1,721,188 research outputs found
Shock response spectrum in plates under impulse loads
No full textIn this paper, the study of a plate under impulse loads and the correlated Shock Response Spectrum (SRS) has been carried out. The Reissner-Mindlin plate have been considered and the modal analysis technique used to develop the solution. The influence of the impulse (rise function, rise time) and geometric parameters (thickness of the plate, distance of the measure point from the point load) has been evaluated. (C) 2007 Elsevier Ltd. All rights reserved
Il valore della prossimità. Transizione nei Balcani e sviluppo delle regioni adriatiche
No full text
Optimal Placement of Piezoelectric Plates for Active Vibration Control of Gas Turbine Blades: Experimental Results
No full textIt is well known that the gas turbine blade vibrations can give rise to catastrophic failures and a reduction of the blades
life because of fatigue related phenomena. In last two decades, the adoption of piezoelectric elements, has received
considerable attention by many researcher for its potential applicability to different areas of mechanical, aerospace,
aeronautical and civil engineering. Recently, a number of studies of blades vibration control via piezoelectric plates and
patches have been reported. It was reported that the use of piezoelectric elements can be very effective in actively
controlling vibrations. In one of their previous contributions, the authors of the present manuscript studied a model to
control the blade vibrations by piezoelectric elements and validated their results using a multi-physics finite elements
package (COMSOL) and results from the literature. An optimal placement method of piezoelectric plate has been
developed and applied to different loading scenarios for realistic configurations encountered in gas turbine blades. It has
been demonstrated that the optimal placement depends on the spectrum of the load, so that segmented piezoelectric
patches have been considered and, for different loads, an optimal combination of sequential and/or parallel actuation and
control of the segments has been studied. In this paper, an experimental investigation carried out by the authors using a
simplified beam configuration is reported and discussed. The test results obtained by the investigators are then compared
with the numerical predictions
Introductory PZT actuators optimal working configuration experimental study in a turbofan engine fan rotor blade
No full textVibration suppression systems are often crucial to extend the life cycle of the structures in several engineering fields. The passive systems are the most commonly used but, in case of dynamic loads, the active systems show a greater efficiency. Since the external forces acting on a rotating blade may excite several vibrational modes simultaneously, an active multi-modal damping device could enhance the damping action. The piezoelectric (PZT) actuators seem to be the most promising but their placing on the structure plays a crucial role. In this paper, some PZT actuators have been mounted on the surface of an actual rotor blade from the second fan stage of a turbofan engine and their working configuration has been optimized on the basis of a previously developed model. Thereby, the actuators are able to efficiently damp the most detrimental resonant mode or a resonant modes coupling. The experimental results show that the proposed system well suits the application and may be considered as an alternative method to deal with vibration issues in turbomachinery blades
A Piezoelectric MEMS Microgripper for Arbitrary XY Trajectory
Full text linkIn this paper, a piezoelectric microgripper for arbitrary 2D trajectory is proposed. The desired trajectory of the specimen under consideration was obtained by the deformability of a structure consisting of 16 straight beams and 12 C-structures. The mechanical action that deforms the structure was obtained by an electrical voltage supplied to piezoelectric plates. In order to verify the proposed model a FEM software (COMSOL) was used and some of the most commonly used trajectories for medical applications, micropositioning, micro-object manipulation, etc., were examined. The results showed that the proposed microgripper was capable of generating any parametrizable trajectory. Parametric studies were also carried out by examining the most relevant parameters highlighting their influence on specimen trajectories
- …
