The fragmentation of a drop of liquid (water, alcohol, glycerin) under the action of an air shock wave with a pressure of 0.2 and 3.2 atmg is studied experimentally and theoretically. The experiments are carried out using an air shock tube, and the liquid drop diameter is approximately 0.6 and 2 mm. The process is studied using high-speed video recording. Dispersed liquid particles from ≈5 μm in size are detected, liquid particle size distributions are plotted, and the particle velocities are determined. The experimental results are compared with the results of computational–theoretical estimation.

The results of four experiments on studying preliminarily statically compressed gaseous helium and deuterium during their subsequent compression in explosive spherical cascade structures providing quasi-isentropic gas compression are presented. For helium, the following parameters were achieved: in one experiment, the compression pressure is P mean ≈ 4.9 TPa at a density ρ max ≈ 6.4 g/cm 3 and the compression ratio is δ = ρ/ρ 0 ≈ 320; in another experiment, P mean ≈ 10.9 TPa, ρ max ≈ 10.3 g/cm 3 , and δ ≈ 470. For deuterium, these parameters are P mean ≈ 3.4 TPa, ρ max ≈ 6.0 g/cm 3 , and δ ≈ 162 in one experiment and P mean ≈ 13.3 TPa, ρ max ≈ 11.4 g/cm 3 , and δ ≈ 520 in another experiment. The gas density was determined by an X-ray method using the position of the boundaries of the steel shells compressing a gas. The experiments are simulated with a one-dimensional gasdynamic software package, in which the Kopyshev–Khrustalev equations of state are used for the gases under study. The pressures are determined using calculations, in which the dynamics of gas compression is satisfactorily simulated for the entire set of experiments.

This paper presents the results of an experimental study of particle ejection into low (0.05 atm) vacuum from a narrow (0.2–0.8 mm) rough ( Rz = 20–50 μm) surface of a lead sample subjected to a shock wave of intensity about 17 and 34 GPa. The ejecta was recorded with a video camera in the microscopic mode with short laser irradiation. Due to the small optical thickness of the ejecta, particle spectra at approximately 80% of the ejecta height measured from the front of the ejecta were obtained. It was found that when lead is in the solid state (17 GPa), jets consisting of a lot of particles are ejected from the rough surface; when the lead is in the liquid state (34 GPa), a lot of thin (from 7 μ m) microcumulative jets are ejected from the metal surface, and with time they break up into particles.

Experiments were performed to study the spherical compression of deuterium and helium to pressures of ≈3000 GPa in a quasi-isentropic regime. The process was recorded by a multiframe radiographic system which produces up to nine x-ray images of a cavity with gas at different times in one experiment. X-ray images show that explosive devices provide a nearly spherically symmetric shape of the cavity with gas up to the maximum compression of the gas. The experimental data are in good agreement with the results of calculations using the equations of state of the gases studied. From the results of these calculations, the parameters of the region of the compressed gas states obtained in the experiments were determined: for deuterium, a density of 5.5 g/cm3 and a pressure of 3.6 TPa; for helium, a density of 4.7 g/cm3 and a pressure of 2.4 TPa.

This paper presents the results of numerical simulation of Zaretskii’s experiments on loading of natural uranium in the phase-transition region at temperatures of 27–862°C. Simulation of these experiments is of interest because of the observed features of spall fracture of uranium in the phase-transition region. Spall fracture and compaction was simulated using the DGC-L model of the dynamics of growth and compaction in a liquid medium, which takes into account the effect of strength properties, pressure, surface tension, viscosity, and inertial forces on the growth and collapse of pores. Calculations were carried out according to the UP program— a Lagrangian method for calculating deformation problems of continuum mechanics in a onedimensional approximation.

Single-wall carbon nanotubes (SWNTs) promise wide applications in many technical fields. As a result purified SWNT material is sold now on the West market at more than $1000 per 1 gram. Thus developing an effective technology for SWNTs production rises to a very important scientific problem. The perspectives of three existing methods providing raw material in the technology of SWNT production have been analyzed. They are i) pulsed laser evaporation of graphite/metal composites, ii) evaporation of graphite electrodes with metal content in the arc discharge process, and iii) catalytic decomposition of the mixture of CO and metal carbonyl catalyst precursor. The observed dynamics of SWNT market points to replacing the laser method of SWNTs production by the arc process. The conclusion has been made that the technology based on the arc process will be the major one for the fabrication of purified SWNTs at least for the next five years. A reliable estimation of a low price limit of SWNTs was derived from a comparison of two technologies based on the arc discharge process: the first one is the production of SWNTs and the second one is the production of a fullerene mixture С60 + С70. The main conclusion was made that the price of purified SWNTs should always be more by 2-3 times the price of fullerene mixture. The parameters of a lab-scale technology for the production of purified SWNTs are listed. A large-scale application of the developed technology is expected to reduce the price of purified SWNTs by approximately ten times. The methods now employed for the characterization of products containing SWNTs are briefly observed. It is concluded that electron microscopy, thermogravimetric analysis, absorption and Raman spectroscopy, measurement of the specific surface aria, optical microscopy – each in separation is not enough for extensive characterization of a sample containing SWNTs, and all these methods should be used together.

A model for the spall fracture and compaction of a damaged material based on a description of the motion of a single pore is proposed. The model takes into account the strength properties, the effect of pressure, surface tension, and viscosity of materials and inertial forces. Equations describing the dynamics of growth and collapse of pores are presented. The proposed model can be used to calculate the spall fracture and compaction of liquids and metals in both solid and liquid (molten) states.

Burning rates of hydrazine borane at a pressure of 20–100 atm have been measured. Spectroscopic and electron microscopic studies have demonstrated that the condensed combustion product is a fine powder of boron nitride. Thermal decomposition of hydrazine borane has been studied. The obtained kinetic data and physicochemical properties of the materials and the foam combustion model have been used to calculate the pressure dependence of the burning rate of hydrazine borane, which agrees with the experimental one. The obtained degree of conversion of the material to boron nitride indicates the possibility of using hydrazine borane and similar compounds in high-performance systems.

The quasi-isentropic compressibilities of deuterium and helium plasmas are measured in the pressure range 1500–5000 GPa at densities up to 8 g/cm 3 using spherical experimental devices and an X-ray complex consisting of three betatrons and a multichannel optoelectronic system for taking X-ray images. The experimental results demonstrate the possibilities of high-energy-density experimental physics to reproduce the extreme states of substance typical of the Universe under laboratory conditions using the energy of traditional condensed explosives.

The possibilities of measuring complex Pylenie, which is intended for studying the parameters of the particles ejected from the free surface of a shock-loaded material and was created at the Institute of Experimental Gas Dynamics and Detonation Physics RFNC-VNIIEF, are demonstrated. The operation of the complex is based on the following three methods, which are based on different physical principles and supplement each other: laser-optical method (macro- and microfilming), pulsed X-ray method, and piezoelectric pressure sensors. This complex is used to study the ejection of particles from the free surface of lead samples when a shock wave with a pressure of 7, 16, and 23 GPa at its front reaches this surface. The effect of the surface roughness and the pressure amplitude at the shock wave front on the quantitative characteristics of the process is shown. The calculation-theoretical simulation is performed by two-dimensional numerical calculations of gasdynamic flows, and the calculation results are used to estimate the “ejecta” characteristics in terms of the developed phenomenological model of the process.

Рентгенографическим способом изучена плотность дислокаций в сохраненных образцах меди и тантала с различным размером зерна после высокоскоростного нагружения ударными и квазиизэнтропическими волнами амплитудой 20–100 ГПа. Скорость деформации составляла 106 109 с-1. Подтверждено, что высокоскоростное нагружение генерирует в меди бoльшую плотность дислокаций, чем квазистатическая деформация, а ударноволновое нагружение – чем квазиизэнтропическое. В образцах меди наблюдается максимум в области давления Р = 30–40 ГПа (что соответствует деформации 0.25–0.3), за которым следует падение. Такое падение объясняется отжигом дефектов при адиабатическом нагреве в результате сжатия. Отмечается увеличение в меди с уменьшением температуры образца. В тантале с увеличением давления в ударной волне зафиксирован монотонный рост плотности дислокаций. Влияния разогрева на отжиг дефектов в тантале даже при максимальном давлении не обнаружено. Как в меди, так и в тантале наблюдается рост с увеличением среднего размера зерна.

The dislocation density ρ in copper and tantalum specimens with various grain size that remained after high-strain-rate loading by shock and quasi-isentropic waves with amplitudes of 20–100 GPa has been studied using X-ray diffraction analysis. The deformation rate was 10 6 –10 9 s −1 . It has been confirmed that high-strain-rate loading generates a higher dislocation density in copper than does quasi-static deformation, as well as that the shock-wave loading generates a higher dislocation density than quasi-isentropic loading. In copper, a maximum of ρ has been found in the pressure range of P = 30–40 GPa, which corresponds to a degree of deformation of 0.25–0.3, followed by a drop. This drop in ρ is explained by the partial annealing of defects during adiabatic heating resulting from compression. An increase in ρ in copper with decreasing specimen temperature has been noted. In tantalum, an increase in the shock wave pressure leads to a monotonic increase in the dislocation density. No effect of heating on the annealing of defects in tantalum has been found, even under the maximum pressure. As the average grain size increases, ρ increases in both copper and tantalum.

In the work, we analyzed the Hall–Petch law relating yield strength and microhardness to grain size in metals. The material under study was copper with a grain size of 20 and 110 mm annealed at an initial dislocation density of ~10 8 cm –2. Unlike the available data on Hall–Petch dependences, the coefficients in the equations relating the yield strength to the grain size were taken for a fixed dislocation density. Copper specimens with a grain size of 20 and 110 mm and dislocation density of 9.7 × 10 10, 3.6 × 10 10, and 1.7 × 10 10 cm –2 (six specimen types in total) were subjected to Hopkinson split bar tests at a strain rate of ~10 3 s –1 and normal temperature; the results of the experiment were analyzed. Photos of the microstructure of all specimen types were taken and their microhardness was measured. The copper specimens with different dislocation densities were obtained by impact loading at an amplitude of ~11 GPa with subsequent annealing. This procedure made it possible to obtain different dislocation densities in the specimens with no change of their grain size. The results of the study demonstrate that varying the grain size increases the yield strength by a mere ~7 %, while its further increase depends on the dislocation density.

The structure of copper formed after high-rate loading up to pressures of 20–80 GPa with a strain rate of 10 5 –10 9 sec −1 is considered. In situations with pressures above 20 GPa and strain rates above 10 6 sec −1 , the deformation twins are grouped into packets, which are seen in an optical microscope as parallel bands of localized strains inside individual grains. The number of bands in the structure increases with increasing grain size and strain rate, with decreasing sample temperature, and with increasing period of sample loading. The characteristic time of formation of twin bands in copper is estimated as 0.3 µsec.

The nucleation and evolution of damage in annealed coarsely crystalline M1-type copper subjected to fast loading to a pressure P ∼ 32 GPa, followed by the action of tensile stresses σ p with an intensity of ≈−2.0 GPa for a time t ≈ 0.3–1.5 μs, have been investigated numerically and experimentally. It has been shown that, at a specific combination of amplitude-time characteristics of the tensile stress pulse, damage localization in some cases at t < 1 μs has been observed in zones (∼10–14 mm in size) alternating with “dead” zones (∼3–5 mm in size) containing no visible damages. Pores are connected by “yield streamlets.” The existing multistage models of fracture kinetics have neither explained nor predicted the formation of a “band” damage structure or the presence of “yield streamlets” in specimens.

It is shown that preloading of fine-grained copper with a the grain size of 0.5 m by a shock wave of intensity ≈25–50 GPa does not lead to changes in its internal microstructure and mechanical properties, and the dislocation density increases only slightly from 1.8 · 1011 cms-2 in the initial state to (3.1–3.6) · 1011 cms-2 after shockwave loading. An increase in shock wave intensity to pressures > 55 GPa leads to a decrease in the dislocation density to 2.5 · 109 cms-2, an increase in the grain size to ≈19 fum, the occurrence of microtwins inside the grains, and a reduction in the mechanical properties of fine-grained copper to the level of coarse-crystalline copper.