Multi-modal wave propagation in smart structures with shunted piezoelectric patches

International audienceThe propagation of wave modes in elastic structures with shunted piezoelectric patches is dealt with in this work. The wave finite element approach, which is based on the finite element method and periodical structure theory, is firstly developed as a prediction tool for wave propagation characteristics in beam like structures, and subsequently extended to consider shunted piezoelectric elements through the diffusion matrix model (DMM). With these numerical techniques, reflection and transmission coefficients of propagating waves in structures with shunted piezoelectric patches can be calculated. The performance of shunted piezoelectric patches on the control of wave propagation is investigated numerically with the DMM. Forced response of the smart structure can also be calculated, and based on which the time response of the structure can be obtained via an inverse discrete fourier transform approach. These general formulations can be applied to all types of slender structures. All these numerical tools can facilitate design modifications and systematic investigations of geometric and electric parameters of smart structures with shunted piezoelectric elements

Dynamics of stochastic and periodic structures in mid-frequency range

International audiencea hybridization of the Wave Finite Element Method (WFEM) with the Generalised Polynomial Chaos Expansion (GCE). The WFE is a spectral method dealing with wave propagation in periodic structure. This method proved its efficiency in different domains; structural vibration, non-destructive testing, etc. However, the WFE is limited to deterministic media. Knowing that uncertainties affect dynamic behavior in Mid- and High frequencies, the combination of WFE and GCE is used to predict the effect of uncertainties on the dynamic response of periodic media. The uses of the GCE is based on the iso-probabilistic transformations for usuel distributions to Gaussian one to use the Hermite-Chaos expansion.The presented approach is validated for two periodic waveguides connected through a junction with uncertain parameters. The obtained results are verified vs Monte Carlo simulations

Strontium-loaded mineral bone cements as sustained release systems : Compositions, release properties, and effects on human osteoprogenitor cells

This study aims to evaluate in vitro the release properties and biological behavior of original compositions of strontium (Sr)-loaded bone mineral cements. Strontium was introduced into vaterite CaCO3-dicalcium phosphate dihydrate cement via two routes: as SrCO3 in the solid phase (SrS cements), and as SrCl2 dissolved in the liquid phase (SrL cements), leading to different cement compositions after setting. Complementary analytical techniques implemented to thoroughly investigate the release/dissolution mechanism of Sr-loaded cements at pH 7.4 and 37°C during 3 weeks revealed a sustained release of Sr and a centripetal dissolution of the more soluble phase (vaterite) limited by a diffusion process. In all cases, the initial burst of the Ca and Sr release (highest for the SrL cements) that occurred over 48 h did not have a significant effect on the expression of bone markers (alkaline phosphatase, osteocalcin), the levels of which remained overexpressed after 15 days of culture with human osteoprogenitor (HOP) cells. At the same time, proliferation of HOP cells was significantly higher on SrS cements. Interestingly, this study shows that we can optimize the sustained release of Sr2þ, the cement biodegradation and biological activity by controlling the route of introduction of strontium in the cement paste

Développement de la microchimie élémentaire et isotopique (87Sr (86Sr) des otolithes de saumons Atlantique)

Le saumon Atlantique fait partie du patrimoine écologique et économique du bassin de l Adour. Dans le cadre de la gestion actuelle du saumon dans ce bassin, l origine natale des géniteurs, le taux de retour des individus d origine piscicole, le taux de homing sur chaque sous-bassin ou encore le soutient par des géniteurs extérieurs au bassin de l Adour sont des thématiques qui restent sans réponses. Ce projet propose donc de tester le potentiel de la géochimie des otolithes sur le saumon Atlantique du bassin de l Adour. Nos travaux démontrent que la variation géographique de la composition chimique de l eau dans 12 rivières colonisées par le saumon, associée à un enregistrement dans l otolithe proportionnel à la signature géochimique du milieu de vie, permettent de discriminer l origine géographique des individus. La combinaison des signatures élémentaires (Sr:Ca et Ba:Ca) et surtout l isotopie du Sr (temporellement plus stable et sans fractionnement biologique) dans les otolithes améliore la précision du classement à l échelle de la rivière de développement. En se basant sur la transmission de signatures géochimiques (élémentaires et isotopiques) transgénérationelles entre la femelle reproductrice et les otolithes des embryons produits par cette dernière, nous avons discriminé avec succès les individus nés en rivière de ceux nés en pisciculture. Le classement des géniteurs (180 individus) selon leur rivière natale a confirmé que le sous bassin du gave d Oloron, et plus particulièrement le gave d Ossau, reste le lieu qui produit le plus de saumon de retour. De façon non négligeable, le gave de Pau contribue lui aussi au renouvellement de la population (10 d origine piscicole et 6 d origine naturelle). 18 saumons sur 180 sont issus de l alevinage (soit 10%); la majorité s étant développée dans le sous-bassin du gave de Pau. Par ailleurs, nous avons mis à jour l existence de périodes au cours de la vie des juvéniles (changements de milieu: sac vitellin milieu extérieur et pisciculture rivière) durant lesquelles l enregistrement du Ba dans l otolithe n est pas en relation avec la chimie de l eau. L originalité de notre approche est d avoir étudié l influence des facteurs endogènes et environnementaux chez des poissons ayant vécu dans le milieu naturel ou ayant séjourné en milieu naturel contrôlé. Nos travaux mettent l accent sur la complexité de l intégration du rapport Ba:Ca dans l otolithe et démontrent l utilité des éléments traces et des isotopes du Sr comme tag naturel pour distinguer l origine natale du saumon Atlantique.The Adour basin holds one of the largest populations of Atlantic salmon in southern Europe exploited by commercial and sport fisheries. Determining the relative contributions of individual rivers and hatcheries to the Adour basin populations becomes crucial to understand key sources that contribute the most to its persistence. We successfully used Sr:Ca, Ba:Ca and 87Sr:86Sr ratios as natural tags for determining the natal origins of adults from 12 tributaries. Success in discriminating between fish from different sites was greatest using Sr isotopes since the latter remained relatively constant across years at a given location. Geochemical signatures from core regions of the otolith were also used to identify fish from hatchery or naturally spawned sources. The predominance of adults spawned in the Ossau River among returning adults corresponded with long-term juvenile production trends in the Ossau River. Despite the limited upstream accessibility of the Pau River, our study demonstrated that Atlantic salmon recruits can successfully leave this river to join the adult population in the Adour basin. We observed relatively clear separation between hatchery and wild juveniles using both Sr:Cacore (wild > 2.5 and hatchery 0.710). The return of hatchery reared fish as adult spawners represented 10% of the total sampled fish we analyzed. Almost all adults, previously identified as belonging to the Ouzom River, were hatchery produced. Adults originated from the Pau River were either wild or hatchery reared fish. We also conducted field controlled experiments that characterized the elemental uptake process in juvenile Atlantic salmon otoliths during freshwater residency. Physiological effects influenced Ba deposition. Ba:Ca otolith profiles from hatchery-reared and field collected fish were characterised by a peak at yolk absorption mark. Hatchery-reared fish stocked in a river also displayed a peak of Ba:Ca following transfer which was not related to the water chemistry. Our experiment revealed a 20-day lag time between initial Ba:Cawater changes and Ba:Caotolith saturation. Results suggested that such effects should be considered during any attempts to determine rivers of origin of Atlantic salmon based on otolith elemental composition or reconstruct the movement of individual fish among and within streams.PAU-BU Sciences (644452103) / SudocSudocFranceF

Conception et développement d'un système d'inspection par ondes guidées pour la détection des défauts dans les tubes

Le système d'inspection conçu permet d'acquérir des signaux de mesure sur une canalisation et de fournir des indications sur la localisation des défauts avec des idées sur leurs natures. Le générateur des ondes guidées permet l'émission des ondes de torsion et la réception des échos réfléchis. Certains outils de traitement du signal pour le filtrage et l'analyse des signaux enregistrés sont utilisés dans le but d'éliminer les bruits de fonds et les parasites pour extraire les informations les plus pertinentes

Multimodal wave propagation in smart composite structures with shunted piezoelectric patches

International audienceWave propagation in composite structures with shunted piezoelectric patches is investigated in this study. The wave finite element approach is first developed as a prediction tool for wave propagation characteristics such as dispersion curves in composite structures, and subsequently extended to consider shunted piezoelectric elements through the diffusion matrix model. A three-layered composite beam equipped with a pair of resistor-inductor shunted piezoelectric patches is modeled and analyzed carefully with these numerical techniques. Reflection and transmission coefficients of propagating waves in this smart composite structure are calculated, and the performance of shunted piezoelectric patches on the control of wave propagation is investigated numerically with the diffusion matrix model. Another finite element formulation, named modified wave finite element method, which is dedicated to the analysis of wave propagation in multilayered composite structures, is proposed and developed for considering piezoelectric elements in the structures. It is a dynamic substructuring technique that allows the dynamics of a typical layer cross section to be projected on a reduced local wave mode basis with appropriate dimensions. Results issued from this method are compared to those issued from the classical wave finite element and diffusion matrix model formulations to demonstrate the pertinence of the modelings

Approche énergétique pour des guides d'ondes stochastiques : formulation et validation

La Caractérisation de la propagation d'énergie dans des guides d'ondes viscoélastique aléatoires sera discutée dans ce papier. Cette approche est basée sur une méthode spectrale stochastique appelée « Stochastic Wave Finite Element ». Cette méthode est une extension de la WFE pour les milieux aléatoires. Cette approche permet de prédire la dispersion des quantités énergétiques en tenant compte des incertitudes (géométriques et incertitudes de la propriété). Des simulations prouvent l'efficacité de notre approche. Les résultats sont validés par des simulations de Monte Carlo

Medium frequency phenomena on heavy vehicles: experimental analysis and numerical applications

Driveline vibrations of a truck are a cause of strong discomfort for drivers, and have to be investigated in pre-design phases. In order to develop numerical and analytical tools for the prediction of noise and vibration of such a complex structure, a deep knowledge of the physical phenomena involved is imperative. Few experimental studies have been performed on truck vibrations, and they mostly concerned single components of a vehicle. Therefore an Experimental Modal Analysis (EMA) of a complete truck has been performed in order to observe vibratory phenomena and determine influencing parameters involved in the vibration transmission. This study brings new insights into the field of truck vibrations. The results of the test campaign have been used for correlation with a numerical model and for the identification of dynamic behaviour and related frequency ranges. This work constitutes the preliminary part for an on-going project aiming at the development of reduced numerical models for the prediction of sound and vibration in truck cabins

Predicting the broadband response of a layered cone-cylinder-cone shell

The dynamic response of an aerospace layered structure composed of a combination of conical and cylindrical shells is hereby modelled. In the low and the mid-frequency ranges a WFEM derived ESL approach implemented within a FEM is used in order to predict the response of the shell. Furthermore, in the high frequency range the CLF of the connected subsystems are calculated using a WFEM/FEM approach. These CLF are implemented within a SEA approach in order to predict the structural response. The accuracy and robustness of the developed approaches are exhibited by comparisons to experimental measurements on a layered conical-shell-conical configuration