Статті КПММ

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Browsing Статті КПММ by Author "Asgarov, Hangardash"

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    Influence Factors on Electrophysical Parameters of Composite Varistors
    (Український державний університет науки і технологій, м. Дніпро, 2023) Ahadzade, Shafag; Vakulenko, Igor A.; Asgarov, Hangardash
    ENG: Purpose. The work is aimed to evaluate the influence of the structural state of polymer phase on the response voltage and nonlinearity coefficient of a multilayer varistor based on zinc oxide. Methodology. Zinc oxide consisted of 97% zinc oxide and 3% total oxides of Bi2O3, Co3O4, MnO2, B2O3, SbO3, ZrO2, Al2O3. To obtain the composite of thermoplastic polymers and zinc oxide, non-polar and polar polymers, high pressure polyethylene and polyvinyli-denefluoride were used. The composites were obtained by hot pressing at the melting temperature of the polymer phase and a pressure of 15 MPa. After that, using silver paste measuring electrodes 10 mm in diameter were applied to the surface of the synthesized samples and then current–voltage characteristics were measured. Modification of composites under the action of gas-discharge plasma was carried out in a special cell that creates a dielectric-gas-composite system. The composites structure was studied by X-ray diffraction analysis and IR spectroscopy. Findings. The obtained experimental results show that the size of inorganic phase particles significantly affects the cur-rent-voltage characteristics of the composite varistor: at a given thickness of the composite varistor, the operation voltage decreases markedly, and the nonlinearity coefficient increases. The influence of electric discharge plasma on the polymer zinc oxide-composite results in a significant change in the permittivity and the concentration of local levels at the separation boundary of the composite. The results research showed that electrical plasma effect on the response voltage depends on the polarity of polymer matrices. Moreover, plasma processing itself significantly changes the structure of the polymer phase in the composite. Originality. The magnitude of the potential barrier at the phase boundary is mainly determined by the volume fraction and size of the main structural element of ZnO ceramics. The change in the structural state of the polymer matrix allows adjusting the response voltage and nonlinearity coefficient of volt-ampere characteristic of the multilayer varistor. Practical value. The discovered development of electron-ion processes in the polymer phase of the varistor indicates the need of taking into account the change in its service characteristics from the duration and intensity of use. The result obtained shows not only the reason for the properties change, but also the need to develop the measures to increase the service life of varistor.
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    Influence Structure on the Plasticity of Carbon Steel of the Railway Wheel Rim in Operation
    (Silesian University of Technology, Poland, 2022) Vakulenko, Igor A.; Vakulenko, Leonid I.; Bolotova, Dariy M.; Kurt, Bulent; Asgarov, Hangardash; Çölova, Ömer
    ENG: Summary. When simulating the operating conditions of the rim of a railway wheel, an analysis of change in the structural state from the possible degree of plastic deformation and the heating temperature of steel near the rolling surface was carried out. The development processes of spheroidization and coalescence of cementite during heating of the cold-worked steel change its ability to strain hardening. Substructure changes during heating to temperatures of 500-550°C deformed steel are accompanied by a simultaneous decrease in its ability to strain hardening and the level of plasticity. When heated above 500-550°C, the development of ferrite recrystallization processes provides a gradual transition of the metal from substructure hardening to hardening from grain boundaries with large angles of disorientation. It is shown that regardless of the nature of the main structural element, the ability of steel to strain hardening and the level of plasticity after heating are related by a proportional relationship.