Search results for "VIBRATIONS"
showing 10 items of 46 documents
Vibrational damping properties of finite microperforated plates
2023
Microperforated plates (MPP) are traditionally used to advantageously absorb acoustic waves in sound control technologies. However, less is known concerning the additional structural damping they can induce. The latter is activated through exchanges in the viscous and thermal boundary layers near the fluid-structure interface of the microperforations. MPPs therefore offer an alternative to, or can be used together with, viscoelastic materials, commonly implemented to damp vibrations at medium and high frequencies. In this work, the structural damping capabilities of MPP are investigated. To this end, the damping performance of a finite size MPP is explored analytically through an alternativ…
Added viscous damping in a finite-size microperforated plate within a nonlinear framework
2023
Increasing the damping properties of a structure while limiting the addition of mass is a challenging task. Originally developed for their acoustic absorption capabilities, microperforated plates (MPP) are simple devices that can feature additional viscous damping at low frequencies. Dissipation arises in the boundary layers of the microperforations through viscous friction mechanisms induced by the relative motion between the solid and the fluid in which the MPP is immersed. This leads to sound absorption in an acoustic context and to an added viscous damping in a solid dynamics context. The added viscous damping exhibited by the MPP can be captured by considering adapted fluid-solid inter…
INNOVATIVE MASS-DAMPING-BASED APPROACHES FOR SEISMIC DESIGN OF TALL BUILDINGS
2021
Mass damping is a well known principle for the reduction of structural vibrations and applied in tall building design in a variety of configurations. With mass usually small (around 1% of building mass), the properly “tuned” mass damper (TMD) shows great effectiveness in reduc-ing wind vibrations, but minor advantages under earthquake excitations. The above limitation can be surpassed by utilizing relatively large mass TMD. For this pur-pose, two different solutions are here proposed. In both cases, the idea is to separate the building into two or more parts, thus allowing for a relative motion between them, and acti-vating the mass damping mechanism. In the first solution, the building is …
Complex composite structures with integrated piezoelectric transducers
2016
International audience; Nowadays, in different industrial fields as transport or aerospace, a research effort is conducted to reduce the structural weight. One of the most promising solutions is the use of composite structures due to their high stiffness, their low mass density and their low damping factor. At the same time, there is an intensification of the operational dynamic environment and an increase of durability requirements. These different expectations seem to be contradictory. One solution to manage these points is to design and manufacture smart composite structures with a fully distributed set of integrated piezoelec-tric transducers. These structures are able to modify their m…
On the critical velocities and free vibrations of axially moving elastic webs
2014
Enhancing Optomechanical Coupling via the Josephson Effect
2013
Cavity optomechanics is showing promise for studying quantum mechanics in large systems. However, smallness of the radiation-pressure coupling is a serious hindrance. Here we show how the charge tuning of the Josephson inductance in a single-Cooper-pair transistor (SCPT) can be exploited to arrange a strong radiation pressure -type coupling $g_0$ between mechanical and microwave resonators. In a certain limit of parameters, such a coupling can also be seen as a qubit-mediated coupling of two resonators. We show that this scheme allows reaching extremely high $g_0$. Contrary to the recent proposals for exploiting the non-linearity of a large radiation pressure coupling, the main non-linearit…
Forced vibration analysis of magneto-electro-elastic beam
2009
Free vibrations analysis of cracked variable stiffness composite plates by the eXtended Ritz method
2022
Variable stiffness composite laminates show advantageous structural features related to their enlarged design space. They are attractive candidates for advanced engineering applications where the assessment of static and dynamic behavior and strength in the presence of cracks is often required. In the present work, a single-domain extended Ritz formulation is proposed to study the free vibrations of cracked variable stiffness composite plates. The plate model is based on the first-order shear deformation theory whose primary variable, i.e. displacements and rotations, are approximated via a set of orthogonal polynomial trial functions enriched with a set of special crack functions. These fu…
A system for detecting hand-arm vibration in the use of portable shakers for olives harvesting
2012
The mechanization of olive harvesting is very important both to reduce the costs of production and to assure the oil quality because the manual harvest does not allow to operate at the right time and also need a long period to be completed. The use of portable shakers, that are spreading more than others typologies, can give a solution to the problem. However, the use of such equipment may involve risk of exposure to hand-transmitted vibration. The aim of this study was to assess the level of exposure to hand-arm vibration of the operators using portable shakers (reference standards UNI EN ISO 5349-1:2004, Italian Low Decree 81/2008). An effective approach would rather involve to equip the …