Browsing by Author "Tsonevska T."

Now showing 1 - 5 of 5
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    Development of model-based simulation and optimization software for electron beam melting and refining
    (2023-01-01) Koleva E.; Koleva L.; Tsonevska T.
    In this paper the development of a software for electron beam melting and refining (EBMR) of different materials is presented. It has the following functional characteristics: simulation of the temperature distributions in the cast ingots, investigation and optimization of the form of the liquid pool during the process of EBMR and estimation of the inclusion refining rates, depending on the EBMR process parameters. The temperature distributions in the cast ingots are simulated by the implementation of quasi steady-state two-dimensional heat model and three-dimensional time-dependent thermal model for different refined metals. Empirical models are estimated, integrated in the developed software and used for the investigation of the molten pool geometry parameters, the content of impurities after the electron beam refining process, refining rate, overall inclusion removal efficiency and the material losses. The influence of EBMR process parameters such as electron beam power, casting velocity, refining time, and electron beam radius are considered. Multicriterial optimization software functions can be implemented for solving concrete technological requirements for each practical use-case.
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    Empirical modeling of high-intensity electron beam interaction with materials
    (2018-04-05) Koleva E.; Tsonevska T.; Mladenov G.
    The paper proposes an empirical modeling approach to the prediction followed by optimization of the exact shape of the cross-section of a welded seam, as obtained by electron beam welding. The approach takes into account the electron beam welding process parameters, namely, electron beam power, welding speed, and distances from the magnetic lens of the electron gun to the focus position of the beam and to the surface of the samples treated. The results are verified by comparison with experimental results for type 1H18NT stainless steel samples. The ranges considered of the beam power and the welding speed are 4.2 - 8.4 kW and 3.333 - 13.333 mm/s, respectively.
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    Heat distribution simulation in electron-beam surface modification of 316L stainless steel samples
    (2020-06-02) Koleva E.; Tsonevska T.; Koleva L.; Vutova K.; Mladenov G.; Naplatanova M.; Trushnikov D.; Varushkin S.
    A time-dependent heat model is implemented for the simulation of the heat distribution in 316L stainless steel samples during electron-beam irradiation. The influence is studied of the electro-beam power and processing time on the temperature field produced in the samples. The simulation results are compared with real experimental data of electron-beam surface modification of 0.5-mm-thick 316L stainless steel samples using the ELIT-60 installation in the Institute of Electronics BAS. The simulation and the experimental results show good agreement.
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    Model-based multicriterial optimization of electron beam melting and refining of copper
    (2022-04-04) Koleva E.; Koleva L.; Vassileva V.; Vutova K.; Tsonevska T.
    Experimental results on the quality of electron beam melting and refining of copper samples by implementing the ``method of washers``are analyzed by using an empirical model estimation approach. The influence is studied of the process parameters - melting power and time of refining, on the residual content of impurities, the refining rate, the overall removal efficiency and the material losses. A graphical user interface is designed and developed for calculation, investigation and multicriterial optimization of the quality of the refined copper samples.
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    Modelling the shape of electron beam welding joints by neural networks
    (2018-10-19) Tsonevska T.; Koleva E.; Koleva L.; Mladenov G.
    This article discusses the experimental results from multi-pool electron beam welding, with dynamic positioning of the electron beam (beam splitting) [1], resulting in the formation of two consecutive welding pools. The 12Cr18Ni10Ti stainless steel samples are welded with a change in the process parameters: the distance between the two electron beams (electron beam positions) and the ratio between the two mean electron beam powers, the frequency of the deflection signal, the beam current and the welding velocity. The focusing current is kept at a constant value. The weld cross-sections, experimentally obtained at different process parameters, are used to train, validate and test neural models. The accuracy of prediction of the shapes of the welds (the form of the molten pool) is discussed and compared with that of an estimated regression model.