Air Shock Research Articles

Preparation of spherical DAOAF with micro-nano structure by emulsion method: To improve short-pulse initiation performance

In order to take into account the advantages of good processing performance of micron 3,3′-diamino-4,4′-azoxyfurazan(DAOAF) and high sensitivity of short-pulse initiation of nano DAOAF, Spherical DAOAF products with nano-microstructure were prepared by oil-in-oil emulsion method. The laser-induced air shock wave detonation performance, mechanical sensitivity and short-pulse initiation sensitivity of raw DAOAF and spherical DAOAF were tested and compared. The results showed that the optimum process conditions of emulsion stability were as follows: using Tween-80 as the surfactant at a concentration of 0.3 g·mL−1, a solvent-non-solvent volume ratio of 1:3, and emulsion standing time less than 10 minutes. Compared to the raw DAOAF, the crystal structure of DAOAF sample prepared by emulsion method did not change, only the morphology changed. The DAOAF sample prepared by emulsion method is spherical, and the surface is self-assembled by nanorod-like DAOAF, the particle size distribution is uniform and the dispersion is good. The thermal decomposition peak temperature of spherical DAOAF did not change significantly, but the activation energy of thermal decomposition decreased by 30.07 kJ·mol−1, the characteristic velocities of the laser-induced micro-explosion shock waves increased 12.4 %, the 50 % short-pulse initiation current of the impactor decreased from 3.8 kA to 2.3 kA, and the mechanical sensitivity of DAOAF showed no significant change before and after spherical transformation.

Enhancement of aluminum powder reaction behavior at high temperatures—Aluminum powders with “sea urchin structure” coated by AP

To solve the problem of high ignition temperature of aluminum powder and easy to burn into blocks at high temperatures, “sea-urchin-structured” aluminum powders (μAl@nAl) obtained by electro-explosion were coated by ammonium perchlorate (AP) on its surface. AP in a high-temperature environment has a rapid decomposition, then the gas production will promote the dispersion of aluminum powder into micro-clusters, thus preventing the aluminum powder agglomeration during the combustion process. The micro-nano composite aluminum powder (μAl@8 %nAl) and physical mixed aluminum powder (μAl + 8 %nAl) coated by AP were completed by solvent volatilization method. The coating surface was observed by scanning electron microscopy. The heat of combustion and pressure curves for different AP contents were tested using a chamber with a constant volume, and the ignition and combustion performance of the AP samples were investigated using a carbon dioxide (CO2) laser ignition device. The AP samples shortened the ignition delay time and improved the combustion performance in the fixed-volume combustion and laser ignition tests. Under atmospheric air, taking into account the theoretical calorific value, pressure curve, and combustion performance, the optimal AP content is 10 %. The thermal decomposition process of two samples was further analyzed using the thermogravimetric and differential scanning calorimetry (TG-DSC) method. The decomposition of AP advanced the first oxidation peak of aluminum powder; however, in the second step oxidation peak, the peak temperature of μAl@8 %nAl@10 %AP sample was delayed compared to μAl + 8 %nAl@10 %AP sample. High-voltage electrical explosions and high-energy laser-induced air shock waves were created to simulate the high-temperature environment of the detonation reaction zone, and pictures of the reaction process and pressure change curves of the “sea urchin structure” aluminum powder coated by AP at high temperatures were recorded. The results showed that the “sea urchin structure” aluminum powder coated by AP exhibited better combustion performance, and the reaction degree of the aluminum powder had been deepened.

Analysis of the building on the air shock wave by direct dy-namic method (with LIRA-FEM soft-ware)

Calculation of the impact of air shock waves on buildings is extremely important for our country, which is in a state of war. Studying the structural safety and survivability of load-bearing reinforced concrete structures under influence is an important task, especially for critical infrastructure facilities. A blast scenario can be carried out directly in an FEA program as a time history analysis evaluate varying levels of structural damage and to minimize loss of life.The article is devoted to the features of the calcula-tion of buildings under the influence of air shock waves using the finite element method using the LIRA-FEM software complex. The features of ex-plosive loads, typical shock wave parameters, and the order of analysis for explosive loads are taken into consideration. The primary distinctions be-tween shock or explosion impacts and regular loads are explained. In-depth consideration is given to the problems of determining shock wave parameters and how they affect structures. Also included are the techniques for evaluating structures for explosive impacts.Using LIRA-FEM software, a preliminary analysis of the explosion resistance of a one-story building with a metal frame and sheet metal wall infill is carried out. It is demonstrated how to define impulse loads from a shock wave to the side walls, roofs, rear walls, and walls facing the explosion. The article describes the peculiarities of the "Time History Analysis" system in the LIRA-FEM program for ex-plosion dynamics problems.This analysis helps in the assessment of risks in the design of protective structures, development of pro-ject solutions and conducting research in the field of explosion safety.

Experimental studies of the explosion resistance of steel plate with an energy-absorbing layers

The aim of this paper is to examine explosion resistance of a composite structure which consists of the steel plate and energy-absorbing layers. With this end, an experimental study of the deformation of 2-3 mm thick steel plates containing different protective layers, namely, an aluminum honeycomb plate, an aluminum sheet, tubular core, polyurethane foam, or an aramid fabrics layer, subjected to explosion generated air shock wave load, has been carried out. At the initial stage of testing, absorbing properties of various composites were examined under relatively low intensity dynamic loads (820 kPa). The dynamic response was assessed by applying bending attenuation and plate center acceleration attenuation factors. This was followed by testing sandwich structures under critical load conditions, when the plate was demolished or subjected to a substantial residual deformation. The study has shown that the composite containing an aluminum honeycomb plate has higher explosion resistance as compared to other tested composites. The proposed design ensures retention of explosion resistance under relatively high dynamic impacts at a reduced distance W = 0.46 m/kg1/3.

Forensic characteristics of injuries from thermo-baric explosive device

Since the beginning of the Russian Federation's invasion of Ukraine in 2022, explosive trauma has become an extremely urgent problem, as the main source of bodily injury among both the military in the combat zone and the civilian population in cities has been the impact of explosive devices. The aim of the study is the examination of the forensic characteristics of damage to biological objects that were formed from thermal exposure and shock wave as a result of the explosion of a cumulative munition and in the conditions of an experimental explosion model. The objects of the study were the materials of two examinations on the death of Ukrainian soldiers who died in the war zone (archival "Conclusions of the medical examination" of the Kyiv City Clinical Bureau of Forensic Medical Examination in 2023). Under the conditions of the experiment, studies of pathomorphological changes in the liver and small intestine of 30 white outbred rats from the action of an artificially created air shock wave with an overpressure of 31.62±4.84 kPa were carried out. The injuries were examined macroscopically and using standard laboratory histological techniques. Microscopy of histological sections was performed using an Axio Imager 2 microscope (Zeiss, Germany) at magnifications of ×200 and ×400. Statistical processing of the obtained quantitative results was carried out using the STATISTICA 6.1 software product. Under the condition of the explosion of the ammunition with the cumulative effect of the rocket-propelled infantry flamethrower "Bumblebee" on sectional incisions of the skin and muscles of the thigh in the projection of areas of redness, a picture of a gelatinous consistency of bright red color was macroscopically determined due to abundant blood impregnation of muscles and subcutaneous fat and partial loss of muscle structure with the release of myoglobin. The bright red color of the skin of the thigh and pelvis without burning the hair may indicate the superficial thermal effect of the explosive device and the protection of the skin by clothing. Diffusely located numerous both paired and single abrasions and shallow wounds, small rounded, oblong, circular in shape, which are the result of fragments of a rocket-propelled grenade equipped with a fire mixture, were also determined. The effect of an air shock wave with an overpressure of 31.62±4.84 kPa on the liver parenchyma of rats was determined by focal hemorrhages with rupture of the terminal central vein of the hepatic lobule, edema of the parasinusoidal spaces, and sludges in the sinusoids. In the wall of the small intestine, acute hemodynamic disorders occurred in the form of vasodilation of arterial vessels, venular and capillary stasis. There was layering and swelling of the small intestine wall, rupture of veins, focal hemorrhage. Thus, the revealed characteristic pathomorphological signs of the destructive effect of overpressure as a result of a blast wave (barotrauma) are typical and common both in the areas of the human thigh and pelvis, and in biological objects of experimental animals. The obtained results are consistent with the pathomorphological manifestations of barotrauma in areas of the human body as a result of the action of an explosive device with a cumulative effect.

An enhanced compressible two-phase flow model with detailed chemistry under the adaptive mesh refinement frame

In the present study, an enhanced compressible two-phase flow model is advanced, considering the effect of chemical reactions within a detailed mechanism. In this model, two immiscible fluids (liquid and gaseous mixture) are accurately separated with the resolved interface. Unlike the classical five-equation two-phase flow model, the thermal properties of gases are no longer assumed to be constant but rather vary as functions of temperature. A modified mechanical relaxation procedure is proposed and employed at the gas-liquid interface to prevent the occurrence of nonphysical pressure oscillation. In the gaseous mixture, numerous gas components are included and resolved by their mass fraction among the gaseous mixture. In this model, the heat release effect is simulated by a detailed chemistry. Furthermore, the numerical results of several benchmark problems in one dimension and two dimensions demonstrate the efficacy of the proposed compressible multiphase flow model, such as the air shock tube, the gaseous detonation tube, the shock-droplet interaction, and especially the detonation-droplet interaction that has received little focused interest and investigations. Moreover, a self-developed adaptive mesh refinement strategy is performed for a high efficiency of numerical solving.

Curved Polymeric Sandwich Composites Subjected to Air Shock: An Experimental Investigation

BackgroundThe vulnerability of polymeric composite sandwich structures in marine applications to air explosions highlights a significant gap in our understanding of the dynamic behavior of the curved sandwich structures, which is essential for design improvements.ObjectiveThis study aims to explore the dynamic response and failure mechanisms of curved sandwich composite panels subjected to air-blast loading, providing insights into their structural integrity under such conditions.MethodsExperiments were performed using laboratory-simulated air shocks generated by a shock tube, employing high-speed photography and digital image correlation to measure deflections on the back surface of the panels. The panels, made with PVC closed-cell foam cores of two densities (H45 and H130), were tested across three curved geometries (radii of 112 mm, 305 mm, and infinity) under various boundary conditions.ResultsFindings indicate an increase in deformation with a decreased radius of curvature under simple support conditions, a trend that reverses under arrested displacement conditions. Moreover, a reduced radius significantly enhances panel strength and resistance to interfacial damage, with the primary failure mode transitioning from core shear cracking to interfacial debonding as core density increases.ConclusionsThe study reveals that the radius of curvature, boundary conditions, and core density significantly affect curved sandwich panels’ dynamic response and performance. Panels with smaller radii and higher core densities exhibit increased strength, though boundary conditions introduce variable effects on deformation behavior.

TECHNIQUE OF LAND RECULTIVATION OF PLACES OF AMMUNITION DISPOSAL AND DESTRUCTION

The relevance of the research and the need to develop methods that allow restoring the lands of the ammunition disposal and destruction sites during the application of measures for their recultivation are shown. The criteria for evaluating the safety level of the process of recultivation of the lands of the ammunition disposal and destruction sites based on the use of a regulatory approach and significant indicators were determined, namely: the probability of an explosion, the amount of excessive pressure in the air shock wave, and the level of degradation of the lands of the ammunition disposal and destruction sites. For the first time the technique of land recultivation of places of ammunition disposal and destruction was developed. It includes three stages: Stage 1 – monitoring of land of places of ammunition disposal and destruction based on unmanned aviation monitoring system; Stage 2 – demining of land of ammunition disposal and destruction by specialized pyrotechnic units of the State Emergency Service of Ukraine using the results of the monitoring conducted at Stage 1; Stage 3 – biological treatment of land of the ammunition disposal and destruction using the phytoremediation method.

Histopathological and ultrastructural changes in the rats brain after air shock wave impact

The using of explosive substances and devices can lead to brain injuries, the diagnosis of which requires the determination of primary biomarkers. Therefore, the aim was to establish and study histopathological and ultrastructural changes in the rats brain after exposure to an air blast wave. The study was carried out on 18 male Wistar rats, which were randomly divided into two groups: sham (n=9) and experimental (n=9). The animals of the experimental group were anesthetized with halothane and gently fixed in a horizontal position on the abdomen with the front part of the rat's muzzle at a distance of 5 cm from the device opening and subjected to an excess pressure of 26-36 kPa. Animals of both groups were decapitated, brains were removed, fixed, histopathological and ultrastructural analyzes were conducted using standard methods. Intergroup differences were assessed by Mann-Whitney U-test. Light microscopy revealed primary lesions in the form of small focal, multifocal hemorrhages, cerebral vessel ruptures and microscopic ruptures of the brain substance. In almost all brain samples, there is a significant saturation of the venous vessels with the presence of erythrocyte stasis. Violation of the blood-brain barrier, the presence of edema of the perivascular space, and petechial hemorrhages in the neuropil were registered ultrastructurally. Based on the study results, a morphological algorithm for assessing primary histostructural intracranial brain injuries and their consequences after exposure to an air shock wave was proposed. The injuries were found to be caused by the direct traumatic effect of the air shock wave. In the acute post-traumatic period, histopathological and ultrastructural changes in the brain can manifest as changes in neurons and in the blood-brain barrier and be accompanied by perivascular multifocal small-focal hemorrhages, neuropil ruptures, edema of pericellular and perivascular spaces, which together can be considered as biomarkers of primary traumatic changes after exposure to an air shock wave.

Study on the Earth-Covered Magazine Models under the Internal Explosion

The use of earth-covered magazines (ECMs) is increasingly prevalent in protective engineering due to their concealment and cost-effectiveness. To explore the optimal thickness of earth covering for ECMs, scaled model tests were conducted under explosive charges equivalent to 30 kilograms of TNT. The resulting overpressure outside the model in the 180° direction was measured. Subsequently, computational analyses were conducted employing LS-DYNA software to examine these experimental findings. The findings indicate that increasing the thickness of the rear soil can mitigate peak overpressure, delay the air shock wave’s arrival time, and reduce the impulse of the positive phase. The numerical calculations closely align with experimental data, with peak overpressure deviation remaining under 10%. The shock wave initially impacts the top of the model before reaching the rear, with soil scattering more pronounced in the 90° direction compared to the 180° direction. Furthermore, an analysis of soil energy absorption rate variation was conducted based on energy conservation principles. These results provide valuable insights for optimizing the design and construction of ECMs.

LOCOMOTOR ACTIVITY OF RATS WITH BLAST-INDUCED TRAUMATIC BRAIN INJURY IN A COMPLEX MAZE

Aim – to investigate the peculiarities of rats with blast-induced brain injury movement in the complex maze.Material and methods. The study was carried out on 15 sexually mature Wistar rats. All animals were randomly divided into 3 groups: experimental group (n=5), which was anesthetized and exposed to an air shock wave with an overpressure of 26-36 kPa; sham group (n=5), which was only anesthetized, and intact group (n=5). The study of locomotor activity was performed using a complex maze for 5 consecutive days, starting on the 1st day after the simulation of blast-induced brain injury. The route of rat`s movement through the maze of three groups was graphically depicted and visually analyzed.Results of the study. The complex maze is considered to be complicated due to the presence of a central zone and T-shaped branches to the right and left, ending with feeders. The complication of the situation and task lead to fear with rapid adaptation of healthy rats. However, if the brain functions are impaired, the experimental animal loses its physiological ability to adapt and shows signs of anxiety. The analysis of the images of the movement paths showed that on the 1st day of training, the rats of the experimental group moved more actively, despite the fact that the animals did not yet know that food was waiting for them. They performed monotonous movements and went to the side sectors more often. On 2nd day, the experimental rats were more active and explored the maze more stereotypically than intact animals. On 3rd and 4th days, clear signs of spatial memory impairment in the experimental group were found in terms of lengthening the path to the feeder. On the 5th day, it was found that the experimental rats were still poorly oriented in the maze, with a monotonous examination of the side sectors.Conclusions. Thus, mild blast-induced traumatic brain injury leads to persistent impairment of spatial memory, as well as behavioral disorders in the form of anxiety. The rats of the experimental group demonstrated stereotypical locomotor activity, as evidenced by the examination of the lateral sectors of the complex maze. At the same time, the memory for food reinforcement was well developed and retained.

EXPLORATORY ACTIVITY OF RATS IN THE ACUTE PERIOD OF MILD BLAST-INDUCED TRAUMATIC BRAIN INJURY

The relevance of this work is related to the widespread use of explosive devices in military conflicts. More common and "invisible" is mild blast-induced brain injury. This can manifest through anxiety, emotional dysregulation, and spatial memory impairments. However, significant variability exists in modeling blast-induced traumatic brain injury and spatial memory assessment methods. This study aimed to investigate the exploratory activity of rats during the acute phase of mild blast-induced traumatic brain injury modelled by using a newly developed device.
 The study carried out on 18 sexually mature male Wistar rats weighing 220-270 g. The selected rats were divided into three groups: an experimental group (n=6), animals were modeled with blast-induced trauma by generating an air shock wave with an overpressure of 26.4±3.6 kPa, sham group (n=6), animals were subjected only to inhalation anesthesia with halothane and fixed in a horizontal position, and an intact group (n=6). The exploratory activity was recorded by the iPhoneXR camera; the route of movement through the maze of rats from three groups was graphically depicted and visually analyzed, as well as the number of entries into the "false shelters" was counted and the performance of experimental, sham and intact rats was compared. On the 1st day of the post-traumatic period, the experimental rats explored a greater number of "false shelters", by 72% (p<0.01) compared to intact animals and by 65% (p<0.05) compared to control animals. On the 3rd day, this activity was higher by 53% (p<0.05) compared to intact and by 67% (p<0.05) compared to control rats. On day 7, experimental rats explored more, by 86% (p<0.01) compared to intact rats and also by 86% (p<0.01) compared to control animals. The obtained results indicate an increase in the exploratory activity of rats in the acute period of mild blast-induced brain injury.

Changes of rat’s brain vesseles after air shock wave exposure

Mild blast-induced traumatic brain injury is common among the military, resulting in cognitive impairment, reduced socialization, which leads to disability and, as a result, a deterioration in the quality of life. It is considered that blood-brain barrier disruption and microvascular dysfunction are the key to this type of injury. The purpose of study was to study changes in brain vessels after air shock wave exposure. The study was carried out on 48 mature male Wistar rats, which were randomly divided into 2 groups: an experimental group, in which animals were subjected to inhalation anesthesia using halothane and exposed to a shock wave with an overpressure of 26.4±3.6 kPa, and a Sham group. After simulation of injury on days 1st, 3rd, 7th, 14th, and 21st, the rats were euthanized and the brain was removed and after all subjected to standard histological procedures and stained with hematoxylin and eosin. For immunohistochemical studies, as primary antibodies were used eNOS. The finished preparations were examined by light microscopy and photographed. Disorders of the cerebral vessels in experimental rats were detected from day 1st of the posttraumatic period. It was found that the blast wave led to vascular rupture, as well as increased vascular permeability with diapedesis of red blood cells and cerebral edema for up to 21st days. Focal violations of the vascular wall integrity in cortical and hippocampal hemocapillaries, venular link of the submembrane vessels; changes in the morphology of the metabolic vessels endothelium; uneven blood filling of the brain vessels were of major importance. These changes indicate that increased eNOS expression leads to dilation of cerebral vessels, which is a compensatory mechanism in response to injury to improve cerebral blood circulation. However, eNOS is not involved in vasodilation, which we observed up to 21st day post-trauma.

Energy and blast performance of beryllium in a model thermobaric composition in comparison with aluminum and magnesium

A direct comparison is made between the effectiveness of Al, Mg, and Be powders as additional fuels in model thermobaric compositions containing 20% fuel, 20% ammonium perchlorate, and 60% RDX (1,3,5-Trinitro-1,3,5-triazacyclohexane) passivated with wax. Experimentally determined calorimetric measurements of the heat of detonation, along with the overpressure histories in an explosion chamber filled with nitrogen, were used to determine the quasi-static pressure (QSP) under anaerobic conditions. Overpressure measurements were also performed in a semi-closed bunker, and all blast wave parameters generated after the detonation of 500 g charges of the tested explosives were determined. Detonation calorimetry results, QSP values, and blast wave parameters (pressure amplitude, specific and total impulses) clearly indicate that Be is much more effective as an additional fuel than either Al or Mg in both anaerobic post-detonation reactions as well as the subsequent aerobic combustion. The heat of detonation of the RDXwax/AP/Be explosive mixture is over 40% and 50% higher than that of the mixture containing aluminum and magnesium instead of beryllium, respectively. Moreover, the TNT equivalent of the Be-containing composition due to the overpressure in the nitrogen-filled explosion chamber is 1.66, while the equivalent calculated using an air shock wave-specific impulse at a distance of 2.5 m is equal to 1.69. The high values of these parameters confirm the high reactivity of beryllium in both the anaerobic and aerobic stages of the thermobaric explosion.

Cylindrical single-wall and double-wall structures with or without internal water subjected to underwater shock loading

A series of experimental studies were conducted for cylindrical structures subjected to underwater shock loading to understand their dynamic responses and failure characteristics. All tests were performed inside an anechoic water tank. The submerged test cylinders were freely suspended, and an underwater shock loading was generated by the Compressed Air Shock Pipe Underwater Release (CASPUR) system. Cylinders were made of two different materials. The first group of cylinders was fabricated from carbon fiber and resin using the filament winding technique. The winding angles were ± 45° resulting in the same properties along axial and hoop directions. The second group of cylinders was constructed using a 3-D printer with polylactic acid (PLA) material. The 3-D printed cylinders had an orthotropic material property with different values in the axial and hoop directions. Both single-wall and double-wall cylindrical structures were tested. The latter consisted of two concentric cylinders of different diameters with uniform spacing between them. In addition, within the single-wall cylinders and the annuli of double-wall cylinders, the water fill was varied at 0%, 50%, or 100%. Pressure and strain gages were used to measure the shock pressure and deformation of the cylinders. The number of cylinders such as single-wall or double-wall and the internal water resulted in significant effects on the measured dynamic response (i.e., strain gage response) as well as the failure loading and failure characteristics including major failure locations. Internal water reduced the strain on the cylinders and made them withstand greater shock loading for both single-wall and double-wall cylinders.

Damage Characteristics and Dynamic Response of RC Shells Subjected to Underwater Shock Wave

Underwater bottom-sitting shell structures face threats from underwater explosion shock waves. To investigate the damage characteristics and dynamic response of bottom-sitting shell structures under underwater explosion shock waves, three-dimensional numerical models of semi-spherical and semi-cylindrical bottom-sitting reinforced concrete (RC) shells under underwater shock waves were established based on the Arbitrary Lagrangian–Eulerian (ALE) algorithm using LS-DYNA software. The influences of the shock wave transmission medium, explosive equivalent, explosive distance, hydrostatic pressure, and reinforcement on the damage characteristics and dynamic response of semi-spherical and semi-cylindrical bottom-sitting RC shell structures were studied. The results indicated that the damage and center vertical deformation of RC shells under underwater shock waves are significantly greater than those under air shock waves. With an increase in explosive equivalent or decrease in explosive distance, the damage and center vertical deformation of RC shells are increased. The damage to the inner surface of RC shells is more severe than the outer surface. The damage and center vertical deformation of RC shells can be reduced by bottom reinforcement and an increase in the diameter of the steel bar. The ‘hoop effect’ caused by hydrostatic pressure restrains the horizontal convex deformation and slightly decreases the macroscopic damage and vertical center deformation of the semi-spherical RC shell with an increase in hydrostatic pressure within the range of 0–2.0092 MPa. The hydrostatic pressure restrains the horizontal convex deformation of the semi-cylindrical RC shell. However, inward concave deformation of the shell center is increased by hydrostatic pressure, inducing an increase in the damage to and center vertical deformation of the semi-cylindrical RC shell. These findings may offer a reference for the construction and design of protective measures for underwater bottom-sitting shell structures.

DETERMINATION OF THE AMOUNT OF LOAD ON PROTECTIVE STRUCTURES OF CIVIL DEFENSE AGAINST THE INFLUENCE OF A SHOCK WAVE ACCORDING TO DBN V.2.2-5:2023

The main types of explosions and their differences between each other are considered, as well as the difference in excess pressure in the air shock wave is shown. The definition of the calculated load on various load-bearing elements depending on the type of building, its location and structural inhomogeneities of building structures according to DBN B.2.2-5:20023 [1] is given. One of the extreme effects, the danger of which must be taken into account when designing protective structures of civil protection, is an external explosion, which can be caused by both man-made and military factors. The explosion generates a whole complex of loads and impacts. The pressure at the front of the air shock wave, as well as the duration of the compression and rarefaction phases, depend on the amount of explosives and the distance to the center of the explosion or cloud boundary. In general, a detonation explosion is characterized by the possibility of significant pressure on the front of the air shock wave and the short duration of the action (tenths and even hundredths of a second). The air shock wave, when interacting with the structure, affects its above-ground and underground parts. This process is complex: at the beginning of the interaction process, the air shock wave affects the external structures of the above-ground part of the building and the surface of the soil in front of the building, causing a compression wave in it, which, in turn, affects the front outer face of the underground part. Further, the air shock wave, passing through the structural inhomogeneities of building structures in the form of window and door openings, affects the internal load-bearing and non-load-bearing structures of the building, as well as the covering of the underground part. At the same time, compression waves in the soil affect the side and rear walls of the underground part.

Method of calculation of satellite flow parameters behind the point of Mach reflection

A mathematical model for the calculation and express analysis of triple configurations of air shock waves arising from an “elevated” explosion of a condensed high-energy material is presented. The considered blast waves with a long duration of the positive phase (compression phase) can take place in industrial and agricultural applications: in the explosion of fuel-air mixtures, explosive dust in elevators and granaries, as well as high-energy materials for agricultural and industrial applications based on ammonium nitrate and explosive saltpetre mixtures with petroleum products. The developed mathematical model uses exact and semi-empirical relationships developed earlier in the theory of optimal shock wave systems.

Защита человека от ударных волн средствами инженерно-технической укреплённости

Purpose. Protective screens (barriers) are used in areas with large crowds of people to reduce the likelihood of human injury from explosive devices used in terrorist acts. To assess the effectiveness of protective screens, it is necessary to determine the following initial data in advance: the weight of the explosive device in TNT equivalent; the area being protected, and the acceptable probability of human injury within it. The article presents a general methodology for determining the effectiveness of protective barriers against terrorist-directed explosive devices. An example is given of using the developed methodology to determine the most optimal solution for protective barriers for a specific object. Methods. Various numerical simulation methods are used to solve gas dynamics problems. When modeling explosions accompanied by shock impacts, the Godunov’s scheme – solving the breakdown of an arbitrary discontinuity problem – is used. The problem of the breakdown of an arbitrary discontinuity in numerical schemes is reduced to a system of nonlinear equations related to the pressure and velocity of the medium at the discontinuity point, which determine the mass and momentum fluxes exchanged between adjacent computational cells. Findings. The author's experimental research methodology allows obtaining all the necessary information about the parameters of explosive loads formed during internal accidental explosions. Research application field. The research results can be used in the design of anti-terrorist protective structures. Conclusions. Blast loads are presented for the placement of anti-terrorist protective structures. Reduction in blast loads is shown for three different placement options of protective structures. The conditional probability of human injury by an air shock wave is determined. Based on the found parameters, the effectiveness of anti-terrorist protective structures is assessed for three different placement options.

Review and analysis of damage and existing systems of protecting tower cranes under the influence of a blast wave

Problem. The problem of assessing the technical condition of stationary tower cranes of various types by expert organizations in order to determine the possibility of their further operation and the methods of capital repair is relevant. At the same time, one should take into account the nature of the consequences of damage to metal structures and the type of repair, if it is at all possible. The topic of the article is of a practical nature. An attempt was made to have an initial representation and visual analysis of the condition of different types of tower cranes under the conditions of explosive air shock waves depending on the distance to the cranes. The article attempts to substantiate the consequences of the destruction of metal structures, mechanisms or protection systems and to point out some regularities that require close attention during the operation of tower cranes and their further research. Goal. The purpose of the work was to make a damage survey of the different types of tower cranes that have been damaged and their existing protection systems and to provide assumptions for further research on the stability of tower cranes in the conditions of air shock waves. Methodology. The approaches adopted in the work to solve the set goal are based on the conditional division into categories of damage to stationary tower cranes under the action of air shock waves. The results. The analysis of damage to tower cranes will make it possible to take into account in the future the development of typical projects in accordance with the technical documentation regarding their disassembly-assembly, types of repairs, etc. Originality. The study of the stability of tower cranes under the conditions of air shock waves is a rare and specific direction in the field of engineering research. Therefore, the results of this study will fill the gaps in scientific literature and engineering practice. Practical meaning. The results of the study can lead to the development of new approaches and recommendations for the design of tower cranes taking into account possible air shock waves. This will allow engineers to create safer and more reliable designs for working in hazardous environments