Liste des publications

Nombre total de résultats : 541
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Study of Optical and Morphological TiO2 Nano-Films Properties Deposited by MagnetronSputtering on Glass Substrate

K. Bedoud, H. MERABET, L. Alimi  (2019)
Publication

In this paper, TiO2 nano-films were deposited by RF magnetron sputtering using a TiO2ceramic target of pureTi of 3" diameter and 0.250" thickness with a purity of 99.99%, onto heated glass substrates in a temperature range of200 to 450°C. This study determines the temperature effect on the structural, optical and morphological properties ofTiO2 nano-films. For this, we used X-ray diffraction for structural characterization and optical transmission spectroscopyUV-Visible for optical characterization and atomic force microscopy (AFM) for morphological characterization of thefilms produced. The (101), (400), (112), (200), (105), (211), (213), (204) peaks of the anatase structure and the (210),(102), (-112) (710) peaks of the monoclinic structure are observed. In addition, the peaks are sharp and intense whichimplies a good crystalline structure. Otherwise, the films optical gap variation is proportional to the temperature variationfrom 3,9eV to 3,92 eV for T=200°C and T=450°C, respectively. The surface roughness of TiO2 nano-films range from1,031nm to 4,665nm. Voir les détails

Mots clés : Thin films, sputtering, semiconductor, TiO2 nano-films, gas sensors, nano-films, RF magnetron sputtering, DRX, UV-Vis, AFM.

Propriétés Optique de TiO2 et Application de la Méthode de Swanepoel pour la Détermination de l’Épaisseur Optique et de l’Indice de Réfraction

K. Bedoud, H. MERABET  (2019)
Publication

Dans ce travail, des nano-films de dioxyde de titane « TiO2 » ont été déposés par pulvérisation cathodique en utilisant une cible en céramique de Ti pur de 3" de diamètre et 0,250" d'épaisseur avec une pureté de 99,99% sur des substrats en verre à des épaisseurs (e) différents. Nous visons par ce travail d’étudier l’effet de l’épaisseur sur les propriétés optiques de TiO2 nano films. Pour cela, nous avons utilisé la spectroscopie de transmittance optique UV-Visible pour la caractérisation optique. La variation du gap optique des films est inversement proportionnelle à la variation de l’épaisseur de 3,6 eV à 3,8 eV, respectivement. Pour la détermination de l'indice de réfraction et l'épaisseur du film nous avons utilisé la méthode proposée par Swanepoel, qui s’articule sur l’utilisation des franges d’interférence. On observe que, l'indice de réfraction n augmente avec l’augmentation de l'épaisseur de la couche déposée. Voir les détails

Mots clés : couches minces, pulvérisation, semi-conducteur, TiO2, nano-films, UV-Vis, épaisseur, indice de réfraction, Swanepoel

Real-Time Switches Fault Diagnosis for Voltage Source Inverter Driven Induction Motor Drive

H. MERABET, T. BAHI, K. Bedoud, D. DRICI  (2019)
Publication

Induction machine is the frequently used for electrical drive applications in almost many industrial processes due to its simple and robust construction. Speed control of induction machine is required depending on the type of application. Speed of the induction motor can be varied by varying frequency or by variation of the terminal voltage. Variable voltage can be fed to induction machine using the voltage source inverter which is found efficient technique of controlling induction motor drive. The potential faults that occur in inverter are the open and short circuit switch fault. The cost of this schedule can be high, and this justifies the development of fault diagnostic methods. In this paper we present a reliable strategy for diagnosis and detection of open and short circuit switch faults in plush width modulation of voltage source inverter (PWM-VSI) using the fuzzy logic approach. The principle of the proposed approach is based on the acquisition of stator currents, to calculate the average absolute values of currents (AAVC), which allows the real-time detection and localization of inverter IGBT open or short-circuit faults using just the motor phase currents. A model of the system is built using MATLAB/SIMULINK. Simulation results are presented showing the monitoring approach performance under distinct operating conditions. Voir les détails

Mots clés : open circuit fault, short circuit fault, Fuzzy logic, modeling, simulation

Inspections, statistical and reliability assessment study of corroded pipeline

O. Bouledroua, D. ZELMATI, M. HASSANI  (2019)
Publication

The purpose of this work is to examine some points of views on the burst pressure standards assessment for a pipeline with internal and/or external corrosion defects. The proposed work contains three major parts. First, we used several analytical and numerical methods with the use of Ansys Software. The goal is presenting different aspects concerning burst pressure standards computation of real burst test. The second part shows an experimental study in order to check the inspections standards using an intelligent pig tool over a 48?km of a pipeline located in Algeria. All detected defects in the corroded pipeline are statistically analyzed. The final part, the reliability index β of the corroded pipeline subjected to internal pressure is estimated by using the SORM reliability approach. Voir les détails

Mots clés : Corroded pipeline burst test, Probability of failure, Failure assessment diagram, Finite Element Analysis

Remaining Life Estimation of the High Strength Low Alloy Steel Pipelines by Using Response Surface Methodology

D. ZELMATI, O. GHELLOUDJ, M. HASSANI, A. AMIRAT  (2019)
Publication

This paper presents a probabilistic study to estimate the remaining lifespan of cracked steel pipeline by using the response surface technique. The purpose is to assess the reliability index of the high strength low alloy steel (HSLA) pipelines for a limit state function without closed-form. The implicit objective function is approximated by a polynomial representing a quadratic response surface and the assessment of the failure probability is obtained using Second order reliability method (SORM). The presence of a semi-elliptical crack defect in the longitudinal direction of the pipe steel will intensify the stress field at the crack tip and will decrease the limit state function. Exhaustive and costly tensile and Charpy V notch tests prepared from the longitudinal direction of the parent tube were achieved in order to study the mechanical behavior of API X70 steel grade and integrating the uncertainties of the engineering model parameters through their probabilistic densities. The assessment of the stress intensity factor is conducted by using the finite element methods. The estimation of the reliability index and the probability of failure are carried out by coupling the mechanical model, and the finite element method based on the commercial code ABAQUS. This coupling based on the response surface methodology, could be used as a decision making support for any repair or replacement of the damaged pipeline. Voir les détails

Mots clés : Reliability, Elliptical crack, Response surface, Uncertainties

Characterization of the Polylactic acid stretched uniaxial and annealed by Raman spectrometry and Differential scanning calorimetry

A. Bouamer, N. Benrekaa, A.Younes, H. Amar  (2019)
Publication

In this work, we have been interested in the characterization of the effect of heat treatment and mechanical treatment on the crystallinity of polylactic acid (PLA) film by two techniques, DSC and Raman spectroscopy. The results obtained by the DSC for the stretched film shows the appearance of a broad peak of crystallization around 120 °C, a rise in melting peak in a significant way, which shows that the uniaxial stretching has increased the crystallinity of the PLA, whereas for the annealed film appearance of a double melting peak. The result obtained by Raman spectroscopy shows new peaks appears at 922 cm−1 and 540 cm-1 after stretching and annealed process, indicating the crystallization process. Voir les détails

Mots clés : PLA, glass transition, Raman spectroscopy, DSC

Effect of heat treatment on surface hardness and tribologicalbehavior of XC38 steel—approach by the experiments plans

M Bourebia, S Meddah, H Hamadache, A Taleb, A Gharbi, L Laouar  (2019)
Publication

This work aims at predicting the micro-hardness of XC38steel using the experiments plans as well asstudy of tribological behavior of thissteel. The heat treatments were considered by adopting thefactorial plans 22 methodology at two factors (temperature ‘T’ and holding time ‘t’), each at two levels(-1, +1). The results obtained allowed lead to a mathematical model predicting the micro-hardness‘Hv’ in every point of the study field. Moreover, the curves of the responses surfaces clearly show theinfluence of two factors studied (T, t) on ‘Hv’. Mechanical characterization of treated samples showedasignificant increase in the micro-hardness, which achieve to 76% for the treated sample at 850 °Cduring 2 h compared to untreated state. An investigation of wear tracks morphology shows thatfriction under a load of 10 N results in predominant adhesive wear, while a load of 2 N favorabrasive wear. Voir les détails

Mots clés : heat treatment, factorial plans, prediction, superficial hardness, tribological behavior

Physical and photo-electrochemical characterizations of ZnO thin films deposited by ultrasonic spray method: Application to HCrO4−photoreduction

N. ZEBBAR, M. Trari, M. Doulache, A. Boughelout, L. CHABANE  (2014)
Publication

ZnO thin films, prepared by ultrasonic spray onto glass substrate, crystallize in the wurtzite structure. The XRD pattern shows preferential orientation along the [0 0 2] direction. The films deposited at 350 consist of 60 nm crystallites with an average thickness of ∼150 nm and SEM images show rough surface areas. The gap increases with increasing the temperature of the substrate and a value of 3.25 eV obtained for films deposited at 350?C. ZnO is nominally non-stochiometric and exhibits n-type conduction because of the native defects such as oxygen vacancies (VO) and/or interstitial zinc atom (Zni) which act as donor shallows. The conductivity is thermally activated and obeys to an exponential type law with activation energy of 57 meV and an electron mobility of 7 cm2V−1s−1. The capacitance-voltage (C−2measurement in acid electrolyte (pH ∼ 3) shows a linear behavior with a positive slope, characteristic N-type conduction. A flat band potential of −0.70 VSCE and a donors density of 5.30 × 1016cm−3are deter-mined. The Nyquist plot exhibits two semicircles attributed to a capacitive behavior with a low density of surface states within the gap region. The centre is localized below the real axis with a depletion angle of 16?ascribed to a constant phase element (CPE) due to the roughness of the film. The energy band diagram assesses the potentiality of ZnO films for the photo-electrochemical conversion. As application, 94% of chromate (3.8 × 10−4M) is reduced after 6 h under sunlight (AM 1) with a quantum yield of 0.06%and the oxidation follows a first order kinetic. Voir les détails

Mots clés : ZnO, thin film, Ultrasonic spray, Photo-electrochemical, Chromate, Sunlight

CONTRIBUTION TO RECONFIGURATION OF FAULT-TOLERANT INVERTER APPLIED TO THE WIND PARK CONNECTED TO THE ELECTRICAL NETWORK

Omar Fethi BENAOUDA, Azzedine Bendiabdellah, KAHLA SAMI  (2019)
Publication

This paper proposes a new diagnostic technique based on Park vectors associated with polar coordinates for the detection and location of open circuit (OC) faults, as well as the integration of fault-tolerant reconfigurable inverter in order to enable continuity of service of the wind farm system. The model used is that of a variable speed wind turbine coupled to a double-fed induction generator (DFIG) connected to the power grid via a fault-tolerant converter to improve performance after the appearance of the fault. This converter is used based on IGBT to obtain an acceptable accuracy with high switching frequencies. This model is well suited for the observation of harmonics and the dynamic performance of the control system over relatively short periods of time (typically hundreds of milliseconds to one second). This method allows extracting the maximum wind energy during a low wind speed by optimizing the turbine speed while minimizing the mechanical stress on the turbine during gusts of wind. To illustrate the diagnostic improvement of fault-tolerant inverter open circuit faults, several results are presented and discussed in this article. Voir les détails

Mots clés : DFIG Turbine, Inverter, diagnosis, Detection, Location, Reconfiguration, fault, Open-Circuit, IGBT

Microstructure and microindentation of Ti3SiC2–Titaniumfiller brazedjoints by tungsten inert gas (TIG) process.

Y. Hadji, A. Tricoteaux, M.G. Ben Ghorbal, M. Yahi, R. Badji, T. Sahraoui, M. Hadji, M.W. Barsoum  (2017)
Publication

Herein we study the joining of Ti3SiC2- a MAX phase - with a Tifiller (Ti3SiC2/Ti-filler) using a TIG-brazingprocess. The microstructures of the interfaces were investigated by scanning electron microscopy and energydispersive spectrometry. When Ti3SiC2comes into contact with the molten Ti -filler during the TIG-brazingoperation, it starts decomposing into TiCxand a Si-rich liquid. Simultaneously, the molten Ti infiltrates into theTi3SiC2resulting in a 200 µm thick duplex region, comprised of TiCxand a Ti-rich phase with some dissolved Si.Both Si and C are found in the solidified Ti; the Si source is from the Si-rich liquid, while the presence of Cindicates that some of the C diffused into the Ti. Upon cooling, C- containing Ti- rich lamellae form the solidifiedTi. Microindentation results of the decomposed Ti3SiC2layer show an increase in hardness and a decrease inelastic modulus relative to T3SiC2. Notably, no cracks were observed Voir les détails

Mots clés : MAX Phases, Microstructures, Joining, hardness, Micro-indentation