Search results for "Damping"
showing 10 items of 128 documents
Recherche d'indicateurs de la résistance des sols aux maladies d'origine tellurique
2014
Numerical vibroacoustic analysis of plates with constrained-layer damping patches
2011
International audience; A numerical vibroacoustic model that can manage multilayered plates locally covered with damping patches is presented. All the layers can have an on-axis orthotropic viscoelastic behavior. Continuity of displacements and transverse shear stresses at each interface is enforced, which permits to write the entire displacement field in function of the displacements of the-common-first layer, leading to a two-dimensional plate model. The problem is then discretized by Rayleigh-Ritz's method using a trigonometric basis that includes both sine and cosine functions in order to treat various boundary conditions. The excitation can be of mechanical kind (concentrated or distri…
Optimization of Passive Constrained Layer Damping (Pcld) Treatments for Vibration Reduction
2015
An efficient method to reduce the frequency averaged transverse vibration level of aplate by optimizing the position of attached passive constrained layer damping PCLD is presented.This method uses a multilayer anisotropic plate model which is an equivalent single layer platemodel (ESL) where transverse shear stresses and displacements are continuous at each layer’sinterfaces. Hence, for a laminate composed of an arbitrary number of layers, all the quantities arerelated to those of the first layer. The optimization process is based on the use of the ESL platemodel combined with the genetic algorithm (GA) and Latin Hypercube Sampling (LHS) algorithmimplemented in a Rayleigh-Ritz resolution p…
IDENTIFICATION OF THE VISCOELASTIC CONSTITUTIVE EQUATIONS OF FLAX FIBREREINFORCED LAMINATESBY VIBRATION ANALYSIS
2015
International audience; Experimental and numericalapproaches to identify the viscoelastic properties of flax fibrereinforced epoxy composite laminatesare proposed in this study. The method used consisted theidentification of the evolutions of both loss factor and stiffness through the use of the frequency responses. Several free-free symmetrically guided beams were excited on the dynamic range of 10 to 4000 Hz with a swept sine excitation focused around their first’s modes. A fractional derivative Zener model was used to predict the behaviourof on-axis ply complex moduli. The modified ply constitutive law was then implemented in Classical Lamination Theory (CLT) calculation routine. The pro…
Pythium deliense causing severe damping-off of cucumber seedlings and its biological control by soil bacteria
1996
Abstract Pythium deliense Meurs was isolated from cucumber plant debris and was found to be highly pathogenic to cucumber seedlings, causing severe damping-off disease. The fungus however was completely inhibited by a soil bacterium SU-48.1. In vitro and in vivo studies reveal that the disease can be controlled by using this bacterium. The details of the parasitic fungus, the antagonism between the fungus and the bacteria, and the biological control of the disease, are described in this article.
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 …
A Quantitative Analysis of the Thermoelastic Effect in CFRP Composite Materials
2010
: In this study the thermoelastic signal from carbon fibre-reinforced plastic (CFRP) laminates is investigated. A comparison between the theoretical and experimental values of the thermoelastic signal is reported, with the theoretical predictions obtained from two different quantitative models. These models are based on the classic thermoelastic effect law extended to the case of orthotropic materials (by using the mesomechanical or bulk approach), and the modified law assuming that the surface resin-rich layer behaves as a strain witness of the laminate. It is found that the theoretical predictions of the two models can be strongly and differently influenced by the intrinsic orthotropy of…
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…