problems and several unknowns are pointed out, including hybrid rocket motor scalability issues, large motor combustion instabilities, combustion efficiency of metalized fuels, propellant volumetric performance and mass of fuel residuals in case of wagon wheel grain geometry. It is discussed whether new-space hybrid launch vehicles, while typically with limited stage reusability, may be cost-competitive in regard to other chemical rocket propulsion system developments. The paper is summarized with a list of potential future advances and technical opportunities. The main purpose of the conducted research is to provide a comparison between different hybrid propulsion technologies available, or currently under development, worldwide.