Detonation Of Explosives Research Articles

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.

On the Dynamic Response of Laminated Glass Exposed to Impact Before Blast Loading

In this study, the effect of fragment or bullet impact before blast loading on laminated glass is studied experimentally. First, laminated windows consisting of two 3.8 mm thick annealed float glass plates and a 1.52 mm thick PVB interlayer were blast loaded in a shock tube with various pressures as a reference. In these tests, the blast loading was successively increased until fracture occurred not only in the glass plates but also in the PVB interlayer. Second, a diamond drill was used to make a 5 mm diameter centrally placed hole in some windows before they were blast loaded with the same pressures as those used for the undamaged windows. Third, windows were impacted by 7.62 mm AP bullets, both with and without the brass jacket, before they were blast loaded. Such bullets may have similar mass and velocity to typical primary fragments from an explosive detonation. The results are finally compared with each other and discussed with respect to the blast protection offered. It is found that the capacity is significantly reduced if the laminated glass is perforated by a fragment or a bullet before it is blast loaded and that such impacts should be considered in the design of blast-resistant windows.

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.

Impact mitigating capabilities of a spray-on elastomer coating applied to concrete

Structural protection against the effects of a nearby explosive detonation is an area of growing importance. Spray-on elastomer coatings are of interest as a practical and low cost protective solution. Recent research has demonstrated the effectiveness of such coatings for blast mitigation. However, there are two loading scenarios of concern for these applications: blast pressures and fragment impacts. To date, there remains a need to understand the merits of this protective solution for impact indentation of concrete structural elements. In this work, we examine whether, and by what mechanism, an elastomer coating can offer protection in this case. A series of quasi-static indentation and dynamic impact experiments are performed using a 0.1 kg circular cylindrical (i.e. blunt) projectile. It is demonstrated that the coating displays a significant protective capability over the full range of impact velocities considered, c. 45–150 m s−1. The coating remains intact until impacted at a velocity of c.120 m s−1 when it fails by a ductile, tearing mechanism, forming a plug which undergoes large elastic contraction after projectile penetration. A finite element model of the impact indentation of uncoated and coated concrete cubes is developed and validated against the experiments. Focusing on the early time steps and damage initiation in the concrete, the numerical model is used to interrogate the mechanism by which the elastomer achieves its mitigating effect. It is found that the way in which the elastomer alters the stress distribution in the concrete, and its time evolution, is key to its performance. These findings provide a basis for optimising protective coatings for concrete structural elements.

Numerical simulation on complete process of three-dimensional bench blasting in an open-pit mine based on CDEM

Blasting mining is the most important part of the total cost control in an open pit mine, and numerical simulation is an effective method to optimize the design of blasting mining and to analyse blasting effect. By using the continuum-discontinuum element method (CDEM), the three-dimensional bench blasting process of the open pit mine is simulated. The Landau explosive model is adopted to precisely calculate the blasting effect, and the elastic-damage-fracture constitutive law is used to describe the damage and fracture process of rock. By adopting the semi-spring target face and semi-edge target edge combined contact algorithm, the collision, flying and accumulation process of large number of fragments is simulated efficiently. The numerical simulation of the small scale blasting process with the single free surface is carried out. The block distributing curve and volume of the crater obtained by numerical simulation are more or less the same as those obtained by experiment, which demonstrates that CDEM and corresponding models described in this paper are good at simulating the rock blasting process. Based on the blasting technology in the south region in Anqian open-pit mine, a generalized three-dimensional bench blasting model with 3 rows and 21 bore holes is set up, and the complete process from explosive detonation to muckpile formation is carried out. Numerical results show that, except the tensile crack behind the blasting area, the muckpile shape and heaving height obtained by numerical simulation are accordant with the ones obtained by field test to some extent, which demonstrates the feasibility to simulate the three-dimensional bench blasting by CDEM.

Blasting Delay Pattern Development in the Light of Rockburst Prevention – Case Study from Polish Copper Mine

In order to reduce the risk of induced seismicity related to underground mining, a number of preventive actions are applied in the form of passive and active prevention methods. The former are mainly of an organisational nature and their effectiveness is usually considered in the long term, while the active methods are mostly based on the detonation of explosives and are aimed to release the seismic energy accumulated in the rock mass. In this paper, modifications of the firing pattern aimed to concentrate the paraseismic vibrations while maintaining the appropriate excavation of the mining face has been verified on the basis of underground tests. The evaluation was based on fragmentation analysis. The obtained results confirmed, that the blasting pattern modifications related to the reducing of the face firing time do not cause significant differences in terms of the appropriate excavation of the mining face.

Numerical Study of Separation Characteristics of Piston‐Type Explosive Bolt

An explosive bolt is a simple, highly reliable, and efficient pyrotechnic release device widely used in spacecraft and rocket launchers. High shock transient response is generated during the separation of a release device, which tends to damage the nearby micromechanism and hardware. The purpose of this article is to predict the shock response of an explosive bolt. In this paper, the separation process of a piston‐type explosive bolt is simulated by using a hydrocode named AUTODYN and the influence of the charge amount on separation time, separation speed, and separation shock is analyzed. Results show that piston‐type explosive bolts obey a tensile fracture mechanism and that the critical charge amount for separation is 354–398 mg of PETN. The separation shock of such an explosive bolt mainly includes two aspects: the shock caused by explosive detonations and the impact of the piston at the end of the stroke. As the charge amount increases, the separation time decreases, the speed of the piston and screw increases first and then decreases, and the separation shock first increases and then stabilizes. On a simple aluminum plate, the shock response decreases as the distance from the shock source increases, obeying the power function attenuation law.

Creation of Detonation Chamber for Experimental Determination of Thermodynamic Characteristics of Modern Explosives

The subject of investigation represents the designing data of explosion chamber and calorimetric device. The latter will allow the determination of the parameters of the detonation and energetic characteristics of low-sensitivity, emulsion and outdated explosives. Research methodology provides the study of standard explosives of published data only, which, at experimental investigations in the above-mentioned cases, do not agreed with the reality. The question problematical character is lied in the fact that the reduction of explosives sensitivity causes the increase of critical and limiting diameters of tested charge which, for its part, is associated with the increase of charge mass. Above-mentioned increases significantly the limiting values of designed dynamic loads, acting on the walls of explosion chamber and presents a serious hazard to the construction integrity. For problem, solving the new experimental explosion chamber together with calorimetric device was designed. In the chamber, for reduction of quasistatic pressures channels were designed the total area of their surfaces were calculated by theoretical methods together with other designed data of explosion chamber and calorimetric device. The procedure of the devise manufacturing is proceeding.

Detonation of Low-Density Explosives

Electromagnetic measurements of the particle velocity are performed in a situation when the detonation wave reaches the interface between a powdered high explosive (HE) and a window made of an inert material (Plexiglas). PETN, RDX, and HMX with densities close to the natural bulk density are studied. In order to measure not only the averaged velocity profile, but also possible fluctuations at scales of the order of the HE grain size, small sensors with the working arm length approximately 1 mm are used. In most experiments, profiles with clear chemical spikes are obtained; in some of the measured results, however, the chemical spike cannot be detected on the background of strong signal oscillations, which may be considered as manifestation of the nonclassical mechanism of wave propagation (explosive burning suggested by Apin). Along withour previous study, the present results suggest parallel operation of the shock and convective mechanisms with domination of each mechanism at different segments of the wave front.

Detonation of Low-Density Explosives

Detonation of Low-Density Explosives

Estimating Chemical Conversion Rates for Composite Explosives on the Basis of Experimental Data on Pseudo-Ideal Detonation

The conditions for the appearance of a plateau-like region called pseudo-ideal detonation in the dependence of the velocity of detonation (VOD) of composite explosives on the diameter of a charge were considered. A theoretical model of steady-state non-ideal detonation with a slightly curved front and a two-stage mechanism of chemical reaction was used for analysis. The calculations were performed for a trinitrotoluene-50% ammonium nitrate mixture and a mechanically activated ammonium perchlorate-20% aluminum mixture. The coefficients of the equations describing the global chemical conversion rates of components were fitted in the calculations. In both cases, the dependence of the VOD on the diameter of the reciprocal charge with a plateau-like region was obtained for an increasing conversion rate of the major explosive (trinitrotoluene and ammonium perchlorate, respectively).

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.

Numerical simulation of the stress-strain state of a coal seam caused by an explosion of a blast-hole charge with an annular gap

The computer simulation of the propagation of a blast wave generated by various explosives is carried out. The simulation used numerical methods to solve dynamic problems in the mechanics of a deformable solid, which allow one to investigate the development of waves during the explosion of charges of various shapes at different speeds of detonation of explosives and various conditions of placement of charges in the hole. The novelty of the research is related to analysis of conditions for the formation of a tensile pulse, which determines the opening of natural and induced defects in a zone remote from the explosion (from 20 to 100 radii of charge), which is known as the zone of explosive pre-fracture.

Features of initiating the light-sensitive explosive composites for safe blasting of borehole charges in coal mines

The purpose of paper is to study physical and chemical patterns for starting detonation in the explosive charges by means of laser pulse radiation. Studies of the physical and chemical properties of the mechanism for stimulating the detonation of explosives by pulse radiation of an optical quantum generator have been carried out. Methodology of experimental and theoretical studies as well as mathematical modeling, involving gas-dynamics equations, has been applied. Basic research results as for studying sensitivity of the explosives being initiated by pulse light radiation have been analyzed. Numerical modeling was performed taking into consideration the real process of igniting the explosive by infrared laser radiation. The proposed mathematical model makes it possible to study the peculiarities of initiating the explosive transformation of bursting explosives by means of short light pulses. Tetranitropentaerytrite (PETN) was used to show that the process is determined completely by the parameters which characterize radiation intensity and absorption properties of the explosive. Depending on these parameters values, initiation processes may be implemented qualitatively – either on the surface or inside the explosive. In the latter case, the release of chemical energy results in the formation of so-called “chemical” pressure peak. With the use of lead azide, it has been shown experimentally that the initial temperature does not affect the increase in explosive sensitivity even in case when laser radiation takes place in the nanosecond pulse mode. Experimental results are applied while developing light-sensitive composites with the preset explosive and physical-chemical properties. The determined patterns were used in the development of the light-sensitive explosive composites for blasting agents of explosive charges.

Structural damage analysis of explosive testing experimental bay using HEXDAM Modelling software

Modelling of structural damages is a tool for making blast damage assessments resulting from an explosion on a localized area. This can be used as a damage/ injury assessment tool to determine the amount of blast damage/injury done to individual structures/ persons in a certain geographical area due to the detonation of explosives at ground level or at a specified height above the ground. This paper deals with prediction the structural damages of an experimental bay building when subjected to explosive testing, using HEXDAM (High Explosive Damage Assessment Modelling) software. The modelling software helps to predict the blast parameters at various points and the structural damages caused to the structures with in a facility. The basic outputs of HEXDAM are designed to provide data such as before/after blast display; damage/injury table; damage vs distance; pressure contours; damage/injury contours and the data tables for overpressure, dynamic pressure and damage/injury at each grid point. The experimental bay building along with the facility building was scientifically modelled with the trial set up using this software. The structural damages to the experimental bay and the nearby facilities are analysed when the building set up is subjected to the explosive loading at the height of 1m. The over pressure data at various points from the ground level to the height of 9m have been generated in this modelling. The Outputs are in the form of Damage vs injury tables, before and after blast displays, pressure and damage vs injury contour plots and Damage, injury-versus-distance graphs.

Initiation and development of exothermic reactions during solid-phase synthesis under explosive loading

The previous numerical and experimental studies of the solid-phase synthesis of porous reactive mixtures (Al-S and Al-Tf) placed into cylindrical ampoules subjected to explosive detonation revealed the sharp increase in temperatures and pressures. The results have shown that high heat release and high increase in pressure due to exothermic reactions in the mixture, on the one hand, promote the faster development of reactions and, on the other hand, contribute to the formation of a gas phase that, in turns, may lead to the damage or even fracture of ampoules. This problem is solved by adding an inert porous aluminum layer to the bottom part of the mixture. Computations are carried out using the model of a multicomponent medium and the finite element method. Numerical simulation has shown that in this case the fracture of cylindrical ampoules is not observed.

Numerical simulation of separation shock characteristics of a piston type explosive bolt

A piston type explosive bolt is modeled by using a hydrocodes AUTODYN. The influence of the charge amount on the separation shock is analyzed. The results show that the separation shock of the piston type explosive bolt mainly includes two aspects: the shock caused by explosive detonation and the impact of the piston at the end of stroke. As the charge amount increases, the collision speed of piston first increases and then decreases, and the separation shock first increases and then stabilizes.

Granularity impact on hotspot formation and local chemistry in shocked nanostructured RDX

The nanostructuration of energetic materials results in interesting properties. In particular, the detonation of carbon-rich explosives leads to the formation of nanodiamonds, the size of which is linked to the initial size of the explosive nanograins. This correlation could come from the role played by the granularity in the shock properties, especially the local temperature, which could be enhanced when the shock front crosses the various interfaces and nanoporosities of the material. More generally, the granularity-dependent reactivity also concerns some aspects of the sensitivity of energetic materials and subsequent inhibition or safety issues. In order to investigate this hypothesis, we perform classical and reactive molecular dynamics shock-simulations on cyclotrimethylene trinitramine (RDX), a common high-explosive. We design various nanogranular structures using the body-centered-cubic stacking of nanoparticles shaped as Kelvin cells (truncated octahedra) with slightly-bumped faces. The nanograin size and the bump radius allow to independently control the porosity value and its nanostructure. We show that the global shock properties, especially the temperature, are sensitive to the porosity value but not to the nanograin size. The porosity nanostructure has a local impact, enhancing the temperature heterogeneities between the inter- and intra-grain regions by a few hundred degrees and slowing down the thermal homogenization. For a given porosity, the larger the nanograins, the larger and the hotter the hotspots. In such hotspots, the local chemistry is significantly modified, resulting in a larger reactivity with a quicker formation of some final products. We suggest that the quicker consumption of heteroatoms (namely, H, O, and N) along with higher local temperatures is likely to impact the formation process of solid carbonaceous phases.

Simulations for three-dimensional landmine detonation using the SPH method

The simulation of the soil fragmentation under buried explosive detonation is an extremely difficult task. In this paper, the modified smoothed particle hydrodynamics method (SPH) in combination with the elastoplastic and hypoplastic constitutive models is introduced to simulate the three-dimensional (3D) landmine detonation for the first time. The modified continuity equation is incorporated to tackle the multiphase interfacial problems with high density ratios. The elastoplastic and hypoplastic constitutive models are employed to describe the soil mechanical behavior. Furthermore, the in-house SPH code is parallelized using the Open-MP program interface to solve problems with large number of particles efficiently. At the end, the simulation results are compared with the experimental data, which shows that the SPH method in conjunction with these two constitutive models can tackle landmine detonation problems involving large deformation very well.

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.