Particle ejection from the shocked free surface of metals and diagnostic methods for these particles

Огородников, В. А.; Ivanov, A. G.; Михайлов, А. Л.; Kryukov, N. I.; Tolochko, A. P.; Golubev, Valery A

doi:10.1007/bf02672705

Cited by 45 publications

(14 citation statements)

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“…The decreased density of the sample material observed in the X-ray photographs in the regions of convexities ( Fig. 2b and c) is apparently caused by particle ejection (dusting) due to the microcumulation of particles resulting from the presence of the initial microrelief (in the experiments, the surface roughness was R z 20) [3]. Evidence for this is that in the regions located under the initial convexities, the velocity of the FS segments is 3.4 km/sec, i.e., it is somewhat higher than the calculated velocity of the continuous material of 3.2 km/sec under the given loading conditions.…”

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confidence: 93%

“…Much weaker influence on the calculated jet parameters is exerted by the shear fracture parameters, effective viscosity, and pressure, which determine the rate of pore formation in the presence of tensile stresses. We note that the main parameters of the kinetic fracture model were chosen from a large series of hydrodynamic experiments (see [3,4,9,10], etc.). Figure 4 also gives experimental data obtained by processing X-ray photographs (see Fig.…”

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confidence: 99%

“…The normal incidence of a shock wave (SW) on the free surface (FS) of a condensed material sample without macroscopic features can lead to a number of effects due to the deviation of the SW velocity from the doubling law, velocity dispersion, particle ejection (dusting) from the FS [1][2][3]. However, the FS can have macroscopic features in the form of defects, artificial conical or hemispherical cavities and attached masses or a certain profile of, for example, a sinusoidal shape, whose amplitude a and wavelength λ far exceed the parameters characteristic of the FS microrelief.…”

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Modeling jet flows caused by the incidence of a shock wave on a profiled free surface

Огородников

Михайлов

Romanov

et al. 2007

J Appl Mech Tech Phys

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The problem of the incidence of a shock wave with a front-pressure amplitude of about 30 GPa at the profiled free surface of an aluminum sample is studied. It is shown that in the case of large perturbations (amplitude 1 mm and wavelength 10 mm), jet flows occur on the free surface. The data obtained are described using a kinetic fracture model that takes into account the damage initiation and growth in the material due to tensile stress and shear strain.The normal incidence of a shock wave (SW) on the free surface (FS) of a condensed material sample without macroscopic features can lead to a number of effects due to the deviation of the SW velocity from the doubling law, velocity dispersion, particle ejection (dusting) from the FS [1-3]. However, the FS can have macroscopic features in the form of defects, artificial conical or hemispherical cavities and attached masses or a certain profile of, for example, a sinusoidal shape, whose amplitude a and wavelength λ far exceed the parameters characteristic of the FS microrelief. The occurrence of microroughness is due to the surface finish (a R z and λ R z , where R z is the height of the surface microroughness). The incidence of a SW on a FS with defects, cavities, and attached masses is accompanied by ejection of cumulative flows of particles [4][5][6], which complicates the numerical modeling and prediction of the fragmentation and dispersion of structural materials under shock-wave loading. The processes occurring on a profiled FS upon incidence of a SW, especially for λ a R z , have been studied inadequately. The present paper reports new experimental and calculation results from studies of the generation and propagation of perturbations caused by the incidence of a SW of intensity 30 GPa on the FS of AMts aluminum samples of sinusoidal shape with an initial amplitude 2a = 1 mm and a wavelength λ = 10 mm. A diagram of the experiments is given in Fig. 1.A cylindrical charge of a high explosive (HE) 120 mm in diameter and 60 mm high was initiated by a plane SW generator, which provided for a time difference for SW arrival at the sample of not more than 50 nsec. The FS of the sample in the form of a 130 × 130 mm plate 10 mm thick had cavities of sinusoidal shape, which allowed the use of a soft x-ray radiographic technique. Figure 2 gives X-ray photographs obtained at various times in the experiments (the dashed curves are drawn over the convexities of the sample relief). An analysis of the X-ray photographs shows that the displacements of the FS of the sample by 5 and 12 mm relative to the initial position, which correspond to the times in the X-ray photographs t γ = 29 and 31 µsec from the moment of HE initiation, leading jet flows are formed in the sample regions located under the initial concavities, and in the region of the initial convexities, there is deceleration of the sample material of lower density. The decreased density of the sample material observed in the X-ray photographs in the regions of convexities (Fig. 2b and c) is apparently caused by particl...

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Modeling jet flows caused by the incidence of a shock wave on a profiled free surface

Огородников

Михайлов

Romanov

et al. 2007

J Appl Mech Tech Phys

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“…Collapse of the contact gap gives rise to three-dimensional flow near the interface, resulting in air entrainment in micropores and viscoplastic heating of the inner pore surface [11]. We also note that interface is heated by deceleration of the microjets [12] spreading form the surface of the upper plate. Near the interface all these mechanisms produce considerable thermal inhomogeneities, whose temperature exceeds the equilibrium temperature of the solid material.…”

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Light emission from polytetrafluoroethylene in a shock of intensity 51 GPa

Bordzilovskii

Karakhanov

2007

Combust Explos Shock Waves

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The location of light emission sources in shocked polytetrafluoroethylene is analyzed. It is found that the state of the plate-sample interface has a great effect on the emission profile. Time-correlated pressure and emission profiles and electrical resistance profiles of polytetrafluoroethylene sample were recorded, which allowed the times of the occurrence and the duration of the emission signals to be determined. The emission pulse profile was calculated under some simplifying assumptions on the emittance of the shock-compressed part of the sample. It is shown that, ahead of the shock front, a zone arises in which the resistance of polytetrafluoroethylene decreases by nine to ten orders of magnitude, depending on the state of the interface. It is suggested that a photoconductivity wave induced by the light occurs ahead of the shock front.

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“…The strong shock wave released from the metalvacuum/gas interface may eject a great number of metal particles. [1][2][3][4][5][6] Most of these particles are of micrometer-scale in size. This phenomenon of ejecta, or microjetting, was first observed by Kormer et al in a plane impact experiment in the 1950s.…”

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confidence: 99%

Reconstruction and interpretation of photon Doppler velocimetry spectrum for ejecta particles from shock-loaded sample in vacuum

Shi,

Ma,

Dang

et al. 2020

Preprint

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The photon Doppler velocimetry (PDV) spectrum is investigated in an attempt to reveal the particle parameters of ejecta from shock-loaded samples in a vacuum. A GPU-accelerated Monte-Carlo algorithm, which considers the multiplescattering effects of light, is applied to reconstruct the light field of the ejecta and simulate the corresponding PDV spectrum. The influence of the velocity profile, total area mass, and particle size of the ejecta on the simulated spectra is discussed qualitatively. To facilitate a quantitative discussion, a novel theoretical optical model is proposed in which the single-scattering assumption is applied. With this model, the relationships between the particle parameters of ejecta and the peak information of the PDV spectrum are derived, enabling direct extraction of the particle parameters from the PDV spectrum. The values of the ejecta parameters estimated from the experimental spectrum are in good agreement with those measured by a piezoelectric probe.

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Particle ejection from the shocked free surface of metals and diagnostic methods for these particles

Cited by 45 publications

References 2 publications

Modeling jet flows caused by the incidence of a shock wave on a profiled free surface

Modeling jet flows caused by the incidence of a shock wave on a profiled free surface

Light emission from polytetrafluoroethylene in a shock of intensity 51 GPa

Reconstruction and interpretation of photon Doppler velocimetry spectrum for ejecta particles from shock-loaded sample in vacuum

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