Liste des documents
DIAGNOSIS OF ROTOR FAULT USING NEURO-FUZZY INFERENCE SYSTEM
The three-phase induction machine (IM) has a large importance and it is widely used as electromechanical system device, and because of their; robustness, reliability, and simple design with the well developed technologies. In spite of all cited advantages, the induction machines are suscptible to various types of electrical and mechanical faults that can lead easly to excessive downtimes, which can lead to tuge losses in terms of maintenance and production. This work presents a reliable approach for diagnosis and detection of broken bar faults in induction machine. The detection of faults is based on monitoring of the stator current signal. Also the calculation of relative energy value for each level of signal decomposition is determinated by using package wavelet, and this method will be useful as data input of Adaptive Neuro-Fuzzy Inference System (ANFIS). In the ANFIS approach the adaptive Neuro-Fuzzy inference system is able to identify the rotor of induction machine state with high precision.This method is applied by using the MATLAB®/Simulink software. Voir les détails
Mots clés : Induction machine, Neuro-Fuzzy inference system., Inductoion Machine
Effect of Grain Size of Nano Composite on Raman and Magnetic Proprieties
Based Iron-cobalt alloys exhibit particularly interesting Raman and magnetic properties, with high Curie temperatures, the highest saturation magnetizations, high permeability, and low losses and is relatively strong and partial oxidation of Fe and Co. The cost of these alloys has confined them, since their discovery by Elmen in 1929, to applications where the volume is small and high magnetic performances are critical. Sintering is the procedure of formation and compaction of a material. We have prepared the nano crystalline alloy by the mechanical milling process in a high energy planetary ball-mill PM400. Morphological, micro-structural, magnetic characterizations of the powders milled several times were investigated by scanning electron microscopy, X-ray diffraction, vibrating manometers sample and Raman spectroscopy. The coercivity value increase during millingtime from 0.018 to 185.9 Oe and saturation magnetization value from 42.7 to 51.1 emu/g, respectively. Voir les détails
Mots clés : Mechanical Alloying, Nanostructured FeCo, Magnetic and Raman characterization
Structural optical magnetic properties of Co doped -MoO3sprayedthin films.
this works deals with the synthesis of Cobalt doped MoO3thin films which were grown on glass sub-strates by the spray pyrolysis at 460?C. First, X-ray diffraction analysis shows an orthorhombic structurerelated to -MoO3allotropic variety with (020) and (040) preferred orientations. The surface topogra-phy performed by atomic force microscopy (AFM) shows that the grain size varies from 150 to 280 nm.Second, optical parameters, such as optical band gap, Urbach energy, refractive index and dielectricconstants were studied in terms of Co content. This optical study shows a direct transition of all pre-pared thin films and normal dispersion of the refractive index showing both Cauchy and Wemple &Di-dominico variations. On the other hand, PL measurements show transition bands mainly in blue andgreen domains related to band-to-band transitions as well as to oxygen vacancy in all films. Finally, mag-netic measurements at room temperature using vibrating sample magnetometer (VSM) technique reveala ferromagnetic behavior of such doped films. Voir les détails
Mots clés : MoO3, Thin films, optical properties, Magnetic Properties, Spray pyrolysis
Study of structural and thermal properties of SiO2 and Al2O3 in the Diatomite
Diatomite, also known as diatomaceous earth, is the naturally occurring fossilized remains of diatoms. Diatoms are single-celled aquatic algae. They belong to the class of golden brown algae known as Bacillariophyceae. Diatomite is a near pure sedimentary deposit consisting almost entirely of silica. The Greeks first used diatomite over 2,000 years ago in pottery and brick.In this work we determine the structural and thermal properties of SiO2 and Al2O3 in the diatomite using the plane wave method and linearized augmented (LAPW) in the functional theory of density (DFT).The potential for exchange and correlation is calculated by the generalized gradient approximation (GGA).Regarding thermal properties, we calculated the free enthalpy G, S entropy, specific heat C, thermal conductivity λ ..... etc of SiO2 and Al2O3 component. The temperatures used in this work are 1400, 1450 and 1500 respectively;The results are in good agreement with some experimental data. Voir les détails
Mots clés : DFT1, diatomite, thermal proprieties
Signal Quality Improvement Using a New TMSSE Algorithm:Application in Delamination Detection in Composite Materials
This paper introduces a novel method to improvethe quality of ultrasonic phased array signals for localizingwith accuracy delamination defects. The improvementis achieved by the introduction of a new threshold for theShannon energy. In first, we have applied the threshold modifiedS-transform algorithm (TMST) in the case of ultrasoundB-scan. Thereafter, we have adapted and applied the StransformShannon energy (SSE) algorithm in the field ofultrasonic testing. At last, we have proposed a novel algorithmbased on threshold modified S-transform and Shannonenergy (TMSSE) to increase the improvement of the ultrasoundB-scan. A simulation study has been carried outsimulating a composite material containing three defects indifferent positions in order to highlight the phenomenon ofdelamination. Experimental tests were performed on a sampleof carbon fiber reinforced polymer composite material(CFRP) with a delamination defect close to the front face.Both experimental and simulated results show that the proposedmethod can improve the quality of ultrasound B-scanwhich enhances the localization of delamination defects. Voir les détails
Mots clés : Ultrasonic signal
Corrosive effects of the electromagnetic induction caused by the high voltage power lines on buried X70 steel pipelines
This paper diagnoses the corrosive effects of the electromagnetic induction caused by double circuit high voltage power lines (HVPL) on the buried X70 steel pipelines. To achieve this objective, firstly the electromagnetic interference between the double circuit HVPL and the X70 steel pipeline (the distribution of the magnetic field and the induced AC current densities in the buried X70 steel pipeline) and the factors affecting this interference such as the vertical distance between the double circuit HVPL and the X70 steel pipeline, and the conductor phase sequence orientation were studied. Then, electrochemical measurements were used to characterize the corrosion polarization properties of X70 steel in simulated soil at various AC current densities. The results show that with an increase in the AC current density, the corrosion rate of the X70 steel increased, indicating that the induced AC current density has accelerated the corrosion degree of X70 steel, by comparison with that in the absence of the AC current density. We can conclude from these results that the electromagnetic induction caused by the double circuit high voltage power lines affects the electrochemical characteristic of the X70 steel pipeline and accelerates the corrosion of the pipeline. Voir les détails
Mots clés : Electromagnetic induction, high voltage power line, induced AC current density, X70 steel pipeline, corrosion, Finite element method.
Effect of the Inclination of Mold Walls on Primary Cooling During the Continuous Casting of Steel
The principal function of a continuous casting mold is to receive the liquid steel, and ensure its cooling in order to permit the formation of a solidified skin, and sufficiently resistant, this is the phase of primary cooling. The efficiency of this process depends on several parameters such as the casting speed, the temperature exchange between the walls of the mold and the thin crust of the slab as well as the conicity of continuous casting mold. Latter has been the subject of this work, which consists in observe the influence of the conicity of mold on the variation of the temperature field, and friction generated during lowering of the slab. the curves reflect changing the factors cited previously as a function of the conicity. The numerical simulation was conducted by FLUENT 6.0 code. Voir les détails
Mots clés : continuous casting, conicity of mold, temperature field
Reliability of the high strength pipeline steel under corrosion defect
The demand of energy such as hydrocarbon, gas and oil requires more and more construction of new pipeline. Therefore, the assessment of the remaining life of these pipelines structure became more and more important to ensure the continuity of production and distributions operations. The reliability of these industrial facilities is largely conditioned by specific characteristics for each system, in its conditions of use, its environment. Generally the causes of deterioration of hydrocarbon transportation pipelines are related to the presence of apparent defects (pinholes, cracks, corrosion.....etc.). This manuscript is a study to estimate the reliability of these structures. The B31G mechanical model of degradation was used to assess the probability of failure through dimensions of defects. Voir les détails
Mots clés : Reliability, pipeline, Defects, Mechanical Model.
Influence of Vanadium on the Corrosion Behavior of High Manganese Steel in 0.5 M H?SO? Solution
The effect of vanadium on the corrosion behavior of high manganese steel in 0.5 M H?SO? solution has been investigated using scanning electron microscopy, potentiodynamic polarization and impedance spectroscopy. The results have shown that the addition of vanadium to high manganese steel decreases the corrosion current density from 2.1 mA cm¯² to 1.29 mA cm¯². Impedance diagrams show the existence of a high frequency capacitive loop and a low frequency inductive loop. The addition of vanadium increases charge transfer resistance from 5.18 Ω cm² to 12.45 Ω cm². Voir les détails
Mots clés : corrosion, Manganese, EIS, Tafel
Characterization of Structural Noise Patterns and Echo Separation in the Time-Frequency Plane for Austenitic Stainless Steels.
The aim of this study is to characterize the structural noise for a better flaw detection in heterogeneous materials (steels, weld, composites...) using ultrasonic waves. For this purpose, the continuous wavelet transform is applied to ultrasonic A-scan signals acquired using an ultrasonic non destructive testing (NDT) device. The time-scale representation provided, which highlights the temporal evolution of the spectral content of the A-scan signals, is relevant but can lead to misinterpretation. The problem is to identify if each pattern from the wavelet representation is due to the structural noise or the flaw. To solve this problem, a detection technique based on statistical significance testing in the time-scale plane is used. Information about the structural noise signals is injected into the decision process using an autoregressive model, which seems relevant according to the spectral content of the signal. The approach is tested on experimental signals, obtained by ultrasonic NDT of metallic materials (austenitic stainless steel) then on a weld in this steel and indeed enables to distinguish the components of the signal as flaw echoes, which differ from the structural noise. Voir les détails
Mots clés : Austenitic stainless steels, Structural noise, Flaw detection, Wavelet transform, Autoregressive model, Significance testing