Combined Blast Research Articles

Representation of damage caused by fragmentation impact in design and analysis of reinforced concrete barriers

This paper presents methodology and calculation models that aim to enable a more realistic design of reinforced concrete (RC) protective barriers. The proposed methodology considers the global effect of fragmentation impact, which is commonly neglected in current design procedures. The analysis considers a non-uniform, two-zone damage model over the span, where the damage caused by fragment strikes is represented in the model in terms of reduced equivalent cross-section heights. It is shown that one of these zones, denoted ‘intense strip’, is significantly more damaged than the other zone. This representation of a damaged barrier, inside and outside the intense strip, should be considered for its global analysis. The proposed model was validated by comparison of its predictions with measured static load-deflection curves of plate specimens, which had been damaged by fragmentation impact in previously performed field tests. The models that are described in this paper, which provide an equivalent slab dimensions, can be used in further, more realistic dynamic analysis of the structural behavior of RC elements, subjected to combined blast and fragmentation loading.

Steel column response to thermal and long duration blast loads inside an air blast tunnel

All explosions emit both thermal and blast energy. In recent years there have been several accidental explosive events that have emitted high thermal loads with the potential to cause thermo-mechanical damage to structures. Attempts to experimentally simulate these thermal loads and observe the response of structures to combined thermal and blast loads have not proven successful. This paper focuses on the design of, and results from a series of experimental trials investigating the response of steel columns to combined thermal loads from ceramic heating elements and long-duration blast loads within an Air Blast Tunnel (ABT). The combined effect of compressive loads from heavy-duty springs is also shown. The trials concluded that the ceramic heating elements were suitable to heat steel columns to levels initiating thermo-mechanical damage. Results from the tests showed an increased structural response in the columns subject to high thermal, compressive and blast loads compared to the isolated blast load. Numerical modelling of the columns is detailed and compared to trial results, providing validation for the computational methods. The experimental trials set a benchmark for future trials and provided results to validate the synergistic response of steel structures to combined blast and thermal loads from explosive events.

Experimental study on the combined damage of liquid cabin structure subjected to charge explosion with preset fragments

As an important part of multicompartment protective structure in naval vessels, the structure of liquid cabin plays a major role in resisting blast wave and high-speed fragments. The aim of this study was to evaluate the damage of a liquid cabin structure under combined blast wave and fragment loading created by charge explosion with preset fragments. A series of experiments were conducted to investigate the effects of free surface inside liquid cabin and fragment type on structural damage. Moreover, to facilitate the evaluation of failure modes of structure under combined loading, the liquid cabin under bare blast loading was also assessed. The experimental tests were analyzed using pressure sensors and residual displacement of structure walls. It is shown that free surface can decrease the intensity of pressure pulse and reduce the deformation of liquid cabin. A large nummular fragment caused a stronger shock wave and more severe structural damage than a dense fragment cluster. The deformation direction of front plate of liquid cabin induced by the blast wave is opposite to that of fragment loading. Therefore, the superposed or enhanced damage of combined loading on front plate is not shown, and fragment loading is the main factor causing the damage of liquid cabin structure.

MATHEMATICAL MODELS OF CRITERIA TECHNOLOGICAL PROCESSES OPTIMIZATION CRITERIA OF THE BLAST FURNACE SMELTING

The mathematical models of optimality criteria of blast, fuel additives and steam consumption for blasting moisture have been developed. The criterion for optimal blast consumption is the furnace performance, which should be maintained at the highest possible level. The maximum possible level of performance varies over time, even at a constant value of blasting. Therefore, optimal amount of blasting search is carried out continuously every 5 to 10 minutes. The mathematical model of furnace efficiency has been developed. It is determined by information on the amount of combined blast and its content of reducing gas, the oxidation of the charge, the amount of gasified oxygen of the charge from one filing, the amount of cast iron, which is smelted from the charge of one feed, the output of the dry blast furnace gas. The mathematical model of the optimization criterion of fuel additives consumption includes mathematical models: the coke coefficient of substitution by a fuel additive; the amount of coke replaced by a fuel additive; the amount of profit from the additive use. The coefficient of coke substitution is defined as the ratio of the heating power in the blast furnace to of coke combustion heat, based on information on the composition of the blast furnace gas, the composition of the fuel additive and coke. The amount of coke substituted by a fuel additive is determined by the value of the substitution coefficient and the fuel additive consumption. The amount of profit from the additive use is determined by the information on the consumption of fuel additive and oxygen, fuel additive price, oxygen and coke, the furnace efficiency. The mathematical model of the optimization criterion of steam consumption for blas-ting moisture includes models; the amount of heat consumed for steam decomposition; the heat input at the expense of improving the degree of hydrogen and carbon monoxide use; the intensity change of carbon combustion in the tuyeres; required mass of coke for heat compensation expended on the decomposition of the blow moisture in the furnace; total savings or over-consumption of coke mass when humidity changes; increase in the furnace's efficiency due to changes in the moisture content of the blast; money saving from steam using for moistening.

Numerical investigation of composite laminate subjected to combined loadings with blast and fragments

Composites are considered as effective materials in absorbing the energy of blast and impact, and have been often used in complex loading environments. A numerical model is developed to analyze the response and damage of S-2 glass/SC-15 epoxy composite laminate subjected to combined loadings with blast and fragments. A composite progressive failure model is used to investigate the damage and the failure of the material. The proposed numerical model is validated by its comparison with the experimental data obtained from the literature. Three different types of loading combinations: (1) ammunition fragments impact loading, (2) bare blast loading, and (3) the combinations of blast and fragments loading, correspond to the scenarios of the near-field and the far-field explosions. Moreover, the response and the damage evaluation of the composite are analyzed here. It is concluded that the damage modes of the laminate are correlated to the type of the loading. Furthermore, the synergetic effects for the composite laminate subjected to the combined blast loading and the fragments impact are verified and evaluated. By comparing the energy absorption and the damage zone in the laminate, the synergetic effect is attributed to the conjunction of damage and the continuous pressure of the detonation products.

Differences in Post-Traumatic Stress Disorder Symptoms among Post-9/11 Veterans with Blast- and Non-Blast Mild Traumatic Brain Injury.

The relationship between traumatic brain injury (TBI) and post-traumatic stress disorder (PTSD) has been difficult to disentangle, in part due to the commonality of incidents that can cause both conditions, as well as high rates of comorbidity between the two conditions. Inconsistent findings may be related to different study characteristics and types of mild TBI (mTBI) sustained (e.g., blast, non-blast). The objective of this study was to determine the association of blast- versus non-blast-related TBIs with long-term PTSD symptoms after controlling for demographic variables and trauma exposure. The sample included 230 post-9/11 veterans who experienced a blast-related mTBI (n = 29), non-blast mTBI (n = 74), combined blast and non-blast mTBI (n = 40), or no TBI (n = 87). As hypothesized, a between-groups analysis of covariance (ANCOVA) revealed that, after controlling for demographics, combat exposure, and prior trauma, PTSD symptoms among individuals with blast-related mTBI and combined blast and non-blast mTBI were significantly higher compared with non-blast-related mTBI and no TBI. These data suggest that blast-related mTBI is associated with more severe long-term PTSD symptoms.

Influence of the Quality of Iron Ore and Coke on Blast-Furnace Performance

Excellent blast-furnace performance is observed when using screened sinter that is free of fines, with the alternation of tuyeres of normal and enlarged diameter. If the total mechanical energy of the combined blast at the tuyere mouth and the total mechanical energy of the blast-furnace gas increase in these conditions, the combustion zone becomes longer and the blast-furnace gas penetrates further toward the furnace axis. In that case, the benefits of the high-quality raw materials may be maximized.

Study of transition processes of blast-furnace smelting by the mathematical model method

In work possibilities of the developed computer model system for forecasting of a thermal condition of a blast furnace (on change of the maintenance of silicon in pig-iron) in a mode of real time are considered. The basis of the model is the fundamental knowledge of the theory and practice of the modern blast-furnace process, the use of regularities in the processes of heat and mass transfer, gas dynamics, slag formation processes in modern blast furnace melting. When solving the dynamic problem, it is envisaged to use the analytical (obtained on the basis of fundamental knowledge), but the linearized model of the domain process, the principle of small deviations and the natural-mathematical approach. In the algorithm for solving problems in transient blast furnace processes, the calculation of the dynamics of the change in the heating of the bottom of a blast furnace (based on the silicon content in cast iron) was performed according to the additivity rule by summing the predicted silicon concentrations in cast iron when the loading parameters (ore load) and the control actions on the thermal load the state of the furnace from the bottom - the consumption of natural gas, the concentration of oxygen in the blast and the humidity of the blast. Examples of calculations of the transient processes of the gas-dynamic resistance of the batch layer, the thermal state, and the productivity of the blast furnace are shown in the context of the changes in the properties and composition of the iron-ore materials being loaded and the parameters of the combined blast are applied to the conditions of PJSC “Magnitogorsk Iron and Steel Works” (MMK).

Characteristics of combined blast and fragments loading

In this paper, the combined loading caused by blast and fragmentation impact has been studied. While there are methods for predicting the reflected blast wave pressure and impulse time history, the multi-fragment impulse has been rarely studied, and in fact, it is frequently neglected. This study deals with several aspects regarding the combined loading of blast and fragmentation impact and presents a simplified approach to assess the multiple fragment impulse in a way that would enable evaluation of its significance, relative to that of the blast. Results of the simplified approach were validated by their comparison with experimental data. Additionally, results for two different charges at various standoff distances were compared with those of numerical simulations, which had been previously validated. While the simplified approach provides estimates of the fragment impulse, it does not provide their detailed pressure-time history, which requires knowledge of the fragment shapes and penetration depths. Hence, the pressure time history was evaluated for three fragment shapes that represent upper and lower bounds for the peak pressure, as well as an intermediate case. The proposed approach indicates that there are cases where the fragment impact should not be ignored in the design of a protective barrier.

3D reconstructions of a controlled bus bombing

Abstract Objectives to demonstrate the usefulness of 3D reconstructions to better understand the dynamic of a controlled bus bombing. Materials and methods 3D models of the victims (pigs) were created from post-mortem CT scanning using Mimic software; 3D models of the crime scene (bus) were generated by means of photogrammetry and modelling techniques, using Photomodeler and 3Ds max software applications. Combinations and visualizations of the scene before and after the explosion were created using 3Ds max. Results several 3D reconstructions of the scene before and after the explosion were re-created to better visualize the dynamic of the incident and the blast injuries. All the pigs suffered extensive blast injuries. The bomb pig and the green pig (adjacent to the detonation site) underwent traumatic amputation and destruction due to a combination of blast injuries. Primary blast injuries and secondary injuries were found in all the other pigs. Fractures both due to tertiary or combined blast injuries were found in all the pigs except the yellow one (far from the detonation side). Three different “injury zones” could be identified based on the severity of the injuries of the pigs, as evaluated from autopsy and CT scanning. Conclusion 3D reconstructions give a clearer and more comprehensive view of the scene and the victims, allowing a better understanding of the entire scene. CT scanning has proved to be an important tool in evaluating blast injuries in dead victims.

Numerical investigation of the response of I-core sandwich panels subjected to combined blast and fragment loading

The LS-DYNA software was employed to investigate the dynamic response of I-core sandwich panels under combined blast and fragment loading. The combined blast loading was simulated by placing pre-fabricated fragments at the bottom surface of bare explosive. To facilitate evaluating the synergistic effect under combined blast loading, the resistance of sandwich panels under bare blast loading was also assessed. The results demonstrated that the damage caused by combined blast loading was more severe than that by bare blast loading. The roles of charge mass, face-sheet configuration and core configuration on the deformation/failure behavior and energy absorption characteristics of panels were analyzed and discussed in detail. Under combined blast loading, the panels exhibited a perforation and tearing failure mode accompanied by structural fragments from failed front face. The charge mass is relevant to whether the residual momentum of fragments is large enough to penetrate the back face. The face-sheet configuration that had thick front face and thin back face was favorable in mitigating the damage response. The core configuration with dense core webs provided more assistance in preventing the appearance of failure pattern with a large connected region. The face-sheet configuration and core configuration have negligible influence on the total energy absorption, but they would redistribute the energy dissipation among each panel component. Furthermore, the comparisons of blast resistance between sandwich panels and conventional monolithic counterparts were made. It turned out that the sandwich panels experienced lower level damage failure on back face but dissipated similar energy relative to equivalent solid plates.

The influence of different pre-formed holes on the dynamic response of square plates under air-blast loading

Abstract Studying the blast response of plates with pre-formed holes under blast loading serves as a significant method to decouple dynamic response of plates with pre-formed holes under combined blast and fragment loading. Based on material test system (MTS) and Split Hopkinson tension bar (SHTB), the mechanical properties of experimental steel under different strain rates were obtained. Then, the experiments on the responses of plates with square, diamond and circular holes under air-blast loading were carried out and the failure modes of plates with diamond holes were derived. Later, the deformation curves of target plate were obtained by laser reverse forming technique. Next, a constitutive model program considering strain rate, stress status and temperature effect was adopted to carry out numerical simulation calculation, which verified the accuracy of this numerical simulation. Finally, discussions were carried out on the damage level at places where cracks might form, the dynamic stress concentration coefficient and stress status change, and then the influence which pre-formed holes have on the failure mode was analyzed. The results of this study show that: (1) A fortran vectorized user-material subroutine (VUMAT) program considering strain rate, stress status and temperature effect can effectively predict the dynamic response of metallic materials; (2) the shape of pre-formed holes affects the damage level, dynamic stress concentration coefficient and stress status. Besides, failure occurs more easily in plates with diamond pre-formed holes; (3) pre-formed holes have an obvious influence on the failure modes of plates under different blast distance.

Recent observations on design and analysis of protective structures

Recent studies at the Center for Infrastructure Protection and Physical Security (CIPPS) have focused on both active and passive protection, the definition and characterization of combined blast and fragment loads on structural elements, the influence of Ultra High Performance Concrete (UHPC) on the behavior of structural elements, and evaluating analysis approaches for progressive collapse assessment. Those studies have highlighted important issues that have not been sufficiently addressed previously, and this paper is aimed at describing the observations from the CIPPS studies that could be used to treat such difficult issues.

Development of heat-transfer circuits in the blast furnace

The development of heat-transfer circuits in the blast furnace as the technologies of blast-furnace smelting are improved are considered. It is shown that there are two zones of intense heat-transfer, and in modern conditions, when different kinds of iron ore are smelted, the use of combined blast with high parameters is a prerequisite for the stability of blastfurnace smelting operation and the smelting efficiency.

Unravelling the effect of clostridia spores and lysozyme on microbiota dynamics in Grana Padano cheese: A metaproteomics approach

Grana Padano is a typical Italian Protected Designation of Origin (PDO) hard cheese largely consumed all over the world. The major problem during its production is represented by late blowing. Clostridia are gasogen bacteria responsible of the swelling during ripening, and they are partially counteracted by the use of egg white lysozyme as additive. In this work was applied, for the first time in cheese, a metaproteomic approach that identified the functional dynamics of microbial consortia in relation to the number of clostridial spores and lysozyme treatment using experimental samples of Grana Padano cheese. We used a combined custom BLAST+/MEGAN/STAMP approach to obtain a global taxonomic view associated to low and high clostridial spores cheese without and with lysozyme. Main differences were highlighted in the bacilli class. Functional analysis with SEED provided a deep view into several metabolic pathways, highlighting the subsystems “amino acid and derivatives” and “clustering-based subsystem” as the targeted subsystems during lysozyme treatment in the high spore group. In these subsystems, acetate kinase from clostridia was one of the main enzymes affected by the lysozyme treatment. Biological significanceMetaproteomics is a very promising and useful technique in the control of food safety and quality, from fresh products until ‘ready to eat’ food. Tools able to identify at molecular level the dynamic fingerprinting of food microbiota could be of great help to improve food safety and quality.

Numerical simulation of steel plates subjected to the impact of both impact waves and fragments

The main objective of this study is to explore the deformation feature and damage pattern of a steel plate under the synergetic effects of blast and fragments loading. The combined blast and fragments loading effects under the condition of cast TNT and prefabricated fragments acting on a steel plate, are sim-ulated using the finite element program ANSYS/LS -DYNA. The flight of fragments driven by the charge is predicted, and the blast loading and fragments loading are analyzed respectively, while the deformation and damage characteristic under the combined loading are compared with experiment results. The simulation re-sults agree relatively well with the experimental results. Meanwhile, it is seen that the fragment at the cen-ter of the charge bottom has the highest velocity and the lowest velocity occurs at the edge. Under the exper-imental condition, blast reaches the structure first and fragments impact subsequently, and the total kinetic energy of fragments is much larger than that of blast wave and explosion products transmitted to the struc-ture. The punched hole appearing in the central region of the steel plate is mainly caused by the dense frag-ment cluster, which should be treated as the main target load for protective structures.

Magnetoencephalography (MEG) Slow-Wave Imaging for Diagnosing Non-acute Mild Traumatic Brain Injury

Mild traumatic brain injury (mTBI) is a leading cause of sustained impairment in military and civilian populations. However, mTBI is difficult to detect using conventional MRI or CT, even in patients with persistent postconcussive symptoms (PCS). Injured brain tissues in mTBI patients generate abnormal slow-waves (1–4 Hz) that can be measured by resting-state magnetoencephalography (MEG). We describe a voxel-based MEG slow-wave imaging approach for detecting abnormality in mTBI patients with persistent PCS on a single-subject basis (Huang et al., Neuroimage Clin 5:109–119, 2014). A normative database from 79 healthy control subjects was established for all brain voxels. High-resolution MEG source magnitude images were obtained by the Fast-VESTAL method (Huang et al., Neuroimage 84:585–604, 2014). In 84 mTBI patients (36 from blasts, and 48 from non-blast causes), this method detected abnormalities with positive detection rates of 84, 86, and 83 % for the combined (blast plus non-blast), blast, and non-blast mTBI groups, respectively, with no false-positives in the control subjects.

ASPEN Plus simulation of coal integrated gasification combined blast furnace slag waste heat recovery system

This article presented a model for the system of coal gasification with steam and blast furnace slag waste heat recovery by using the ASPEN Plus as the simulating and modeling tool. Constrained by mass and energy balance for the entire system, the model included the gasifier used to product syngas at the chemical equilibrium based on the Gibbs free energy minimization approach and the boiler used to recover the heat of the blast furnace slag (BF slag) and syngas. Two parameters of temperature and steam to coal ratio (S/C) were considered to account for their impacts on the Datong coal (DT coal) gasification process. The carbon gasification efficiency (CE), cold gasification efficiency (CGE), syngas product efficiency (PE) and the heating value of syngas produced by 1kg pulverized coal (HV) were adopted as the indicators to examine the gasification performance. The optimal operating temperature and S/C were 800°C and 1.5, respectively. At this condition, CE reached above 90% and the maximum values of the CGE, PE and HV were all obtained. Under the optimal operating conditions, 1000kg/min BF slag, about 40.41kg/min DT pulverized coal and 77.94kg/min steam were fed into the gasifier and approximate 6.64kmol/min syngas could be generated. Overall, the coal was converted to clean syngas by gasification reaction and the BF slag waste heat was also recovered effectively (reached up to 83.08%) in this system, achieving the objective of energy saving and emission reduction.

Experimental Study of the Jet Engine Exhaust Flow Field of Aircraft and Blast Fences

A combined blast fence is introduced in this paper to improve the solid blast fences and louvered ones. Experiments of the jet engine exhaust flow (hereinafter jet flow for short) field and tests of three kinds of blast fences in two positions were carried out. The results show that the pressure and temperature at the centre of the jet flow decrease gradually as the flow moves farther away from the nozzle. The pressure falls fast with the maximum rate of 41.7%. The dynamic pressure 150 m away from the nozzle could reach 58.8 Pa, with a corresponding wind velocity of 10 m/s. The temperature affected range of 40°C is 113.5×20 m. The combined blast fence not only reduces the pressure of the flow in front of it but also solves the problems that the turbulence is too strong behind the solid blast fences and the pressure is too high behind the louvered blast fences. And the pressure behind combined blast fence is less than 10 Pa. The height of the fence is related to the distance from the jet nozzle. The nearer the fence is to the nozzle, the higher it is. When it is farther from the nozzle, its height can be lowered.

Bombings specific triage (Bost Tool) tool and its application by healthcare professionals.

Bombing is a unique incident which produces unique patterns, multiple and occult injuries. Death often is a result of combined blast, ballistic and thermal effect injuries. Various natures of injury, self referrals and arrival by private transportation may lead to "wrong triage" in the emergency department. In India there has been an increase in incidence of bombing in the last 15 years. There is no documented triage tool from the National Disaster Management Authority of India for Bombings. We have tried to develop an ideal bombing specific triage tool which will guide the right patients to the right place at the right time and save more lives. There are three methods of studying the triage tool: 1) real disaster; 2) mock drill; 3) table top exercise. In this study, a table top exercise method was selected. There are two groups, each consisting of an emergency physician, a nurse and a paramedic. By using the proportion test, we found that correct triaging was significantly different (P=0.005) in proportion between the two groups: group B (80%) with triage tool performed better in triaging the bomb blast victims than group A (50%) without the bombing specific triage tool performed. Development of bombing specific triage tool can reduce under triaging.