Search results for " Vibrations"
showing 10 items of 28 documents
Mechanically Based Nonlocal Euler-Bernoulli Beam Model
2014
AbstractThis paper presents a nonlocal Euler-Bernoulli beam model. It is assumed that the equilibrium of a beam segment is attained because of the classical local stress resultants, along with long-range volume forces and moments exchanged by the beam segment with all the nonadjacent beam segments. Elastic long-range volume forces/moments are considered, built as linearly depending on the product of the volumes of the interacting beam segments and on generalized measures of their relative motion, based on the pure deformation modes of the beam. Attenuation functions governing the space decay of the nonlocal effects are introduced. The motion equations are derived in an integro-differential …
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…
On the vibrations of a mechanically based non-local beam model
2012
The vibration problem of a Timoshenko non-local beam is addressed. The beam model involves assuming that the equilibrium of each volume element is attained due to contact forces and long-range body forces exerted, respectively, by adjacent and non-adjacent volume elements. The contact forces result in the classical Cauchy stress tensor while the long-range forces are taken as depending on the product of the interacting volume elements and on their relative displacement through a material-dependent distance-decaying function. To derive the motion equations and the related mechanical boundary conditions, the Hamilton's principle is applied The vibration problem of a Timoshenko non-local beam …
Nonlinear free vibrations of composite structures via the X-Ritz method
2020
The analysis of large amplitude vibrations of thin-walled cracked structures build as plate assembly is considered in this study. The problem is addressed via a Ritz approach, called X-Ritz, based on the first order shear deformation theory and von K´arm´an’s geometric nonlinearity assumptions. The trial functions are expressed as series of regular orthogonal polynomial products supplemented with special functions able to represent the crack behaviour; boundary functions are used to guarantee the fulfillment of the kinematic boundary conditions. Results are presented, which illustrate the influence of cracks on the stiffening effect due to large amplitude vibrations.
Nonlinear free vibrations analysis of cracked composite stiffened plates via X-Ritz approach
2019
Thin and moderately thick composite multi-layered plates are widely employed in naval and aerospace structures. They can experience the presence of cracks, generated for example by corrosion, fatigue or accidental external causes, which aect their static and dynamic behaviour. As regard the dynamic characteristics of plates, many studies have focused on the linear vibration analysis of both isotropic and composite thin and thick plates, providing for a comprehensive knowledge of the plate dynamic behaviour. However, for an accurate appraisal of the plate dynamics, in some applications it is needed to investigate the nonlinear free vibration problem; a literature survey evidences that the la…
Périphérique d'interaction apte à contrôler un élément de toucher et de préhension d'objets virtuels multidimensionnels
2012
Ne pas le transférer sur HAL (déjà déposé sur HAL par le co-auteur (hors ENSAM)) L’invention concerne un périphérique d’interaction (1) apte à contrôler un élément de toucher et de préhension d’objets virtuels multidimensionnels, comportant au moins deux modules d’interaction (20), chaque module d’interaction (20) étant destiné à être actionné par un doigt d’un opérateur et comportant un capteur de commande permettant de commander un déplacement, selon un nombre de degrés de liberté prédéterminé, d’une partie de l’élément de toucher et de préhension d’objets virtuels par déplacement en flexion/extension et/ou adduction/abduction du doigt de l’opérateur, et un vibreur apte à émettre une vibr…
The Influence of the feedback control of the hexapod platform of the SAAM dynamic driving simulator on neuromuscular dynamics of the drivers
2012
Multi sensorial cues (visual, auditory, haptic, inertial, vestibular, neuromuscular) [Ang2] play important roles to represent a proper sensation (objectively) and so a perception (subjectively as cognition) in driving simulators. Driving simulator aims at giving the sensation of driving as in a real case. For a similar situation, the driver has to react in the same way as in reality in terms of ‘self motion’. To enable this behavior, the driving simulator must enhance the virtual immersion of the subject in the driving situation. The subject has to perceive the motion of his own body in the virtual scene of the virtual car as he will have in a real car. For that reason, restituting the iner…
Recent developments in the acoustical properties of perforated and porous materials containing dead-end pores
2017
It was shown recently in Nevers, France, Sherbrooke, Canada and Salford, UK, that porous materials with semi-opened pores or materials with open pores bearing lateral cavities or resonators at the microscopic scale of the pores can result in peculiar sound absorption properties. Various examples of these materials can be found in engineering and in everyday life including bio-based materials. The cavities and resonators can be assimilated to dead-end pores, which are opened at one end and closed at the other. The dead-end pores are known to geophysicists. We studied them more recently in the field of engineering acoustics where the saturating fluid is air. The closed ends prevent the fluid …
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 …