Search results for "vibration"
showing 10 items of 823 documents
Fast response vibration sensor based on Bragg gratings written in tapered core fibres
2007
Bragg gratings written in tapered core fibres permit a direct measure of mechanical vibrations with a time response better than 10 µs. The intrinsic properties of the sensors lead to a simple interrogation technique and wavelength multiplexing capacity. The sensor system is operated at 800 nm and is compact and low-cost.
A closed-form solution for natural frequencies of thin-walled cylinders with clamped edges
2016
Abstract This paper presents an approximate closed-form solution for the free-vibration problem of thin-walled clamped–clamped cylinders. The used indefinite equations of motion are classic. They derive from Reissner׳s version of Love׳s theory, properly modified with Donnell׳s assumptions, but an innovative approach has been used to find the equations of natural frequencies, based on a solving technique similar to Rayleigh׳s method, on the Hamilton׳s principle and on a proper constructions of the eigenfuctions. Thanks to the used approach, given the geometric and mechanical characteristics of the cylinder, the model provides the natural frequencies via a sequence of explicit algebraic equat…
Discrete-time static output-feedback semi-decentralized H<inf>&#x221E;</inf> controller design: An application to structural vibratio…
2012
In this work, we present a new and effective method to design discrete-time static output-feedback H ∞ controllers. This new method, based on a Linear Matrix Inequality (LMI) formulation, introduces a suitable transformation of the LMI variables that allows to obtain an explicit expression for the output-feedback gain matrix. Moreover, for problems involving a set of subsystems with information exchange constraints, a convenient structure on the LMI variables can be imposed in order to design semi-decentralized controllers, where the corresponding output-feedback gain matrix has a prescribed zero-nonzero structure. To illustrate the proposed methodology, discrete-time static velocity-feedba…
METHOD FOR DETECTING A SONIC IMPRINT OF A THREE-DIMENSIONAL OBJECT AND RELATED APPARATUS
2013
Non invasive method used to detect a “sonic imprint” of three-dimensional objects, particularly suitable for the identification and monitoring of artworks, consisting in acquiring the vibrations caused by a source of elastic waves and using a set of detectors fixed in various predetermined points of the external surface of the object. An apparatus, cheap and simple to utilize, suitable to execute this method, is also described.
Risk exposure to vibration and noise in the use of tracklaying tractors
2014
Human exposure to mechanical vibration may represent a significant risk factor for exposed workers in the agricultural sector, with particular reference to the operators driving tractors. Also noise in agriculture is one of the risk factors to be taken into account for the evaluation of workers health and safety. In particular, one of the major sources of discomfort for the workers operating a tractor is the noise to which they are subjected during work. In Italy, Law Decree 81/2008 has defined the obligations of vibration and noise assessment and risk management.The aim of this study is to evaluate the risk of exposure to whole-body vibration for the operator driving a tracklaying tractor …
Stato dell’arte degli interventi sulla sorgente per la mitigazione delle vibrazioni generate da sistemi di trasporto su ferro
2008
La crescente esigenza di mobilità registrata negli ultimi anni in molte città italiane ha condotto all’elaborazione di importanti progetti per la realizzazione, o l’ampliamento, di reti di trasporto di massa in ambito urbano. In molti casi le scelte progettuali prevedono la realizzazione di infrastrutture su ferro, come tram, metropolitana, o ferrovia urbana. Tuttavia, soprattutto nelle città caratterizzate da importanti patrimoni edilizi storici, la realizzazione di tali tipologie infrastrutturali comporta enormi problemi di inserimento ambientale dovuti agli impatti acustici e vibrazionali prodotti dall’esercizio dei vettori. Un caso emblematico che ha mobilitato l’attenzione pubblica, na…
Analytical solution for the transient response of symmetric magnetoelectric laminated beams
2010
In this paper an analytical solution is presented for the forced vibration problem of magnetoelectric symmetric laminated beams. In deriving the mathematical model the Timoshenko’s beam theory is used and the electric and magnetic fields are assumed to be quasi-static. The model is written for a magnetoelectric sensing device by applying proper magnetoelectric boundary conditions on the beam top and bottom surfaces. The model highlights that the magneto-electro-mechanical couplings affect the bending stiffness and that the magnetoelectric inputs can be treated as equivalent bending moments. Forced vibration analyses are presented to assess the reliability of the solution.
Vibration-based identification of mechanical properties of orthotropic arbitrarily shaped plates: Numerical and experimental assessment
2018
Abstract An innovative procedure is introduced for the identification of the mechanical parameters of orthotropic plates of arbitrary shape, under various boundary conditions, based on vibration data. The method employs a combination of a convenient Rayleigh-Ritz approach and Particle-Swarm Optimization to estimate elastic constants of the orthotropic material in a straightforward manner, without requiring computationally demanding iterative Finite Element analyses. Specifically, the pb-2 Rayleigh-Ritz procedure is extended and applied to deal with orthotropic plates, simplifying the approach to more easily treat generic plate shapes, taking advantage of the Green's theorem. The method is t…
MODELING TORQUE TRANSMISSIBILITY FOR AUTOMOTIVE DRY CLUTCH ENGAGEMENT
2008
The dry clutch is a fundamental component in many automotive drivelines. For instance, the clutch torque transmissibility characteristic severely influences gearshift performance in automated manual transmissions. In this paper a novel model of the torque transmissibility of dry clutches is proposed. The dependence of the transmissibility characteristic on wear, slip speed and friction pads geometry and the influence of the diaphragm spring, the flat spring and the torsional damper springs is taken into account and pointed out. The sensitivity of a clutch engagement control scheme with respect to the clutch characteristic uncertainties is analyzed.
The effects of intensity, frequency, static load, and shore hardness on different parameters in vibration sensitivity measurements.
1987
The effects of shore hardness, static load, frequency, and intensity of vibration on the amplitude and dynamic force effects of vibration were studied in conditions corresponding to those occurring in vibrotactile sensitivity measurements. The measurements were performed on three silicon plates of known shore hardness. The results indicated that the effect of differences in elasticity on the vibration amplitudes was evident at lower frequencies up to about 200 Hz whereas at higher frequencies the amplitudes remained at the same level, regardless of elasticity. On dynamic force the effect of elasticity was observed at all frequencies studied (50-500 Hz). The static load of the contractor had…