An analytical model of an elementary elliptical cell forming an alveolar elastic material under plane stress

This paper analyzes the static behavior of alveoled materials that is about to be developed for dynamic optimization of structural panels. It deals precisely with materials made of elliptical thin cells, filled with polymer material. The main contribution of the paperconsists in elaborating an analytical approach describing the material. The considered problem represents an unidirectional stress, the goal being to calculate the elastic energy and strain globally obtained in the material. The wall of the elementary cell is represented in accordance with the classical BRESSE's theory of thin beams, with specific adaptation for elliptical shape. The polymer material filling the cell is modelized with ABSI!s method of equivalence, which allows a direct approximation of various continuous media by equivalent spring segments. This method is presented and discussed for the present configuration, with its specific adaptation. The final result obtained by these analytical approaches is then compared to results from a finite element model. In spite of local differences between the analytical results and numerical computation, it appears clearly that the precision obtained by the proposed analytical approach is better than 95%, which is sufficient for this kind of material. Thus, the proposed analytical calculation and methodology allows robust and quick determination of material characteristics for elementary cells of such alveoled materials. The resulting laws can then be introduced into global models of a grid of cells

A truncated low approach of intrinsic linear and nonlinear damping in thin structures

An adaptive approach of vibrating thin structures is proposed here. The method consists in applying an equivalent adimensional damping ratio to each potential resonance. This ratio is deduced from experimental data obtained in vacuum facility, in relation with frequencies, for several structural technologies. Consequently, it is possible to calculate the structure in a linear non-dissipative context, valid out of resonance bands, and truncated in those bands. Thus, the equivalent damping ratio is directly used to define adimensional resonance truncation bandwith and level. The contribution consists in tested and applied modal methodology and algebraic representations of damping including several dissipations-viscous and internal microfrictions-inducing non-monotonous model. The here aim is to provide realistic recommendations for simple vibrational analysis of aerospace thin structures-panels and sti

A self-mixing laser sensor design with an extended kalman filter for optimal online structure analysis and damping evaluation

We have developed a new algorithm based on the extended Kalman filter, in order to improve the resolution of an optical displacement sensor. This new non contact sensor which provides vibration measurement with a very good accuracy might be used for online quality control by measuring the damping of excited mechanical structure. This self-mixing sensor subject to weak feedback has been tested in comparison with a commercial vibrometer, to measure the frequency response function of a plate with a passive damping to be characterized, in order to show the efficiency of a damping treatment

Développement et optimisation d'un revêtement alvéolaire pour le contrôle passif de vibrations

Cette étude est une contribution aux techniques passives de réduction des vibrations destinées à réduire le bruit d'origine solidienne. Le traitement proposé met en œuvre une technologie innovante qui utilise les performances des matériaux viscoélastiques (d'un point de vue amortissement) et d'un ampli cateur elliptique (d'un point de vue dissipation). Le comportement mécanique d'une alvéole elliptique est étudié à l'aide de deux approches (analytique et numérique). Puis sur structure poutre, une étude des performances et des relations entre les paramètres géométriques et la réponse est menée à l'aide de trois types de modèles : analytique, numérique et expérimental. Ces approches montrent l'importance de l'ampli cateur sur l'amortissement de la réponse vibratoire. Suite à ces modélisations, une étude est réalisée sur une structure de type plaque. Deux types de configuration du concept alvéolaire ont été mis en œuvre, la première travaillant en extension (FLD) et la seconde en cisaillement (CLD). La méthode des réseaux de neurones est employée pour établir les relations entre les paramètres d'entrée et de sortie pour chacune de ces configurations. Elles sont ensuite optimisées et permettent d'atteindre une réduction du niveau vibratoire moyen de 50% sur la plage de fréquence (O, 2000Hz) par rapport aux produits commerciaux préexistants. Enfin, une méthode d'homogénéisation est également développée pour caractériser les paramètres homogènes du concept en con guration FLD. La pertinence des résultats de cette méthode a été véri ée et présente un SAC de 98% par rapport au modèle hétérogène.TOULOUSE-ISAE (315552318) / SudocSudocFranceF