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Author: Donii O.

  • MATERIALS

    Influence of the rate of cooling on the formation of non-equilibrium eutectics in preeutectic alloys of the AL-SI system

    • Donii O.
    • Khristenko V.
    • Kotliar S.
    • Narizhna T.
    Machines. Technologies. Materials., Vol. 15 (2021), Issue 8, pg(s) 331-333
    • Abstract
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    Computer experiments were carried out with a simulation model of alloy crystallization in this work. The model was preliminarily calibrated for alloys of the Al-Si system. The presence of a non-equilibrium eutectic in pre-eutectic alloys with a silicon content of 1.0% – 1.6% has been detected. The minimum cooling rates at which the formation of an eutectic in these alloys is possible have been determined.

  • MATHEMATICAL MODELLING OF TECHNOLOGICAL PROCESSES AND SYSTEMS

    MODELING OF TEMPERATURE DEPENDENCIES TO DETERMINE THE CONTENT OF SOLUBLE ELEMENTS IN THE BASIS OF DISPERSIONLY-HARDENING ALLOYS

    • Khristenko V.
    • Donii O.
    • Kotliar S.
    • Boguk Ju.
    Mathematical Modeling, Vol. 3 (2019), Issue 2, pg(s) 63-65
    • Abstract
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    The possibility of assessing of the temperature stability of the hardening phases of dispersion-hardened alloys with the help of polytherms of electrical resistance is experimentally confirmed. For alloys compositions of which belong to the quasi-binary Cu – Ni2Si cross section of the state diagram of the Cu – Ni – Si system, a procedure has been developed for calculating of the content of elements dissolved in the phase, based on copper, using data on temperature dependences of the electrical resistivity on temperature, presented in the form of regression equations. In the future, it is possible to use the developed model to assess the temperature stability of dispersed phases in alloys of more complex systems (for example, such as Cu – (Ni – Si) – (Fe – Cr – C)).

  • Mathematical models of calculations of parameters of crystallization of binary alloys by means of computer thermal analysis

    • Donii O.
    • Khristenko V.
    • Omelko L.
    • Kotliar S.
    Mathematical Modeling, Vol. 2 (2018), Issue 3, pg(s) 99-101
    • Abstract
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    Mathematical models of crystallization of binary metal alloys crystallizing in the temperature range are proposed. These models are intended for use in the composition of quality control systems for cast alloys based on computer thermal analysis. The proposed models make it possible to calculate the time dependences of the relative amounts of the solid and liquid phases using the data of the cooling curve, as well as to determine the intensity of the increase of the amount of the solid phase. The method of determining the temperature dependences of the specific heat and latent crystallization heat using the data on the temperature-concentration dependences of the free energies of the phases forming the system under study was used.

  • Influence of the external magnetic field on the structure and properties of the hypereutectic aluminum-silicon alloy

    • Donii O.
    • Narizhna T.
    • Voron M.
    • Berest D.
    Materials Science. Non-Equilibrium Phase Transformations., Vol. 4 (2018), Issue 3, pg(s) 79-82
    • Abstract
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    The effect of a constant magnetic field during the crystallization of a hypereutectic aluminum alloy on its structure in the solid state investigated. It is shown that the superposition of the magnetic field positively affects the structure of the alloy. A uniform distribution of the doped phases and eutectic in the volume of the alloy is observed. The phase of primary silicon significantly changes the size and the shape. It is established that the influence of an external magnetic field reduces the dimensions of the shrinkage defects. In general, the effect of an external magnetic field on the structure of the alloy leads to an improvement in the operational properties. The obtained measurement results showed more stable hardness values over the cross section of the sample in comparison with the alloy that was not processed.

  • CALCULATION OF TEMPERATURE DEPENDENCES OF THERMAL EFFECTS AT COOLING OF METAL ALLOYS

    • Khristenko V.
    • Omelko L.
    • Donii O.
    Machines. Technologies. Materials., Vol. 12 (2018), Issue 9, pg(s) 374-377
    • Abstract
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    A method is proposed for determining the temperature dependences of thermal effects (the amount of heat released when the temperature changes) based on data on the temperature-concentration dependences of the free energies of the phases of metallic systems. These dependences are necessary for modeling of the processes of crystallization of alloys. They make it possible to obtain temperature dependences of the dimensions of the thermal effects without introducing the results of measurements of direct calorimetry. The peculiarity of calculating of the temperature dependences of thermal effects upon cooling of binary metal systems from the liquid state to room temperature (including crystallization) is shown using the example of the alloy of the system Pb-Sn.

  • MATHEMATICAL MODELLING OF TECHNOLOGICAL PROCESSES AND SYSTEMS

    COMPUTER SYSTEM FOR PREDICTING THE STRUCTURE AND PROPERTIES OF CAST METAL PRODUCTS

    • Donii O.
    • Kulinich A.
    • Khristenko V.
    Mathematical Modeling, Vol. 1 (2017), Issue 4, pg(s) 180-183
    • Abstract
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    The basic principles of functioning of subsystems of the information-technological complex, which is intended for the forecast of structure and properties of the cast metal, are presented. The basis of subsystems are mathematical and simulation models of crystallization. The subsystem of thermal analysis is based on mathematical models, which were developed within the framework of the dynamic theory of metallic castings The subsystem of modeling of crystallization is based on a combination of mathematical models of heat conduction and diffusion with cellular automata. The model makes it possible to investigate in computational experiment the effect of various cooling conditions on the process of formation of the structure during crystallization. The results of computer experiment are shown.

  • MATHEMATICAL MODELLING OF SOCIO-ECONOMIC PROCESSES AND SYSTEMS

    SIMULATION MODELING OF AUDITORY FUNCTION

    • Donii O.
    • Pisanko V.
    • Kulinich A.
    • Kotliar S.
    Mathematical Modeling, Vol. 1 (2017), Issue 2, pg(s) 117-120
    • Abstract
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    The hypothese concerning encoding of information in the peripheral part of the human’s auricular analyzer are presented. A brief critical analysis of contemporary trends in theoretical concepts concerning principles of work of the cochlea of the inner ear are conducted. Prerequisites for the construction of an alternative theory of coding of information in it are formulated in order to optimize the design and software of cochlear implants. The principle of constructing an imitation model of the generation of electric signals formed in the cochlea of the inner ear are proposed.

  • MODELING OF METAL CRYSTALLIZATION BY MEANS OF CELLULAR AUTOMATON

    • Donii O.
    Materials Science. Non-Equilibrium Phase Transformations., Vol. 3 (2017), Issue 4, pg(s) 150-153
    • Abstract
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    Simulation model of crystallization, which is based on combination of mathematical modeling methods and a probabilistic cellular automaton, is presented here. Such combination makes it possible to predict process of metals and alloys structure formation whiles crystallization under various cooling conditions, and also to study this process both in the course of homogeneous and heterogeneous nucleation.

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