The results are presented with regard to experimental studies of dynamic strength characteristics of samples made of 12Cr18Ni10Ti steel powder. They were obtained through selective laser melting with various parameters of a technological process at shock-wave compression up to pressures of ~7 GPa. Critical parameters of a process, in addition to powder characteristics, include laser operating conditions: a laser spot diameter, laser power, a laser beam scanning velocity, as well as a powder layer thickness, protective atmosphere, etc. It has been demonstrated that an increase in the scan laser power and a decrease in a powder layer thickness bring about a decrease in a number of internal defects in initial structures of samples. The results are given, which compare strength characteristics of these steels with properties of steel produced by a traditional technique of hot rolling. Shock-wave experiments were carried out using a light gas gun-type facility, which makes it possible to accelerate flat impactors to speeds of ~700 m/s; internal wave processes in samples were reproduced when recording a rate of movement of the sample's free surface via a PDV laser interferometer; a degree of spall fracture was determined by the help of a metallographic analysis of samples recovered in tests. It has been showed that steel samples made through a selective laser melting technique have high spall strength and a lower degree of damage compared to hot-rolled steel under the same conditions of high-speed shock loading. According to the results of the metallographic studies, the presence of internal defects in initial structures of samples associated with a choice of operating conditions of a manufacturing process does not affect a degree of their spall damage. At the same time, a wave pattern of shock wave propagation differs significantly for samples with and without defects.

Приведены результаты цикла исследований по определению динамических прочностных характеристик образцов, изготовленных по технологии селективного лазерного плавления порошков на основе стали 12Х18Н10Т, и их сравнение со свойствами стали 12Х18Н10Т, полученной по традиционной технологии горячекатаного проката, при ударно-волновом нагружении в диапазоне давлений сжатия 3 ÷ 7 ГПа. Показано, что образцы из стали, изготовленные по технологии селективного лазерного плавления, имеют большую сопротивляемость кратковременному растяжению, возникающему в результате взаимодействия встречных волн разгрузки, по сравнению с горячекатаной сталью 12Х18Н10Т. This paper presents the results of a series of studies to determine the dynamic strength characteristics of samples manufactured using selective laser melting technology of 12Kh18N10T steel powders and compares them with the properties of 12Kh18N10T steel obtained by traditional hot rolling under shock-wave loading in a compression pressure range of 3–7 GPa. It is shown that the steel samples manufactured using selective laser melting technology have greater resistance to short-term tension resulting from the interaction of counter-current unloading waves compared to the hot-rolled 12Kh18N10T steel.

Experiments on shock-wave loading and spall fracture of tungsten alloys with nickel and iron have been carried out. The alloys have been shown to fracture along the iron–nickel bonding and not to involve tungsten particles. One-dimensional defects, supposedly of twin origin, have been detected in the tungsten alloy (95 wt

The quantitative characteristics of the products of dispersion and the cascade of dissipative structures arising in metals under shock-wave loading are determined. The fractal dimension df and the Hurst exponent H (standardized range of dissipative structures) of the cascade of hydrodynamic modes, the roughness of the fracture surface, and the dispersion products are determined. Destructive processes occurring in loaded samples are numerically simulated using the Lagrangian technique TIM 3D [1, 2]. It is shown that a cascade of dissipative structures at different scale–temporal levels (nanolevel, mesolevel I, mesolevel II, and macrolevel) is a fractal cluster, and it is a percolation cluster on the threshold of a macrofracture, when there is connectivity in the system of dissipative structures [1, 2]. The self-similarity of dissipative structures is due to the self-organization in nonequilibrium systems; and the dynamic fracture and dispersion processes are examples of scale invariance. The scale invariance of the dissipative structures indicates the nonequilibrium system has reached a critical state.

Based on the results of experiments carried out using a gas gun, data are obtained on the fracture of a VNZh-90 alloy (90% W-7% Ni-3% Fe) under a shock wave load in a pressure range of 2.5–4.0 GPa. Spall strength, which is a function of the degree of fracture and varies in a range of 1.00 to 1.25 GPa, and the nature of fracture are determined. Metallographic analysis is used to determine the damage parameter values. It is revealed that, under these conditions, the fracture comprises several stages, occurs in a (Ni-Fe) bond, and the tungsten particles do not fracture. It is shown that experimental results are in good agreement with the results of numerical calculations.

In this paper, we aimed to establish the similarity of dispersion of various metals at high-intensity loading. Characteristics of the dispersing products and the cascade of arising dissipative structures (the inner surface roughness of the destruction centers, the cascade of the slip bands of the crystal lattice, the cascade of destruction centers, and the roughness of the destruction surface) were quantified on the basis of fractal geometry using the interactive image analysis system (IIAS) package. We numerically simulated destruction in loaded samples using the TIM 3D Lagrangian technique.

The structure of bismuth samples after shock-wave loading at pressures of 0.7–2.4 and 22–32 GPa was studied. Before loading, the samples were at room temperature or heated to 230–240°C. Loading by a pressure of 1.5–2 GPa at an initial temperature of 233–240°C led to a structural change in bismuth, indicating melting of the sample in the shock wave. The time of shock-wave loading was ≈0.7 μ s.

Depending on the geometry and amplitude–time characteristics of external impact, there may be accumulation of shock-wave energy in the samples, which reduces the time during which the structural materials retain their functional properties. Dispersion from the free metal surface of samples without and with pre-applied perturbations in the form of pyramids is considered. Under certain amplitude–time characteristics of external impact, dispersion from the tips of the pyramids occurs. The quantitative characteristics of dynamic destructive processes at different amplitude–time characteristics of external impact are determined for the purpose of introducing them into two- and three-dimensional codes to predict the behavior of metals under extreme conditions.

This work presents the results of experiments on the compression of a spherical copper shell loaded by the detonation of a plastic explosive layer. A U-70 accelerator is used for radiographic recording of the convergence of the shell to the center, and metallographic analysis of the copper shell preserved after the experiment is performed. The results of multiframe proton radiography of the convergence of the inner boundary of the copper shell to the center are compared with the results of numerical simulations.

Variants of experiments in which prefractured samples (in tests on spall fracture) are further compacted by shock reloading are considered on the example of aluminum. The results of the experimental-computational study and metallographic analysis of recovered samples in the tests are used to determine the pressure of compacting aluminum, which is ≈2 GPa.

The paper presents results obtained by numerical simulation of brittle spall fracture of Armco-80 iron under conditions of high-velocity deformation in one-dimensional counter waves of expansion. The spall fracture process is described by the two-stage kinetic model (NAG). The paper authors analyze peculiarities of kinetics of the damage accumulation process in the destruction zone. For comparison with the calculated results, the experimental information on motion velocity W(t) of the free boundary of a loaded Armco-80 sample was used.

The results of application of kinetic two-stage microstatistical model with internal values (of the NAG type) to describe the spall fracture of metals are presented. The model describes adequately experimental data for natural uranium, copper, aluminum and some other metals. Some peculiarities of transient process of spall fracture are under analysis.

Numerical simulation results of the elastic precursor relaxation and evolution of wave fronts are presented in consideration of relaxation processes in Armco iron. The dislocation dynamics of Gilman is applied to problem of elasto-plastic flow. Numerical calculation was carried out for case of plate impact. Thicknesses of impactor and target and impact velocity were varied. Chosen parameters of the model allowed to obtain sufficiently good description of experimental results W. Arnold. In experiments free surface velocity of the sample-target was measured with VISAR system. Calculations shown that using of dislocation models of deformation allows to obtain realistic description of material behaviour in shock wave, as compared, for example, with the model of ideal elasto-plastic medium. In turn, this gives an opportunity to obtain more qualitative numerical simulation results of the spallation and phase transition in Armco iron.

This communication presents the results of numerical modelling of viscous destruction of copper under conditions of high-rate strain in one-dimensional counter-propagating expansion waves resulting from collision and loading with a normal plane detonation wave. Destruction through spalling is approximated by a two-stage microstatistical kinetic model (NAG model). The kinetics of damage accumulation is analyzed, and the results of model calculations are compared with experiment.

Results are presented from a theoretical analysis of the conditions of cleavage fracture of plutonium and its alloy with 1.6 wt. % gallium under shock loading. Experimental data obtained earlier are used to determine the critical tensile stresses corresponding to the initial stage of macroscopic cleavage fracture of specimens. The elastoplastic properties of the materials and polymorphic transformations that occur in the alloy at normal and high (315°C) temperatures were taken into account in the calculations.

We present the results of numerical analyses of the conditions of cleavage fracture of beryllium under impact loading performed for the cases of a fixed value of cleavage strength and of the kinetic description of fracture processes according to the model of initiation and growth of damage. It is shown that the results obtained by using fixed values of the cleavage strength of beryllium agree fairly well with the experimental data.

The two-stage microstatistic kinetic model (NAG) allows experimental observations of armco-iron spallation to be adequately described. This makes it possible to use the results of numerical modeling for analyzing the damage kinetics in the destruction zone and its correlation with the experimental data. Results of this analysis are discussed.