Liste des documents
Étude expérimentale du délaminageen mode I des tubes fabriquéspar enroulement filamentaire
The good behavior of composite materials under mechanical loading, make it aserious competitor to traditional materials. Inter laminar defects induced duringimplementation or during stress are the main sources of its interlaminar progressive damagecausing separation of the layers known as the delamination. This work is an experimentalstudy of mode I delamination of a laminated composite [±θ°] manufactured as a tube by thefilament winding process. Technical delamination characterization by DCB test specimens(Double Cantilever Beam) are used to determine the energy release rate in mode I andevolution of delamination resistance curves R. Tests were performed according to ASTMD5528 standard and the energy release rate in mode I (GIC) of two configurations isdetermined by the method of Berry. Voir les détails
Mots clés : matériaux composites, enroulement filamentaire, endommagement, délaminage, mode I, taux de restitution d’énergie, courbes-R
MicroFluidic Oscillator: A Technical Solutionfor MicroMixture
The diffusion flux given by the Fick’s law characterizethe mixing rate. A passive mixingstrategy is proposed to enhance mixing of two fluids through perturbed jet low. A numerical studyof passive mixers has been presented. This paper is focused on the modeling of a micro-injectionsystems composed of passive amplifier without mechanical part. The micro-system modeling isbased on geometrical oscillators form. An asymmetric micro-oscillator design based on amonostable fluidic amplifier is proposed [2,7]. The characteristic size of the channels is generallyabout a few hundred of microns. The numerical results indicate that the mixing performance can beas high as 99 % within a typical mixing chamber of0.20 mm diameter inlet and 2.0 mm distance ofnozzle - spliter. In addition, the results confirm that self-rotation in the circular mixer significantlyenhances the mixing performance. The novel micro mixing method presented in this study providesa simple solution to mixing problems in microsystem. Voir les détails
Mots clés : Micro oscillator, modeling, Micro mixture, diffusion, Size effect.
Numerical Simulation of Droplet Breakup, Splitting andSorting in a Microfluidic Device
Droplet generation, splitting and sorting are investigated numericallyin the framework of a VOF technique for interface tracking and a finite-volumenumerical method using the commercial code FLUENT. Droplets of water-in-oilare produced by a flow focusing technique relying on the use of a microchannellequipped with an obstacle to split the droplets. The influence of several parameterspotentially affecting this process is investigated parametrically towards the endof identifying "optimal" conditions for droplet breakup. Such parameters includesurface tension, the capillary number and the main channel width. We show thatthe capillary number plays a crucial role in determining droplet properties and theefficiency of the related generation process. An obstacle configuration can be effectivelyused to split a droplet, with the droplets being naturally sorted at the endof the main channel. Larger values of the capillary number generally lead to anincrease in the droplet frequency and a decrease in its typical size. Voir les détails
Mots clés : Water droplet, flow focusing, splitting, sorting, CFD, VOF, microchannel
Microdrops in Microfluidic: Estimation of Geometrical Form
Manipulation of small-sized liquid quantities is one of the key issues in technology, biology, chemistry and medicine.Where the increased surface-to-volume ratio making surface effects more dominant [42], which allows toreduce time of reaction and economies the costs of manufacturing products. The microdrop is a typical example of asmall-sized liquid quantity; that can be considered as samples, reagents and supplementary indicator to approach us inthe direction of reaction and the state of microdrop. The creation of reproducible in stable geometrical form ofmicrodrop makes a critical step during the manufacturing of microdrop. Pressure based manufacturing of microdropnowadays a common way to create reproducible and stable small-sized drops. Many geometrical form of microdropcan be generated in different techniques. Proofed that microdevices based on pressure based manufacturing ofmicrodrops has already been successfully implemented. This paper serves as a review of the most importantcontributions, in the development of the creation of reproducible and stable microdrops in the past decades. Besidesserving as a reverence for researchers in this area, this paper is also a resource for everybody who wants to identify theeasiest way to precise microdrops geometrical form for a particular application by simple analysis. Voir les détails
Mots clés : form, microdrop, description and theoretical analysis.
Structural, microstructural and magnetic properties of 1% Fe-doped ZnO powder nanostructures prepared by mechanical alloying.
ZnO powder nanoparticles were doped with iron (mixing produced by mechanical alloying). Their structure, microstructure and magnetic properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). ZnO starting pure powder exhibits a hexagonal crystal structure with space group P63mc.Otherwise, with the addition of 1% Fe in the ZnO milled powder, the hexagonal ZnO phase remained unchanged, whereas the microstructural parameters were subject to significant variations due to the introduction of Fe atoms into the ZnO hexagonal matrix to replace oxygen ones. The size of crystallites and microstrains were milling time-dependent. Voir les détails
Mots clés : microstructure; ZnO; mechanical alloying; XRD; SEM-VSM.
Study of the structural and magnetic properties of Fe-doped ZnO
In this work we study the ZnO powder nanoparticles mechanically alloyed doped with iron to investigate the structural, microstructural and magnetic properties using X-ray diffraction (XRD) and Vibrating Sample Magnetometer (VSM). The ZnO starting pure powder exhibited a hexagonal crystal structure with space group P63mc of ZnO, however, with the introduction of 1% Fe in the ZnO milled powder, the hexagonal ZnO phase remained unchanged, whereas the microstructural parameters were subject to significant variations due to the introduction of Fe atoms into the ZnO hexagonal matrix to replace oxygen ones. Voir les détails
Mots clés : microstructure, ZnO, Mechanical Alloying, DRX, VSM
On-Off control based particle swarm optimization for maximum power point tracking of wind turbine equipped by DFIG connected to the grid with energy storage
In this paper, particle swarm optimization (PSO) is proposed to generate an On-Off Controller. On-Off Control scheme based maximum power point tracking is proposed to control the rotor side converter of wind turbine equipped with doubly fed induction generator connected to the grid with battery storage. The Grid Side Converter (GSC) is controlled in such a way to guarantee a smooth DC voltage and ensure sinusoidal current in the grid side. Simulation results show that the wind turbine can operate at its optimum power point for variable speed and power quality can be improved. Voir les détails
Mots clés : DFIG, Energy storage, Maximum Power Point Tracking, On-Off Control, Particle Swarm Optimization (PSO)
Energy storage based on maximum power pointtracking in photovoltaic systems: A comparisonbetween GAs and PSO approaches
In this paper, a comparison between GAs and PSO Approaches is considered to select andgenerate an optimal duty cycle which varies with photovoltaic parameter in order toextract the maximum Power from Photovoltaic System using real values of temperatureand insolation. The energy storage has very important role in renewable energy. To illustratethe energy storage, we have used a battery type lead-acid simulated in Matlab/Simulink. The obtained simulations results show the effectiveness and the robustness ofthe proposed approaches. Voir les détails
Mots clés : Photovoltaic systems, Chopper, MPPT, PSO, GAs, Energy storage
Rechargement d’un acier faiblement allié par Soudage TIG et Brasage
Ce travail s’intéresse à l’évolution microstructurale de l’interface acier 20NCD2/alliage d’argent allié au nickel obtenue après rechargement par brasage et par soudage TIG, dans le but d’établir un comparatif entre ces deux procédés. Sur la base de profils chimiques établis par EDS (Energy Dispersive Spectrometry), de profils de microdureté HV0.1 et de dureté HV10 nous comparerons l’interface acier/alliage d’apport des échantillons rechargés par les deux techniques considérées. Afin de mettre en évidence, les éventuelles interactions entre les différents constituants de la zone d’adhérence et l’effet thermique des deux procédés. Voir les détails
Mots clés : rechargement, brasage, soudage TIG, interface.
Caractérisations mécaniques et métallographiques d’un joint de soudure réalisé par TIG en acier inoxydable duplex 2205
Notre étude vise la caractérisation mécanique et métallographique d’une soudure autogène dont, le matériau est un acier inoxydable duplex 2205 soudé avec le métal d’apport ER 2209. Ces matériaux de par leurs très bonnes propriétés mécaniques et leurs tenues en milieux corrosifs ainsi que l’aptitude au soudage, ont acquis une importance considérable dans diverses industries. Dans une première partie, nous avons mis en évidence certaines propriétés structurales et mécaniques des aciers inoxydables duplex 2205 (bi-phasé austénite, CFC/ferrite, CC), ainsi que leur évolution structurale suite à une opération de soudage (TIG).Dans une deuxième partie nous avons étudié expérimentalement les caractéristiques mécaniques et métallographiques de l’acier inoxydable duplex 2205. Le comportement de notre acier en traction, délivre des valeurs excellentes sur ces propriétés mécaniques. Le métal de base présente une bonne résistance au choc, même à basse température. Cependant la résistance de zone fondue a sensiblement diminué en raison de la formation de phases dures riches d'austénite secondaires et de la ségrégation inégale des éléments d'alliage. Voir les détails
Mots clés : soudage TIG, acier duplex, Joint de soudure.