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Dynamics of Machines and Mechanical Systems with Interactions : DYMAMESI 2018
Zolotarev, Igor ; Pešek, Luděk ; Kozieň, M.
The Colloquium Dymamesi is continuing near the 20 years history of two conferences Dynamics of Machines and Interaction and Feedbacks. From 2017 the Colloquium is organized within the Czech-Polish (IT ASCR Prague & CUT Crakow) collaboration and the first one was held in CUT in Cracow. The prezentations were divided into the three sections: dynamics of machines, interactions and energetics. The Colloquium DYMAMESI 2018 was for the first time supported also by Programme Strategy 21 (AV21).\n
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Experimental analysis of bladed wheel modelwith tie-boss couplings – steady and rotational states
Pešek, Luděk ; Bula, Vítězslav ; Šnábl, Pavel ; Cibulka, Jan
Experimental modal analysis of the proposed model of bladed wheel with tie-boss couplings was performed for validation of the numerical FE model. The pre-stresses in contacts were set and evaluated indirectly by the magnetic torque sensor. Then dynamical tests of bladed wheel under revolutions were performed. Theelectromagnetic synchronized pulses were used for excitation of forced vibration of the wheel. The Campbell diagram of the wheel with prestressed contacts was created from the measurement under revolutions. From the attenuation of resonant vibration of the wheel the dampingwas evaluated.
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EXPERIMENTAL ANALYSIS OF BLADED WHEEL MODEL WITH TIE-BOSS COUPLINGS – STEADY AND ROTATIONAL STATES
Pešek, Luděk ; Bula, Vítězslav ; Šnábl, Pavel ; Cibulka, Jan
Experimental modal analysis of the proposed model of bladed wheel with tie-boss couplings was performed for validation of thenumerical FE model. The pre-stresses in contacts were set and evaluated indirectly by the magnetic torque sensor. Then dynamical tests of bladed wheel under revolutions were performed. The\nelectromagnetic synchronized pulses were used for excitation of forced vibration of the wheel. The Campbell diagram of the wheel with prestressedcontacts was created from the measurement under revolutions. From the attenuation of resonant vibration of the wheel the dampingwas evaluated.
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Deformation energy of Yeoh hyperelastic model and constant hyperelastic proportional damping
Šulc, Petr ; Pešek, Luděk ; Bula, Vítězslav ; Košina, Jan ; Cibulka, Jan
The paper deals with a proposal of the dissipated energy of hard rubbers as a function of the deformation energy expressed by the Yeoh hyperelastic model. Then the deformation energy may be dependent only on the first invariant of deformation. Based on the experiment, a “hyperelastic proportional damping” (HPD) is proposed for hard rubbers under finite strains. It is analogical to the model of proportional damping in the elastic theory, i.e. the dissipated energy is proportional to the deformation energy multiplied by the frequency of dynamic harmonic loading. The Yeoh model is chosen since the deformation function is dependent only on the first strain invariant for a description of the simple shear of a surface cylinder. The constants are used to an enumeration of the deformation energy of the Yeoh model for the specific cases of tested rubbers. The coefficients of hyperelastic proportional damping are evaluated on the basis of experimental results,too.
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Fast estimation of flutter parameters of steam turbine blades using boundary element methods
Prasad, Chandra Shekhar ; Pešek, Luděk
In the present paper the classical flutter parameters in turbomachinery cascade such as aerodynamic damping estimation using fast numerical method is described. The unsteady aerodynamic loading and the aerodynamic damping (AD) coefficient of the vibrating cascades is estimated by 2D boundary elementmethod such as source and doublet panel method (PM). To estimate the flutter parameters aerodynamic influence coefficient traveling wave mode (TWM)method is adopted. The experimental aerodynamic damping is compared against simulated results. The result demonstrate that potential flow based boundary elements method can estimate the AD with desired accuracy and less computational time.
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Vibration stability of a vertical flywheel lifted by permanent magnetic rings
Zapoměl, Jaroslav ; Ferfecki, P. ; Sudhakar, A. ; Kozánek, Jan
Lifting the vertical flywheels by permanent magnets is used to reduce energy losses in the support elements. Unstable equilibrium position of pairs of magnetic rings, material damping of the shaft, and nonlinear properties of the support elements can arrive at the flywheel unstable oscillations. Therefore, evaluation of the vibration stability is the essential part of the design process of flywheel devices. In the developed computational procedure the flywheel is represented by a beam-like body, to which an absolutely rigid disc (the actual flywheel) is attached. The determination of the force action between the magnetic rings is based on mutual interaction between two magnetic dipoles. The steady state response of the flywheel on the unbalance excitation is calculated by means of the trigonometric collocation method and its stability is evaluated by application of the Floquet theorem. The developed computational procedures and learning more on behaviour of flywheels lifted by magnetic rings are the main contributions of the carried out research.\n
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Self-excited oscillation properties of the profile NACA0015 in subsonic flow
Zolotarev, Igor ; Vlček, Václav ; Kozánek, Jan
Self-excited oscillations of the profile NACA0015 in subsonic flow were realized in the wind tunnel. The plunge support had the same elasticity for all experiments, the pitch support had seven different elasticity parameters. During our experiments different types of selfexcited vibration (flutter, stall flutter) were observed. Range of Mach numbers was M = 0.08–0.45, corresponding range of Reynolds numbers is Re = (1–5)·105, when the chord length is used as the characteristic dimension of the profile.\n
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