Hasil untuk "Explosives and pyrotechnics"

Zhuguo ZHANG, Zhibin WU, Jiadong WANG et al.

In response to the insufficient lightweight issue of the baffle plate for the nose end frame with an aluminum alloy stiffened structure in active civil aircraft, a new type of aluminum foam sandwich baffle structure is proposed based on an in-depth exploration of the energy absorption mechanism of aluminum foam sandwich structures against bird impact. This innovative design employs an asymmetric panel configuration that includes a highly ductile 2024-T3 aluminum alloy upper face sheet, a high-strength 7075-T6 aluminum alloy lower face sheet, and an aluminum foam core layer in between. It replaces the traditional aluminum alloy stiffened panel, aiming to significantly reduce structural weight while ensuring excellent bird strike resistance. First, the effectiveness of the bird body constitutive model and its contact algorithm was verified by comparing the high-speed bird body impact test on aluminum alloy flat plates with the simulated strain data. Based on previous experimental data, combined with parameter inversion and simulation cases, the simulation data of homogeneous and gradient aluminum foams are in good agreement with the test results, which verifies the accuracy and applicability of the aluminum foam material constitutive model. Furthermore, using the professional Pam-crash software, transient impact dynamics simulations of bird strikes were conducted on both the stiffened panel structure and the aluminum foam sandwich structure end frame. Combined with the damage and deformation conditions of each component and energy absorption data, a comparative analysis was made on the differences in their impact response characteristics and energy absorption mechanisms. The study shows that the stiffened panel mainly absorbs the energy of bird body impact through its plastic deformation, while the aluminum foam sandwich structure absorbs energy synergistically through the compressive collapse failure of the core layer and the large plastic deformation mechanism of the upper face sheet. The optimized aluminum foam sandwich structure is significantly superior to the traditional stiffened panel structure in terms of energy absorption efficiency. Subsequently, a full-coverage optimization design scheme for the baffle was completed based on the energy absorption characteristics of the aluminum foam sandwich structure. According to the full-coverage bird impact simulation results, the proposed aluminum foam sandwich baffle design achieves a structural weight reduction of more than 30% while maintaining the same bird strike resistance performance as the in-service structure. This research provides reliable technical references and innovative ideas for the lightweight bird strike-resistant design of the civil aircraft nose bulkhead.

Mingyu Li, Ruixiao Li, Vladimir Zarko et al.

Nano-sized boron (nB)-based composite energetic materials (CEMs) are an emerging class of high-energy-density fuels with excellent combustion performance, offering broad potential applications in space propulsion and explosives. In this paper, we review the various preparation techniques for nB-based CEMs (comparing their respective advantages and limitations) and discuss the combustion characteristics and reaction mechanisms of these materials, while also surveying current development trends and future challenges. Recent findings show that incorporating nB significantly improves the ignition characteristics, burning rates, and overall energy release efficiency of B-based energetic formulations. In particular, nB-based composites exhibit faster reaction kinetics, higher energy release rates, and greater gas generation than their micro-sized boron (μB) counterparts. These enhancements underscore the promise of nB-based CEMs for next-generation propellants, explosives, and pyrotechnics, and existing research has already laid a solid foundation for further progress in designing such advanced energetic systems.

Chunjie Zuo, Kai Zhong, Chaoyang Zhang

Thermal stability is both a fundamental property and an important performance of energetic compounds, and is prone to be understood and predicted by molecular dynamics simulations; still, it is faced up a great challenge in qualitatively correlating the simulations and experimental determinations. This work attempts to address this challenge by correlating ab initio molecular dynamics (AIMD) derived characteristic indexes with DSC and DTG determined onset decomposition temperatures of six energetic compounds, including 1,3,5-triamino-2,4,6-trinitrobenzene, 1,3-diamino-2,4,6-trinitrobenzene; 1,3,5-trinitro-1,3,5-triazinane, 1,3,5,7-tetranitro-1,3,5,7-tetrazocane, 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane, and pentaerythritol tetranitrate. As results, high correlations (R2) are confirmed therein, i.e., those of the height of potential energy climax and corresponding temperatures, and the temperatures corresponding to low reaction depths (within 0.1 to 0.5) between onset temperatures from DSC test are 0.83, 0.89, and 0.94, respectively; meanwhile, when the proportion of remaining solids reaches 0.98, the correlation between the AIMD simulated temperature and the onset temperature in DTG test is as high as 0.95. Despite a small sample set of six compounds herein, it still exhibits a perspective of first-principles design of energetic materials from molecule to material, instead of molecule only, to remedy the shortcoming of machine learning.

Cheng Xu, Min Zhang, Yiying Zhang et al.

Diazidoglyoxime (DAzG), a pivotal intermediate in the synthesis of dihydroxylammonium 5,5′-bis-tetrazole-1,1′-diolate (TKX-50)—a high-energy-density explosive with growing applications in defense and aerospace—was comprehensively investigated to elucidate its thermal decomposition behavior and assess safety risks during synthesis. Differential scanning calorimetry (DSC) analyses were conducted on both the precursor dichloroglyoxime (DCG) and product diazidoglyoxime (DAzG), revealing distinct thermal degradation profiles. The onset decomposition temperatures were determined to be 197.8 °C for DCG and 156.9 °C for DAzG, highlighting DAzG’s lower thermal stability. Reaction calorimetry (RC1) studies under varied synthesis conditions further quantified the thermal dynamics of the azidation step, identifying a maximum temperature of the synthesis reaction (MTSR) of 4.9 °C. To evaluate secondary decomposition hazards, accelerating rate calorimetry (ARC) was employed, measuring a TD24 (the temperature at which the time-to-maximum rate under adiabatic conditions, TMRad, reaches 24 h) of 20.4 °C for the reaction residue. This low TD24 value indicates a high propensity for thermal runaway at near-ambient temperatures, necessitating stringent thermal control protocols. Based on Francis Stoessel’s thermal risk classification framework, the thermal risk of DAzG is classified as class 2, signifying moderate but manageable thermal risks during synthesis and handling. The findings emphasize the critical need for real-time temperature monitoring, controlled cooling systems, and hazard mitigation strategies in industrial-scale DAzG production. This study not only advances the understanding of DAzG’s thermal behavior but also provides actionable guidelines for enhancing safety in the manufacturing of advanced energetic materials like TKX-50.

Jiayao LI, Rongzhen LIANG, Xianzhong HU

Oxy-fuel combustion is one of the effective means to reduce greenhouse gases. To grasp the combustion characteristics of the clean fuel acetylene in O2/CO2 atmosphere and to investigate the effect of different CO2 volume fraction on the lower flammable limit of acetylene, the lower flammable limit of acetylene was experimentally measured in a 5 L cylindrical explosive reaction device. With the increase of CO2 volume fraction from 14% to 85%, the experimental value of the lower flammable limit of acetylene increased from 2.64% to 3.93%, which was linearly increased in a small range. Compared with hydrocarbon fuels such as ethylene, ethane, and propylene, the lower flammability limit of alkanes, olefins, alkynes decrease sequentially, indicating that alkynes have a larger combustion range and a higher hazard factor. Based on the calculation model of limiting laminar burning velocity method, a prediction model applicable to the lower flammability limit of acetylene was established. Through the verification of experimental data, the average absolute error of this prediction model using the USC Ⅱ combustion reaction mechanism is at 0.52%, and the model is accurate and reliable. To explain the reason for the existence of the lower flammability limit from the perspective of the competition between the temperature rise of the heat generation from fuel consumption and the temperature drop of the heat dissipation from the expansion of the fuel body, this study examines the thermodynamic, chemical, and transport effects of CO2 on the lower flammability limit. The combustion reaction mechanism of USC Ⅱ is modified to incorporate the virtual substances FCO2, TCO2, and MCO2, and comparing the flammability limits of the three virtual substances as well as those of the five atmospheres of N2 and CO2. The thermodynamic, chemical and transport effects of CO2 on the lower flammability limit were discussed. The results show that the average proportion of thermodynamic effect is 64%, chemical effect is 35% and transportation effect is 1%.

Salim Chelouche, Djalal Trache, Amir Abdelaziz et al.

The present study was devoted to setting a universal T-independent predictive model of equivalent in-service-time (EIST) for homogenous solid propellant (HSP) to surpass the limits of the van't Hoff law particularly when high aging temperatures and/or extended aging durations are employed in artificial aging plans. To achieve this objective, four double base rocket propellants (DBRP) underwent artificial aging for 4 months at temperatures of 323.65 K, 338.65 K, 353.65 K, and 368.65 K, with sampling conducted every 20 days. Fourier Transform Infrared spectrometry (FTIR) showed that the homolytic scission of the ONO2 bonds and the hydrocarbon chains of the nitrate esters are the main processes occurring during the chemical decomposition. With the heating temperature increase, the chemical decomposition becomes more predominant. Furthermore, the scatter plot from Principal Component Analysis (PCA) of FTIR spectra obtained from each aging temperature showed, respectively, that over than 88.9 %, 94.3 %, 97.4 %, and 98.6% of the variances were described by the first principal component. This latter value was found 97.6 % when PCA was applied to all FTIR spectra. Using the PCA/FTIR approach recently developed, EIST was assessed for all the investigated samples. Subsequently, an individual predictive model of EIST was set for each heating temperature, which were used to establish the T-independent predictive model. The final model computed the EIST with a relative deviation of 5.3 % compared to those from the PCA/FTIR experimental way. Moreover, two similar DBRPs aged at different temperatures and durations have been used to validate the predictive model, and the associated mean absolute percentage error (MAPE) was found 4.6 %. The conducted comprehensive statistical analysis highlighted the excellent goodness-of-fit of the model. Furthermore, all the error metrics were found to decrease with the increase of the natural aging of the propellant and the heating temperature.

Björn Kischelewski, Benjamin Guedj, David Wahl

Landmine removal is a slow, resource-intensive process affecting over 60 countries. While AI has been proposed to enhance explosive ordnance (EO) detection, existing methods primarily focus on object recognition, with limited attention to prediction of landmine risk based on spatial pattern information. This work aims to answer the following research question: How can AI be used to predict landmine risk from landmine patterns to improve clearance time efficiency? To that effect, we introduce RestoreAI, an AI system for pattern-based risk estimation of remaining explosives. RestoreAI is the first AI system that leverages landmine patterns for risk prediction, improving the accuracy of estimating the residual risk of missing EO prior to land release. We particularly focus on the implementation of three instances of RestoreAI, respectively, linear, curved and Bayesian pattern deminers. First, the linear pattern deminer uses linear landmine patterns from a principal component analysis (PCA) for the landmine risk prediction. Second, the curved pattern deminer uses curved landmine patterns from principal curves. Finally, the Bayesian pattern deminer incorporates prior expert knowledge by using a Bayesian pattern risk prediction. Evaluated on real-world landmine data, RestoreAI significantly boosts clearance efficiency. The top-performing pattern-based deminers achieved a 14.37 percentage point increase in the average share of cleared landmines per timestep and required 24.45% less time than the best baseline deminer to locate all landmines. Interestingly, linear and curved pattern deminers showed no significant performance difference, suggesting that more efficient linear patterns are a viable option for risk prediction.

Hong'e Liu, Jiawei Cao, Yiyi Teng et al.

The relationship between the pressure of pyrotechnic agents and the density of charges is the basic performance parameters for the research and design of charge density, charge amount and detonation characteristics of pyrotechnics. In this experiment, the relationship between the pressure pressure and the charge density of Lead styphnate and carboxymethyl cellulose barium styphnate with two charge diameters of 3.4 mm and 4.7 mm was studied by volumetric method, and the fitting formulas and relationship curves between the pressure pressure and the charge density were obtained, and the relationship between the porosity of the two charges and the pressure was obtained.

B. Gierczyk, M. 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.

Tomasz Otłowski, M. Zalas, B. Gierczyk

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 H_2O_2. 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. H_2O_2-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 H_2O_2 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 H_2O_2-based HMEs.

Chengbo Ru, Lihong Chen, Hongguo Zhang et al.

Understanding the properties of explosives is the basis for investigating and analyzing explosion cases. To date, due to the strict legal control of standard explosives and initiators, homemade pyrotechnics composed of oxidizers and fuels have become popular explosive sources of improvised explosive devices (IEDs) threatening greatly social stability and personal safety. The reactivity of pyrotechnics strongly depends on their intrinsic characteristics and operating conditions, which determine the efficiencies of heat and mass transfer between the reaction zone and the unreacted zone. Herein, the tests of thermodynamics, pressurization characteristics, and combustion propagation behaviors are conducted to explore the effects of oxidizer species, particle size, and loading density on the reactivity of homemade binary aluminum-based pyrotechnics. The results show that the pyrotechnics with potassium chlorate (KClO3) have the strongest reactivity with the highest pressurization rate (dp/dt) and the shortest combustion duration. Compared with their counterparts based on aluminum microparticles(mAl), pyrotechnics consisting of Al nanoparticles (nAl) possess superior reactivity as expected, which results from the relatively short heat and mass transfer distances. The nAl-based pyrotechnics have a low reaction exothermic peak temperature, great heat release, great aluminothermic reaction completeness, and high produced peak pressure with several orders of magnitude higher pressurization rate. Increasing the loading density of the pyrotechnics over a certain value can change the dominant mode of heat transfer from convective to conduction, sharply decreasing the pressurization characteristics and combustion front propagation velocities (vp). The results of theoretical calculations using the NASA-CEA codes show that loading density can alter the reaction process of the pyrotechnics, leading to a decrease in the predicted pressure per unit mass for Al/KNO3 or Al/AP, and an increase for Al/KClO3. For nAl/potassium nitrate (KNO3), the density is between 1.0 and 1.25 g cm−3, across which dp/dt decreases by one order of magnitude from 0.148 to 0.014 MPa ms−1. In addition, vp decreases by three orders of magnitude from 0.040 to 0.078 m s−1. Distinct pressurization behaviors of nAl/AP are observed at a density of 1.5 g cm−3, while the variation in nAl/KClO3 reactivity fluctuates. These results are beneficial for the damage assessment of scenes caused by an explosion and for inversely calculating charge parameters.

Yang Liu, Wei Wang, Dong Li et al.

Plasticizers are functional additives that have been widely utilized to enhance the mechanical properties and processing technology of explosive systems. However, due to the increasing demand for energetic formulations of explosives and propellants, traditional plasticizers are gradually being replaced by energetic plasticizers. Azido plasticizer, a type of energetic plasticizer, possesses excellent thermal stability and low glass transition temperature. However, the incorporation of a single azido group can lead to issues such as decreased oxygen balance and reduced density. In recent years, novel azido plasticizers containing various energetic groups have been developed. Among these, the introduction of a nitramine group into the azido plasticizer has shown significant improvements in oxygen balance, density, and sensitivity compatibility. This makes azidonitramine plasticizers a promising research direction in the development of energetic plasticizers. Despite the existence of approximately twenty different types of azidonitramine plasticizers over the past few decades, a comprehensive review of these compounds is lacking in the literature. Therefore, this paper provides an inductive review of the synthesis, application, and performance characterization of azidonitramine plasticizers with the aim of inspiring further research in this field.

Bojun Tan, Hongchang Mo, Jing Zhang et al.

Photothermal dual-curing adhesive is not only required to realize the basic curing function, but also has the characteristics of rapid setting and strong curing, which possesses a vital role in the molding speed, stability and structure integrity for 3D-printed propellants and explosives. Herein, the acrylate hydroxyl terminated polybutadiene, as novel photothermal dual-curing binders, were designed and synthesized utilizing cationic ring opening polymerization and active monomer mechanism as the strategy of photothermal dual-curing reaction. The mechanical properties and thermal stability of the photothermal dual-curing elastomers were systematically investigated. The results suggested that the target MAHTPB(Acrylate hydroxy‑terminated polybutadiene)-based adhesives could be cured rapidly within 5 s under UV light irradiation and completely cured in 1.5 h under heating conditions. Specifically, the elastomer film formed by MAHTPB-based photothermal dual-curing has a tensile strength of 4.63 MPa and an elongation of 386%, which exhibits stronger mechanical properties than the elastomer film formed by single photo- or thermal-curing. As a result, the synthesized photothermally cured adhesives have performed 3D printing experiments and achieved relatively satisfactory printing effects. Our study aims to solve the problems of short photocuring time, slow curing rate and incomplete curing for traditional photocuring, which lays a solid foundation to achieve rapid prototyping and precise performance control in 3D printing of propellants and explosives.

Aaron J. Horrocks, D. Detata, Kari Pitts et al.

Chlorates and perchlorates, inorganic salts known for their potent oxidizing properties, find utility in various products such as pyrotechnics, matches, and disinfectants. Their chemical properties also make them suitable for homemade explosives, resulting in their extensive use by criminals. Hence, the forensic analysis of these compounds is vital for investigating crimes involving their utilization. A wide array of analytical techniques is available for detecting and quantifying these substances, offering forensic investigators an extensive toolkit to effectively analyze and identify chlorates and perchlorates in various samples. Recent research highlights the potential for leveraging the information obtained from analyzing these materials, including for intelligence purposes. The future of forensic analysis in this domain lies in extracting additional information, such as source attribution, through methods like chemometrics, thereby enhancing forensic intelligence capabilities.This article is categorized under: Forensic Chemistry and Trace Evidence > Explosive Analysis Forensic Chemistry and Trace Evidence > Trace Evidence Forensic Chemistry and Trace Evidence > Emerging Technologies and Methods

Clint Guymon, Ming Liu, J. 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.

Wen Qian, Jing Huang, Shitai Guo et al.

1,1-dinitro-2,2-diamino ethylene (FOX-7) is typically representative of low sensitivity and high energy compound. In this work, analogues of FOX-7 are screened using a combined method of high-throughput computation (HTC) and machine learning (ML). The molecules are generated with typical unsaturated hydrocarbons backbones and random combination of substituents -H, -NH2 and -NO2, then HTC is performed based on 200 sample molecules. ML models are established based on the HTC results, with detonation parameters predicted using the most accurate model of extreme gradient boosting (XGB). Finally, stability of the filtered high energy molecules are confirmed by quantum chemistry calculations, and besides FOX-7, 8 more energetic molecules with high energy as well as high stability (detonation velocity ≥ 8841.1 m/s, detonation pressure ≥ 34.6 GPa and stability parameter bond dissociation energy ≥ 201.7 kJ/mol) are achieved. This work has shown the efficiency of HTC and ML methods in searching new target molecules.

Boris E. Krisyuk, Timofey M. Sypko, Igor N. Zyuzin

The mechanism of thermal decomposition of 1-tert-butyl-2-methoxydiazene-1-oxide and 1-ethyl-2-methoxydiazene-1-oxide was investigated by quantum chemistry methods at the CCSD/aug-cc-pVDZ level. It was shown that thermolysis of both compounds occurs by the same mechanism – hydrogen atom transfer from the CH3 of ethyl or tert-butyl group to the N-oxide oxygen atom via a five-membered cyclic transition state in the limiting stage. More precise calculations at the DLPNO-CCSD(T)/aug-cc-pVTZ level were performed for this reaction channel. It was shown that the activation enthalpy at all calculation levels for this reaction channel and for both compounds is 150-170 kJ/mol, which corresponds to the experimental data. The experimental thermolysis products composition of the 1-tert-butyl-2-methoxydiazene-1-oxide completely coincides with the calculated one.

Jianxin Li, Panpan Heng, Baoshan Wang et al.

High-energy-density materials (HEDMs) have a wide range of applications in many usages. Recently synthesized 3,4-bis(3-fluorodinitromethylfuroxan-4-yl) furoxan (BFTF-1), composed of furoxan rings and fluorodinitromethyl groups, has shown advanced properties comparing to other existed HEDMs, such as density and enthalpy of formation. Understanding the decomposition mechanism for BFTF-1 could provide insights into future designs of HEDMs, and the initial decompositions are critical steps in the mechanism. In the present study, we employed quantum mechanics calculations and reactive molecular dynamics simulations to explore the initial decomposition steps. The electronic structural analysis and bond dissociation energy calculations suggested that the nitro moieties in the fluorodinitromethyl groups and the furoxan rings could begin the bond breaking process in BFTF-1. The reactive molecular dynamics simulation showed that the increase of the nitro moieties was concurrent with the decrease of BFTF-1, proving the nitro moieties were the first product for the decomposition of BFTF-1. The present study laid the ground for the theoretical understanding of decomposition mechanisms for BFTF-1 and shed light on further designs of advanced HEDMs.

Gary D. Yngve, James F. O'Brien, Jessica K. Hodgins

In this paper, we introduce techniques for animating explosions and their effects. The primary effect of an explosion is a disturbance that causes a shock wave to propagate through the surrounding medium. This disturbance determines the behavior of nearly all other secondary effects seen in explosions. We simulate the propagation of an explosion through the surrounding air using a computational fluid dynamics model based on the equations for compressible, viscous flow. To model the numerically stable formulation of shocks along blast wave fronts, we employ an integration method that can handle steep gradients without introducing inappropriate damping. The system includes two-way coupling between solid objects and surrounding fluid. Using this technique, we can generate a variety of effects including shaped explosive charges, a projectile propelled from a chamber by an explosion, and objects damaged by a blast. With appropriate rendering techniques, our explosion model can be used to create such visual effects such as fireballs, dust clouds, and the refraction of light caused by a blast wave.

Sankha S. Basu, Sayantan Roy

Paraconsistency is commonly defined and/or characterized as the failure of a principle of explosion. The various standard forms of explosion involve one or more logical operators or connectives, among which the negation operator is the most frequent and primary. In this article, we start by asking whether a negation operator is essential for describing explosion and paraconsistency. In other words, is it possible to describe a principle of explosion and hence a notion of paraconsistency that is independent of connectives? A negation-free paraconsistency resulting from the failure of a generalized principle of explosion is presented first. We also derive a notion of quasi-negation from this and investigate its properties. Next, more general principles of explosion are considered. These are also negation-free; moreover, these principles gradually move away from the idea that an explosion requires a statement and its opposite. Thus, these principles can capture the explosion observed in logics where a statement and its negation explode only in the presence of additional information, such as in the logics of formal inconsistency.