Explosive Compaction Research Articles

ИССЛЕДОВАНИЕ ВЛИЯНИЯ ДАВЛЕНИЯ ВЗРЫВНОГО ПРЕССОВАНИЯ НА СТРУКТУРУ И ТЕРМОМЕХАНИЧЕСКИЕ СВОЙСТВА ПОЛИИМИДА, НАПОЛНЕННОГО БРОНЗОЙ

Comparative studies of the influence of explosive pressing pressure and subsequent sintering on the thermo-mechanical properties of polyimide filled with 10 and 30% bronze were carried out. The explosive compaction pressure in the shock front was 0.2-0.3 GPa and 0.4-0.5 GPa. A decrease in thermomechanical deformations and an increase in softening temperatures of filled polyimide with an increase in explosive pressing pressure and subsequent sintering in a closed volume have been established, which is associated with an increase in adhesive interaction.

SiC-based materials produced by explosive compaction of powders without sintering

SiC-based materials produced by explosive compaction of powders without sintering

Upconversion Luminescence from Sol-Gel-Derived Erbium- and Ytterbium-Doped BaTiO3 Film Structures and the Target Form

Sol-gel technology has attracted attention in the fabrication of diverse luminescent materials and thin film structures, with forms that range from powders to microcavities. The optical properties of sol-gel-derived structures depend on the sol composition, deposition, and heat treatment conditions, as well as on the film thicknesses and other factors. Investigations on the upconversion luminescence of lanthanides in film structures and materials are also ongoing. In this study, we synthesized three different types of materials and film structures using the same sol, which corresponded to a Ba0.76Er0.04Yb0.20TiO3 xerogel, as follows: (a) the target form, which used the explosive compaction method for sol-gel-derived powder; (b) single-layer spin-on xerogel films annealed at 450 and 800 °C; and (c) microcavities with an undoped SiO2/BaTiO3 Bragg reflector surrounding a Ba0.76Er0.04Yb0.20TiO3 active layer. The BaTiO3:(Er,Yb)/SiO2 microcavity exhibited an enhancement of the upconversion luminescence when compared to the BaTiO3:(Er,Yb) double-layer film fabricated directly on a crystalline silicon substrate. The reflection spectra of the BaTiO3:(Er, Yb)/SiO2 microcavity annealed at 800 °C demonstrated a deviation of the maxima of the reflection within 15% for temperature measurements ranging from 26 to 120 °C. From the analyses of the transmission and reflection spectra, the optical band gap for the indirect optical transition in the single layer of the BaTiO3:(Er,Yb) spin-on film annealed at 450 °C was estimated to be 3.82 eV, while that for the film annealed at 800 °C was approximately 3.87 eV. The optical properties, upconversion luminescence, and potential applications of the BaTiO3:(Er,Yb) sol-gel-derived materials and structures are discussed in this paper.

Heat transfer and pressure drop correlations for a gas flow in unidirectional porous copper tubes

In this study, to develop a heat exchanger having small-scale and high performance, the heat transfer performance and the pressure drop in a gas flow are evaluated for six types of unidirectional porous copper tubes fabricated by explosive compaction. Furthermore, correlation equations for the effective heat transfer coefficient and the friction factor are constructed. The maximum enhancement ratio of the effective heat transfer coefficient in the porous copper tubes is four times as high as a swirl tube, which is a typical heat transfer promoter. The performance of these porous tubes becomes high with increasing the Reynolds number based on the superficial velocity. The correlation equation for effective heat transfer coefficient can predict with the error within ±10% regarding 70% of obtained experimental data, that for the friction factor is high accuracy regarding when the number of pores is relatively small and the pore diameter is relatively large.

Upconversion Luminescence of Er3+ Ions from Barium Titanate Xerogel Powder and Target Fabricated by Explosive Compaction Method

Upconversion Luminescence of Er3+ Ions from Barium Titanate Xerogel Powder and Target Fabricated by Explosive Compaction Method

Effect of explosive compaction on microstructure of ODS FeCrAl alloy fabricated by oxidation method

A fabrication process of 14Cr ODS FeCrAl alloy including direct oxidation treatment, explosive compaction and vacuum post-sintering was proposed herein. A thin oxide layer formed on the powder surface during a low-temperature oxidation treatment was crushed in the explosive compaction, resulting in the redistribution of oxides at prior powder boundary (PPB) and the subsequent formation of an exclusive iron oxide layer between the grains of compacted materials. A large number of defects (dislocations and grain boundaries) were also produced in the compacted particles. Through characterizing the evolution of oxide dispersoids during the course of fabrication, the contribution of explosive compaction to dislocations, nanoscale precipitates and mechanical properties was clarified. The results show that the iron oxide layer became the container for transporting oxygen and was dissolved during the post-sintering, which affected the composition of nanoscale precipitates. The high-density dislocations not only became the rapid diffusion paths of oxygen, aluminum and yttrium atom, but also became the preferential sites of Y-Al-O precipitation. With the manufacturing method, the more uniform distribution of oxide nanoparticles and the higher microhardness of ODS alloy were obtained.

Numerical and in-situ evaluation of explosive compaction effectiveness in railway subgrade improvement

Owing to its huge area coverage, explosive Compaction (EC) is as an attractive improvement technique in railway projects. Despite many EC case studies in the literature, few experimental tests are conducted to be used for calibration of numerical models. Thus in this study, a field test is conducted on a railway subgrade and simulated with an advanced numerical model followed by a parametric study on detonation delay. Beside showing promising advantages of the numerical model, it can also distinguish the effects of detonation delay such as change in wave arrivals or instant compaction in EC.

Analysis of SiC mixture densification in explosive compaction

The paper presents the results of research into how the binder content and the Shockwave compression parameters affect SiC and Ti powder mixture densification in explosive compaction. The microstructure of the resulting compacted metal was studied by scanning electron microscopy. Phase and chemical composition was studied by X-ray crystallography and energy-dispersive analysis. It was found that at higher silicon carbide concentrations and higher powder heating temperatures, Shockwave compression reduced the residual porosity of the compacted metal to 2%. The microstructure was a carbide-silicon matrix with titanium inclusions. The obtained material matched the initial components in phase composition.

Chemical Composition and Structure of Interfacial Boundaries in Cr3C2–Ti Powder Hard Alloys after Explosive Compaction and Subsequent Heating

Chemical Composition and Structure of Interfacial Boundaries in Cr3C2–Ti Powder Hard Alloys after Explosive Compaction and Subsequent Heating

Formation of the Structure of Powder Materials Based on Silicon Carbide by Explosive Compaction

The possibility of producing powder composite materials in the SiC–Ti system by explosive compaction without subsequent sintering was studied. It was found that, under these conditions, the densification of SiC and Ti powder mixtures is due to the interparticle displacement and deformation of particles of the carbide phase. It was shown that the main condition for the consolidation is the heating of the initial powder mixture by shock-wave compression to temperatures above 780°C.

Development of Unidirectional Cellular Structure with Multiple Pipe Layers and Characterisation of Its Mechanical Properties.

This study is concerned with the development of a new unidirectional cellular (UniPore) copper structure with multiple concentric pipe layers. The investigated UniPore structures were grouped into three main types, each having a different number of pipes (3, 4, and 5 pipes per transversal cross-section) and different pore arrangements. The specimens were fabricated by explosive compaction to achieve tightly compacted structures with a quasi-constant cross-section along the length of the specimens. The bonding between copper pipes was observed by a metallographic investigation, which showed that the pipes and bars were compressed tightly without voids. However, they were not welded together. The mechanical properties were determined by quasi-static compressive testing, where the typical behaviour for cellular materials was noted. The study showed that porosity significantly influences the mechanical properties, even more so than the arrangement of the pipes.

Fabrication and Mechanical Properties of Rolled Aluminium Unidirectional Cellular Structure

The paper focuses on the fabrication of novel aluminium cellular structures and their metallographic and mechanical characterisation. The aluminium UniPore specimens have been manufactured by rolling a thin aluminium foil with acrylic spacers for the first time. The novel approach allows for the cheaper and faster fabrication of the UniPore specimens and improved welding conditions since a lack of a continuous wavy interface was observed in the previous fabrication process. The rolled assembly was subjected to explosive compaction, which resulted in a unidirectional aluminium cellular structure with longitudinal pores as the result of the explosive welding mechanism. The metallographic analysis confirmed a strong bonding between the foil surfaces. The results of the quasi-static and dynamic compressive tests showed stress–strain behaviour, which is typical for cellular metals. No strain-rate sensitivity could be observed in dynamic testing at moderate loading velocities. The fabrication process and the influencing parameters have been further studied by using the computational simulations, revealing that the foil thickness has a dominant influence on the final specimen geometry.

Explosive Compaction of Ni–Mg Master Alloys

Explosive Compaction of Ni–Mg Master Alloys

Investigation of the Structure and Distribution of Chemical Elements between the Phases of Hard Alloys of the Cr<sub>3</sub>C<sub>2</sub>-Ti System, Obtained at Various Modes of Explosive Compaction

The Article presents the findings of the studies of the microstructure, chemical and phase composition of the Cr3C2-Ti system alloys obtained by the explosion. Scanning electron microscopy, energy dispersive and x-ray diffraction analyses were used. The program Thermo-Calc software was used to calculate the equilibrium phases. The phase composition of the compact was shown to fully correspond to that of the initial powder mixture during explosive pressing in the modes of heating from 300 ̊С to 600 ̊С. When heated above 600 ̊С, the chemical interaction of the initial components begins with the formation of new boundary phases. Meanwhile, there is a change in the sample destruction nature and a significant increase in hardness, which points to the hard alloy consolidation. The increase in the powder mixture heating in shock waves to 1000 ̊С leads to intensive macrochemical interaction of the powder mixture components and to formation of an equilibrium phase composition. The established temperature limits determine the most appropriate parameters of shock-wave loading when producing hard alloys by explosive pressing.

Physical and Mechanical Properties of Cuw20 Composites Synthesized by Explosive Compaction of Bimetallic Nanoparticles

The paper considers the physical and mechanical properties of bimetallic tungsten-copper powders after explosive compaction. This method is used to produce rather dense powder compacts from tungsten-copper nanoparticles. The structural analysis and the analysis of physical and mechanical properties of the obtained composites show that the pressure reduction and an increase in the time of explosive compaction considerably improve the composite hardness and mechanical properties.

Fabrication of Composite Unidirectional Cellular Metals by Using Explosive Compaction

Development of a small and highly efficient heat exchanger is an important issue for energy saving. In this study, the fabrication method of unidirectional (UniPore) composite cellular structure with long and uniform unidirectional cells was investigated to be applied as a heat exchanger. The composite UniPore structure was achieved by the unique fabrication method based on the explosive compaction of a particular arrangement of thin copper and stainless steel pipes. Slightly smaller thin stainless steel pipes filled with paraffin are inserted into small thin copper pipes, which are then arranged inside bigger and thicker outer copper pipes. Such an arrangement of pipes is placed centrally into a cylindrical explosion container and surrounded with explosive. Upon explosive detonation, the pipes are compacted and welded together, which results in a UniPore structure with a stainless steel covered inner surface of unidirectional pores to improve the corrosion resistance and high temperature resistance performance. Two different composite UniPore structures arrangements were studied. The microstructure of the new composite UniPore structure was investigated to confirm good bonding between the components (pipes).

Chemical interaction of components and fine microstructure of interfaces in solid alloys obtained by explosion of Cr3C2-Ti system

Changes in the phase microstructure and composition of the Cr3C2 – Ti system of powdered solid alloys made though explosive compaction were considered at temperatures from 300 to 1200 °C in an oxidizing atmosphere. Measurements were taken with scanning transmission electron microscopy (FEI Versa 3d), energy dispersive X-ray (EDAX Apollo-X), and thermographic analysis (NETZSCH STA 449 F3 Jupiter). The results show the temperature ranges at which the chemical reactions between carbide and metal phases with atmospheric oxygen and with each other occur.

Numerical evaluation of square arrangement of charges in explosive compaction

Explosive Compaction (EC) or Blast Densification (BD) is a common deep soil improvement technique where loose, saturated granular soils are compacted with a huge compression force of the explosion. The design of EC is often conducted using empirical equations and/or preliminary explosion tests. The former is based on limited experiments and provides rough estimation, whereas the latter is costly. Recently, the numerical approach has shown advantages in capturing complex condition of such problems and pose itself as a robust alternative. In this study, a numerical method is evaluated as a design tool to optimize EC. A fixed volume of soil is therefore considered to be densified with a specific amount of explosive charges. All charges are located at the same depth and are horizontally placed using square pattern arrangement. An estimation of EC design is achieved using an empirical equation. Subsequently, numerous numerical simulations are performed to achieve the efficient design in terms of the optimum equivalent weight of TNT and arrangement distance. The induced pressure in the soil, as well as the surface displacement, is used as measures of efficiency. Results show that the empirical equations provide a rough or inaccurate design while by use of the numerical approach this range is narrowed. Also, by reaching the optimum distance a more uniform compaction is achieved which reduces the unwanted surface heaving caused by cumulative upward waves. A compaction variation of about 30% was observed due to settlement variation, whereas the compaction variation due to change in explosive weight was approximately 80%. By applying the detonation delay the surface heaving is reduced up to 50%, which improves the EC efficiency.

Structural Features of Pseudoalloys Formed in the Course of Explosive Compaction of Ni–Ag and Fe–Pb Bimetallic Nanoparticles

Structural Features of Pseudoalloys Formed in the Course of Explosive Compaction of Ni–Ag and Fe–Pb Bimetallic Nanoparticles

Synthesis of Ultrafine Fe-W-Al-Ti-Ni-C-B Powders by Mechanical Alloying

The goal of the presented research was syntheses of the ultrafine and nanopowder blends by Mechanical Alloying from Fe-W-Al-Ti-Ni-B-C compositions for further application as a precursor for fabrication bulk High-Entropy Alloy (HEA) by explosive compaction technology. The presented paper describes the preliminary investigations of mechanical alloying of Fe-W-Al-Ti-Ni-B-C powders. Laboratory vibrating sieve equipment was used for sorting the initial powders for the reduction of particle size. For the experiments were used powders of Fe-W-Al-Ti-Ni-B-C system consisting of five major metallic and two minor non-metallic B and C elements were used for mechanical alloying. The crystalline coarse Aluminum, Titanium, Carbon and Nickel, fine-grained iron and tungsten and amorphous Boron powders were used as initial components. The Fe, W, Al, Ti and Ni powders were preliminary checked by “Explorer 5000 XRF” by Skyray instrument and verified. Based on the literature review, theoretical investigation and phase diagrams for mechanical alloying were selected two compositions with the following molar ratio: Fe20W15Al15Ti20Ni20B5C5; Fe25W25Al10Ti15Ni15B5C5; The mechanical alloying was realized on the high energy ball mill with zirconium oxide jars and balls. The ball to powder mass ratio was 10:1, the rotation speed was 500rpm. The process was carried out in dry conditions. The time of mechanical alloying was 5h, 10h and 14 h. The powders were prepared for preliminary analyses and assessment of particle size. The SEM and optical microscopy results of mechanical alloying are presented in the paper.