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Abstract

Contemporary tools which help to design technical objects refer to the conclusions drawn from studying the changes of physical processes accompanying the exploitation, especially to vibroacoustic processes. The main problem is to define such vibroacoustic measures, where their changes would model the analyzed physical phenomena in the best way. Basing on simple indicators which refer to occurring phenomena, it is possible to obtain accurate solutions with a satisfactory reliance level without using complex computing techniques needing detailed descriptors. According to the author, the indicators which are based on the analysis of vibroacoustic energy propagation are very useful in solving engineering problems. These indicators are useful while diagnosing the condition of technical systems, identifying and minimizing the vibroacoustic risks. The possibilities of using such indicators in order to find design solution are illustrated by sample results of the research of the structures with vibroacoustic elements which reduce the noise of rail vehicles by the rail vibration damping.
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Abstract

In vibration control with piezoceramics, a high coupling of the piezoelement with the structure is desired. A high coupling improves the damping performance of passive techniques like shunt damping. The coupling can be influenced by a the material properties of the piezoceramics, but also by the placement within the structure and the size of the transducer. Detailed knowlegde about the vibration behavior of the structure is required for this. This paper presents an in-depth analysis of the optimal shape of piezoelectric elements. General results for one-dimensional, but inhomogeneos strain distribution are provided. These results are applied to the case of a longitudinal transducer and a bending bimorph. It is obtained that for maximum coupling, only a certain fracture of the volume should be made of piezoelectric material&
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Abstract

The steam turbine blades of low pressure stages are endangerd by the high-cyclic fatigue due to the combined loading of dynamic stresses by the steam time-variant pressure and the pre-stress from centrifugal forces. Therefore, the importance of their experimental dynamic analysis in the design stage is critical. For laboratory tests of the blades, the piezo actuators placed on the blades, unlike electromagnets placed in the stationary space, give a possibility to excite the flexural vibration of the blades within the bladed disk by time continuous forces independently of the rotor revolutions. In addition, the piezo actuators can be also used to control the vibrations of the blade. Therefore, several dynamic experiments of the clamped model blade equipped with PVDF films were performed for the force description of the piezo foils and their behavior as actuators of the blade vibration. The numerical beam models were used for numerical analysis of the vibration suppression effects both by additional parametric excitation and by active damping. The optimal phase shift of piezo actuator voltage supply was ascertained both for amplitude amplification and suppression. The results contribute to the knowledge of the actuation and active damping of blade vibration by the piezo elements
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