Численное моделирование поведения карбидов при высокоэнергетическом воздействии

The results of research on modeling thermodynamic parameters of shock-wave loading of carbides with different stoichiometric ratios are presented. The carbides are considered as a mixture of carbon with the corresponding component. The calculations of pressure, compression and temperature values under shock-wave loading for solid and porous carbides in the range of pressure values above 3 GPa are performed. The model calculations are compared with the known experimental results on the shock-wave loading of carbides with different porosity values. The possibility of modeling the behavior according to the proposed method for carbides for which there are no experimental data at high dynamic loads is shown.

STUDY OF STEEL BARRIER SURFACE AFTER HIGH-SPEED EXPOSURE OF W AND TIC POWDERS

The surface layer of an obstacle made of U8 steel is investigated after high-speed exposure to a flow of powder particles. After analyzing the frames of high-speed photography, the average velocities of movement of particles of tungsten and titanium carbide powders were determined. It is shown that the shock-wave loading of the barrier material and the effect of particles accelerated by the explosion energy provide a change in the physical and mechanical properties of the surface and the volume of the steel barrier material.

SHOCK-WAVE INITIATION OF SYNTHESIS IN NI-AL POWDER MIXTURE INSIDE TITANIUM MATRIX

This study presents the results of studying the effect of shock-wave loading on the initiation of synthesis in Ni-Al powder mixture inside titanium matrix. X-ray phase analysis (XRD) and measurement of the microhardness of the intermetallic layer showed that this layer consists of a monophase product NiAl, which is formed directly during explosive loading at a given impact velocity of the plate. Thus, the use of shock-wave loading made it possible to obtain a layered material with a strengthening intermetallic layer. The results obtained are promising for the development of new structural materials with special performance properties.

Modeling of shock-wave loading of carbides as mixtures of components

The results of numerical experiments on the modeling of shock wave loading of solid and porous carbides with various stoichiometric compositions are presented. The model is based on the assumption that all the components of the mixture, including gas, have similar pressure, velocity and temperature. The model allows describing the behavior of porous materials and mixes in a wide range of porosity and pressures with precision of experiment. The behavior of complex materials such as carbides is considered as a mixture. The model accurately describes the behavior of the carbides with equal shares of the components of WC, TiC, TaC, NbC and the behavior of boron carbide B4C. Comparison for data of calculation and experimental data was held for carbides with different porosity.

Strongly Anisotropic Thermomechanical Response to Shock Wave Loading in Oriented Samples of the Triclinic Molecular Crystal 1,3,5-Triamino-2,4,6-Trinitrobenzene (TATB)

All-atom molecular dynamics simulations were used to study shock wave loading in oriented single crystals of the highly anisotropic triclinic molecular crystal 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). The crystal structure consists of planar hydrogen-bonded sheets of individually planar TATB molecules that stack into graphitic-like layers. Shocks were studied for seven systematically prepared crystal orientations with limiting cases that correspond to shock propagation exactly perpendicular and exactly parallel to the graphitic-like layers. The simulations were performed for initially defect-free crystals using a reverse-ballistic configuration that generates explicit, supported shocks. Final longitudinal stress components are between »8.5 GPa and »10.5 GPa for the 1.0 km s^-1 impact speed studied. Orientation-dependent properties are reported including shock speeds, stresses, temperatures, compression ratios, and local material strain rates. Spatio-temporal maps of the temperature, stress tensor, material flow, and molecular orientations reveal complicated processes that arise for specific shock directions. The results indicate that TATB shock response is highly sensitive to crystal orientation, with significant qualitative differences for the time evolution of the stress tensor and temperature, elastic/inelastic compression response, defect formation and growth, critical von Mises stress, and strain rates during shock rise that span nearly an order of magnitude. A variety of inelastic deformation mechanisms are identified, ranging from crumpling of graphitic-like layers to dislocation-mediated plasticity to intense shear strain localization. To our knowledge, these are the first systematic MD simulations and analysis of explicit shock wave propagation along non-trivial crystal directions in a triclinic molecular crystal.