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Study of additional parametric excitation on reduction of forced resonance vibrations
Šulc, Petr ; Pešek, Luděk
This contribution deals with active reduction of unacceptable vibrations by means of parametric excitation fulfilling certain conditions. It is studied on the case of 2DOF system with additional parametric excitation under harmonic force excitation. On the contrary to the selfexcited vibrations or parametric resonances, the parametric excitation of the forced resonance vibrations of the studied system leads to suppression of the resonance not by "damping" but "splitting" effect.
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Dynamics of Machines 2014
Pešek, Luděk
The aim of the Colloquium was to facilitate the exchange of up to date information and knowledge among specialists in solid mechanics. The main attention was focused on: continuum dynamics, impact and non-linear phenomena, crack propagation, constitutive models, dynamics of linear and non-linear systems, identification, chaos, vibrations, interaction of mechanical systems and fluids, modern computational mechanics and experiments.
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Dual-system Magnetoresistive Sensor of Turbine Blades Vibration
Procházka, Pavel ; Vaněk, František ; Hodboď, Robert
The paper is focused on new methods of non-contact sensing vibrations and deflections of rotating machine parts, especially blades of steam turbines. Special attention is paid to the methods and magnetoresistive sensors developed in the Institute of Thermomechanics for non-contact measurements of characteristics of rotating blades inside steam turbines under operation. Principles of non-contact sensors based on measuring deflections are described and compared, including new types of magnetoresisitive sensors.
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Properties of damping couple at very high frequencies
Půst, Ladislav ; Pešek, Luděk ; Košina, Jan ; Radolfová, Alena
The contribution deals with the application of dry friction couples for noise and vibration damping at high frequency of several kHz what brings new problems connected with the small amplitudes of relative slipping motion of contact surfaces. The most important information from the of experimental results is knowledge that the value of evaluated friction coefficient can have different physical sense according to the magnitude of excitation force and to the frequency of applied vibrations. If amplitudes of motion are very small, then the external harmonic force produces only elastic micro-deformations of contacting bodies, where no slip occurs and then the traction contact force is proportional only to elastic deformation of the sample.
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Stochastic resonance in a simple duffing equation
Náprstek, Jiří
The response of a dynamic nonlinear single degree of freedom system with cubic characteristic to a combination of additive random Gaussian white noise and external deterministic periodic force is studied. It is coming to light that under certain circumstances the jumping between wells of the bistable elastic potential can occur leading to interwell hopping. The frequency of this hopping can be for certain combination of input parameters nearly constant and corresponding to external periodic force frequency. This state leads to high ratio of periodic component amplitude and intensity of the random component of the response process. In such a case the system can be used as a harmonic selective resonator detecting the useful weak harmonic signal in the high noisy background.
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