Search results for "Engineering sciences"
showing 10 items of 2347 documents
Étude Du Comportement Thermomécanique De Structures Recouvertes De Patchs Visco-Contraints
2018
International audience; La thermographie infrarouge est une méthode qui permet d'obtenir la carte de luminance de la scène thermique observée, de la convertir en température apparente et d'afficher ou d'enregistrer le résultat sous la forme d'une image de la distribution de la température. Nous l'utilisons ici, pour la détection à distance, des sources d'énergie dans des structures formées de poutres recouvertes de patchs viscoélastiques.
Fabrication De Matériaux Composites À Fibres De Lin En Vue D’une Application De Mobilier Urbain Ultraléger Et Mobile
2017
International audience; L’effet de massification automobile qui accompagne les besoins croissants de mobilité terrestre et l’offre de nouvelles infrastructures routières qui soutient de nouvelles demandes rendent les modèles de mobilité actuels de plus en plus difficilement acceptables. En effet, les personnes souffrent de l’inconfort des villes engorgées (nuisances), de l’insécurité lors de transports du fait de défaillances techniques ou humaines, de la très grande difficulté d’optimiser ses itinéraires en fonction des horaires ou circonstances exceptionnelles (accident par exemple). Par ailleurs, la mobilité se heurte toujours aux contraintes liées aux rigidités des infrastructures compo…
Assessment of the Performance of Trim Materials : Modeling and Validation by Mean of Several Measurement Strategies
2014
International audience; Trim materials are designed to minimize sound transmission and maximize sound absorption. Often, a balance between those two quantities is desired with an emphasis on one or another depending on the application in hand. Porous material are typically used as they allow for both sound absorption and transmission loss while minimizing the added mass. In this paper, the performance of a melamine foam panel is assessed. The considered sample is glued on the A2-size opening of a heavy concrete cabin designed for material testing in absorption (Alpha-cabin-like) and transmission (from the cabin to surrounding environment). The material is excited through a random sound fiel…
Low Frequency Sound Absorption in a Porous Material with Periodically Distributed Dead-End Pores
2015
International audience; A theoretical and numerical study of the sound propagation in air-saturated porous media with straight pores bearing lateral cavities (dead-ends) is proposed. The straight pores can be considered as the main (Biot) pores. The lateral cavities are located at ”nodes” periodically spaced along each ”main pore” axis. The effect of periodicity in the distribution of the lateral cavities is studied and the low frequency limit valid for the closely spaced dead-ends is considered separately. It is shown that the absorption coefficient and transmission loss are influenced by the viscothermal losses in the main pores as well as their perforation rate. The presence of long or s…
Comparative study by design of experiments of linear and nonlinear constitutive models and geometric parameters effects on PEMFC performances
2019
International audience; Proton Exchange Membrane Fuel Cell (PEMFC) appears to be a promising technology to take up the challenges of energy transition, therefore it appears necessary to optimize the systems to use the right amount of raw materials. In our study, we have addressed the mechanical aspects and their impacts on performance of it. More specifically, the main objective of the proposed work is to understand the influence of fuel cell core design and mechanical properties on electrical resistances of internal system contacts. Indeed, electrical contact resistances are one of the important sources of losses and therefore require special attention. To achieve this, a Design of Experim…
Assessment of the performance of trim materials: validation by mean of several measurement strategies
2014
International audience; Trim materials are designed to minimize sound transmission and maximize sound absorption. Often, a bal-ance between those two quantities is desired with an emphasis on one or another depending on the application in hand. Porous material are typically used as they allow for both sound absorption and transmission loss while minimizing the added mass. In this paper, the performance of a melamine foam panel is assessed. The considered sample is glued on the A2-size opening of a heavy concrete cabin designed for material testing in absorption (Alpha-cabin-like) and transmission (from the cabin to surrounding environment). The material is excited through a random sound fie…
Propriétés acoustiques de matériaux perforés comprenant des pores dead-end périodiques pour des applications basses fréquences
2016
International audience; Pour un matériau absorbant tel que la mélamine et pour une épaisseur assez faible (inférieure à 5 cm), l'absorption acoustique devient supérieure à 0.8 à partir d'une fréquence de l'ordre de 1000 Hz. Une étude récente [1] a montré que des matériaux perforés peu épais comportant le long des perforations des pores dead-ends (DE) régulièrement espacés peuvent permettre de produire des pics d'absorption supérieurs à 0.8 en basses fréquences (quelques centaines de Hz). Les dimensions des pores DE ainsi que leur périodicité peuvent être millimétrique ou submillimétrique de sorte que l'épaisseur totale du matériau soit de seulement quelques centimètres. Ces pores DE peuvent…
On the design of novel access and methodology for optical diagnostics inside internal combustion engines under severe operating conditions
2018
International audience; Fluid Dynamic Processes in Direct Injection Engines and this anniversary is wortha celebration! It indicates that THIESEL has acquired over the past 20 years aconsolidated position as a meeting point between industry, research institutionsand academia involved in R&D for automotive engines. And naturally, it strives toremain a reference forum for the next 20 years.True, combustion engines are widely unpopular nowadays and manufacturersface even tougher environmental challenges. However, no doubt combustionengines will remain the main propulsion system in transport for the next 20 to 50years, at least for as long as alternative solutions cannot provide the flexibility…
Transfer matrix modeling and numerical verification of locally reacting acoustic mosaics
2012
International audience; This paper deals with the modeling of the acoustic behavior (absorption and transmission) of an acoustic mosaic having heterogeneous surface properties. On the surface, the material can be viewed as a collection of independent cells reacting locally. Each cell is filled with an absorbent material different from its neighbors. Such a mosaic may be seen as a generalization of the typical case of a honeycomb liner filled with absorbent materials. The originality of the study lies in the modeling of such heterogeneous material by an Admittance Sum Method (ASM) and a Transfer Matrix Method (TMM). The transfer matrix modeling of the heterogeneous material uses the summatio…
Green Fleet Management Architecture : Application to Economic Itineary Planning
2012
International audience; Over the last decade, great efforts are invested in reducing emissions of greenhouse gases at a world scale. We should therefore elaborate new global solutions to this type of pollution, in which fleets of vehicles are heavily contributing. In this paper, we propose a novel green architecture for global fleet management that considers the most important actors. The proposed architecture allows to collect useful information from several fleets of vehicles and their environment, and provides real-time services to companies that own one of these fleets. One important service is the calculation of economic itinerary. We propose a new "green" calculation method that is ba…