Liste des publications
Microstructure and mechanical behavior in dissimilar 13Cr/2205stainless steel welded pipes
Thiswork aims to investigate the microstructure and themechanical behavior of dissimilar 13Cr Supermartensitic/2205 Duplex stainless steelwelded pipes. A wide variety ofmicrostructures resulting fromboth solidification andsolid state transformation is induced by the fusion welding process across the weld joint. The tensile tests showthat the deformation process of the dissimilarweld joint ismainly controlled by the two basematerials: the duplexsteel at the beginning of the deformation and the supermartensitic one at its end. This is confirmed by the microtensiletests showing the overmatching effect of the weld metal. The fatigue tests conducted on dissimilar weldedspecimens led us to conclude that the weld metal is considered as a weak link of the weld joint in the high cyclefatigue regime. This is supported by its lower fatigue limit compared to the two basematerials that exhibit a similarfatigue behavior. Voir les détails
Mots clés : Dissimilar welding, microstructure, Tensile testing, High cycle fatigue
Sensor Monitoring of the Concentrations of Different Gases Present in Synthesis of Ammonia Based On Multi-Scale Entropy and Multivariate Statistics
This paper presents powerful techniques for the development of a new monitoring method based on multi-scale entropy (MSE) in order to characterize the behaviour of the concentrations of different gases present in the synthesis of Ammonia and soft-sensor based on Principal Component Analysis (PCA). Voir les détails
Mots clés : Ammonia synthesis, Concentrations of different gases, Soft sensor, Multi-scale entropy, multivariate statistics.
Effects of a circular defect size and position on the damage progression in hybrid laminates under compressive loading.
The effects of a circular defect size and position on the post-damage response of the FMLs laminates under compressive loading have been studied. Compression tests are performed on composite plates comprising a hole having different diameters (8mm, 12mm and 16mm) and located at different positions (25%, 50% and 75%) in the loading direction. A numerical analysis using the finite element method FEM has permits the identification of the initiation zones and the description of the damage evolution in these laminates. The results of the numerical simulation are in good agreement with the experimental results. The FEM has well predicted the critical damage zones. Voir les détails
Mots clés : Defect, damage, hybrid laminate, FEM
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
Theoretical estimation of the production of biogasfrom the landfill of Batna city and its electricalconversion by a SOFC
Amongst the interests in fuel cells is exploring the possibility of using different fuel types;one of them is biogas or Landfill gas (LFG) from landfills or from controlled digesters.Biogas; a gas produced by an anaerobic digestion of organic waste represents an environmentalproblem that could turn to a renewable energy source. The valorization ofbiogas into energy (electricity, heat, fuel) will save other sources of energy. The authors ofthe study are interested in evaluating three technologies: fuel cells, micro turbines andinternal combustion engine.In this paper, we discussed the conversion of biomass into electricity in two steps: thefirst step (biomass-to-biogas) is based on an evaluation of biogas potential generated bysolid waste of landfill the Batna city (Algeria) by the kinetic model (U.S.EPA, 1993). In thesecond step (biogas-to-electricity), the paper considers the technology of a stack of standardsolid oxide fuel cells (Ni-YSZ/YSZ/LSM) SOFC; this allowed us to determine the besttemperature, hydrogen concentration and electrolyte thickness for maximum powerdensity in the fuel cell SOFC. At a temperature T = 1273 K and thickness of electrolyte of theorder of 0.1 mm and at higher hydrogen concentration, a maximum power density ofP = 1.4 W/cm2 was obtained. Voir les détails
Mots clés : LFG, Biogas, Anaerobic digestion, Electricity, SOFC
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