Ukrainian Journal of Mechanical Engineering and Materials Science

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    Simulation of the stress-strain state and determination of the natural frequency of the laboratory centrifuge shaft vibration using ansys and kisssoft
    (Видавництво Львівської політехніки, 2023-02-28) Lavrenko, Iaroslav; Sydora, Tetiana; Sushchenko, Maksym; Chaikovska, Olena; National Technical University of Ukraine "Ihor Sikorsky Kyiv Polytechnic Institute"
    The rotor is a key element of high-speed mechanisms that are widely used in various industries, such as laboratory centrifuges used to separate mixtures of different fractions, gas turbines, industrial compressors, engines, and others. The main requirement for such mechanisms is reliability and safety during operation. To ensure the above requirements, it is necessary to determine the stress-strain state of the most loaded structural elements of the system and the dynamic characteristics. This paper presents an analysis of the stress-strain state of a rotor system using the example of a Pico21 laboratory centrifuge. The Ansys and KISSsoft software packages were used for 3D modelling of the finite element model. The system consists of a flexible shaft with a rotor, the rotor mass was changed during the simulation and supports, the role of which is performed by bearings. A comparative analysis of the obtained results of the stress-strain state is presented, which further makes it possible to carry out appropriate calculations taking into account stress concentrators to determine the durability and lifetime of high-speed mechanisms. The stresses are determined according to the von Mises and Tresca criteria. The paper also presents the results of the calculation and analyses the natural frequencies of the rotor system. Further studies, it is planned to determine the natural frequencies of vibration, taking into account gyroscopic effects, which are necessary to determine the resonant frequencies and zones of stable operation of the system.
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    Two-mass vibratory conveyor-manipulator with three-component electromagnetic drive
    (Publishing House of Lviv Polytechnic National University, 2016) Vrublevskyi, Іgor
    Vibratory conveyor with three-component oscillations provides the opportunity to move the piece goods and details for any trajectory on a plane. Phase difference between independent horizontal (longitudinal or transverse) and vertical (normal) oscillations releases elliptical vibration of conveyor in plane perpendicular to the conveyor’s track. Elliptical vibrations allow increasing conveying velocity and inclination angle of conveyor’s track in comparison with the simplest linear vibrations. Three-component oscillations of the conveyor’s track are implemented by independent exciters of oscillations in the direction of conveying (longitudinal oscillations), oscillations in the direction perpendicular to conveying in plane (transverse oscillations) and oscillations in the direction perpendicular to conveying plane (normal oscillations) with phase difference between them. Conveying velocity of details moving upon the track varies with the change of phase difference angle and reaches a maximum with a certain angle, depending on several parameters. When electromagnetic exciters of longitudinal and normal oscillations are turned on, conveying details move in longitudinal direction. When electromagnetic exciters of transverse and normal oscillations are turned on, conveying details move in transverse direction. When electromagnetic exciters of longitudinal and transverse oscillations are turned on, conveying details rotate around their axes. When all three exciters are turned on, conveying details move at any trajectory. The change in the ratio of longitudinal and transverse amplitudes and phase difference angles between them allows changing the trajectory of details moving on conveyor’s track, making them not only move forward but rotate as well. That’s why such conveyor can be called a manipulator. The resilient system of two-mass vibratory conveyor-manipulator with three-component oscillations should have elastic pliability in three mutually perpendicular directions. It includes four resilient elements; each of them consists of two latticed leaf springs, fixed at the right angle to each other. The working body with conveying track is joined with reactive frame by resilient elements. Electromagnetic drive includes four electromagnetic exciters of longitudinal oscillations, four electromagnetic exciters of transverse oscillations and one electromagnetic exciter of normal oscillations. The bodies of electromagnets are fixed on the reactive frame and their anchors are fixed on the working body of conveyor-manipulator. A block diagram of the electrical control of conveyor-manipulator is referred. A voltage is supplied from two phases of threephase electricity to the coils of electromagnets through diodes, auto-transformers, switches and phase-shifter. The amplitudes of oscillations are regulated with aid of auto-transformers, phase difference between them and the change of conveying modes are carried by switches and phase-shifter. The oscillating system of vibratory conveyor-manipulator has six degrees of freedom and respectively six frequencies of natural oscillation. The formulas for calculating the vibratory conveyor-manipulator’s frequencies of natural oscillation are derived. Vibratory conveyor-manipulator with three-component electromagnetic drive was designed and manufactured. Its research and testing show the possibility of conveying details and piece goods at any trajectory.