Liste des documents
Effet du soudage TIG sur la microstructure d’un superalliage à Base de Nickel (738 LC)
Dans ce travail; l’effet de soudage TIG sur un superalliage à base Nickel a été étudié. Il est le procédé le plus utilisédans la reparation des ailettes des turbine à gaz productrice de l’électricité.Le superalliage 738 LC (polycrystallin) est utilisé courament dansla fabrication des ailettes des turbines a gaz. Il doit résister à des gradients de chaleur et de contraintes très importantes. Dans cet ordre différentes méthodes de caractérisation structuraleont étaient utilisées: telles les observations microscopiques, DSC et DRX dans la caractérisation des pièces soudées Voir les détails
Mots clés : soudage TIG, Ni738LC, ZAT, ZE
Influence of cutting parameters on the surface qualityof machined metal “Applied materials: St70-2 andCf45”
The quality of the machined parts is generally determined by the errors of shape and degree of finishing of the surface of the items during their machining [1]. The state surface of a machined workpiece plays an important role in the wear resistance, ductility, and fatigue of the piece. This surface state therefore cannot be neglected in the design phase of the work [2].A machined surface is the result of the geometric and kinematic reproduction of the shape and the trajectory of the tip of the tool on the machined material [5]. In practice, several factors such as the nature of the material being machined, the cutting conditions,the geometry of the tool, the vibration of the machine tool duringmachining, the influence on chip formation and thus the roughness of the surface produced [7]. This complex system requires explaining the influence of each machining parameter on the state surface of the finished product in order to master the machining process and to meet the requirement of dimensional accuracy of the parts produced. Our work is to investigate variation of the roughness of the machined feature cutting parameters selected when cutting metal parts Voir les détails
Mots clés : Roughness / State surface / Parameters cutting /Factors influences / Experiences Plan
Simulation en 2D du soudage par induction des tubes en Acier
Notre approche est essentiellement basée sur l’étudede modilisation et simulation de soudage par indection electromagnetique a haut frequence des pipes ligne il s’agit d’assembler deux tubes de diamètre quelconque.Nous avons décrivons les modèles mathématiques électromagnétiques et thermiques de notre configuration à souder que nous utilisons et étudier en détaille l’influence des différant paramètres sure la qualité de soudage Voir les détails
Mots clés : soudage par indection; pipes ligne; modèles électromagnétiques et thermiques
Interface and electrical properties of Au catalysts(dots) on Ge(111)
We investigate the interface between Au nanodots and a Ge(111) substrate. Au dots are achieved by dewetting an Au layer above the Au-Ge eutectic temperature TE(TE= 362°C). Surface and interface structural properties are analysed by using scanning tunnelling microscopy, transmission electron microscopy and scanning electron microscopy measurements while electrical characterizations are performed a by 4-points I-V probe Voir les détails
Mots clés : Au-Ge contacts, eutectic, Au droplets, germanium
Performance Analysis of Control techniques of Full-Bridge Resonant Inverter for Induction Metal Surface Hardening
In this paper, several control techniques for induction metal treating are examined to assess their performances using resonant series inverter. In fact, many types of steel are treated with heat to increase toughness and resistance to wear. Induction heating seems to be appropriate and provides several advantages in comparison with conventional techniques. In this paper, these techniques are evaluated comprehensively, through simulation and experiment, and compared to each other in terms of heating rate and efficiency, using one metal sample hardened to 1mm in depth up to 700°C, with a 400 W power supply. The simulation results obtained are satisfactory, and agree with those of the experiments. Furthermore, the study shows the control strategy based on frequency may not be sufficient, but should be associated with other control techniques in order to address appropriately the hardening pr ocess, bearing in mind processing time and efficiency. The strategy with frequency associated with phase shift control appears to fit well metal treating during the hardening, and can be easily tailored to its hardening requirements, compared to the other techniques Voir les détails
Mots clés : Induction metal hardning; Resonant Inverter; Power control
Digital Load Adaptive Control for Resonant Inverter for Surface Metal Heating
Induction heating is a well-known technique to produce very high temperature at reduced time for well specific applications such as in melting steel, brazing, and hardening.Series resonant converter proves to suit better to surface metals treatment and hardening. Efficiency reaches its highest level in the resonant mode, where switching losses are minimized by operating the IGBT at a resonant frequency for switching at the zero crossing point of current or voltage.However, as heat rises during hardening metal process, the metal exhibits parameter variations, which ultimately affects the overall system performances. Therefore, the inverter system with an effective load-adaptive control circuit with short response time is highly sought to let the system operate efficiently regardless of any variation of the load parameters. This will bring back the system under resonant mode to allow the system to operate at its optimal performances. In this paper, an analysis of a series resonant inverter performance is conducted, in which the control frequency is monitored and continuously adapted using phase-locked loopaimed to metal hardening. The control technique is characterized by its flexibility, low cost hardware, and shortresponse time. The system comprises analogue and digital circuits, microcontroller based. The experimental bench is built for the purpose in the range of 1 to 5 kW power, with 01to 50 kHz operating frequency. First, the process principle and the design procedure of the inverter system with the proposed control scheme are described through modelling and simulation. Then, experimental results are presented to show the validity of this technique, and to evaluate the system performances Voir les détails
Mots clés : Series resonant inverter, Load adaptive control
Étude de la propagation des ondes de Lamb dans une plaque fissure
La propagation des ondes de Lamb, dans un guide d’onde élastique, a été étudiée expérimentalement et numériquement. Ce guide d’onde est une plaque d’acier d’épaisseur e = 1.51 mm. Cette plaque comporte un défaut (une rainure de largeur de 3 mm et d’épaisseur de 0.5 mm) situé à 4 cm par rapport à l’extrémité libre de la plaque. La simulation a été faite en utilisant la méthode des éléments finis sous le logiciel Comsol Multiphysics. Les ondes de Lamb ont été expérimentalement générées par contact au moyen d’un transducteur piézoélectrique monté sur un sabot en plexiglas d’angle fixe. Quant à leur détection, un vibromètre laser a été utilisé. Dans cette étude, nous nous sommes intéressés à l’identification des modes de Lamb propagatifs dans la plaque inspectée. Pour cela, nous avons appliqué différentes méthodes de traitement du signal aux résultats obtenus numériquement : la représentation espace-temps, la transformée de Fourier spatiotemporelle ainsi que la Pseudo-Distribution de Wigner-Ville Lissée. Cette dernière a été également utilisée pour traiter les résultats expérimentaux. L’étude révèle un bon accord entre les résultats numériques et expérimentaux. Nous montrons que la Pseudo-Distribution de Wigner-Ville Lissée est très efficace en terme de détection du défaut existant dans la plaque ainsi quepour l’identification des modes de Lamb multiples résultant de l’interaction de l’onde incidente avec la rainure Voir les détails
Mots clés : Ondes de Lamb; simulation par éléments finis ; analyse temps-fréquence
NDT methods applied on corrosive behaviors of duplex stainless steel 2205 submitted to heat treatment and acidic medium
The present work investigates the corrosion behavior of 2205 duplex stainless steel in 3% HCl and 5% HCl solution after various heat-treatments. The stainless steels were heat-treated at 950° at 2h and 4h with air and water cooling. Each heat-treated sample was examined for their microstructures, before and after emerging the samples in the corrosive medium.The chemical composition and morphological structure of the stainless steel material are respectively characterized by X-ray fluorescence and optical microscopy. Electrochemical tests are carried out in three electrolytes system, the techniques used in this study are potentiometer open circuit ( OCP) , linear polarization (LP) and electrochemical impedance spectroscopy (EIS ) . The impedance spectra and the current - potential curves obtained allowed the estimation of the rate of corrosion in the various electrolytes and showed a variation in the polarization resistance (Rp ) and the degradation kinetics of this material depending on the composition of the study environment.The Nondestructive evaluation is widely used to predict default in materials, the implantation of non destructive testing such as eddy current and hysteresis cycle, can give more information about the modification in structure. In the both solution, when we increase the emerging time for the two environment, we can observe a dissolution of the material, but the degradation is more important in the case of 5% HCl. Voir les détails
Mots clés : duplex stainless steel, NDT, eddy current (DI), VSM, Hysteresis Loop, microstructure, Pitting corrosion, PREN, Electrochemical impedance spectroscopy .
Structural and optical properties of Ni doped ZnO thin films using sol–gel technique
Development and characterization of ZnO thin films is of high interest because of its single electrical properties, optics which make it suitable for applications in different fields of technology, optics, electronics, photovoltaic, In this work, the spin coating sol–gel technique has been successfully used to deposit highly uniform and good adhesion of nanostructure thin films of ZnO doped with different Ni concentrations.0%, 1%, 3%, 5%, 7% and 9% on microscope glass substrates by spin coating technique. X-ray diffraction (XRD) revels that all samples have a polycrystalline in nature with hexagonal wurtzite structure. The structural parameters such as crystallite size, dislocation density and micro strain were calculated from XRD studies. UV-vis has shown that the films were highly transparent in the visible range (400–800 nm). Voir les détails
Mots clés : ZnO; Ni; thin films; XRD; UV-vis
Effet du traitement thermique sur le comportement corrosif d’un acier inoxydable dans des milieux acides
Les ruptures occasionnelles des structures industrielles peuvent en général être attribuées à l'influence de la corrosion. Le mécanisme de ces ruptures n'est souvent pas bien compris. Il est par conséquent difficile d'émettre des recommandations, non seulement pour la conception et l'exécution, mais également pour le choix des matériaux et des systèmes de précontrainte.Dans ce travail nous avons étudié le comportement d’acier inoxydable duplex 2205 traité thermiquement à la température T= 950°C suivi d’un refroidissement à l’air et par trempe à l’eau dans les milieux HCl 3%, et HCl 5%. Voir les détails
Mots clés : acier inoxydable duplex, corrosion, milieu acide, microdureté, traitement thermique.