Detonation Of High Explosives Research Articles

Enhancing blast mitigation in tunnels with expansion chamber subjected to high explosives detonations for protecting underground facilities

This paper presents a numerical investigation into the effect of expansion chamber in mitigating overpressures and impulses in protective tunnels subjected to detonation of high explosives. Blast shockwave propagation in a protective tunnel, with dimensions of 160 m in length, 8.9 m in width and 7.2 m in height, was simulated using a computational fluid dynamics code, Viper::Blast. The design parameters of the expansion chamber cover a broad spectrum chamber lengths between 6.1 and 12.1 m, widths spanning from 10.7 to 97 m, length-to-width ratios from 0.0 (indicating no chamber) to 5.0, heights of 8.0 and 14.9 m, and chamber-to-tunnel width ratios in the range of 1.2 to 10.9 m. Two charge weights of 1000 and 2000 kg of TNT were employed to assess their influences. To ensure the reliability of the CFD model, mesh sensitivity analysis, overpressure stability assessments, and validation studies were undertaken. A parametric analysis was then conducted using the validated model to derive an optimal design for the expansion chamber within the specified tunnel. Recommendations for incorporating an expansion chamber into protective tunnels under blast events are provided.

Passive blast protection of buildings by ductile steel-based envelopes

The growth of industrialization and the rapid expansion of densely populated urban areas have increased the risk caused by technological and man-made hazards. In particular, the accidental or intentional detonation of high explosives (e.g., improvised explosive devices IEDs), can cause damages to buildings and infrastructures and severe harm people. These risks can be minimized by a better planning, design, and construction, e.g., avoiding brittle construction materials, especially within the building envelope, and adopting more robust construction techniques. The study presented in the paper investigates the capacity of light steel-based wall panels to resist the effects of external explosions. The experimental results showed the ultimate capacity of the wall panels is strongly dependant on the initial design conditions and panel-to-structure fastening solution. A numerical model has been also calibrated using Etabs program.

Experimental testing of liner tray walls subjected to near field blast

AbstractExplosions produced in urban or industrial areas due to accidental or intentional detonation of high energy explosives (e.g., improvised explosive devices IED) are low‐probability but high‐impact events. If standoff distance from buildings or other constructions is small, explosions can cause structural failures and serious injuries or deaths of people. Preventing buildings from collapse is essential to minimizing casualties among occupants. However, experience has shown that even if the collapse is prevented, high number of injuries can result from fragments and flying debris generated by the non‐structural components or building envelopes. This risk could be minimized through appropriate design and selection of construction materials for most exposed elements (i.e., building envelopes). Although heavy/stiff systems were long considered appropriate to protect buildings against explosive threats, lighter and flexible systems are increasingly used for modern buildings. By allowing damage (but not fragmentation), the envelope system can provide predictable response, with minimal injuries in case of an explosion.The study presents the results of full‐scale blast tests on liner tray walls attached to a steel frame building. Walls are tested against increasing blast charges until complete failure. The ultimate strength is given by the failure of the end fasteners, after large bolt hole elongations coupled with the pull‐through of the end fasteners.

CFD-Based Overpressure Evaluation Inside Expansion Chamber-Applied Protective Tunnels Subjected to Detonation of High Explosives

CFD-Based Overpressure Evaluation Inside Expansion Chamber-Applied Protective Tunnels Subjected to Detonation of High Explosives

Evaluating the effect of insensitive high explosive residues on soil using an environmental quality index (EQI) approach

The environmental impact of Insensitive High Explosive (IHE) detonation residues to soil quality was assessed using a series of outdoor soil mesocosms. Two different soils were used including a pristine sandy soil and a land-degraded soil collected from a training range. Both soils were spiked with an IHE mixture comprised of 53 % NTO, 32 % DNAN and 15 % RDX at three different concentrations 15, 146 and 367 mg/kg respectively. The concentration levels were derived from approximate residues from 100 detonations over a 2 week training period. A set of five physico-chemical and biological indicators representative of the two soils were selected to develop environmental quality indexes (EQI). It was found that none of the concentrations tested for the pristine soil affected the chemical, biological and physical indicators, suggesting no decrease in soil quality. In contrast, the EQI for the degraded soil was reduced by 24 %, mainly due to a decrease in the chemical and biological components of the soil. Therefore, it is concluded that depending on the soil health status, IHE residues can have minor or severe consequences on soil health. Further studies are needed to determine the environmental impact of IHE on soil and water especially in the case where a larger number of detonations are more likely to be carried out on a training range.

Extinction Imaging Diagnostics for In Situ Quantification of Soot within Explosively Generated Fireballs

AbstractFireballs produced from the detonation of high explosives often contain particulates primarily composed of various phases of carbon soot. The transport and concentration of these particulates is of interest for model validation and emission characterization. This work proposes ultra‐high‐speed imaging techniques to observe a fireball's structure and optical depth. An extinction‐based diagnostic applied at two wavelengths indicates that extinction scales inversely with wavelength, consistent with particles in the Rayleigh limit and dimensionless extinction coefficients which are independent of wavelength. Within current confidence bounds, the extinction‐derived soot mass concentrations agree with expectations based upon literature reported soot yields. Results also identify areas of high uncertainty where additional work is recommended.

Blast behaviour of precast segmental vs monolithic concrete beams prestressed with unbonded tendons: A numerical investigation

This study aims to numerically investigate the response of precast/prefabricated segmental concrete girders/beams (PSCBs) under detonations of high explosives. A new and effective method of applying prestressing force in tendons in LS-DYNA is explored and used. The working mechanisms of PSCBs vs conventional monolithic beams in resisting blast loads are comprehensively examined and discussed. The numerical results show that blast-induced damage to the beams is primarily caused by three different mechanisms, namely the propagations of blast-induced stress waves and plastic hinges, and the beam free-vibration deflection (global response). There are similar stress wave propagation and the resultant damage in the monolithic and segmental beams at the early stage when the joints are closed. The different damage patterns in these two beams are mainly due to the propagation of plastic hinges and the beam's free-vibration deflection. Damage is more severe and well distributed in the monolithic beam whereas damage to PSCB mainly concentrates in the segment next to the explosive and around the joints. The energy absorption mechanism provided by the relative movement between the segments is the main reason for the reduced damage in the PSCB. Although having larger displacement, the PSCB shows better blast resistance compared to the monolithic beam. Either increasing the prestressing reinforcement ratio or effective prestressing stress reduces the peak and residual displacement of the beam but increases concrete damage. Increasing the number of segments leads to a larger beam displacement response but reduces concrete damage. Energy dissipation (ED) bars are found to effectively unite the segments and hence result in the segmental beam having a similar blast behaviour as the monolithic counterpart.

Assessment of Passenger Security in Paratransit Buses

The main objective of this study was to assess usefulness of 3-D, nonlinear dynamic, explicit computer codes for transit safety and security research. An analysis of response of a paratransit bus structure under loading caused by high explosive (HE) detonation is presented. It was assumed that the cubic HE charge detonates in the air near the bus. The ground was modeled as a rigid stationary wall. The problem was studied using LS DYNA, an explicit, 3-D, dynamic, nonlinear finite element program. The HE detonation and the processes of shock propagation in the air were modeled using the mesh with the Euler’s formulation. The Euler’s mesh was modeled as a rectangular prism sufficiently large enough to cover the entire bus structure. The nonreflecting boundary conditions on the top and side surfaces of the Euler’s domain and the sliding interface on the bottom side for the contact with the ground were assumed.A finite element model of the Ford Eldorado Aerotech 240 paratransit bus was developed for this study. This model consisted of 73,600 finite elements and had 174 defined properties (groups of elements with the same features) and 23 material models.Computational analysis provided useful information about dynamic deformations and damage inflicted to the bus structure under load blast wave activated by the HE detonation. It allowed for detailed, rigorous analyses of time histories of accelerations, velocities, deformations, and stresses. Resulting acceleration and overpressure histories were correlated with expected blast injuries of the bus passengers. The data obtained can be used to improve passenger safety and to reduce the threat of suicidal terrorist attacks against public transit. Changes in the bus structure and replacement of some materials to build a safer class of vehicles can be carefully considered and implemented.

Two-stage carbon condensation model during detonation of high explosives

During detonating of high explosives with a negative oxygen balance, one of the products of the chemical reaction is condensed carbon. However, the lack of experimental data does not allow us to give a quantitative assessment of the carbon condensation process today. In this paper, a two-stage model of carbon condensation during the detonation of high explosives is proposed. We used small-angle X-ray scattering method to study the dynamics of the formation of carbon nanoparticles during the detonation of charges of a mixture of TNT and RDX.

High temperature and pressure regime soot: Physical, optical and chemical signatures from high explosive detonations

High temperature and pressure regime soot: Physical, optical and chemical signatures from high explosive detonations

On the kinetics of chemical reactions at the detonation of organic high explosives

The model of electrical conductivity developed earlier allows one to use electrical properties as a tool for the diagnostics of the reaction zone at the detonation of organic high explosives. The comparison of experimental data on electrical conductivity with both the results of experimental research and numerical modeling using Arrhenius kinetics is carried out. The contradiction of the thermal concept of the mechanism of the development of a chemical reaction during detonation is clearly demonstrated. An alternative based on the ideas of A. N. Dremin, J. J. Dick, C. S. Coffey, and F. E. Walker is discussed.

Extended JCZ3 Equation of State and JAGUAR Implementation for High Explosives

AbstractAn extended JCZ3 based equation of state for the modelling of high explosive detonation products has been implemented in the JAGUAR computer model. This development includes the parameterization of EXP‐6 potentials for individual products species, as well as mixing rules for the combination of species. Non‐linear variable metric optimization was used for the species parameterization, as well as for the solution of free energy minimized states. Explosive detonation and products expansion are typically modelled for JWL and JWLB high explosives thermodynamic equation of state development. An analytic c ylinder test model was developed for the comparison to experimental cylinder expansion test data and for the characterization of explosive products expansion and work output. Examples and comparisons to data are presented. Historically, streak photography was used for cylinder testing, whereas photon‐doppler velocimetry (PDV) is now standard. This has resulted in some changes in cylinder testing data reduction. A JAGUAR MSIAC web‐based application is currently under development for use by the MSIAC member nations.

Experimental analysis of fluid–structure interaction between a blast wave and a sandwich add-on armor

In various situations, targets with different characteristic dimensions are being exposed to blast waves generated by high explosive detonation. One of the existing mitigation methods consists of protecting the target from the explosion with a sandwiched crushable core between a front plate and the target. The pressure generated by the explosion is converted into the planar displacement of the front plate, which compresses the crushable core, delaying the transmission of the load to the target. The influence of the crushable core on the transmitted load in the form of a plateau stress is well described in the literature contrary to its influence on the transferred momentum. In this paper, momentum transmission during the crushing of the core has been experimentally investigated, taking into account the fluid–structure interaction effect, the mechanical behavior of the core, and the pneumatic effects generated by the air trapped into its cells. It is shown that the beneficial effects of fluid–structure interactions are often counterbalanced by the mechanical behavior of the core and that analytical models from the literature are sufficient to describe the order of magnitude of the uniaxial crushing process.

Verification of a Specialized Hydrodynamic Simulation Code for Modeling Deflagration and Detonation of High Explosives

Abstract A specialized hydrodynamic simulation code has been developed and verified for the simulation of one-dimensional unsteady problems involving the detonation and deflagration of high explosives. To model all the relevant physical processes in these problems, a code is required to simulate compressible hydrodynamics, unsteady thermal conduction, and chemical reactions with complex rate laws. Several verification exercises are presented which test the implementation of these capabilities. The code also requires models for physics processes such as equations of state and conductivity for pure materials and mixtures as well as rate laws for chemical reactions. Additional verification tests are required to ensure that these models are implemented correctly. Though this code is limited in the types of problems it can simulate, its computationally efficient formulation allows it to be used in calibration studies for reactive burn models for high explosives. This study demonstrates how a series of verification tests can be used to ensure that the various physics processes needed to simulate complex phenomenon can be tested to ensure that they are correctly implemented.

Ultraviolet Emissions from Explosive Detonation Breakout.

Detailed spectroscopic measurements of high explosive detonation breakout in the ultraviolet region are presented. Molecular features associated with CN, NH, OH, and N2 are observed and analyzed. Spectra indicate extreme temperatures well in excess of 5000K in the first few microseconds after breakout. Molecular bands are found to originate from the detonation products, as opposed to the ambient air, and are strongly attenuated in the presence of oxygen. Implications for forensic analysis of source explosive are discussed.

Dependence of spallstrength on temperature, grain size and strain rate in pure ductile metals

When a shockwave, which can be generated by high velocity impact or explosive detonation, reflects from the free surface of a metal, it usually creates tensile stress inside the metal. While the tensile stress is large enough, voids nucleation, growth and coalescence happen inside the metal, causing the metal to spall. As one of the main contents of the spallation damage research, the spallation strength, which is often characterized by features of the free surface velocity history measured in spallation experiments, represents the maximum tensile stress that the material can withstand, and is actually a complex interaction among several competing mechanisms. Optimizing the spallation strengths of metals is important for their applications in the aerospace, automotive, and defense industries, and can be achieved by using the advanced manufacturing strategies, if we can know better the meaning and present analytic model of the spallation strength of metal. A large number of experiments show that the spallation strength of ductile metal is strongly dependent on the tensile strain rate, grain size and temperature of material. Based on the analysis of early spallation evolution and influence of grain size and temperature on the material, a simple analytic model of spallation strength is presented in this paper, which takes into account the effects of strain rate, grain size and temperature in materials. The applicability of this model is verified by comparing the calculated results from the model with the experimental results of spall strength of typical ductile metals such as high purity aluminum, copper, and tantalum.

Field tests of fiber reinforced concrete slabs subjected to close-in and contact detonations of high explosives

This paper presents an experimental research to study the behavior of fiber-reinforced concrete slabs with varying fiber volume and type, subjected to contact and close-in detonations. A total of 25 full-scale blast tests were carried out. The results are analyzed, discussed and compared to fast-running tools. For the close-in detonations, the damage was manifested by a global flexural response and the fiber volume did not affect slab performance. For the contact blasts, localized damage in the forms of cratering, spalling, and in some cases perforation, was observed. For these tests, increasing fiber volume was found to improve slab performance.

Repetitive Blast Exposure Increases Appetitive Motivation and Behavioral Inflexibility in Male Mice.

Blast exposure (via detonation of high explosives) represents a major potential trauma source for Servicemembers and Veterans, often resulting in mild traumatic brain injury (mTBI). Executive dysfunction (e.g., alterations in memory, deficits in mental flexibility, difficulty with adaptability) is commonly reported by Veterans with a history of blast-related mTBI, leading to impaired daily functioning and decreased quality of life, but underlying mechanisms are not fully understood and have not been well studied in animal models of blast. To investigate potential underlying behavioral mechanisms contributing to deficits in executive functioning post-blast mTBI, here we examined how a history of repetitive blast exposure in male mice affects anxiety/compulsivity-like outcomes and appetitive goal-directed behavior using an established mouse model of blast mTBI. We hypothesized that repetitive blast exposure in male mice would result in anxiety/compulsivity-like outcomes and corresponding performance deficits in operant-based reward learning and behavioral flexibility paradigms. Instead, results demonstrate an increase in reward-seeking and goal-directed behavior and a congruent decrease in behavioral flexibility. We also report chronic adverse behavioral changes related to anxiety, compulsivity, and hyperarousal. In combination, these data suggest that potential deficits in executive function following blast mTBI are at least in part related to enhanced compulsivity/hyperreactivity and behavioral inflexibility and not simply due to a lack of motivation or inability to acquire task parameters, with important implications for subsequent diagnosis and treatment management.

Numerical Estimation of Variation of Pressure and Temperature of Expanding Blast Wave with Time due to Detonation of High Explosives in Air

AbstractHigh explosives on detonation generate high pressure shock waves moving initially at very high velocities in the ambient medium and damage the encountered targets. The expanding hot gases in blast waves are also responsible for the damage. The extent of damage to a target depends on the magnitude of pressure or impulse and also on temperature due to explosion. A theoretical analysis is carried out to predict the temperature produced in the expanding blast as a function of distance and time by solving analytically the governing equations. The initial peak pressure and temperature of a blast wave, which are required in the theoretical analysis, were calculated making use of the blast wave theory. Results obtained for blast pressures at different distances using this theory were published by the authors earlier. The same numerical analysis is used for obtaining variation of pressure and temperature with time and presented in this paper. High explosives namely TNT, Composition ‘B’, PBX, and Hexolite of varying weights are considered in the present study.

Kinetics of carbon condensation in detonation of high explosives: First-order phase transition theory perspective.

The kinetics of carbon condensation, or carbon clustering, in detonation of carbon-rich high explosives is modeled by solving a system of rate equations for concentrations of carbon particles. Unlike previous efforts, the rate equations account not only for the aggregation of particles but also for their fragmentation in a thermodynamically consistent manner. Numerical simulations are performed, yielding the distribution of particle concentrations as a function of time. In addition to that, analytical expressions are obtained for all the distinct steps and regimes of the condensation kinetics, which facilitates the analysis of the numerical results and allows one to study the sensitivity of the kinetic behavior to the variation of system parameters. The latter is important because the numerical values of many parameters are not reliably known at present. The theory of the kinetics of first-order phase transitions is found adequate to describe the general kinetic trends of carbon condensation, as described by the rate equations. Such physical phenomena and processes as the coagulation, nucleation, growth, and Ostwald ripening are observed, and their dependence on various system parameters is studied and reported. It is believed that the present work will become useful when analyzing the present and future results for the kinetics of carbon condensation, obtained from experiments or atomistic simulations.