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Application opportunity of IT's contactless vibrodiagnostic system for measurement of dynamic behaviour of rotor bladed wheels.
Vaněk, František ; Pešek, Luděk ; Procházka, Pavel ; Cibulka, Jan ; Turinský, M. ; Laštovka, B.
Variable excitation forces evoke a rotor blade vibration at jet engines. For description of the blade vibrations, parameters such as modes, frequencies and amplitudes, are evaluated in different operational regimes of engines. Since the operational forces are not fully known and mechanical parameters of the blades changes during sirvece the vibrodiagnostic measuring system VDS.IT was developed in IT AS CR. This system can be used for long-term measurement of vibration of all free-ended blades of rotors. Since the latest development of shrouded blades this system has been modified and fully tested in the Experimental laboratory of Škoda Power, Plzeň. The changes and results are discussed in this contribution.
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Teplotní účinek na rheologické vlastnosti pryžového prvku
Půst, Ladislav ; Pešek, Luděk ; Vaněk, František ; Bula, Vítězslav
Deformation and temperature data of a vibro-damping element measured in laboratory condition at harmonic loading with constant prload F st =6kN were elaborated with the aim to build termo-mechanical characteristic of rubber-like material. It is shown that the increase of temperature during harmonic loading at various amplitudes F0=(0,75,3) kN and frequencies fe(10,30) Hz is exponential in time and proportional to the square of loading amplitude. The proposed mathematical model of dynamic characteristic of specimen gained by the regression procedure consists of linear, quadratic and fourth root function of displacement amplitude Xo and of the linear correction function of temperature.
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Measurement and analysis of tram wheel vibration at riding on track
Pešek, Luděk ; Vaněk, František ; Cibulka, Jan ; Vaněk, P. ; Boháč, T.
In the contribution the design, realization and results of vibro-acoustic measurements on the riding tram wheel is presented. The operational tests were performed on the tram KT8D5 of DPMB Brno. The tram wheel with a special rubber padding design was equiped with add-on vibro-acoustic dampers. Efficiency of the add-on dampers was evaluated from comparison tests on the tram wheel with and without these dampers. Third octave and time-frequency analysis of the measured vibro signals is herein presented for a bow track passage. For analysis of operational vibration modes the FE model of the wheel with add-on dampers was developed and applied.
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Computational acoustic modal analysis of selected parts of a steam pipe system
Zolotarev, Igor ; Horáček, Jaromír ; Pešek, Luděk
The repart deals with frite element modelling and computations of the frequency-modal acoustic characteristics of selected parts of complicated pipe systems conveying water steam. In all cases studied, first 10 acoustic natural frequencies were in the frequency range up to 150 Hz. No lateral acoustic natural mode of vibration appeared in this frequency range and all modes were longitu-dinal, that can be approximately described by 1D theory for acoustic wave propagation in cylondrical ducts.
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Evaluation of vibrational eigenfrequencies and eigenmodes and loss factor for monoblock rail wheel
Pešek, Luděk ; Veselý, Jan
The aim of this research was evaluated experimentally eigenfrequencies, eigenmodes and loss factors for the monoblock rail wheel in two options: a) without acoustic damping disc, b) with acoustic damping disk. Excitation was realized by an electrodynamic vibrator with different levels of excitation and by hammer. The raill wheel was forced on a wheel set placed on a special frame. Frequency range of modal analysis was up to 6400Hz with step 0.25Hz. The measurement and analysis was performed for all identifiable eigenfrequencies with emphasis on eigenmodes having from two up seven node radials without node cirles. Pro determination of eigenfrequencies and loss factors corresponding eigenmodes the modal analysis was carried out for all options of the damping disk.
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Design, development and realization of vibration measurement on riding metro wheel with and without add-on damper
Pešek, Luděk ; Vaněk, František ; Vaněk, Petr ; Cibulka, Jan
The aim of this research was design, developement and realization of vibration measurement (acceleration) of the riding metro wheel with and without add-on damper. The radiotelemetric method with four measurement channels was used for the operational measurement of vibration and noise. The solution was devided into four steps a) design and devolopement, laboratory tests and production of modified radiotelemtric equipment for measurement on the tram wheel; b) installation of the sensors and radiotelemetric equipment; c) realization of vibration operational measurement; d) measured data processing. In the report there is described a methodology of measurement and dynamic analysis used for comparision of the wheel with and withoud add-on dampers. The different riding regimes and tracks, i.e. direct, bow , were analysed. The third octave spectra nd amplitude time-frequency characteristics of accelerations and acoustic pressure were evaluated from the digital recorded time signals.
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Design, development and realization of vibration measurement on riding tram wheel with and without add-on damper
Pešek, Luděk ; Veselý, Jan ; Vaněk, František ; Cibulka, Jan ; Bula, Vítězslav
The aim of this research was design, developement and realization of vibration measurement (acceleration) of the riding wheel with and without add-on damper. The solution was devided into four steps a) design and devolopement, laboratory tests and production of modified radiotelemtric equipment for measurement on the tram wheel; b) installation of the sensors and radiotelemetric equipment; c) realization of vibration measurement of the carriage KT8D5; d) measured data processing. In the report there is described a methodology of measurement and dynamic analysis used for comparision of composed rim-rubber-disk wheel with and withoud add-on dampers. The different riding regimes and tracks, i.e. direct, bow and cross, were analysed.
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FE model termomechanické interakce pryžového bloku při cyklickém dynamickém zatížení
Pešek, Luděk ; Šulc, Petr
The COMSOL code based on weak formulation of PDE’s problem was used at a solution of feedback thermo-mechanical interaction in pre-pressed rubber block used for resilient elements of the composed tram wheels. The structural motion and heat conduction equations are solved interactively as time dependent problems. The equality of heat energy density and dissipation energy density realizes the coupling between the equations. The dissipation energy density is computed according to the assumed proportional damping model. In the paper the results of thermo-mechanical processes in cases of a plane strain and 3D space deformation under static pre-pressed and cyclic dynamic loading are presented and analyzed.
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