Liste des documents
Effet du régime de refroidissement sur l’évolution mécanique et microstructurale des produits longs dans un laminoir du fil et rond
Des investigations expérimentales ont été effectuées pour comparer et évaluer l'effet des transformations du modèle de refroidissement sur les propriétés mécaniques du rond pour différentes catégories en acier et pour différents diamètres produits élaborés à l’échelle industrielle. Deux diamètres du rond (10 mm et 12 mm) et deux catégories en acier, l’un à faible teneur en carbone et l’autre à moyenne teneur en carbone ont été choisis pour le travail expérimental. La limite d’élasticité, la résistance à la traction, l'élongation, la dureté, la taille du grain, et la microstructure ont été déterminées pour chaque échantillon afin de caractériser ces produits. Des tableaux et les représentations des relations entre les paramètres indépendants (la catégorie et le diamètre) et les résultats mesurés (microstructure et propriétés mécaniques) ont été développés. Ces relations indiquent que la variation du refroidissement en appliquant deux régimes différents (standard et différé) influence les propriétés finales du produit. L'observation la plus remarquable était que, tandis que le retardement du refroidissement abaisse les propriétés de résistance, une augmentation des propriétés de ductilité. La structure de l'acier est composée d'un mélange de ferrite-perlite. Des relations empiriques entre la limite d’élasticité et la taille du grain ont été élaborées. Voir les détails
Mots clés : Modèle de refroidissement, propriétés mécaniques, microstructure, taille de grain
Study of the morphology of oxide scale formedon hot-rolled steel
Mechanism of oxide scales formation on steel during hot rolling process is delicately determined and their structures are extremely complex. This work is part of larger studies made to understand the oxide scale behavior. Therefore, the morphology of oxides is determined by optical microscopy. Identification of the mechanical properties of oxide scales is achieved by micro-hardness measurement. The work has revealed a variation of microstructure in several layers of oxide. It was obtained that the oxide scales consisting mainly of wüstite FeO, magnetite Fe3O4 and hematite Fe2O3 owing to the formation of voids and cracks in the scales, especially on the outer layer where it is high porous. The intermediate layers is thicker than others oxide layers. The outer layer has a lowest hardness and highest porosity. Voir les détails
Mots clés : oxide scales; steel; hardness; metallographicmorphology
Synthesis and Characterization of TiO2 thin films prepared by non-aqueous sol–gel method
TiO2 thin films for gas sensing applications are prepared by non-aqueous sol–gel method on glass substrates. The structural evolution of TiO2 films with thickness is investigated by X-ray diffraction and Raman Spectroscopy. Prepared films are in anatase phase. The grain size calculated from XRD patterns increases with thickness from 14 to 22 nm. Uv–vis transmission spectra show that the absorption edge shifts to longer wavelength as the thickness increases, which is correlated with the change in the optical band gap value. The determination of the refractive index and thickness of TiO2 thin films by m-lines spectroscopy is presented. Refractive index is found to vary slightly with thickness. Calculation of the film density confirms the behavior of refractive index. The films exhibit one guided TE0 and TM0 polarized modes. Voir les détails
Mots clés : Sol–gel, TiO2, anatase, Refractive index, Optical band gap, m-lines.
APPLICATION OF OPTICAL FIBER IN INDUSTRY
This work presents a study on optical fiber sensors and their importance in various fields. Despite the existence of electrical sensors used through many years in measuring physical and electrical phenomena but there are still problems such as transmission losses, susceptibility to electromagnetic interference (noise) ....... etc.. [1]. which makes them less efficient use. To solve these problems and saw the need for sensors in the industry, researchers found that the most excellent solution is to be replaced by optical sensors that are now used in most systems, instrumentation as well as communication systems and control. Voir les détails
Mots clés : fiber optic sensor, optical fibre, waveguide.
An Improved Method for Gear Fault diagnosis
Envelope analysis is especially suitable for fault diagnosis inducing periodic shocks or amplitude modulations such as gears and bearings and has been applied widely for mechanical fault detections over the last few decades. However, a critical limitation of this technique is that it requires a prior knowledge on filtering band. Due to this drawback, detecting machine defects at the incipient stage when defect-characteristic components are weak in amplitude and without a distinctive spectral pattern poses a challenge to the conventional enveloping spectral analysis technique .In order to overcome this limitation, this work gives a new signal processing approach for gear faults diagnosis based on Hilbert Transform (HT) and Fast Fourier Transform (FFT). It is applied on real measurement signals collected from an experimental vibration system. The monitoring results indicate that the proposed method improves the gear faults diagnosis relatively to other common techniques. Voir les détails
Mots clés : Vibration signal Analysis, gear Fault diagnosis, Hilbert Transform (HT), Envelope Analysis (EA), Fast Fourier Transform (FFT).
Properties of Co-doped ZnO thin films grown by pulsed laser deposition on glass substrates
Undoped and Co-doped ZnO (CZO) polycrystalline thin films (Co: 3, 5 at.%) have been deposited at 450ºC onto glass substrates using pulsed laser deposition method. The used source was a KrF excimer laser (248 nm, 25 ns, 2 J ∕ cm2). X-ray diffraction patterns showed that the Co-doped ZnO films crystallize in a hexagonal wurtzite type structure with a strong (002) orientation, and the grain sizes calculated from these patterns decrease from 37 to 31 nm by increasing Co doping. The optical waveguiding properties of the films were characterized by using prism-coupling method. The distinct M-lines of the guided transverse magnetic (TM) and transverse electric (TE) modes of the ZnO films waveguide have been observed. In the aim to study the optical properties of the ZnO films, an accurate refractive index and thickness measurement apparatus was set up, which is called M-lines device. An evaluation of experimental uncertainty and calculation of the precision of the refractive index and thickness were developed on ZnO films. The optical transmittance spectra showed a good transparency in the visible region. Calculated optical band gap varying from 3.23 to 3.37 eV when the content of Co doping increases from 0 to 5 at.%. Voir les détails
Mots clés : Thin films, ZnO, pulsed laser deposition, Waveguiding properties, Optical transmittance
Sliding Mode Control Based Bacterial Foraging Optimization of Wind Energy Conversion Systems
In recent years, the energy production by wind turbines has been increasing, because its production is environmentally friendly. In this paper, Bacterial Foraging Optimization (BFO) is proposed to generate a Sliding Mode Controller. The Sliding Mode Control (SMC) is proposed to control a squirrel-cage induction generator (SCIG) in order to maximize power captured by wind energy conversion system applied to the welding system. Simulation studies are made with Matlab / Simulink to verify the effectiveness of the purposed method. Voir les détails
Mots clés : Squirrel Cage Induction Generator (SCIG), Wind Energy Conversion System (WECS), Sliding Mode Control (SMC), Bacterial Foraging Optimization (BFO), Welding System
On -Off Control based Particle Swarm Optimization for Maximum Power Point Tracking of Variable Speed Wind Energy Conversion Systems
In recent years, there has been an evolution of electricity production based on wind energy, such as the effects of pollution. In this paper, Particle Swarm Optimization (PSO) is proposed to generate an On-Off Controller. On-Off Controller based maximum power point tracking is proposed to control a squirrel-cage induction generator (SCIG) of wind energy conversion system .Simulation studies are made with Matlab / Simulink to verify the effectiveness of the purposed method. Voir les détails
Mots clés : Wind Energy Conversion System (WECS), Maximum Power Point Tracking, On-Off Control, Particle Swarm Optimization (PSO)
Maximum Power Point Tracking For Photovoltaic Systems: A Comparison between GAs and PSO Approaches
Particle Swarm Optimization (PSO) and Genetic Algorithms (GAs) are proposed in this paper to generate a duty cycle. The duty cycle (D) used in Pulse With modulation (PWM) to reproduced control switch for the boost converter by the maximum power point tracking (MPPT) for a photovoltaic (PV) system. As results indicated, using particle swarm optimization (PSO) and Genetic Algorithms (GAs) are used for stabilization of a photovoltaic system (PV). Voir les détails
Mots clés : Photovoltaic systems, Boost, PWM, MPPT, PSO, GAs
PREPARATION DE NANO-COMPOSITES A MATRICE POLYMERE CDTE EN VUE D’PPLICATIONS DANS LE PHOTOVOLTAIQUE
Dans ce travail, nous avons élaboré des nanocompsites DdTe-PMMA (film et pastille),Cdte-PS (film et pastille).Les résultats de la caractérisation par diffraction des rayons X sur les nanocomposites étudiés ont montré l’incorporation des nanocristallites de CDTe dans les deux matrices.Les analyses par spectrométrie Raman et par spectroscopie infrarouge à transformée de Fourier des nanocomposites préparés ont révélé l’existence des modes propres de CdTe. La caractérisation par transmission optique dans la gamme UV-Vis-proche infrarouge amontré que l’incorporation des cristallites de CdTe diminue la transmission et élargit la gamme de transparence des matrices hotes.le spectre de la photoluminescence d’une pastille de CdTe-PS a montré une émission intense et étroite mettant en évidence l’élargissement du gap optique du nanocomposite et a confirmé l’effet du confinement quantique. Voir les détails
Mots clés : Nano-composites, matrices polymère, films, PMMA, PS, CdTe.