Home – Home – Jornals – Combustion, Explosion and Shock Waves 2023 number 3

Explosive welding is a solid-state joining procedure that involves the propulsion of a flyer plate by the explosion of an explosive to produce welds of two or more similar or dissimilar materials. The development of molten intermetallic compounds at the interface degrades the mechanical properties of welded alloys. However, the employment of an interlayer in explosive welding significantly increases the kinetic energy dissipation and prevents the formation of molten intermetallic compounds at the interface, thereby increasing the bonding strength. Earlier researchers employed interlayers having different values of the thickness, yield strength, ductility, and density. The influence of the interlayer on the microstructure and mechanical properties of explosively welded similar and dissimilar alloys is thoroughly reviewed in this study. In addition, the significance of explosive welding in different environments, such as helium, underwater, and gelatin media, is also summarized. Correspondingly, future advancements in joining of materials through explosive welding are forecasted.

The mechanism of promoting the autoignition of rich methanol-air mixtures by small additions of hydrogen peroxide has been studied using the tracer method. It has been shown that with the addition of hydrogen peroxide, the oxidation of methanol with atmospheric oxygen begins with the formation of hydroxyl from peroxide, followed by its interaction with methanol to form CH₃O, CH₂OH and then HO₂ and H₂O₂. The branching factor for hydroxyl is higher with the addition of peroxide higher with than without the addition of peroxide.

The processes of reflection and refraction of a pressure wave as it passes through the boundary of a bubble medium - pure liquid at an oblique incidence of the wave on the interface between the media are considered. The case was studied when the gas inside the bubbles is explosive. A significant decrease in the amplitude of the initial wave capable of initiating detonation in a bubbly liquid due to wave interference at an inclined boundary has been established.

Data on the parameters of explosion and detonation of two- and three-fuel mixtures of methane, coal dust, and hydrogen (with oxygen and air) with varied fractions of the fuels are reported. The novelty of the numerical and graphical arrays is due to previously unknown data on the kinetic energy of detonation initiation, characteristic size of detonation cells, detonation velocity, and energy release in detonation waves. The analysis is performed not only for stoichiometric two- and three-fuel systems, but also for rich and lean systems based on the fuels under study.

The processes of attenuation and suppression of detonation in gas suspensions of aluminum particles by extended clouds of inert particles are studied on the basis of numerical simulations of two-dimensional flows. The normalized detonation velocity is found as a function of the concentration of inert particles. The conditions of detonation failure are determined for non-stoichiometric mixtures with oxygen and for the case with concentration gradients across the channel. It is demonstrated that a one-dimensional approach has certain limitations in determining the detonation failure criteria because transverse waves of cellular detonation favor its reinitiation. Sufficient conditions of detonation suppression for 1µm particles are determined.

An experimental study of the effect of additives of trifluoroiodomethane (CF₃I) - one of the most effective combustion inhibitors that are safe for both humans and the environment - on the shock-initiated ignition in multicomponent combustible mixtures, namely syngas (mixture of hydrogen, CO, and methane) and mine gas (mixture of methane and acetylene). The addition of CF₃I strongly inhibits the ignition of syngas and affects the ignition of mine gas only slightly. Kinetic modeling has been carried out, and a kinetic mechanism describing the observed regularities has been proposed.

It has been experimentally shown that the flameless combustion of RDX mixtures with iron precursors, nitrogen-containing additives, and a polymer binder can lead to the formation of iron nitrides. Nanosized particles of iron nitride (Fe₃N) were obtained by optimizing the ratio of initial components and conditions of flameless combustion of RDX. The developed method for obtaining iron nitrides can be used to obtain nanosized particles of nitrides of other elements.

The effect of pulsed laser radiation (1064 nm, 120 μs, 10 Hz, 1.5 J/cm²) on coal samples in argon is under study. Mass spectrometry is used to analyze the gaseous products of coal pyrolysis. The dependences of the composition of gaseous pyrolysis products of coal samples and the proportion of reacted samples on their technical and genetic characteristics are established. Data on the yield of combustible gases per unit mass of reacted coal samples were obtained.

For the first time, a comparative study of the combustion of powder and granular mixtures Ti + C, (Ti + C) + 20% Cu with granules of different sizes with varying the particle size of titanium from 31 to 142 μm was performed. It has been found that the combustion rate of the (Ti + C) + 20% Cu powder mixture is higher than that of the Ti + C mixture, despite the lower combustion temperature. The use of the “gasless” combustion theory to determine the kinetic parameters of the process from the burning rate of the powder mixture leads to a negative value of the apparent activation energy, which shows the inapplicability of the traditional approach. The results are explained within the framework of the convective-conductive model of combustion by the retarding effect of impurity gases released during heating of component particles ahead of the combustion front. Using the values of the burning rate of granular mixtures with granules 0.6÷1.7 mm, the burning rate of the substance of the granules is calculated, i.e. the burning rate of the powder mixture, in which the influence of impurity gases is leveled. The ratio of the burning rates of a substance inside granules and powder samples determines the measure of the influence of impurity gas evolution on the burning rate of a powder mixture.

The effect of mechanical activation of components and external pressure on the combustion of a heterogeneous Ti + C mixture under SHS compaction conditions has been studied. It is shown that when burning under pressure (15 MPa), a low-speed layered regime (4÷7 cm/s) is realized, without external pressure - non-stationary high-speed combustion modes (50÷70 cm/s): surface-annular and volumetric, carried out due to convective heat and mass transfer. A mechanism for high-speed convective combustion is proposed, based on the ignition of a heterogeneous mixture by a hot impurity gas released in the combustion wave and filtering through layered cracks and other macrodefects in the volume of charge compacts that were formed during the pressing of powder mixtures. Mechanical activation of the components of the reaction mixture reduces the density and strength of the compacts and increases the efficiency of the formation of macrodefects. External pressure has the opposite effect, as it prevents the formation of cracks and the propagation of hot impurity gas through them. Consolidated samples of titanium carbide up to a relative density of 95% were obtained in the bulk combustion mode.

This paper presents a study of the dependence of the acoustic emission parameters recorded during quasi-static compression and the shock-wave sensitivity characteristics of parts made of plastic-bonded HMX on the filler particle size. The dependence of the acoustic emission parameters on the HMX particle size was used to describe the possible variants of degradation of the explosive structure under shock-wave loading, which are considered as the cause of the difference in shock wave sensitivity.

To develop a green primary explosive, we prepare an Al@KIO₄ nano-thermite using spray co-precipitation and then mix it with pentaerythritol tetranitrate (PETN) to form a PETN/Al@KIO₄ composite as a primary explosive. The thermite structure is characterized using X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy, which indicates that the thermite is about 200 nm and well distributed. The combustion performance is investigated using high-speed photography and confined combustion experiments. The results show that the detonation time of PETN/Al@KIO₄ composites is 60 μs earlier than that of pure PETN, indicating that the thermite accelerates the process of the deflagration-to-detonation transition of PETN. The detonation performance of the composites is investigated, and it is verified that PETN/Al@KIO₄ can initiate RDX successfully and be used as a primary explosive. Moreover, the safety performance and long-term storage performance of the composite are evaluated, which shows that the PETN/Al@KIO₄ composite performance is steady and the initiation effect does not change after 20 years of storage.

In this paper, the behind-plate overpressure caused by a polytetrafluoroethylene/aluminum/tungsten (PTFE/Al/W) reactive fragment is theoretically and experimentally analyzed. The theoretical energy of the PTFE/Al/W reactive materials is calculated by analyzing the chemical reaction of these compositions. Furthermore, based on the one-dimensional shock wave theory and the energy release behavior of the reactive fragment, an analytical model of the behind-plate overpressure is developed. By using binary quadratic polynomial fitting, a polynomial expression of the mass loss of the initiated reactive materials is derived based on the experimental data. The results show that the theoretical analysis model can be used for the estimating the overpressure when a reactive fragment impacts an aluminum plate within experimental conditions.

In the development of specialized explosion-proof chambers subject to increased requirements for strength reliability, an important issue is the choice of the material of the power block subjected to pulsed (dynamic and shock-wave) loads. As a rule, such structures are manufactured from industrial pipes of low alloy steel of various standard sizes. This always involves the question of choosing the steel grade, especially at the stage of computational justification of their explosion resistance, since the dynamic strength characteristics of the pipe material is generally unknown. This paper presents for the first time the results of a study of the static, dynamic, and shock-wave compressive and tensile strengths of 17G1S, 09G2S, and 10G2FBYu pipe steel of K60 strength class. In addition, comparative data on the explosion resistance at strain rates of (2÷5) ·10² c^-1 of pipes from 09G2S and 10G2FBYu steels.