Explosive Field Research Articles

Release of overpressures in computational simulations of air-methane explosions

Research in the field of gas explosions has had and continues to have, as its main support, physical experiments performed on various scale models, the construction of real size models are often large consuming materials, time and labor. The rapid development of computing techniques has allowed among other things, the transfer of gas explosions research in the virtual space, for the validation of computational simulations of this type being still considered physical experiments and specialty literature. Within NIRD INSEMEX Petrosani, being an accredited institute in the elaboration of technical reports for gas explosion type events, the phenomenon of rapid combustion virtualization increased in time and as a result, computational simulations becoming an efficient tools in explaining the mechanisms of explosion production. Nevertheless, one of the problems raised by this virtualization process is the limitation of performing computational simulations in closed or partially closed spaces, initial conditions imposed, without the possibility of dynamic modification of these conditions according to the development of overpressures generated by the virtual explosion. This paper presents a computational experiment in which it was possible to transform the boundary conditions at predefined pressure thresholds, from rigid surfaces into surfaces capable of releasing the overpressures developed in closed / partially closed spaces, putting the results of this kind of simulations in line with real dynamic effects of gas explosion events.

Generalized graphic-analytical model for evaluation of the fatality / structural collapse production mechanism on a building affected by an explosion

The paper highlights the generalized grapho-analytical model of analysis and evaluation of the mechanism of occurrence of the event scenario for the production of fatality/structural collapse in the case of a building affected by explosion. This mathematical model is based on research results in the field of civil explosives for the technological/occupational risks estimation and assessment, as well as threats to the security of protected areas that may be vulnerable through acts of malice. The process of quantitative risk assessment associated with explosion phenomena as a result of the detonation of an explosive charge, allows estimating result indicators based on the use of algorithms and models specific to associated hazards, in order to model the effects and consequences of event scenarios.

Analysis of dangerous situations generated by explosive materials in non-compliant operations performed on industrial locations intended for their storage

Design and efficient implementation of OSH management in the field of explosives for civilian use, having the effect of optimizing the activity of preventing unwanted events blast type specific to industrial locations intended for the preparation / storage of explosives for civil use, constitutes it explosion risk assessment which represents the integrated expression of the configuration components of this type of risk within the different accident scenarios. No matter what it's about a component within the location or his integral technical infrastructure such an analysis allows the identification and ranking of site specific accident hazards to be assessed, in order to properly allocate security resources for priority measures to prevent and combat / eliminate the causes of these types of dangerous events. To this end, the ”Security Document” specific to the industrial site intended for specific operations with explosive materials must demonstrate that: an appropriate accident prevention policy and an effective safety management system have been implemented; the dangers of injury are identified and the necessary measures are taken to prevent them and to limit their consequences for man and the environment; in design any installations has been incorporated adequate safety and reliability for construction, operation and maintenance; emergency plans have been drawn up.

Explosive volcanism in Noctis Fossae on Mars

Based on theoretical considerations, basaltic volcanism of explosive character should be common on Mars. Although the record of explosive volcanic fields on Mars continues to grow, many unexplored volcanic fields remain. In this research, we identified a group of 25 volcanic cones and associated lava flows emplaced in the Noctis Fossae region on Mars. To analyze this volcanic field, we used images from the Context Camera (CTX) and High Resolution Imaging Science Experiment (HiRISE) of Mars Reconnaissance Orbiter (MRO). We interpreted those volcanic cones and their geological history by (1) analyzing their spatial distribution, (2) determining the morphometric parameters, (3) measuring orientations of their summit alignments, and (4) dating these cones along with surrounding lava flows. The identified cones are characterized by various states of preservation from almost fully eroded vent relicts to well-preserved edifices of conical shapes accompanied by short-distance lava flows. Morphological data suggest that the whole set of identified cones likely represent explosive scoria cones. Using the crater count dating method coupled with the structural relationship between the lava flows and volcanic cones, we found that the southern and central cones likely formed >300 Ma, while the northernmost cones between 200 and 50 Ma. These results suggest long-lived volcanism in the studied area active until the latest Amazonian period. In addition, to the present state of knowledge, these cones represent the youngest explosive volcanism in Tharsis and support other findings of young explosive-origin features on Mars. This might shed new light on the magmatic plumbing system of the Tharsis region, although magma sources from Syria Planum, or less likely Valles Marineris, are not excluded. Such magmas of explosive nature are probably rich in volatiles, which might derive from water and/or hydroxyl bearing minerals' or subsurface permafrost deposits. In addition, these magmas might be associated with intensive hydrothermal activity in the region.

An Efficient CDEM-based method to calculate full time-space natural fragment field of shell-bearing explosives

The fragment field distribution of shell-bearing explosives is important to ensure safety during the production and storage of inflammable and explosive materials. This study uses the continuous-discontinuous element method (CDEM) for the first time to solve the problems encountered when simulating shell-bearing explosives such as natural fragment generation and cross-scale calculation. With the coupling computation of the finite-discrete element as its core, we design the natural fragment discrete unit generation algorithm by utilizing the shell equivalent layer-detonation product dissipation model based on continuous mechanics, dynamic drag flight calculations, and efficient point-face and face-face contact algorithms. Thus, a method has been established for the complete simulation of a full time-space field for natural fragments (from burst to fragment landing) of shelled explosives. In particular, CDEM, takes into account the complex situation wherein multiple explosions are initiated due to the shelled explosives being stacked on one another during storage. Comparisons with commercial software (AUTODYN) calculations and test data validate the accuracy and efficiency of the method, thereby providing adequate conditions for performing a refined study on fragment distributions and safe distances associated with shell explosives.

Cognition, Application and Discussion on Shaped Charge Hydraulic Smooth Blasting Technology

In the past, the main method of tunnel excavation in China was drilling and blasting, but the biggest shortcoming of the traditional drilling and blasting method is that it is easy to cause serious overexcavation and underexcavation. At the same time, the operation cycle time of this method is long, which leads to a serious waste of resources. Not only that, a large number of toxic gases and dust produced after blasting also do harm to the health of construction workers. So this is an urgent need for a new construction technology to solve this worldwide problem. In this situation, the leading experts in the field of tunnel, "The survey and design master of China" Shi Yuxin, Liu Pei, and well known expert in explosion field, yan-sheng ding, professor Chen Chengguang and Gu Yicheng, the experts group, cooperate with The Fifth Branch of China Railway 18th Bureau in northwest project management department, developed a new technology. This technology has passed the appraisal of scientific and technological achievements organized by Tianjin Science and Technology Commission, which is shaped hydraulic smooth blasting technology. The comprehensive evaluation of the technology is "international leading" level.This paper is mainly aimed at the drawbacks of drilling and blasting construction,combined with the author's cognition and discussion on the introduction of the new technology of cumulative hydraulic blasting and the practical application effect in the tunnel excavation process of the fourth company of China Railway 14th Bureau Group in the second division of the 9th bid section of Zhangjihuai Railway in Huainan Province.

Digital comparative analysis of simulation results of radioactive deposition field of nuclear explosion

The radioactive settlement of nuclear explosion is simulated by Lagrange particle diffusion model. The simulated settlement map and the measured data map are digitally extracted into the same format. The effectiveness measurement (MOE) method and normalized absolute difference (NAD) method are used to conduct numerical comparative analysis between each dose simulation area and the measured area.

Solubilities of 2,4-Dinitroanisole in Pure Organic and Mixed Organic Solvents at Temperatures between 283.15 and 313.15 K

The solubility of 2,4-dinitroanisole (DNAN) was measured in nine commonly used pure organic solvents, including ethanol, acetone, ethyl acetate, n-propanol, i-propanol, butyl alcohol, cyclohexanone, toluene, and cyclohexane, and four binary mixed solvents between 283.15 K and 313.15 K at atmosphere pressure by the gravimetric method. The solubility of DNAN showed a temperature dependence in all test solvents. The order of the solubility of DNAN was acetone ≈ cyclohexanone > ethyl acetate > n-propanol + acetone ≈ ethanol + acetone ≈ toluene > ethanol > n-propanol > water + acetone > n-butanol + acetone > n-butanol ≈ i-propanol > cyclohexane. The experimental mole fraction solubility data were correlated with the modified Apelblat equation, Yaws equation, and van’t Hoff equation. The correlation showed good agreement with the experimental results, and the largest value of the root-mean-square deviation was 11.88 × 10–4. All of the obtained results would benefit the purification and crystallization of DNAN, which would extend its applications in the field of explosives.

Theft-Safe Explosive Mixtures Based on Hydrogen Peroxide: Study of Properties and Built-In Self-Deactivation Kinetics.

The current focus on both environmental and general safety is an important issue in the field of explosives. As such, environmentally-friendly explosives, based on hydrogen peroxide (HTP) as an oxidising agent, are of significant interest. These explosives can be designed to undergo self-deactivation, denying access to them by any unlawful third parties that may attempt scavenging blasting sites for any residual energetic materials. Such deactivation also improves blasting safety, as, after a set time, misfired charges no longer pose any explosive threat. In this work, we have designed HTP-based explosive formulations that undergo deactivation after approximately 12 h. To this effect, Al powders were used both as fuels and HTP decomposition promoters. The shock wave parameters and ability to perform mechanical work of the proposed explosive formulations are comparable to those of dynamites and bulk emulsion explosives, and the details of the changes of these parameters over time are also reported.

Ab Initio Study of the Influence of Alloying Elements on Stability and Mechanical Properties of Selected TixAly Intermetallic Compounds and Their TixAly/Al, TixAly/Ti Interfaces in Explosively Welded Metal\u2013Metal Composites

The overall performance of joints fabricated using the explosive welding method depends directly on the brittleness of created intermetallic phases and their cohesion with metallic substrates. In this article, we used first principles calculations to show that Sn, V, Cu, and Mg alloying elements present in Ti- and Al-based alloys have a significant influence on the elastic properties and plastic deformation ability of γ-TiAl and Ti3Al. Selected solutes exhibit diversified preferential site occupancy in bulk phases and ordered phase/metallic substrate interface regions. The largest positive effect on ductility and cleavage energy was found for Cu addition (25 pct increase in the B/G ratio), while Sn largely deteriorates cleavage resistance (up to 8 pct). The presented results reveal that further development in the explosive welding field can be reached through the design/application of new alloys composed of elements that improve the properties of the ordered phases present in the joints.

Introduction of energetic bis-1,2,4-triazoles bridges: A strategy towards advanced heat resistant explosives

Over the last few decades, the research for energetic materials with ultrahigh heat resistance and good energy level has been a highly severe challenge. In this study, a novel heat-resistant compound, 5,5′-bis(4-nitro-1H-pyrazol-3-yl)−2H,2′H-3,3′-bis-1,2,4-triazoles (BPT-2), was developed through the introduction of an energetic bis-1,2,4-triazoles bridge between two nitropyrazole moieties. This neutral molecule shows an ultrahigh thermal decomposition temperature of 425 °C that is extremely rare in the field of heat resistant explosives, enhanced energy level (detonation velocity: 7503 m s−1) superior to that of the extensively used heat resistant explosive HNS (7164 m s−1), insolubility in water and a facile three-step reaction. These prominent properties of BPT-2 support it as an advanced heat resistant explosive with great promise. Furthermore, an in-depth investigation on the influence of different heterocyclic ring bridges (i.e., bis-1,2,4-oxadiazoles in A, bis-1,3,4-oxadiazoles in B and bis-1,2,4-triazoles in BPT-2) on the thermal stability of the corresponding target compounds was performed.The result indicates that the preferable aromaticity and C-NO2 bond strength of bis-1,2,4-triazoles contribute to the excellent thermostability of BPT-2 in comparison to those of bis-1,2,4-oxadiazoles and bis-1,3,4-oxadiazoles analogues. This work is anticipated to prompt more research on the promising strategy of introducing energetic bis-1,2,4-triazoles bridges in the molecular design and offers guidance for the development of advanced heat resistant explosives.

Research on anti-shockwave performance of the protective equipment for the head of a soldier based on shock tube evaluation

In order to optimize the structure and improve the performance of the head and face protective equipment for an individual soldier, firstly, the blast wave resistance tests of the bare-head model were carried out in real explosion field and shock tube environments, respectively. On this basis, the forward and lateral blast shockwave protective performance tests for helmet-head systems with different structures and protection levels were carried out by using the shock tube method. Finally, the peak values and durations of shockwave overpressure in the front, forehead, top, back, ear and eye areas of the helmet-head systems were compared and analyzed. The experimental results show that the blast shockwave test using a shock tube can be a substitute for the real explosion field test. When subjected to the effect of frontal shock wave, the peak value of the shockwave overpressure measured at the top measuring point of the two-half-helmet head model is about 1/6 compared with that of the nozzle outlet and 1/3 of the bare-head model as well as the integrated-helmet head model. The shockwave splits and relieves pressure at the split structure on the top of the two-half helmets and forms a superimposed reflection, resulting in a prolonged action time (5.5−8.5 ms), but a significantly decreased peak overpressure. For the rear measuring points, the peak overpressure (365 kPa) of shockwave measured by the integrated-helmet head model is slightly higher than that (303 kPa) measured by the two-half-helmet head model, and about 2.5 times as high as that (148 kPa) measured by the bare head model. By improving the structural airtightness of individual head and face protective equipments (such as wearing glasses, earmuffs or protective masks), shockwaves can be effectively prevented from entering the helmet-head systems, the stacking convergence effect can be weakened, and the protective performance of individual head and face equipments can be improved.

Characteristics of Homemade Explosive Materials and the Possibilities of their Identification

Abstract One of the greatest challenges for explosive ordnance disposal operators is the disarming process of an improvised explosive device. These dangerous devices are often made from homemade explosive. Committing a bomb attack in urban areas is a basic weapon of terrorists, which may claim civilians’ lives. The main aim of experts is to avoid any lethal attack and to stop terrorists who endanger our life. Identifying homemade explosives may also help during the fight against terrorism since information may be provided this way, which is essential for professionals who work in the areas of operations. Usage of high-tech equipment provides stable and reliable background in the field of explosives’ analysis.

Establishing the interface layer on the aluminum surface through the self-assembly of tannic acid (TA): Improving the ignition and combustion properties of aluminum

Aluminum powder is widely used in the field of propellants and explosives due to its high energy density. However, the dense oxide film on its surface will hinder the combustion of aluminum powder. Herein, Al@TA-Fe with core-shell structure was prepared by self-assembly of tannic acid (TA) and Fe(III) ion on the surface of aluminum, and was characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and thermogravimetry-differential scanning calorimetry (TG-DSC). The results show that the TA-Fe interface layer in Al@TA-Fe can effectively promote the ignition of aluminum powder, which can make the aluminum powder be ignited at the temperature far below the melting point of aluminum. Meanwhile, the carbides formed by the decomposition of tannic acid are beneficial to the cracking of the alumina on the surface of the aluminum powder, which can promote the internal aluminum to participate in the reaction and improve the reaction efficiency of aluminum. The TA-Fe layer can inhibit the agglomeration of molten aluminum during the combustion of aluminum and can effectively improve the corrosion resistance of aluminum powder. The iron ions in the TA-Fe interface layer can successfullycatalyze the thermal decomposition process of ammonium perchlorate (AP). In addition, Al@TA-Fe can effectively increase the burning rate of the propellant compared with pure aluminum powder.

Synthesis and characterization of energetic compounds based on N-oxidation of 5-Nitroso-2,4,6-triaminopyrimidine

The N-oxidation of 5-Nitroso-2,4,6-triaminopyrimidine leads to the successful synthesis of 5-Nitro-2,4,6 triaminopyrimidine-1,3-Dioxide (NTAPDO) 1 and 5-Nitro-2,4,6-triaminopyrimidine-1-oxide (NTAPMO) 2 by using mild oxidation reactions and the NTAPMO (2) based energetic salts (3–5) were prepared effectively by reacting 2 with the related acids following neutralization reaction. The single-crystal X-ray diffraction, differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA) techniques were applied to manifest the structures and thermal stability of compounds respectively. The compounds 1–5 exhibited high densities in the range of 1.76 -1.87 g.cm−3 and mechanically insensitive towards impact and friction. The heat of formation (HOF) of these compounds was found high positive between the ranges of 207.7 to 768.4 kJ.mol−1. The energetic salts 3, 4, and 5 demonstrated high detonation performance (velocity and pressure) and high volumes of explosion gasses (789.77, 733.85, and 730.61 L•kg−1, respectively). Hence, compounds 1–5 displayed good thermal stability, high positive HOFs, and good detonation performance as well as low sensitivity suggesting their potential to be used as energetic materials in the field of high-performance explosives.

Measurement and calculation technology of temperature compensation of explosion flame based on infrared radiation

In testing explosion flame temperature with radiation thermometry, there is relatively great deviation of empirical value of flame emissivity from flame combustion mechanism. Meanwhile, the distance of measure point from the flame and ambient temperature and humidity also cause attenuation of thermal radiation to different extent, affecting the accuracy of measurement of explosion flame’s temperature. With focuses on foregoing two problems and based on atmospheric radiation theory and the law of optics propagation, a model of radiation path attenuation compensation was deduced in accordance with the functional relation among explosion flame’s radiance, digital output value of thermal imager and explosion flame’s temperature, followed by obtainment of relevant parameters i.e. system responsivity in the model from radiometric calibration of thermal imager; then, the applicability of the gray body hypothesis of TNT explosion flame was confirmed by analyzing the composition of the products of TNT explosion flame. Therefore, a function model of explosion flame’s dynamic average emissivity was deduced concerning onsite atmospheric transmittance, digital output value of thermal imager and explosion flame’s temperature measured by the colorimetric thermometer in accordance with the expression of explosion flame’s radiance; finally, based on the receiver function of thermal imager’s effective radiation, a joint temperature compensation evaluation method, which combines radiation path compensation and dynamic emissivity, was proposed for joint inversion of explosion flame’s temperature at the explosion site and the range of temperature error of inversion was obtained through comparison of measured result with explosion flame’s surface temperature measured by colorimetric thermometer. The test result suggests the error of explosion flame’s temperature measured with the proposed compensation model is reduced to 11.292%−59.077% from previous 55.699%−89.847% before compensation, thus effectively improving the accuracy of measurement of transient flame temperature of explosion at external field and providing a means for accurate infrared thermography-based evaluation of thermal effect in explosion field.

Rational design of gradient structured fluorocarbon/Al composites towards tunable combustion performance

Polytetrafluoroethylene/Aluminum (PTFE/Al) composite with high energy density and combustion reaction performance has received widespread attention in the field of propellants, explosives, and pyrotechnics. In order to precisely control combustion reaction and energy output performance, gradient structured PTFE/Al composite (mass and diameter gradient) has been designed and constructed through 3D printing technology. PTFE/Al ink is prepared by acoustic resonance mixing to control rheological properties (viscosity and modulus) for 3D printing technology. The largest reaction heat (7749.95 J/g) and burning rate (~130 mm/s) are achieved for gradient lines with diameter of 2.42 mm and mass ratio of 60:40 (PTFE/Al). Moreover, the progressive change from steady combustion to deflagration containing three stages of pressure output is observed for gradient structured PTFE/Al cylinder. This work reveals that gradient structure could provide new strategy to tune energy output and combustion performances, which can promote the practical application of PTFE/Al reactive materials.

An efficient energy characteristics and explosion heat improving method of FOX-7-based aluminized explosives

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.

Dynamic vulnerability assessment and damage prediction of RC columns subjected to severe impulsive loading

Reinforced concrete (RC) columns are crucial in building structures and they are of higher vulnerability to terrorist threat than any other structural elements. Thus it is of great interest and necessity to achieve a comprehensive understanding of the possible responses of RC columns when exposed to high intensive blast loads. The primary objective of this study is to derive analytical formulas to assess vulnerability of RC columns using an advanced numerical modelling approach. This investigation is necessary as the effect of blast loads would be minimal to the RC structure if the explosive charge is located at the safe standoff distance from the main columns in the building and therefore minimizes the chance of disastrous collapse of the RC columns. In the current research, finite element model is developed for RC columns using LS-DYNA program that includes a comprehensive discussion of the material models, element formulation, boundary condition and loading methods. Numerical model is validated to aid in the study of RC column testing against the explosion field test results. Residual capacity of RC column is selected as damage criteria. Intensive investigations using Arbitrary Lagrangian Eulerian (ALE) methodology are then implemented to evaluate the influence of scaled distance, column dimension, concrete and steel reinforcement properties and axial load index on the vulnerability of RC columns. The generated empirical formulae can be used by the designers to predict a damage degree of new column design when consider explosive loads. With an extensive knowledge on the vulnerability assessment of RC structures under blast explosion, advancement to the convention design of structural elements can be achieved to improve the column survivability, while reducing the lethality of explosive attack and in turn providing a safer environment for the public.

Professor Dr. Thomas M. Klapötke

Professor Dr. Thomas M. Klapötke