Liste des documents
Remaining Life Estimation of the High Strength Low Alloy Steel Pipelines by Using Response Surface Methodology
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
Inspections, statistical and reliability assessment study of corroded pipeline
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
Real-Time Switches Fault Diagnosis for Voltage Source Inverter Driven Induction Motor Drive
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
Propriétés Optique de TiO2 et Application de la Méthode de Swanepoel pour la Détermination de l’Épaisseur Optique et de l’Indice de Réfraction
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
Study of Optical and Morphological TiO2 Nano-Films Properties Deposited by MagnetronSputtering on Glass Substrate
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.
Development of photovoltaic cell models using fundamental modeling approaches
In this paper, three advanced modelling approaches will be performed to well describe the actual behavior of photovoltaic (PV) cells, in which some total solar irradiance changes are considered. The first one uses a specific solar cell provided by the Sim-Electronics tool of the Matlab software. It is used to simulate the actual behavior of PV cells instead of the conventional electrical circuit based on either single or double diodes. The second approach adopts some physical components provided by the Simscape library to reach the same above mentioned goal. The third approach uses the Simulink blocks to build the mathematical equations describing the PV cell behavior, in which some mathematical operators and functions are used. The three proposed models have the ability to predict the actual behavior of PV cells under different weather conditions. This can improve the extraction of the maximum power and contribute even to the synthesis of the appropriate controller. The performances assessment of each proposed model is established in term of the provided output power as well as the generated current and voltage. Voir les détails
Mots clés : PV cell, Simulink, Simscape, Simelectronics, PV mode
Modeling and Fuzzy MPPT Controller Design for Photovoltaic Module Equipped with a Closed-Loop Cooling System
Electrical energy generated by a photovoltaic (PV) panel depends heavily on two climatic conditions: total solar irradiance and absolute temperature. If high intensity of the solar illumination contributes positively to increasing electrical power, a high degree of absolute temperature has, by contrast, a negative effect on its electrical characteristic. In this paper, the electrical efficiency provided by a conventional PV panel is enhanced using the proposed photovoltaic thermal (PVT) panel. The latter contains serpentines fed by a water tank, which allows cooling its PV cells at high temperature. Accordingly, the desired enhancement needs two main requirements: an efficient PVT panel model that accurately describes the actual PVT panel behavior and an efficient controller that correctly tracks the maximum power point tracking (MPPT). For this reason, a number of experimental test data is firstly recorded from an actual ISOFOTON I-50-PVT module under different climatic conditions. Afterward, the recorded data are fitted by the Curve Fitting Toolbox (CF-Tool), creating therefore a 2-dimensional lookup table, used in the following step. Next, the fuzzy logic control (FLC) strategy is employed to synthesize the proposed MPPT-FLC controller, which should ensure a good extraction of the maximal electrical power. To validate the effectiveness of the proposed MPPT-FLC controller based on a 2-dimensional lookup table, the obtained performance is compared, in terms of electrical power and duty cycle, to those provided by an MPPT-FLC controller for a conventional PV panel in various climatic conditions. Voir les détails
Mots clés : Photovoltaic thermal system, 2-Dimensional lookup table, fuzzy logic control, Maximum Power Point Tracking
Experimental study of chemically aged HDPE pipe material in toluene-methanol mixture and distilled water
Studying the aging phenomenon of plastic pipes presents simultaneously an economic achievement and a technical challenge for water and natural gas transportation systems. Ver y often, they are exposed to aggressive environmental agents such as UV rays, ambient oxygen, acids, bases and some other so lvents, altering the material microstructure, its physical and chemical properties. The high density polyethylene (HDPE) material degradation and loss of performance are usually the consequence of unwanted changes in mechanical behaviors leading to lower resistance. In this s tudy, we examine the effects of distilled water (DW) and a mixture of toluene-methanol (TM) in contact with an HDPE pipe. Morphological properties such as crystallinity and oxidation induction time (OIT) are in vestigated using DSC method. Tensile tests and thermal analysis show that the TM mixture is much more absorbed by the resin as compared to DW. An increase in crystallinity is observed as established from literature for other organic solutions. Finally, the study gives an idea about property variances and their evolution as a function of the pipe thickness which c an be used as an estimation of the structural heterogeneity of the product. Voir les détails
Mots clés : Pipe; HDPE; Aging; Distilled Water; Toluene-Methanol Mixture; Crystallinity; OIT
Study of The Reliability of A Composite Used In The Knee Prosthesis
In orthopedic surgery, the effectiveness of the implants used, such as hip and knee prostheses, depends mainly on their geometries and the type of loading to which they are subjected. In this work a probabilistic approach is chosen to study the reliability of a composite structure used in the manufacture of knee prostheses. The purpose of integrating reliability concepts is to consider uncertainty in several aspects including loading and material properties. The reliability index β is an excellent indication of durability and safety for given operating conditions. β is obtained using failure probability and a mechanical model. The critical stress intensity factor (Kc) is adopted as a criterion to the maximum limit of a numerically calculated KI. The results presented are discussed according to the length of the crack (a), and the limit load used. Voir les détails
Mots clés : Reliability analysis, critical stress intensity factor, crack length, load, reliability index
Magnetic and structural Behavior of Fe-CoO Nanocomposites Mechanically Milled
The Fe60(CoO)40 nanostructured alloys have been prepared from pure iron and cobaltoxide powders by mechanical alloying technique within a high energy planetary ball-mill.Morphology, microstructural and magnetic properties of this powder were investigated by aScanning Electron Microscope (SEM), X-ray diffraction (XRD) and Vibrating samplemagnetometer (VSM). The effect of time of milling on magnetic behaviour of Fe(CoO)nanostructured composite has been investigated. Apparition of new phase polycrystallinesample having a size in the range of 12 and 26 nm, it is confirmed by X-ray diffraction testing.The enhanced magnetic properties and structural behaviour of the nanoparticle are due by thediminution of size of crystallite. After 40 hours of milling, the appearance of spinel structureof CoFe2O4. The reduction in particle size leads to a significant increase in magnetichardening, the coercive field at room temperature increases from 6 Oe to 208 Oe Voir les détails
Mots clés : Fe60(CoO)40 nanostructured alloys, Mechanical Alloying, Magnetic Properties