Liste des Mémoires de Master
Comportement mécanique et métallurgique des jonctions hétérogènes soudées par friction rotative
Rotational friction welding is a solid state welding process, which has seen spectacular development in various industries. It offers the possibility of producing very high quality solder joints in an extremely short time. The objective of this work is to improve the operating parameters of this process by changing the friction time (periods) and fixing the other parameters namely the speed of rotation [round per minute], the forging time [s], the friction and forging pressure [MPa]. The major problem with the disimmilar assembly of aluminum and stainless steel alloys is the low mechanical strength in the welded joint, due to the formation of certain unwanted inter-metal compounds during welding. An experimental procedure was used to obtain an Al6013-T8 /304L stainless steel welded joint with and without copper insertion. Different characterization methods were used namely x-ray diffraction, optical microscopy, HV microhardness and tensile testing. The Al6013-T8 side microstructure reveals the formation of two zones, the HAZ and the TMAZ at the center of the junction, unlike 304L stainless steel, which has not undergone any mechanical deformation. The microhardness of Al6013-T8 increased in the vicinity of the junction, and tensile testing revealed that the mechanical characteristics of the joints increase with increasing friction time. Voir les détails
Mots clés : Rotational friction welding, the speed of rotation, the forging time
Segmentation des images radiographiques
Image segmentation is an important step in any image analysis process. The subject has already been tackled by multiple approaches. These approaches are based on various tools such as mathematical morphology, wavelet decomposition, active contours; some are based on the detection of contours and others on the identification of regions. Each of these classes of methods has its advantages and disadvantages. In this dissertation, we present the different segmentation approaches and we choose a hybrid method for segmenting chest X-ray images composed of two algorithms. One is the FCM as an initial contour for the other segmentation method LEVEL SET which is a variant of the deformable models based on the active contour method, we injecting the images resulting from this segmentation process into a convolutional neural network (CNN) in order to classify them according to the pathological state. Therefore the aim of our work is the implementation of a model for segmentation and classification of medical X-ray images to assist doctors in the detection of pulmonary pathologies. Voir les détails
Mots clés : image segmentation, chest X-ray image, Active contour, FCM, Level set, classification, CNN
Caractérisation des paramètres de fissuration en mode d'ouverture par corrélation d'images et éléments finis d’un alliage d’aluminium 2xxx
In this work, a problem of fracture and crack resistance is studied, the 2000 aluminum alloy series available in market is chosen, in this context of fracture mechanics the structural durability and integrity of materials is investigated. Couple techniques are used, an experimental characterization assisted by the digital image correlation technique and finite elements based numerical simulations, the aim is to study the mechanical behavior in presence of cracks and determine the fracture toughness. Making use of theoretical notions, analytical formulas, experimental tests coupled by the recent digital image correlation technique and numerical simulations constitute an efficient protocol to characterize materials to resist against cracks. At the end of our work, the study was done to know the crack propagation in opening mode (mode I) and the stress evolution on the crack paths by the X-FEM extended finite element method. Voir les détails
Mots clés : failure in mode 1, stress intensity factor (SIF), Cracking, Correlation of digital images (CDI), FEM finite elements, Abaqus, Integral J, Extended finite element method (XFEM)
Etude mécanique et microstructurale des soudures des alliages d'aluminium soudées par friction
This work is related to the study of the friction welding process. This type of welding has many applications in different branches of industry. This process has many advantages. First, the very high quality assemblies can be made. In addition, this process is much faster than any other conventional processes. Furthermore, it can be completely automated so that constant quality is guaranteed. The aim of this study is the optimization of the parameters of friction welding: (by varying the friction time [s] and the rotational speed [rpm], forging time [s] and the friction pressure and forging [MPa] remain constant). An experimental procedure was used to obtain a welded junction (alu-alu), the alloy used is Al 6013-T8. We used several characterization methods, simple but effective and suitable for this kind of research work; such as microstructural characterization by optical microscope and mechanical characterization namely microhardness and tensile testing. We observed that the microstructure has three zones (TMAZ, HAZ and MDZ), The microhardness profile has a certain homogeneity and the tensile tests have shown that the tensile strength, elongation and elastic limit increase with increased friction time. In general, the mechanical properties are influenced by the overall effect of the metallographic structure of the weld. The latter is closely linked to the process parameters. Voir les détails
Mots clés : Friction welding, 6013-T8 alloy, Welded joint, mechanical properties, microstructure, Microhardness
Caractérisation et modélisation numérique d’un composite époxy/Alfa.
Nowdays, natural fiber composites are increasingly getting great interest on an industrial scale. This undeniable success is linked to the intrinsic properties of natural fibers reinforcements and to their ecological character. Our study consists in characterizing the mechanical properties in tensile, bending and ultrasonic as well as morphological characterization by optical and scanning electron microscopy in order to evaluate their aptitude to replace synthetic fiber composites. The material to be characterized is composed of an epoxy matrix reinforced with 20% in weight Alfa short fibers. Numerical modeling using the finite element method allowed us to predict the Young's modulus of our randomly reinforced biocomposites. The ANSYS modeling software was used to generate the 3D representative elementary volume and to calculate the Young's modulus of the composite. The experimental results recorded are close to those obtained by numerical modeling. The latter remains therefore the goal to reach. Voir les détails
Mots clés : natural fibers, Alfa fibers, biocomposites, mechanical characterization, numerical modeling, ecology
Conception et réalisation d’un système de contrôle non destructif par courant de Foucault pulsé
The conventional EC method is used for near-surface defects finding [5] [48] [12] [2]. On the other hand, and in order to control great depths, pulsed eddy currents are used [35] [48] [12] [2]. Through this project we aim to realize an analogue-digital PEC-NDT system, interfaced by a microcomputer. A set of experiments is carried out in order to prove the sensitivity of the designed system towards some parameters [2], where the determined mechanical properties are compared with the results obtained in order to in order to confirm some hypotheses [32]. Voir les détails
Mots clés : cnd, Instrumentation, Courants de Foucault pulsés
DETERMINATION DES PROPRIETES ELASTIQUES PAR LES ESSAISDE TRACTION ET D’ULTRASON DE L’ALLIAGE EUTECTIQE AlSi13
Aluminum has very low mechanical properties. To significantly increase them, we actedon three main modifying factors of the microstructure. Addition to aluminum of a very lowdensity element including 13% silicon which facilitates the flowability of the metal, gravitysand molding and structural hardening treatments.Al-Si alloys are highly indicated by their lightness, their high tensile and corrosionresistance. The study focuses on the influence of maturation on the evolution of the elasticproperties determined by the tensile and ultrasound tests of the Al-13% mass eutectic alloy. Iffor six states: raw casting noted - F and maturation in 6h steps noted - M0h, M6h, M12h,M18h and M24h. The parts produced from this alloy are part of the components used invarious projects by SNVI Rouïba and Electro-Industries de Fréha (covers, pump casing,motor pistons, etc.).All the results of the mechanical and structural properties gathered in Part III of our thesisshow us that we should recommend for the molding of parts whatever the series: the grossreference state designated - F. Voir les détails
Mots clés : Al-Si, sand, ripening, mechanical properties
Élaboration et caractérisation des céramiques supraconductrices YBa2Cu3O7
This work presents bibliographic research and generalities about superconducting materials. The polycrystalline superconducting compound Y123 was developed by solid state reaction (powder metallurgy) from stoichiometric mixtures Y2O3, BaCO3, and CuO. To study the effect of the addition of lanthanum-doped cobalt ferrite (0-5-10%) on magnetic and optical properties, samples of 2g (99.9% Y123 and 0.1% CoFe2O4 (0-5-10%) lanthanumdoped) were prepared, and characterized by VSM and FTIR. Voir les détails
Mots clés : cuprates, supraconducter, Y123, YBCO, magnetic
Effet de l’application d’une peinture anti-corrosion sur le comportement électrochimique de l’acier au carbone en milieu acide
In this work, we are interested in the evolution of the surface roughness of steel (mechanically polished (A2, A3) and shot-blasted (A2G, A3G)) and the thickness of the paint applied to different surface states (mechanically polished (A2P, A3P) and shot blasted (A2GP, A3GP)). Shows that the roughness of grit-carbon steel surfaces is greater than the mechanically polished ones. Although the evolution of the thickness of the paint deposited on mechanically polished and shot-blasted carbon steel, depending on the grade of polishing paper,), shows that the thicknesses of paint deposited on carbon steel surfaces shot blasted are larger than those polished mechanically. The characterization of the samples was determined by scanning electron microscopy (SEM), showing that the surface state of mechanically polished steel (A3) is much better than that of shot-blasted steel (A3G). The surface analysis by SEM also shows that the coatings applied on the shot-blasted steel (A3GP) have a much better morphology than those applied on mechanically polished steel (A3P), and the metallographic micrographic analysis shows that the thickness of the coatings of paints obtained on shot-blasted steel are superior than that obtained on mechanically polished steel, The effect of mechanical polishing and shot blasting on the behavior of carbon steel with respect to corrosion by the use of two electrochemical techniques: potentiodynamic method and electrochemical impedance spectroscopy (EIS). mechanically polished and shot-blasted steel with and without coating for better resistance to corrosion in hydrochloric acid medium. Spectral analyzes by FTIR, shows the evolution of chemical bonds and functional groups present in the paint applied to steel. Voir les détails
Mots clés : surface roughness of steel, shot-blasted steel (A3G), electron microscopy (SEM)
Etude et élaboration d’un nouveau procédé de traitement des effluents industriels contaminés par les métaux par électrodéposition
Currently,Electrochemical methods find wide application in the treatment of industrial effluents to reduce their organic matter content, in inorganic sulphur compounds and nitrogen,or inharmful metals for the environment. Electrochemistry is not only applied to wastewater,but also on contaminated soils, incineration residuesor sewage sludge wastewater from the metallurgical industry. Electrochemistry has proved its effectiveness, which allowed him to integrate the environmental industry. Environmental electrochemical technologies allowto control pollution,to recycle materials,to carry out the rehabilitation of sites,monitoring (monitors and sensors for gases and liquids),the efficient conversion of energy, the prevention of corrosion, removal of contaminantsand disinfection of water. Electrochemical processes can therefore be efficient and economical when properly designed,and they integrate harmoniously with the environmental industry. These processes require compact installationsand can thus integrate into existing industrial waste treatment chains. The present work aims so the elaboration of an electrochemical process of treatmentand purification of industrial effluentscontaminate with metals. Indeed, the use of this technique can allow both the elimination of these metals by electroplating on a cathode,a recovery of metals, a saving of precipitation reagents and a reduction in the amount of sludge to be removed,as well as surface treatmentswhere the applications concern gold recovery, silver, copper, cadmium, nickel, zinc, iron and lead ... etc.The metal that can be recoveredin the form of valorizable cathodes,which allows the depollution of the environment. This work requires in-depth studies of design considerationsand the development of an electrolytic cell. Voir les détails
Mots clés : Electrochemical methods, inorganic sulphur compounds, inharmful metals