Air Shock Research Articles

Nonlinear calculation of reinforced concrete structures to the impact of the air shock wave

Introduction. Researched methods of accounting for the nonlinear operation of reinforced concrete structures on the example of an industrial structure, when exposed to an air shock wave using modern software systems based on the finite element method. The calculation of reinforced concrete construction to the impact of an air shock wave, if no increased requirements for tightness are presented to it, in accordance with current regulatory documents, must be carried out taking into account the elastic-plastic work, crack opening in the stretched zone of concrete and plastic deformations of reinforcement are allowed. Reviewed by new coupling approach to determining the dynamic loads of a shock wave, implemented in the LS-DYNA software package, which allows to take into account the effects of a long-range explosion and wave-wrapping around a structure. Materials and methods. The study of the stress-strain state of the structures was carried out using numerical simulation. For the nonlinear equivalent-static method, a step-by-step calculation algorithm is used, with gradual accumulation and distribution of stresses, implemented in the LIRA-SAPR software package. For the nonlinear dynamic method, the Lagrangian-Eulerian formulation is used using the methods of gas dynamics in the LS-DYNA software package. Results. As a result of numerical simulation, the following was done analysis of existing methods of nonlinear calculations; analysis of the existing loads during the flow of shock waves around the structure; analysis of the forces and movements in the bearing elements, as well as pictures of the destruction of concrete and reinforcement. Conclusions. According to the results of the comparison of the two approaches, conclusions are drawn about the advantages and disadvantages of the methods. Advantages of nonlinear dynamic calculation methods are noted compared to the equivalent-static ones. Use of the combined approach to the description of the shock wave front gives a reduction in time and allows us to describe the interaction of the wave with the structure with sufficient accuracy. The findings indicate the relevance of the study and provide an opportunity to move to more reasonable computational models.

Video Recording of an Air Shock Wave from Initiation of a Light-Sensitive Explosive Composition

Video Recording of an Air Shock Wave from Initiation of a Light-Sensitive Explosive Composition

Controlling of the Environmental Effects of Air Shock Wave Due to Blasting In Quarry Mines

This paper presents controlling the environmental effects of air shock waves due to blasting in quarry mines. The aim of this study is to predict the air overpressure due to blasting, in order to protect the dwelling area adjacent to the quarry. Prediction of air overpressure is important for mine operators who utilize blasting to ensure their blasts will not cause damage to nearby structures and stay within regulatory limits. Airblast is dependent on the size of the blast and air shock wave magnitude is dependent on how far away from the blast a recording device is located. Air shock waves are an integral part of the process of rock blasting and consequently, they are unavoidable. In this paper, important and widely used empirical formulae have been used to predict the air overpressure for quarry mines. Moreover, a comparative analysis between the results obtained for a constant charge per delay of 100 kg, and monitoring distance of 20 m, 30 m, and 40 m were carried out to select the suitable empirical formula. The paper concludes with the guidelines for applying the air overpressure wave based on the various distances and amount of charges per delay.

Propagation Regularity of Air Shock Wave in Turning Roadway

In order to study the propagation law of explosive shock wave in underground turning roadway, the peak overpressure value in the roadway with specific turning angle was compared and analyzed by combining field monitoring experiment with ANSYS numerical simulation. The results show that the blast wave propagates forward in a stable plane wave before turning. Before the explosion air shock wave propagates to the turn, it follows the propagation law in the straight through roadway. After turning, the diffraction and reflection through the wall of the roadway will form a turbulence zone of 10-20m, and then continue to propagate forward in a stable plane wave. The turning roadway has a certain attenuation effect on the propagation of the shock wave. By analyzing the peak overpressure value before and after turning, the attenuation coefficient values of roadways at various turning angles are determined, That is, the attenuation coefficient values corresponding to the turning angles of 30°, 60°, 90°, 120° and 150° are 1.25, 1.31, 1.45, 1.50, 1.65, respectively, and the attenuation coefficient values are fitted with the roadway turning angle formula to obtain the quantitative calculation formula, which can provide reference for the safety of underground personnel, equipment and the design and production of mines.

Пороги инициирования и динамические характеристики взрыва для тонких образцов композитов ТЭН-Al при лазерном воздействии

AbstractIn this paper, we measured thresholds H _cr of explosive decomposition of thin ( h = 1 mm) samples of PETN-Al composites with densities in the range of ρ = 0.9–1.7 g/cm^3 and variations in the concentration of aluminum inclusions in the range of 0.025–1.0 wt % upon exposure to pulses of a neodymium laser (λ = 1064 nm, 14 ns). For each ρ, inclusion concentrations n _opt, at which the threshold for explosive decomposition of H _cr is minimal, are obtained. The velocities of air shock waves (ASWs) were determined depending on sample density ρ, and the times of the start of explosive decomposition were determined depending on the inclusion concentration. The amplitude (in relative units) and time shift of the maximal pressure of an ASW at the piezodetector are determined depending on sample density. It is concluded that the explosion is governed by the SW mechanism at high densities. As sample ρ decreases, the completeness of the explosion increases, with the most likely mechanism for small ρ being explosive burning. The efficiency of explosive decomposition is higher for samples with lower densities.

The defense of staff from air shock waves by controlling their spread in extended buildings

Purpose. Development and research of ways to control the propagation of shock air waves due to constructive and planning solutions for the purpose of protecting personnel during emergency explosions, in conditions of preserving the technological section of canals and workings in extended structures. Justification of the parameters of numerical simulation in CFD models of discontinuous internal flow of a gas stream. Methodology. The research was carried out on the basis of search and analysis of publications on the topic of the work, an analysis of the research object was used for the mathematical formulation of the problem and the justification of the boundary conditions and parameters of numerical simulation. To substantiate the rational configurations of the reflecting-wave chambers, an analytical evaluation of the interaction of the shock air-wave front with the backward step, the chamber wall and the concave angle was performed. By numerical simulation, the physical processes controlling the propagation of shock air waves. Findings. An analysis of the physical processes occurring during the control of the propagation of shock air waves with the aid of chambers of reflecting waves made it possible to reveal a number of qualitative and quantitative laws governing the motion of the wave front at the interface with the branch channels. The mechanism of action of a reflecting wave formed in a chamber by a reflected shock wave on a supersonic flow is shown. To effectively control the propagation of strong shock air waves with an excess pressure of more than 0.1 MPa, it is necessary to use chambers reflecting waves with an inclination angle of the reflection surface close to 45°. Originality. The parameters of the numerical simulation of the propagation of the shock air wave through the system of reflected waves in the FlowVision modeling environment are substantiated. An analytical evaluation of the parameters of the wave front is made during diffraction of the backward step directly in the chambers of the reflecting waves, movement along its wall and reflection on the inclined surface. The dependence of the effectiveness of controlling the shock air-wave on the parameters of the chambers. Practical value. Reasonable rational parameters of the reflecting wave chambers allow to increase the efficiency of personnel protection from the action of shock air waves in the extended structures of civil defense and mining facilities.

Graphitic coated Al nanoparticles manufactured as superior energetic materials via laser ablation synthesis in organic solvents

The large heat release predicted in the early investigations of energetic aluminum nanoparticles (Al NPs) used in solid-state propulsion and pyrotechnics has been offset by hindered diffusion-limited detonation rates due to excess oxide shell formations and surface area loss from aggregations. We address these challenges by manufacturing graphitic shell coated Al NPs (<20 nm sizes) via laser ablation synthesis in solution (LASiS) to preserve high surface areas and interfacial properties of Al NPs. Specifically, we use a high-energy laser to ablate Al pellets confined in either acetone or toluene to coat the laser-ablated Al NPs with graphitic shells generated from the thermal pyrolysis of the organic solvents. Energetic activities of the C/Al NPs were tested via the laser-induced air shock from energetic materials (LASEM) technique. We demonstrate that synthesis parameters such as organic solvents, laser flux and ablation times can be tuned to provide superior control of NP sizes/aggregation with the aid of the C shell formations and, in turn, their energetic behavior. This study unveils the synthesis-structure-property relations in LASiS-based manufacturing of energetic nanocapsules within graphitic shells that are safe to handle and can undergo kinetically controlled spontaneous energy release under desired conditions.

Virtual laboratory of studying processes combustion and explosion in the preparation of civil safety engineers

Purpose. To explain the role and importance of the use of virtual educational laboratories VL-MCE 1.0 Simulation of the propagation of a shock air wave in a shock tube in the study of disciplines from the cycle of industrial safety and labor protection for students in the field of study Civil protection. Qualitative assessment of improving the efficiency of training bachelors and masters using virtual laboratories. Research methods. Analysis and synthesis of theoretical studies in the field of improving the educational process, in particular the methods of forming professional knowledge in the laboratory-practical course, numerical simulation of the gas-dynamic process of detonation combustion of the gas-air mixture, including the model of chemical kinetics of combustion, which generally allows to track the dynamics of the formation of air shock waves in a channels of extended structures. Results. Of particular importance for the development and maintenance of competitiveness of graduates of the specialty Civil Protection is the training of specialists of the appropriate level and qualification, possessing a variety of tools and able to make competent and informed decisions in the field of industrial safety. To study the process of combustion and explosion of the gas-air environment, as well as the formation and propagation of shock air waves in the channels of extended structures, an interactive program VL-MCE 1.0, a virtual laboratory for simulation of combustion and explosion, was developed. The role and importance of the use of virtual laboratories in the study of disciplines from the cycle of industrial safety and labor protection is analyzed in the article. The didactic component of the use of VL-MCE 1.0 consists in the direct assessment by the student of the parameters of the processes under consideration, depending on the initial conditions, this allows you to create design functions in the activities of a civil protection specialist, as well as knowledge at the PS level (productive-synthetic) and develop sign-mental and symbolic -practical professional skills at the C level (independently). Scientific novelty. The meaning, place and form of application of virtual educational laboratories VL-MCE 1.0 “Modeling the propagation of a shock air wave in a shock tube” are determined in the laboratory-practical course of disciplines from the cycle of industrial safety and labor protection for the formation of a higher level of professional knowledge and skills. A didactic clarity in the visualization of fast processes is shown, which allows in time scans to evaluate in detail the relationship and dynamics of changes in the parameters of explosive processes. Practical value. The developed computer program can significantly reduce the cost of conducting laboratory classes and maintaining the laboratory base without reducing the level of development of professional skills.

TECHNOLOGIA REALIZACJI PRAC ROZBIÓRKOWYCH KOMINÓW MUROWANYCH I ŻELBETOWYCH

W referacie dokonano analizy zasadniczych metod prowadzenia prac rozbiórkowo – wyburzeniowych kominów murowanych i żelbetowych, oraz określono wpływ oddziaływania na środowisko negatywnych czynników związanych z zastosowaniem materiałów wybuchowych (MW): powietrznej fali uderzeniowej (PFU) oraz rozrzutu odłamków.

ПОВЫШЕНИЕ БЕЗОПАСНОСТИ ПРИ ВОЗНИКНОВЕНИИ АВАРИЙНЫХ ГАЗОВЫХ ВЗРЫВОВ И РАСПРОСТРАНЕНИИ УДАРНЫХ ВОЗДУШНЫХ ВОЛН В ПРОТЯЖЕННЫХ СООРУЖЕНИЯХ

Purpose. Development and research of shock air waves damping schemes in extended structures, due to constructive and planning solutions, provided that the technological section of the channels and workings is maintained. Substantiation of the parameters of numerical simulation in CFD models of a discontinuous internal flow of a gas stream. Methodology. The studies were carried out on the basis of the search and analysis of publications on the topic of work, the analysis of the object of study was used fo r the mathematical formulation of the problem and the substantiation of the boundary conditions and parameters of numerical simulation. To substantiate the rational configurations of chambers for damping waves, an analytical evaluation of the interaction of the fr ont of a shock air wave with a reverse step and the wall of the chamber was performed. By numerical modeling, physi cal processes of shock air waves damping have been studied. Findings. Analysis of the physical processes occurring during the propagation of shock air waves through the system of chambers for damping waves revealed a number of qualitative and quantitative patterns of motion of the wave front along the backward ledge directly in the chamber and along its wall. The reasons for the low efficiency of previously used expansion chambers with cross sections that significantly exceed the cross sections of the channels are shown. For effective damping of strong shock air waves with an excess pressure of more than 0.1 MPa, it is necessary to use a series of short chambers for damping waves of small reduced width. This type of camera significantly increases the wave resistance of the extended channel due to multiple reflection of a part of the shock wave front on the closing surfaces of the camera. At the exit from the camera system for damping waves of this type, the shock air wave is transformed into a subsonic compre ssion wave, with a decrease in the amplitude of the wave front by 50-80% relative to the baseline. The results of numerical simulation have allowed to establish that such an effect occurs only in chambers for damping waves with a symmetrical arrangement of the wings of the chamber. Originality. The parameters of numerical simulation of the propagation of a shock air wave through a system of cameras for damping waves in the flowVision simulation environment are substantiated. An analytical evaluation of the wavefront parameters is made with the flow around the reverse ledge directly in the chamber for damping waves and moving along its wall. The dependence of the efficiency of dampin g a shock air wave on the size and number of chambers, taking into account th e excess pressure at the wave front, has been established. Practical value. Reasonable rational parameters of wave damping chambers allow increasing the efficiency of personnel protection against the effects of air shock waves in extended structures of civil defense and mining facilities.

Shock attenuation by densely packed micro-particle wall

A wall densely packed with micro-particles is impacted by a planar shock wave in a horizontal multiphase shock tube to investigate the shock attenuation. The incident shock strength $${P_2}$$ is attenuated to the transmitted shock strength $${P_6}$$ . A dimensionless complex $$\theta$$ composed of the pressure drop coefficient $${f_{\text{m}}}$$ , the void fraction $$\varepsilon$$ , the packed particles length $$L$$ , and the particle diameter $$D$$ was derived from the previous experiments of the milli-particle walls to characterize the shock attenuation property of the particle wall. However, the data points of the micro-particle wall are located outside the region surrounded by the relationship of the shock attenuation $${{{P_6}} \mathord{\left/ {\vphantom {{{P_6}} {{P_2}}}} \right. \kern-0pt} {{P_2}}}$$ and the particle wall characteristic $$\theta$$ . Moreover, the data points of the micro-particle wall present a positive correlation between $${{{P_6}} \mathord{\left/ {\vphantom {{{P_6}} {{P_2}}}} \right. \kern-0pt} {{P_2}}}$$ and $$\theta$$ , which is contradictory to the negative correlation presented by the previous experiments. Comparison and analysis of the experimental results reveal that the key factor of the shock attenuation is not the size of the individual particle but of the skeleton densely packed with all particles. And then the individual particle diameter $$D$$ is replaced by the skeleton cross section size $$W$$ , the particle wall characteristic $$\theta$$ is modified. The experimental data points of Bakken et al., Wagner et al., Theofanous et al., and us are all located inside the region based on the modified particle wall characteristic $${\theta ^*}$$ and all obey the negative correlation between $${{{P_6}} \mathord{\left/ {\vphantom {{{P_6}} {{P_2}}}} \right. \kern-0pt} {{P_2}}}$$ and $${\theta ^*}$$ . The modified particle wall characteristic can describe the shock attenuation capability of both milli-particle and micro-particle walls. Numerous particles are densely packed to form a particle skeleton of void fraction $$\varepsilon$$ . The incident shock strength $${P_2}$$ is attenuated to the transmitted shock strength $${P_6}$$ . The circuitous pores among the skeleton provide the passages for the air shock wave. $$\varepsilon W$$ describes the total size of the void on the skeleton cross section, and $${\phi _{\text{p}}}L$$ describes the length of the circuitous pores among the skeleton. The modified particle skeleton characteristic $${\theta ^*}={{\left( {{f_{\text{m}}}{\phi _{\text{p}}}L} \right)} \mathord{\left/ {\vphantom {{\left( {{f_{\text{m}}}{\phi _{\text{p}}}L} \right)} {\varepsilon W}}} \right. \kern-0pt} {\varepsilon W}}$$ describes the shock wave attenuation capability of the particle skeleton and shows the negative correlation with the shock attenuation $${{{P_6}} \mathord{\left/ {\vphantom {{{P_6}} {{P_2}}}} \right. \kern-0pt} {{P_2}}}$$ .

Numerical investigation of an interaction between shock waves and bubble in a compressible multiphase flow using a diffuse interface method

The shock-bubble interaction in a compressible multiphase flow was investigated using a diffuse interface method (DIM) consisting of seven equations. To achieve detailed flow structures and mass transfer information, high-order numerical schemes, including the fifth-order MLP and a modified HLLC Riemann solver, were implemented. The numerical methods were verified via a flow structure comparison of the high-pressure water and low-pressure air shock tubes. A two-dimensional air-helium shock-bubble interaction at the incident shock wave condition (Mach number 1.22) was numerically solved and verified using the experimental results. A very detailed deformation was observed, so unsteady shock patterns such as the incident, transmitted, and reflected shocks could be identified. In addition, the air–water shock-bubble interaction at the same Mach number condition (1.22) was analyzed via the observation of detailed flow structures such as the reflection and transmitted shock inside and outside of the water bubble.

APPLICATION OF THE EMBEDDED MECHANICAL SYSTEMS FOR ENSURING THE PRESERVATION OF MILITARY EQUIPMENT PRODUCTS UNDER DYNAMIC IMPACTS

In the process of providing combat operations, the designs of military equipment products are subject to significant effects of both regular and non-regular dynamic loads, which can lead to their mechanical destruction. Among the dynamic loads acting on military hardware products, it is possible to identify short-term, caused by explosive and shock effects, and long-term vibrational loads that arise during transportation. As a result, there is the problem of ensuring the conservation of mechanical products of military equipment under dynamic impacts during the preparation and conduct of combat operations. The impact of a shock wave on military hardware products has a complex dynamic nature, depending on the wave parameters and the features of the object under consideration. Various results of this impact are possible, such as product destruction, turnover, change in the nature of motion, and others. The conservability of products with respect to the air shock wave is established experimentally. In addition to explosive loads, shock loads affect military equipment. In accordance with this, consider the local and general action of the thrust. Local action is characterized by the occurrence of local deformations and structural damage. The general action is accompanied by significant general deformations and destruction of the entire construction. The effect of prolonged vibration loads on military hardware products is mainly related to transportation processes. With prolonged cyclic loading, the destruction of the material of the structural elements can occur also at a stress amplitude less than the elastic limit. The article gives a definition of embedded mechanical systems and formulates their basic properties, which allow us to propose a hypothesis that in order to ensure the mechanical storage of products subject to dynamic influences, it is necessary to use embedded mechanical systems. Based on the nesting principle of mechanical systems, a method for increasing the retentivity of military equipment was proposed. The use of nested mechanical systems makes it possible to ensure the mechanical retention of military equipment by reducing the total energy supplied to the allowable value for the product to be stored.

Improving the Explosive Performance of Aluminum Nanoparticles with Aluminum Iodate Hexahydrate (AIH)

A new synthesis approach for aluminum particles enables an aluminum core to be passivated by an oxidizing salt: aluminum iodate hexahydrate (AIH). Transmission electron microscopy (TEM) images show that AIH replaces the Al2O3 passivation layer on Al particles that limits Al oxidation. The new core-shell particle reactivity was characterized using laser-induced air shock from energetic materials (LASEM) and results for two different Al-AIH core-shell samples that vary in the AIH concentration demonstrate their potential use for explosive enhancement on both fast (detonation velocity) and slow (blast effects) timescales. Estimates of the detonation velocity for TNT-AIH composites suggest an enhancement of up to 30% may be achievable over pure TNT detonation velocities. Replacement of Al2O3 with AIH allows Al to react on similar timescales as detonation waves. The AIH mixtures tested here have relatively low concentrations of AIH (15 wt. % and 6 wt. %) compared to previously reported samples (57.8 wt. %) and still increase TNT performance by up to 30%. Further optimization of AIH synthesis could result in additional increases in explosive performance.

Laboratory‐scale Investigation of the Influence of Ageing on the Performance and Sensitivity of an Explosive Containing ϵ‐CL‐20

AbstractThe performance and sensitivity of aged composite explosives based on the epsilon polymorph of hexanitrohexaazaisowurtzitane (ϵ‐CL‐20) have been evaluated with the laser‐induced air shock from energetic materials (LASEM) technique using only milligram quantities of material. The LASEM results demonstrated reduced explosive performance (i. e., lower estimated detonation velocities) and higher sensitivity to ignition with increasing ageing. Chemical analysis of the explosive formulation subjected to ambient and accelerated aging was conducted to help understand the LASEM results. The Fourier Transform Infrared (FTIR) spectra revealed no evidence for conversion to lower‐energy polymorphs. Based on the desorption gas chromatography/mass spectrometry (D‐GC/MS) results, the observed decrease in performance and increase in sensitivity for the explosive powder aged at 100 °C (relative to ambient and 70 °C aging) have been attributed to changes related to solvent inclusions in the molding powders.

Общая постановка задачи выбора решений по повышению защищенности объектов жизнеобеспечения населения от воздействия воздушной ударной волны

Общая постановка задачи выбора решений по повышению защищенности объектов жизнеобеспечения населения от воздействия воздушной ударной волны

Numerical Simulation of the Interaction of an Air Shock Wave with a Surface Gas–Dust Layer

Within the framework of the one-velocity and multivelocity models of a dust-laden gas with the use of the Godunov method with a linearized Riemann solver, the problem of the interaction of a shock wave with a dust-laden gas layer located along a solid plane surface has been studied.

Estimating the Relative Energy Content of Reactive Materials Using Nanosecond-Pulsed Laser Ablation

ABSTRACTRecently, a laboratory-scale method for measuring the rapid energy release from milligram quantities of energetic material has been developed based on the high-temperature plasma chemistry induced by a focused, nanosecond laser pulse. The ensuing exothermic chemical reactions result in an increase in the laser-induced shock wave velocity compared to inert materials. Laser-induced air shock from energetic materials (LASEM) provides a method for estimating the detonation performance of novel organic-based energetic materials prior to scale-up and full detonation testing. Here, the extension of LASEM to non-organic energetic materials is discussed. The laser-induced shock velocities from reactive materials such as Al/PTFE, Al/CuO, Al/Zr alloys, Al/aluminum iodate hexahydrate, and porous silicon composites have been measured; in many cases, the high sensitivity of the samples resulted in propagation of the reaction to the surrounding material, producing significantly higher shock velocities than conventional energetic materials. Methods for compensating for this effect will be discussed. Despite this limitation, the relative comparison of the shock velocities, emission spectra, and combustion behavior of each type of material provides some insight into the mechanisms for increasing the energy release of the material on a fast (μs) and/or slow (ms) timescale.

Numerical simulation of the front of an air shock wave in a ground and air explosion in the software package LS-DYNA

Introduction and objectives. When calculating buildings and structures for special combinations of loads caused by the action of air shock waves, it is necessary to determine the main parameters of the actual load. The regulatory approach implemented in modern regulatory documents proposes the use of simplified calculation methods based on the use of equivalent static loads. The aim of the study is to obtain the basic parameters of air shock waves, as well as to consider the nature of the propagation of the shock wave front during an explosion on the ground and in the air, using numerical simulation. Materials and methods. To obtain the basic parameters of air shock waves, high-precision numerical methods implemented in the modern LS-DYNA software package are considered. To describe the explosion process, the LagrangianEulerian approach is used. Results. Isopoles and graphs of excess overpressure Δ Р ф over atmospheric pressure in an air shock wave were obtained when the epicenter of the explosion was located at ground level and in the air, as well as at a distance from the designed structure. Conclusions. The considered method of numerical simulation allows to obtain the main parameters of air shock waves, which can be used for further calculation of building structures.

Radiation Analysis behind Reflected Air Shock Waves

Radiation Analysis behind Reflected Air Shock Waves