B. V. Litvinov

Metallographic investigation of the shock-wave propagation in ball specimens of a 12Kh18N10T steel upon symmetric and asymmetric quasi-spherical explosive loading

Structural changes in two ball-shaped specimens of a 12Kh18N10T steel that were subjected to symmetric and asymmetric quasi-spherical explosive loading have been investigated by metallography, electron microscopy, and microhardness measurements. Propagation and interaction of converging shock waves, structural transformations in Al’tshuler beams, and the phenomenon of cumulation in the center of the specimens have been analyzed.

Structural transformations and deformation localization effects during nonuniform explosive loading of metallic balls

Continuous balls 60 mm in diameter made from steels, brass, and duralumin are subjected to the explosion of a spherical charge initiated from the surface at several points. The microstructural studies of the loaded balls demonstrate that the macro-and microstructural changes in them and their fracture correlate with the geometric conditions of the shock-wave action. Cracks form at the sites of shock-wave intersection according to the loading geometry and the initial fibrous structure of the material. Localized-flow regions are observed near cracks, and the appearance of these regions precedes crack nucleation. In the brass ball, radial cracks coalesce with its central cavity forming in a solid state. The possibility of cumulation for the same loading schemes is shown to depend on the material.

Electron-microscopic investigation of high-strain-rate deformation produced by shock waves in the pearlitic structure of the grade 40 Kh steel

Upon high-strain-rate deformation under the action of shock waves, cementite plates in thin-lamel-lar pearlite are deformed and/or destroyed. “Fragments” of broken plates change their position relative to each other. The local (in a volume of ∼2 μm) shear, tensile, and torsional deformations were determined from regular displacements and rotations of fragments found upon electron-microscopic investigation. The local strain rates of deformations were also estimated.

Structural changes and energy cumulation in an iron-nickel alloy upon quasi-spherical explosive loading

Ball samples of an iron-nickel alloy one of which was in an austenitic state and the other was in a martensitic-austenitic state were subjected to quasi-spherical shock-wave loading under identical conditions. At the central part of the originally austenitic sample, the initial stages of the formation of internal cavity, melting, and recrystallization were observed. Neither cavity nor melting and recrystallization were observed in the martensite-austenite sample. In this sample, an almost complete transformation of martensite into austenite took place under the action of shock waves. The estimates of pressure were performed from the residual-temperature values taken from structural studies. The pressure at the center of the first sample reached 180 GPa and more, while the pressure in the second sample was known to be for sure lower than 100 GPa but higher than 20 GPa. The conclusion is made that under given conditions of experiment the transformation of martensite into austenite occurring with energy absorption weakens the effect of energy cumulation.

Effects of the localization of deformations and mass transfer in converging shock waves

Effects of shock wave interaction and the related phenomena of the localization of plastic deformation, destruction, and mass transfer in metal ball samples subjected to explosive loading at pressures of 36 to 150 GPa are studied. A correlation between the macro- and microstructural changes and the geometrical conditions of loading according to various schemes is found. It is shown that the mass transfer effects are of hydrodynamic origin. The depth penetration of the material was 3.2 mm in narrow channels and 0.3 mm in solid material.

A study of the effects of mass transfer under quasi-spherical loading of a composite spherical sample

Metallography and electron probe microanalysis were used to study the structure of a composite ball, 60 mm in diameter, subjected to quasi-spherical shock-wave loading. The sample consisted of spherical steel and brass shells and a brass cylinder at the center. Converging shock waves were generated by a spherical HE charge, which was initiated at several points uniformly distributed over its external surface. The pressures at the surface and center of the sample were ∼40 and ∼100 GPa, respectively. Brass and steel were observed to penetrate into the narrow channels of the joints between the halves of the shells and into the compact material. The depths of penetration into the joints and compact material were 3.2 and 0.3 mm, respectively. Mass transfer occurred along the radius from the surface to the center of the sample and in the opposite direction. The mass transfer effects revealed are of hydrodynamic nature.

Non-one-dimensional and quasi-spherical loading of metal balls by shock-waves having up to 3 Mbar pressure, with the investigation of the preserved samples

Solid steel, brass and duralumin balls with 60 and 40 mm in diameter were exposed to explosion of spherical explosive charge 10 and 20 mm thick respectively. The explosion was initiated on the charge surface simultaneously in 2, 4 and 12 points, distributed uniformly over the sphere. To preserve the balls, massive case was used in test. In the diametral plane of section there were found either cracks, distributing mainly along the shock-waves collision lines, or the cavity. In most cases, the cavity was surrounded by the metal layer, having dendritic structure. In balls in case of explosion initiation in 12 points the metal motion was quasi-spherical (one-dimensional), in case of initiation in 2 points—two-dimensional and in 4 points—three-dimensional. The pressure evaluations, base on the convergent motion, as well as on the value of the residual temperature on the boundary of dendrits zone, showed, that inside crystallization zone the pressure exceede 2 Mbar.

Structural Changes and Energy Cumulation in an Iron‐Nickel Alloy upon Quasi‐Spherical Explosive Loading

Ball samples of the Fe‐31.8 wt % Ni‐0.05 wt % C iron‐nickel alloy one of which was in an austenitic state and the other was in a martensitic‐austenitic state were subjected to quasi‐spherical shock‐wave loading under identical conditions. A comparison of the results obtained under the same loading conditions on the samples of the same alloy in two different initial states made it possible to establish the influence of the initial phase composition on the structural changes and on the effect of energy cumulation.

Periodic character of the phase transformation in steel accompanying reflection of converging shock waves from the center of focusing

Special conditions in an experiment on the loading of low-carbon steel by converging shock waves made it possible to obtain residual microstructural changes of a periodic character, with a period of the order of 0.2 mm, which are associated with a phase transformation caused by waves reflected from the center of focusing. A model explaining the periodicity of the microstructure and making it possible to predict the behavior of materials under similar conditions is proposed.