UDC 548.33:539.26
AND. IN. Kurdyumov, V. F. Brytun, A. I. Danylenko, V. B. Zelyavsky, S. N. Gromyko, N. I. Borymchuk, V. In Yarosh (Kyiv)
Features of martensitic transformation of graphite-like boron nitride into wurtzite modification during high-temperature shock compression
The phase transformations of graphite-like boron nitride BNg during high-temperature impact compression based on the use of special additives that increase the temperature of the substance under investigation and ensure sharp hardening of the formed high-pressure phases during unloading are investigated. Compression was carried out in ring ampoules, KCl powder was used as an additive. The peak pressure was 30 GPa, and the temperature increased with increasing additive content. Highly crystalline BNg was transformed by the martensitic mechanism with the formation of the wurtzite phase BNv, and partially ordered – by the mixed (martensitic and diffusion) mechanism with the formation of both the BNv and the sphalerite phase BNсf, and with increasing temperature, the relative amount of BNv increased. Peculiarities of the structure of BNv, formed under conditions of high-temperature impact compression, in comparison with the structure of ordinary BNv obtained at lower pressures and temperatures, were studied. It is shown that BN, obtained by the method of high-temperature shock compression, has a significantly more dispersed and defective structure.
UDC 666.3/7:621.931
IN. B. Shipylo, A. G. Dutov, N. IN. Shipylo, V. AND. Komar, I. I. Azarko (Minsk)
The influence of boron on the crystallization of diamond in the manganese-nickel system
The regularities of changes in the degree and speed of the phase transformation of graphite into diamond, its fractional composition, the content of manganese, nickel, and paramagnetic defects in diamonds, as well as the strength of diamonds depending on the level of boron in the initial reaction charge of the Mn—Ni—C system have been established.
UDC 666.233
AND. L. Maistrenko, N. IN. Novikov, G. P. Bogatyreva, N. AND. Oleynyk (Kyiv)
Justification of the concept of selective destruction of the product of diamond synthesis
Physical models of the granule structure — the elementary volume of the heat product of diamond synthesis at various stages of diamond extraction — are considered. The stress-strain state was calculated using the finite element method and the limit state stresses of the model were established. The concept of selective destruction of the synthesis product is substantiated: in order to achieve a high degree of its disclosure without destroying diamond crystals, it is necessary to apply step-by-step destruction with intermediate dissolution of the metal component.
UDC 621.921.343
IN. Yu. Dolmatov (St. Petersburg)
On the question of the structure of a detonation nanodiamond cluster
A number of controversial and controversial presented about the structure of a detonation nanodiamond cluster (particle) are considered. An attempt is made to generalize these concepts and find a connection between them, as well as to explain the variety of properties of detonation nanodiamond, the difference between nanodiamonds and classical diamonds, which is primarily related to the properties and structure of the unusual peripheral intermediate layer.
UDC 553.65:537.226
I. Kh. Abdukadyrova (Tashkent)
Dielectric properties of irradiated corundum single crystals in the temperature range of 25—400 °C
Investigated features of changes in dielectric properties in single-crystal corundum after exposure to ionizing radiation. The regularities of the change in dielectric permittivity as a function of temperature (in the range of 20-400 °С) and frequency were determined, and a significant dispersion of this parameter was established when the frequency varied from 0.3 to 30 kHz. Exponential growth of the value of dielectric permittivity with increasing temperature and its exponential decline with increasing frequency were revealed. A nonlinear change in the dose dependence of the dielectric permittivity of irradiated crystals in the range of absorbed doses of 102—106 Gy was detected, which generally has an extreme course. The loss coefficient was estimated, and the regularities of its temperature dependence in the radiation-treated material were revealed. The possible reasons for the peculiarities of the established temperature-frequency and radiation kinetics of changes in the dielectric parameters of irradiated crystals are discussed.
UDC 661.65:661.55
R. WITH. Shmegera, S. N. Oak (Kyiv)
Investigation of the mechanical behavior of nanovolumes of high-purity copper
The “Nano Indenter II” device was used to investigate the specifics of the elastic-plastic transition under the conditions of local deformation of copper nanoregions by ultralow loads. It is shown that the initial stage of nanoindentation has a purely elastic character even in such a plastic material as copper. The start of plastic flow is prevented by the fact that the contact dimensions at a depth of about 10 nm are much smaller than the average distance between dislocations in the sample. As a result, before the abrupt transition to plastic flow, the contact stresses reach values comparable to the theoretical strength limit of copper. It is shown for the first time that for a deformed sample compared to an undeformed one, small (ε = 0.05) precursor deformations lead to an increase in the load at which plastic flow begins. A further increase in the degree of preliminary deformation of the sample leads to a sharp decrease in the load at the beginning of the plastic flow in the contact.
UDC 62-987:666.233
AND. I. Prykhna (Kyiv)
Extruder for continuous synthesis of diamond and cubic boron nitride
A device in the form of an extruder with a conical worm is proposed, which ensures the continuity of the synthesis of superhard materials. Its use will allow to reduce the cost of the product due to the reduction of the number of preparatory technological operations and higher productivity of the extruder in comparison with the press.
UDC 621.923
P. G. Matyuha, V. B. Strelkov (Donetsk)
Calculation of the volume of ground material in the process of diamond grinding of hard alloy VK8 with periodic electroerosion effects on the working surface of the wheel
A method of calculating the volume of polished hard alloy material when grinding according to an elastic scheme with periodic impacts on the working surface of the wheel is proposed, based on the use of a new concept of the current limited cutting ability of the wheel and the representation of the processing process as repeating cycles of wheel durability—time of electroerosion effects.
UDC 621.923:[621.922:621.921.34]
Yu. D. Filatov, V. I. Sydorko (Kyiv)
Statistical approach to the wear of the surfaces of parts made of non-metallic materials during polishing
The results of the statistical description of the wear of the surface of the part during its final processing are presented. It is shown that the solution of the Fokker-Planck equation for the distribution of the concentration of wear particles in the contact zone of the tool and the workpiece together with the generalized cluster model of wear allows calculating the removal rate of the processed material.
UDC 622.24.051:536.2:004.942
V. A. Dutka, V. M. Kolodnitsky, O. V. Melnichuk, S. D. Zabolotny (Kyiv)
Mathematical model of thermophysical processes during the interaction of rock-destroying elements of drill bits with a rock mass
A two-dimensional numerical model of the temperature field in the rock mass—working element—bit body system is proposed. This model is based on the use of the finite element method and a time-difference scheme and includes three stages. At the first stage, within the framework of the axisymmetric model, the heat dissipation in the bit body and the rock mass from the action of heat sources in the contact zone of the cylindrical working element with the rock mass is determined; at the second stage, using a two-dimensional model in Cartesian coordinates, based on the results obtained at the first stage, the calculated value of the power of the heat sources in the contact zone is adjusted; at the third stage, within the framework of the two-dimensional model in Cartesian coordinates, using the adjusted value of the power of the heat sources in the contact zone, the thermal state of the rock mass—working element—bit body system is calculated, taking into account the movement of the working element of the drill bit relative to the rock mass. The movement of the working element relative to the rock mass is taken into account by directly modeling this movement. At the same time, at each time step, the temperature in the contact zone of the working element with the rock mass is recalculated.
The results of numerical calculations obtained using the proposed model are in good agreement with the results of laboratory temperature measurements in the working element of the drill bit.
UDC 621.9
V. I. Kalinichenko (Kyiv)
Modeling the thermoelastic state of a cutting tool
An approach to modeling the thermoelastic state of a cutting tool using the finite element method is proposed. The results of calculating the stress-strain state of the tool allow us to determine and estimate the zones and values of maximum thermomechanical stresses in its cutting part.
UDC 666.792.34:539.89
D. A. Stratychuk, A. A. Shulzhenko (Kyiv)
A new composite material based on B4C obtained at high p,T parameters.