Liste des documents
Crack propagation resistance in hydrocarbon transport pipelines
The aim of this paper is to determine the propagation resistance of cracks in grade API 5L X70 steel pipes. These pipes are produced by the Algerian company of manufacture of welded pipes (ALFAPIPE), they are intended for the transport of the hydrocarbons. Mechanical tests such as resilience and tensile strength were carried out on specimens taken from pipe ferrules in the longitudinal and transverse directions. The resilience tests are carried out at different temperatures in order to calculate the stress intensity factor. Tensile tests are used to have the mechanical characteristics of the material. The experimental results are then exploited in the modeling part by the software of calculation of the structures using the method of the finite elements, the calculation code is CASTEM 2016. Voir les détails
Mots clés : Tenacity, fracture, Resilience, Modeling.
Influence of heat treatment on the structure and abrasion wear of A105N steel
Wear is the removal of material from a surface by very different mechanisms such as abrasion, erosion, fatigue and corrosion. In the industrial sector, the cost of repairing used parts is very high; the solution in this case is to choose an anti-wear material. To choose an anti-wear material, the first factor is the identification of wear type; however, the conditions of use in the industry are complex so the choice of materials is difficult.Usually the choice of material depends on several factors such as high hardness, high resistance to abrasive wear and low friction coefficient. Thermal treatments are proposed in order to improve these properties. The objective of our work is to study the influence of heat treatment on the structure and abrasion resistance behavior of A105N steel.Samples solution treatment is carried out at a temperature of 900 °C for 2 h then quenched in water. Experimental techniques such as optical microscopy, SEM, EDX and abrasion wear test are used to highlight the effect of heat treatment on the wear resistance of the steel.The microstructural characterization shows that in the initial state, the structure is composed of ferrite and perlite, after tempering, the structure is composed of perlite and bainite. The wear tests by abrasion show a clear difference on the weight losses of up to 50% following the quenching treatment. Voir les détails
Mots clés : wear, abrasion, steel, heat treatment, A105N.
Simplified modeling to avoid breakage of sheet metal during tandem rolling
In the tandem rolling, the simultaneous passage of the sheet between multiple cages poses a control problem of inter-stand tension [1,2]. Manufacturers tend to ask the equal tension between a cage and another, that is to say between the output of a cage and the input of the next cage. This causes a speed regulation problem. Indeed, this generally gives different speeds between the input and pass out of the previous pass. Which may lead to ripples or excessive tension may cause breakage of the strips. To illustrate this situation, we propose to take the data from the tandem mill site steel complex Arcelor-Mittal El Hadjar Algeria. It contains five stand tandem mill. The purpose of this work is to get to determine for each case, the correction to be made to obtain equal speeds and tensions between the output of each cage and the door of the cage that follows.To our simplified calculation model, two Matlab program was developed:-the first: Greenhouse to the rolling calculation (speeds, the neutral plane, ....)-the second: to make corrections tensions in order to obtain equal speed between the output of a cage and the input of the next cage.The Results show the convergence speed after the correction of tension, like that, to avoid the risk of breakage or undulation of the rolled strip and pre calculated magnitudes we do not stray from reality. Voir les détails
Mots clés : modeling, rolling, tension, speed., breakage
EFFECTS OF TOLUENE-METHANOL MIXTURE ON MECHANICAL AND STRUCTURAL PROPERTIES OF HDPE PIPE
The aging of pipes is an economic and technical challenge for drinkable water and natural gas networks. The degradation of HDPE pipes depends on factors such as age, laying and service conditions, environmental temperature, fluids and soils corrosiveness, density and traffic loads. In service, polymer structures are often exposed to aggressive environmental stresses such as UV’s, oxygen, acids, bases and solvents, affecting the nature of the material as well as its microstructure, physical status and chemical composition. Various studies have presented results on HDPE pipes embrittlement, focusing on cracking phenomena under environmental stress cracking, creeping and fatigue cracking. The weakening of the material usually resulted from mechanical behavior modifications which made it unable to withstand loads without breaking under normal service conditions. In this study, we attempted to assess the effects of an equimolar toluene-methanol mixture while considering exposure to air and water as references. Morphological properties such as crystallinity, crystalline lamellae thickness and the oxidation induction time (OIT) are studied using differential scanning calorimetry in order to establish the extent of degradation using DSC. Mechanical tests and thermal analysis show that toluene-methanol mixture is much more absorbed by the resin compared to water, i.e. the degradation is very pronounced. In terms of mechanical properties (E, σy and εf), the nominal values collapsed. In addition, the study shows the evolution of these parameters as a function of pipe thickness in order to get an idea about structural heterogeneity across pipe wall. An increase in the crystallinity together with crystalline lamellae thickness is observed which is confirmed by literature for other organic solutions. This phenomenon is known as chemical-crystallization due to the shrinkage of the amorphous phase during possible chain segmentation process. Voir les détails
Mots clés : HDPE; Environmental effect; Aging; Mechanical properties; Crystallinity; OIT
Approche expérimentale pour la détermination de la distribution des contraintes résiduelles dans un pipe en polyéthylène.
Dans cette étude la détermination des contraintes résiduelles dans un tube en polyéthylène de diamètre 125mm destiné au transport du gaz naturel est réalisée sur la base d’une approche expérimentale. La technique d’usinage successif par enlèvement de matière est utilisée. La paroi du tube est divisée en cinq couches. Les couches découpées suivant la même génératrice ont permis d’identifier la distribution des contraintes résiduelles relaxées dans le tube au cours du temps. Il a été trouvé que des contraintes compressives sont relaxées dans l’extérieur de la paroi. Et d’autres contraintes positives de traction sont libérées à l’intérieur de la paroi. Cette configuration est liée au procédé de fabrication à savoir l’extrusion. Voir les détails
Mots clés : extrusion, Pipe, refroidissement, usinage, contrainte résiduelle
Eccentricity Fault Diagnosis based on Wavelet Transform and Neuro-Fuzzy Inference System in Doubly-fed Induction Generator
he development of wind turbine system is becoming very influential, in conditions of power qualityand very interesting for ecological protection. However, their potential is considerable in the world, thewind energy sources have drawn more and more attention all over the world recent years to improve theserious environment problems and deal with the shortage of fossil fuels in recent years [1]. The doubly-fedinduction generator (DFIG) is one of essential part of wind turbine system and has dominated in the field ofelectromechanical energy conversion system because of robustness and low cost [2]. So, for a substantialprofit, the diagnosis should be properly developed to ensure a production system more make safe.Production systems must be provided with reliable protection systems as any failure can lead to inevitabledamage [3].The occurrence of different faults can be completely in damage this machine type and inevitably cause theprocess to stop, resulting in loss of production consequently [4]. Therefore, it is necessary to develop amodel machine allow to detect the presence of the faults.Wind turbine is prone many failures and because of their size and localization, it is very costly to repair oremplace their component. In generally, mechanical faults are the most encountered in wind turbinessystems at the gearbox. These faults can occur at the level of ball, inner and outer race bearings, andflanges of the machine shaft. In scientific research tasks shows that rotor faults are more frequentbreakdowns, [5, 6]. In this paper we are interested to study the rotor eccentricity faults types [7].The DFIG in this type of faults can be subjected to counteract between the center of rotation of the shaftand the center of the rotor resulting the oscillations in the electromagnetic torque, uneven distribution of thecurrents in the rotor and the unbalance of stator current. This phenomenon is called static or dynamiceccentricity, and both at the same time creates the fault mixed eccentricity, whose origin may be related toincorrect positioning of the bearings during assembly or bearing failure [8, 9].Eccentricity Fault Diagnosis based on WaveletTransform and Neuro-Fuzzy Inference System inDoubly-fed Induction GeneratorMerabet. HichemResearch Center in Industrial Technologies (CRTI) P.O.Box 64, Cheraga, Algeria.h.merabet@csc.dzBahi. TaharElectrical Department, University of Annaba, Algeriatbahi@hotmail.comBedoud. khouloudResearch Center in Industrial Technologies (CRTI) P.O.Box 64, Cheraga, Algeria.k.bedoud@csc.dzDrici. DjalelResearch Center in Industrial Technologies (CRTI)P.O. Box 64, Cheraga, Algeria.d.drissi@csc.dzTSeveral methods of diagnosis are based on spectral analysis of the electromagnetic quantities, using themagnetic flux, stator current and the neutral voltage vibration signal analysis and especially the statorcurrent which requires only a current sensor [10, 11]. Therefore most of the recent research has bennedirected towards non-invasive techniques such as stator current and vibration signal analysis, motorsignature analysis with wavelet transform, courant envelope, Artificial Intelligence such as NeuralNetwork, Fuzzy Logic and Fuzzy Neural Network. The analysis of the stator currents in the waveletdomain remains the most commonly used because the spectrum results contains a source of information onthe majority of electrical and/or mechanical faults and magnetic properties can appear in the machine [12,13].The artificial intelligences based on fuzzy logic system inference, artificial neural network (ANN) orcombined structure techniques of artificial neural fuzzy interference system (ANFIS) are widely used in thenew monitoring[14, 15].Therefore, in order to increase the efficiency and the reliability of the monitoring in the field of the(DFIG) supervision, the proposed technique is based on wavelet transform and Neuro-Fuzzy inferencesystem (ANFIS).In this paper, the investment interest in wind turbine conversion system based on DFIG is presented.Then, we focus on the study of their designs and the development of a global model for doubly-fedgenerator in case of rotor eccentricity faults.Finally, in order to validate the considered method, the proposed model has been simulated and validatedby numerical simulations using MATLAB/Simulink. Voir les détails
Mots clés : eccentricity, fault, diagnosis, wavelet, ANFIS, DFIG
Direct Power Control of DFIG Used in Wind EnergyConversion System
The problems caused by traditional systems on the environment of energy production havesucceeded, in the immediate, the utilization the renewable energies for to preserve theenvironment and to satisfy the energy. So, thanks to the encouragement of governments andthe global orientations, the development of wind energy has grown significantly due to thediversity of exploitable areas and to the relatively attractive costs. Therefore, the wind energyis becoming one of the most important renewable energy sources. Indeed, variable speedWind Energy Conversion System (WECS) have become the industry standard because oftheir advantages over fixed speed ones such as improved energy capture, better power quality.The WECS described in this work is show by figure 1. He includes the wind turbine, gearbox,DFIG, and back-to-back converters whereas the stator winding is fed by back-to-backbidirectional converter. In this system, the wind energy is transmitted Through theturbine to the three-phase DFIG. This energy is transmitted directly through a bridgerectifier and inverter to the electrical network. Voir les détails
Mots clés : Wind energy conversion system; Doubly Fed Induction Generator; Maximum power point tracking; Simulation
Study of the resilience of a composite materialintended for the orthopedic prosthesis of a tibia
This approach is based on the mechanical characterization of a biomaterial which is an organiccomposite with a thermosetting polymer matrix reinforced with a glass fiber; this composite has beenproduced by a conventional casting method. Currently, composite polymer-matrix objects occupy animportant place in the aeronautics, automotive, medical industry etc……, for this purpose, we areinterested in the study of a mechanical property of a thermosetting polymer matrix compositereinforced with glass fiber, this composite is intended for the orthopedic prosthesis of a tibia, thisproperty called resilience. For so doing, we have realized a Charpy shock test on a sample of thepolymer matrix composite reinforced with a glass fiber for the orthopedic prosthesis of a tibia. Wehave also supported this study by a hardness test and microscopic characterization (SEM) to revealthe microstructure of the composite. Voir les détails
Mots clés : composite – mechanical property – resilience –hardness – microstructure
CHARACTERISTICS OF CALAMINE AND NATURAL PIGMENT FOR ANTI-RUST PAINTINGS
Abstract.This work has a double objective. On the one hand, the valorization of natural raw materials, in particular, the oolithic iron ores which do not find their use in iron and steel because of their high phosphorus content and on the other hand the recycling of steel by-products.. The ultimate goal is to synthesize an anti-corrosion paint.In this first part, we will study the characterization of these two components by their chemical analysis, their grinding (fineness) and their thermal analysis (TGA, DSC).Chemical analysis showed that the pigment contains 53.18% of total iron and gangue dominated by silica. Calamine in turn contains 73.83% of iron in the form of iron oxides (FeO, Fe3O4 and Fe2O3).Iron pigment is composed mainly of hematite with a little of goethite.Grinding tests showed that the scale is much more suitable for grinding than pigment. The granulometric analysis measured by a laser granulometer (Hydro 2000MU) gave us a volume distribution of the particles with a size between 0.7 and 32 microns for scale and between 0.6 and 40 microns for the pigment and Their specific areas are 1.6 and 1.5 m2 / g..Thermogravimetric analysis (TGA) and the thermal variation of flow (DSC) showed that the iron pigment loses weight with phase dissolution by consuming energy when the temperature increases. Scale gains weight by the formation of new phase with heat.Exploration picture by scanning electron microscope of red iron pigment shows a grain aggregate formed rounded over at least iron oxide and gangue. The analysis by EDS shows a predominance of iron with a relatively large matrix containing the four predominant oxides in the case of iron ore deposits. Chemical elements forming these four oxides are silicon, calcium, aluminum and magnesium.The observation scale milled for 5 min SEM showed a homogeneous structure composed of sizes of iron oxide grains and shapes ranging from 1 µm to 10 µm. Voir les détails
Mots clés : Pigment iron, scale (calamine), iron oxides, grinding, Simultaneous thermal analysis.
Investigation of Blade Diagnosis by Empirical Mode Decomposition
The bladed disk components are considered as the most common cause of failures in turbomachines. The failure of a single blade can potentially compromise the total integrity of the machine. The aim of this article is to detect the blade failures such as crack, deformations, fracture of blade and blade loss using vibration analysis. Many signal analysis methods are able to extract useful information from vibration data. Currently, the most of these methods use temporal analysis based on scalar indicators. However, these methods present some limitations. In the present work, we are interested to the vibration signal analysis by the Empirical Mode Decomposition (EMD) and Fast Fourier Transform (FFT). The EMD is one of the most important topics in digital signal processing, by using this method the measured signals are decomposed into Intrinsic Mode Functions (IMFs) and then the spectrum of some IMFs are generated. By using the real vibration measurements from a pilot scale, the obtained results show that Blade defects are detected successfully. Voir les détails
Mots clés : Turbomachinery, Blade faults, Scalar Indicators, EMD, FFT