Detonation Of High Explosives Research Articles

Erratum for “Incident and Normally Reflected Overpressure and Impulse for Detonations of Spherical High Explosives in Free Air” by Jinwon Shin, Andrew S. Whittaker, and David Cormie

Erratum for “Incident and Normally Reflected Overpressure and Impulse for Detonations of Spherical High Explosives in Free Air” by Jinwon Shin, Andrew S. Whittaker, and David Cormie

Numerical simulation of the dynamics of a reinforced concrete slab under an air shock wave

Deformation and fracture of a reinforced concrete slab under the effect of an air shock wave are considered. The research involves data from the public experiment "Blind Blast Test". The slab is loaded by an air shock wave resulting from high explosive detonation in a shock tube. The results of calculations and experiments are compared quantitatively and qualitatively. Quantitative comparison is made for the history of movement of the reinforced concrete slab key points during the process of deformation. Qualitative comparison is made for photographs of the destruction of a real reinforced concrete slab and distribution of the damage fields obtained by calculation. The numerical simulation is carried out in the LS-DYNA code, and the finite element method with an explicit time integration scheme is used. The CSCM (Continuous Surface Cap Model) model is used to model the concrete material. This model is an isotropic constitutive model with three-variant surface of ductility; the strength characteristics of the material depend on the rate of loading, and its damage is considered separately for compressive and tensile loads, which allows taking into account the partial recovery of compressive strength. The mathematical description of the model is given as part of the paper. Steel reinforcement of the concrete slab is modeled explicitly with beam finite elements. Finite element meshes of the concrete volume and reinforcing elements are coupled by means of the kinematic automatically calculated equations. The properties of the reinforcement are set within the classical theory of elastic-plastic strengthening material flow with the criterion of limiting states in the form of Huber-Mizes and taking into account visco-plastic effects. The influence of boundary conditions, practical mesh convergence, and capability of the mathematical model to predict the location of zones of material failure, displacement, and deformation of the structure are studied.

Characterization of high-explosive detonations using broadband infrared external cavity quantum cascade laser absorption spectroscopy

Infrared laser absorption spectroscopy provides a powerful tool for probing physical and chemical properties of high-explosive detonations. A broadly tunable swept-wavelength external cavity quantum cascade laser operating in the mid-wave infrared (MWIR) spectral region is used to measure transmission through explosive fireballs generated from 14 g charges of 4 different explosive types detonated in an enclosed chamber. Analysis of time-resolved transmission and emission at a 2 μs sampling rate shows the evolution of fireball infrared opacity in the first 10 ms after detonation. Broadband high-resolution absorption spectra acquired over the spectral range of 2050–2300 cm−1 (4.35–4.88 μm) at a 100 Hz rate are used to measure properties of fireball evolution over longer time scales out to 100 s. Path-integrated concentrations of combustion products CO, CO2, H2O, and N2O are measured and show evolutions over multiple time scales and significant differences between explosive types. Spectral analysis is used to characterize gas temperature and to measure broadband attenuation from absorption and scattering of particulates. Analysis of the results provides information on the MWIR optical properties, gaseous detonation/combustion products, and particulates throughout the explosive process including initial detonation, fireball expansion and cooling, and diffusive mixing in the chamber.

Resolving Detonation Nanodiamond Size Evolution and Morphology at Sub-Microsecond Timescales during High-Explosive Detonations

Characterization of the initial morphology of detonation nanodiamond (DND) has been the focus of many research studies that aim to develop a fundamental understanding of carbon condensation under e...

The Application of Godunov SPH in the Simulation of Energetic Materials

The numerical study of detonation of high explosives has been the interest of researchers over decades. Due to its special advantages in tracking free surface and dealing with large deformation, smoothed particle hydrodynamics (SPH) has been a powerful tool to investigate detonation phenomenon. SPH is a Lagrangian mesh-free method with extensive applications in fluid mechanics and solid mechanics. In the early development of SPH method, artificial viscosity is introduced to suppress unphysical fluctuation. However, the parameters of artificial viscosity often need to be tuned for some simulation, which can be quite time-consuming. Herein, a Riemann solver is integrated in traditional SPH algorithm to eliminate artificial viscosity, which is known as Godunov SPH. First, shock tube problem is studied using the Godunov SPH. The simulation result is compared with that obtained by traditional SPH with artificial viscosity, finite volume method (FVM) and experiment. Then, the Godunov SPH is implemented to investigate the detonation of 1D and 2D polymer-bonded explosive PBX 9501. Various factors that may influence simulation are studied, such as particle density and smoothing length. It is demonstrated that the proposed method is accurate and reliable for the study of detonation of high explosives.

Blast-Wave Clearing for Detonations of High Explosives

AbstractWhen a blast wave impinges on the front face of a structure, rarefaction waves are formed along its free edges and propagate toward the center of the front face, and reduce the reflected ov...

Design and numerical assessment of a rapid-construction corrugated steel-concrete-steel protective structure

A protective structure should be sufficiently resilient to protect its occupants from the harmful effects of an impact or explosion. In many instances, protective structures are also required to be assembled quickly, and be cost-effective. Steel-concrete-steel (SCS) sandwich structures combine the benefits of steel; ductility and anti-scabbing, and concrete; energy absorption and rigidity. Despite these favourable characteristics, the performance of profiled-plate steel-concrete-steel structures under blast and impact loads has yet to be studied in detail. This article presents the results from a numerical study investigating the efficacy of a newly proposed profiled-plate arched steel-concrete-steel structure under the loading from an extremely near-field high explosive detonation. It is observed that as arch thickness (concrete infill depth) increases, a greater proportion of energy is absorbed through concrete crushing and a larger concrete mass is mobilised. It is shown that a 240 mm arch thickness is adequate to resist the blast load from a 5.76 kg TNT charge, therefore proving the suitability of the proposed protective structure.

Initiation and Overdriven Detonation of High Explosives Using Multipoint Initiation

AbstractHigh explosives (HE) with desirable safety and detonation performances are widely used in weapon system and aerospace engineering. Multipoint initiation is utilized to initiate TATB and thus create overdriven state. High‐pressure areas of colliding shock waves are observed by measuring steel dent value and the whole processes, involving multiple wave interactions and overdriven detonation formation, are reproduced using LS‐DYNA3D program. Results indicate that the quadruple point is at the center where four shock waves collide, and the double point is between two initiation points where two shock waves collide. When the height of donor explosive exceeds 5 mm, the retardation time of the quadruple point compared to the double point and the individual point are 180 ns and 260 ns, respectively. In addition, overdriven state may disappear when the height of UF‐TATB exceeds 9 mm, and the delay effect is negligible for initiating PBX‐9502 when the simultaneity of slapper detonators is within 100 ns.

Methods to restore the dynamics of carbon condensation during the detonation of high explosives

Time resolved small angle x-ray scattering (SAXS) experiments on detonating high explosives have been conducted at the Lavrentyev Institute of Hydrodynamics and the Budker Institute of Nuclear Physics. The purpose of these experiments is to measure the SAXS patterns behind the detonation front and restore the dynamics of a carbon condensation process. The deficiency of the experimental data hinders the development of detonation models. In this work we present a new method to restore the dynamic of carbon condensation from time resolved SAXS patterns.

Experimental Measurement of Specific Impulse Distribution and Transient Deformation of Plates Subjected to Near-Field Explosive Blasts

The shock wave generated from a high explosive detonation can cause significant damage to any objects that it encounters, particularly those objects located close to the source of the explosion. Understanding blast wave development and accurately quantifying its effect on structural systems remains a considerable challenge to the scientific community. This paper presents a comprehensive experimental study into the loading acting on, and subsequent deformation of, targets subjected to near-field explosive detonations. Two experimental test series were conducted at the University of Sheffield (UoS), UK, and the University of Cape Town (UCT), South Africa, where blast load distributions using Hopkinson pressure bars and dynamic target deflections using digital image correlation were measured respectively. It is shown through conservation of momentum and Hopkinson-Cranz scaling that initial plate velocity profiles are directly proportional to the imparted impulse distribution, and that spatial variations in loading as a result of surface instabilities in the expanding detonation product cloud are significant enough to influence the transient displacement profile of a blast loaded plate.

Dynamic formation of nanodiamond precursors from the decomposition of carbon suboxide (C3O2) under extreme conditions-A ReaxFF study.

We use molecular dynamics simulations with the ReaxFF-lg potential to model the high pressure pyrolysis of carbon suboxide (C3O2) in mixture with argon as a pressure bath. We show that the reactive simulations catch the experimental behavior of the low-pressure detonation of C3O2 (around 10 bars in shock tube experiments) and allow extrapolations to the high-pressure range of solid-state explosive detonation (up to 60 GPa). While at low pressure carbonaceous nanostructures are formed through the aggregation of species such as carbon dimers C2, it appears that the high pressure deeply modifies the process, with the aggregation of growing CxOy heterostructures, in which the oxygen amount is driven by the pressure and the temperature. Pressures in the order of 60 GPa lead to high oxygen ratios, which prevent carbon atoms to get four carbon neighbors (the first condition to get a diamond structure). But a pressure lowering leads to a substantial carbon enrichment through CO2/CO release and facilitates the formation of pure sp3-carbon phases where diamond precursors can form. These results give new insights on the conditions leading to nanodiamonds during the detonation of carbon-rich high explosives.

On the effectiveness of ventilation to mitigate the damage of spherical chambers subjected to confined trinitrotoluene detonations

This article presents a comparative study on the effectiveness of ventilation to mitigate blasting effects on chambers subjected to confined detonations of high explosives. The pressure time-history that acts on the chamber walls is described by three components: (1) the first shock wave, (2) the train of re-reflected shock waves, and (3) the gas pressure. The radial response of spherical chambers is described by the radial breathing mode and modeled by an equivalent single degree of freedom system. The three pressure components are considered for the calculation of the maximum ductility ratio, which is obtained from the numerical solution of the single degree of freedom chamber response. It is assumed that openings reduce the gas pressure but they have an insignificant effect on shock waves. The dynamic response of fully and partially confined chambers are calculated and compared. Results show that intermediate/small openings (less than 10% of the surface of the chamber) are ineffective to mitigate the chamber response and damage. The vibratory response of the chamber is susceptible to elastic or plastic resonance but it is not considerably modified by the long-term gas pressure because of its high radial breathing mode frequency, allowing concluding that ventilation is ineffective to reduce the maximum response of spherical chambers subjected to internal high explosive explosion.

High Explosive Detonation–Confiner Interactions

The primary purpose of a detonation in a high explosive (HE) is to provide the energy to drive a surrounding confiner, typically for mining or munitions applications. The details of the interaction between an HE detonation and its confinement are essential to achieving the objectives of the explosive device. For the high pressures induced by detonation loading, both the solid HE and confiner materials will flow. The structure and speed of a propagating detonation, and ultimately the pressures generated in the reaction zone to drive the confiner, depend on the induced flow both within the confiner and along the HE–confiner material interface. The detonation–confiner interactions are heavily influenced by the material properties and, in some cases, the thickness of the confiner. This review discusses the use of oblique shock polar analysis as a means of characterizing the possible range of detonation–confiner interactions. Computations that reveal the fluid mechanics of HE detonation–confiner interactions for finite reaction-zone length detonations are discussed and compared with the polar analysis. This includes cases of supersonic confiner flow; subsonic, shock-driven confiner flow; subsonic, but shockless confiner flow; and sonic flow at the intersection of the detonation shock and confiner material interface. We also summarize recent developments, including the effects of geometry and porous material confinement, on detonation–confiner interactions.

The Confinement Effect of Inert Materials on the Detonation of Insensitive High Explosives

The paper aims to theoretically and numerically investigate the confinement effect of inert materials on the detonation of insensitive high explosives. An improved shock polar theory based on the Zeldovich-von Neumann-Doring model of explosive detonation is established and can fully categorize the confinement interactions between insensitive high explosive and inert materials into six types for the inert materials with smaller sonic velocities than the Chapman-Jouguet velocity of explosive detonation. To confirm the theoretical categorization and obtain the flow details, a second-order, cell-centered Lagrangian hydrodynamic method based on the characteristic theory of the two-dimensional first-order hyperbolic partial differential equations with Ignition-Growth chemistry reaction law is proposed and can exactly numerically simulate the confinement interactions. The numerical result confirms the theoretical categorization and can further merge six types of interaction styles into five types for the inert materials with smaller sonic velocity, moreover, the numerical method can give a new type of interaction style existing a precursor wave in the confining inert material with a larger sonic velocity than the Chapman-Jouguet velocity of explosive detonation, in which a shock polar theory is invalid. The numerical method can also give the effect of inert materials on the edge angles of detonation wave front.

The effect of compaction of a porous material confiner on detonation propagation

The fluid mechanics of the interaction between a porous material confiner and a steady propagating high explosive (HE) detonation in a two-dimensional slab geometry is investigated through analytical oblique wave polar analysis and multi-material numerical simulation. Two HE models are considered, broadly representing the properties of either a high- or low-detonation-speed HE, which permits studies of detonation propagating at speeds faster or slower than the confiner sound speed. The HE detonation is responsible for driving the compaction front in the confiner, while, in turn, the high material density generated in the confiner as a result of the compaction process can provide a strong confinement effect on the HE detonation structure. Polar solutions that describe the local flow interaction of the oblique HE detonation shock and equilibrium state behind an oblique compaction wave with rapid compaction relaxation rates are studied for varying initial solid volume fractions of the porous confiner. Multi-material numerical simulations are conducted to study the effect of detonation wave driven compaction in the porous confiner on both the detonation propagation speed and detonation driving zone structure. We perform a parametric study to establish how detonation confinement is influenced both by the initial solid volume fraction of the porous confiner and by the time scale of the dynamic compaction relaxation process relative to the detonation reaction time scale, for both the high- and low-detonation-speed HE models. The compaction relaxation time scale is found to have a significant influence on the confinement dynamics, with slower compaction relaxation time scales resulting in more strongly confined detonations and increased detonation speeds. The dynamics of detonation confinement by porous materials when the detonation is propagating either faster or slower than the confiner sound speed is found to be significantly different from that with solid material confiners.

Behavior of GFRP retrofitted reinforced concrete slabs subjected to conventional explosive blast

Majority of protective engineering in China has typically been designed to resist explosion of nuclear weapon instead of conventional explosive blast. This paper proposed a retrofitting method to improve the blast resistance of existing reinforced concrete (RC) slabs against conventional explosion using externally bonded glass fiber reinforced polymer (GFRP) strips. In order to assess the effectiveness of GFRP strips in enhancing the blast resistance of RC slabs, a series of underground blast tests for the first time were conducted. Five square RC slabs, including one companion control specimen and four GFRP retrofitted slabs, were subjected to blast loading generated from the detonation of high explosives ranging from 400 to 1400 g of trinitrotoluene (TNT). The reflected blast pressure, acceleration and central deflection of the slabs were measured and analyzed as well as the strains of steel bars, concrete and GFRP strips. The post-blast damage and failure mode of each slab were carefully investigated to determine the failure mechanism. The effects of charge burial and standoff distance on the blast pressure and structural response were analyzed in detail. The test results indicate that overall the GFRP retrofitted slabs performed much better and survived higher explosive blast than the control slab. Externally bonded GFRP strips strengthening can effectively increase the ultimate blast resistant capacity of RC slabs against conventional explosive blast.

Evolution of Carbon Clusters in the Detonation Products of the Triaminotrinitrobenzene (TATB)-Based Explosive PBX 9502

The detonation of carbon-rich high explosives yields solid carbon as a major constituent of the product mixture, and depending on the thermodynamic conditions behind the shock front, a variety of carbon allotropes and morphologies may form and evolve. We applied time-resolved small-angle X-ray scattering (TR-SAXS) to investigate the dynamics of carbon clustering during detonation of PBX 9502, an explosive composed of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) and 5 wt % fluoropolymer binder. Solid carbon formation was probed from 0.1 to 2.0 μs behind the detonation front and revealed rapid carbon cluster growth which reached a maximum after ∼200 ns. The late-time carbon clusters had a radius of gyration of 3.3 nm which is consistent with 8.4 nm diameter spherical particles and matched particle sizes of recovered products. Simulations using a clustering kinetics model were found to be in good agreement with the experimental measurements of cluster growth when invoking a freeze-out temperature, and tempora...

Extreme condition nanocarbon formation under air and argon atmospheres during detonation of composition B-3

Novel nanocarbons synthesized by extreme conditions produce products with various chemical and physical properties. Herein through high explosive detonation of Composition B-3 (40% TNT, 60% RDX), pressures and temperatures not classically attainable in laboratory syntheses provide access to interesting carbon allotropes. For example, detonations of Composition B-3 are regularly used to synthesize the now commercially-available nanodiamond (3–5 nm spherical diamond particles) through quenching of the detonation by ice collars at high pressures and temperatures. Detonation conditions of Composition B-3, in this study, were modified by altering the atmosphere (air versus Ar) without quenching, consequently directing nanocarbon formation. X-ray scattering and microscopy elucidate that detonations performed in air produced spherical hollow core-shell nanocarbons, whereas detonations in Ar produced elongated nanocarbons. Although morphology bifurcates, spectroscopy reveals that both major detonation products are comprised of sp2 hybridized carbon. As expected from air atmosphere detonations, surface functionalization is dominated by CO bonding. The absence of oxygen in the Ar atmosphere detonations may propagate extended sheets of graphene that either stack together due to electrostatics or fold upon itself. This work demonstrates that modification of the detonation atmosphere provides an alternative route for the production of new and interesting nanocarbons.

Characterization of laser-induced plasmas as a complement to high-explosive large-scale detonations

Experimental investigations into the characteristics of laser-induced plasmas indicate that LIBS provides a relatively inexpensive and easily replicable laboratory technique to isolate and measure reactions germane to understanding aspects of high-explosive detonations under controlled conditions. Spectral signatures and derived physical parameters following laser ablation of aluminum, graphite and laser-sparked air are examined as they relate to those observed following detonation of high explosives and as they relate to shocked air. Laser-induced breakdown spectroscopy (LIBS) reliably correlates reactions involving atomic Al and aluminum monoxide (AlO) with respect to both emission spectra and temperatures, as compared to small- and large-scale high-explosive detonations. Atomic Al and AlO resulting from laser ablation and a cited small-scale study, decay within ∼10-5 s, roughly 100 times faster than the Al and AlO decay rates (∼10-3 s) observed following the large-scale detonation of an Al-encased explosive. Temperatures and species produced in laser-sparked air are compared to those produced with laser ablated graphite in air. With graphite present, CN is dominant relative to N2+. In studies where the height of the ablating laser’s focus was altered relative to the surface of the graphite substrate, CN concentration was found to decrease with laser focus below the graphite surface, indicating that laser intensity is a critical factor in the production of CN, via reactive nitrogen.

Impact and close-in blast response of auxetic honeycomb-cored sandwich panels: Experimental tests and numerical simulations

Protecting building, critical infrastructure and military vehicles from Improvised Explosive Devices (IEDs) has become a critical task. This study aims to examine the performance of a new protective system utilizing auxetic honeycomb-cored sandwich panels for mitigation of shock loads from close-in and contact detonations of high explosives. Both field blast tests and drop weight tests were performed using the proposed sandwiches asa shield for concrete panels in combination with conventional steel protective plates. The combined shield was found to be effective in protecting reinforced concrete structures against severe impact and close-in blast loadings. The honeycomb core with re-entrant hexagonal cells shows evident auxetic characteristics which contribute substantially to outstanding force mitigation and blast-resistance performances of such sandwich panels. Numerical simulations showed good agreement with the experimental results. The proposed auxetic panels were found to perform better than conventional honeycomb panels of the same size, areal density and material. Both were found to boost the energy absorption of the monolithic steel plate by a factor of 2.5 by changing its deformation pattern under close-in blast loading. In addition, a combination of the steel plate and an auxetic sandwich panel has aerial specific energy absorption (ASEA) higher than either of them, showing great potential for the development of lightweight blast protection of civil, mining, military, nuclear infrastructure and vehicles.