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Nombre total de résultats : 646
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Effect of molybdenum and niobium on the wear behaviour of high chromium white cast iron


High chromium white cast irons are excellent wearable materials. Their wear resistance is due to the presence of high volume fraction of hard carbides in microstructure. Accordingly, this material is very suitable for many applications such as mineral processing, cement production and other industrial fields. Researchers have tried different alloying elements in order to improve wear resistance of this material. An investigation was conducted to determine the effect of alloying elements on the friction and wear behaviour of high chromium cast iron with various concentrations of molybdenum and niobium. The alloys used in this work were made in industrial induction furnace. Alloying elements were added in crucibles after pouring operation. Amounts of molybdenum and niobium were varied between 0 and 3%. A molybdenum and niobium combination of an amount of 0.5% was also studied in this work. Wear investigations were carried out on the as cast and heat treated state of a slightly hypoeutectic high chromium cast iron.Results showed that the studied alloy is composed of netted eutectic chromium carbides embedded in an austenitic matrix. Wear looses carried out on as cast and heat treated cast irons indicates that the best results were obtained by abrasion with 3% Mo alloy. Friction tests has also given good results but less important. Manganese comparing to niobium addition has much more facilitated the abrasion than the friction resistance. These results indicate that the alloying elements do not act similarly on the two type of studied wear. Voir les détails

Mots clés : high chromium cast iron, microstructure, wear, friction, carbide

Magnetic microwave and absorbing properties of Fe-Co alloy synthesisedby mechanical alloying process

Said Bergheul, Ahmed HADDAD, Abdelhamid Tafat, Mohamed Azzaz  (2006)

In this paper, the structure and magnetic properties of nanocrystalline Fe(1–x)Coxmixtures are investigated. These structures are prepared using mechanical alloying based onplanetary ball mill under several milling conditions. The structural effects of mechanicalalloying of powders were investigated by scanning electron microscopy, X-ray diffractionanalysis and bench of microwaves. Consequently, alloy powder with an average grain size of10–13 nm was obtained. Maximum saturation magnetisation Ms was obtained at acomposition value of 65%Co. Microwave measurements were performed on the mechanicallymilled Fe(1–x)Cox powder Voir les détails

Mots clés : powder technology; mechanical alloying; microstructure; microwave.

Extraction and desextraction of a cationic dye using an emulsified liquid membrane in an aqueous solution

Lynda BAHLOUL, Fadhel Ismail, Med El-hadi Samar  (2013)

The removal of methylene blue (C16H18ClN3S) as a cationic dye which might be rejected in textile industry wastewaters during its production or its use was the main objective in this work. The extraction was performed by an emulsified liquid membrane (ELM) consisting of sorbitan mono-oleate (SPAN80) and di(2-ethylhexyl)phosphoric acid (D2EHPA) as a surfactant and an extractant respectively. The internal phase used was sulfuric acid. Effects of important factors (concentration of H2SO4, stirring velocity, quantities of organic, aqueous, phases, external and emulsified phases, concentrations of extractant and surfactant were studied according to the stability of the ELM. Then using favorable conditions for a good stability of the membrane, the extraction and of methylene blue (MB) from an aqueous solution was investigated. Optimal conditions were then determined and the extraction efficiency reached 98.15%. The desextraction of this dye was performed at 81.91% and the membrane was regenerated. Voir les détails

Mots clés : emulsified liquid membrane, emulsion W/O, extraction, methylene blue, desextraction

Structural and magnetic studies of nanocrystalline Fe80Ni20 alloy prepared by high-energy ball milling

Abdelhamid Tafat, Ahmed HADDAD, Said Bergheul, Mohammed AZZAZ  (2008)

Mechanical alloying is a powder metallurgy processing technique involving the cold welding, fracturing and rewilding of powder particles in high energy. It has been used to obtain nanocrystalline alloys. Fe-20 wt. % Ni alloys were synthesised using a planetary ball mill (Retsch PM400). X-ray Diffraction (XRD) was used to identify and characterise various phases during the milling process. It is shown that the bcc Fe(Ni) solid solution was formed after 2 h of milling. The steady state grain size is about 12 nm. Many nanostructures' magnetic materials have exhibited excellent soft magnetic properties, which suit so many applications. We used electromagnetic methods (hysteresis) to characterise the variation of the residual magnetisation and the coercive field.r Voir les détails

Mots clés : nanostructure, nanocrystalline alloys, Magnetic Properties, microstructure, high-energy ball milling, mechanical alloying.

Monitoring of metal powder by eddy current

Ahmed HADDAD, Mourad ZERGOUG, Mohamed Azzaz, Abdelhamid Tafat, Said Bergheul  (2010)

Nanocrystalline Fe(1−x)Cox, Fe, Fe80N120,Cu70Fe18Co12 mixtures have been prepared by mechanical alloying using a planetary ball mill under several milling conditions. Their structures and magnetic properties were investigated. Mechanical alloying is a non-balanced process for synthesis materials. The structural effects of mechanical alloying of powders were investigated by scanning X-ray diffraction analysis. In this report, we examine the applicability of eddy current techniques in-process for monitoring of powder density particle size and the time necessary to structure variation. An eddy current based monitoring system developed to measure metal powder density is expanded for monitoring metal powder diameter in metal compounds. Experimental sensor readings were gathered using four different metal powders with known particle sizes Fe(1−x)Cox, Fe, Fe80N120 and Cu70Fe18Co12. Analysis of the data showed that the sensor output was in relation with different parameter of powder (diameter, density and structure) that the sensitivity of the sensor differed with the type of metal powder. The merit of this technique is its reliance on a simple and inexpensive sensor probe. Voir les détails

Mots clés : metal powders, Mechanical Alloying, Magnetic Properties, Eddy Current, NDT, nondestructive testing, process monitoring, nanocrystalline materials, planetary ball milling, powder density, particle size, structure variation, sensors, sensor probes, nanostructures, nanotechnology.

Adaptive B-Spline Model Based Probabilistic Active Contour for Weld Defect Detection in Radiographic Imaging

N. Nacereddine, L. Hamami, D. Ziou, A. B. Goumeidane  (2010)

This paper describes a probabilistic region-based deformable model using a new adaptive scheme for B-spline representation. The idea is to adapt the number of spline control points which are necessary to describe an object with complex shape. For this purpose, the curve segment length (CSL) is used as criterion. The proposed split and merge strategy on the spline model consists in: adding a new control point when CSL is greater than a certain splitting threshold so that the contour tracks all the concavities and, removing a control point when CSL is less to a certain merging threshold so that the contour aspect maintains its smoothness. Noise on synthetic and real weld radiographic images is assumed following Gaussian or Rayleigh distribution. The experiments carried out confirm the adequacy of this approach, especially in tracking pronounced concavities contained in images. Voir les détails

Mots clés : weld defect, Active contour, adaptive B-spline, split and merge operations

Design and Optimization of Friction Stir Welding Tool

Mouloud Aissani, Saliha Gachi, Fouad Boubenider, Younes Benkedda  (2010)

In Friction stir welding, the tool geometry plays a fundamental role to obtain suited microstructures in the weld and the heat affected zone. In this work, for obtaining an excellent weld appearance without void, cracking, or distortion, an attempt was made to select proper FSW tool for aluminium alloy. So, we have included in the tool a safety system aimed at avoiding premature damage, and allowing the measure of applied pressure. The improved tool was tested on AA2024-T4 and AA7075-T6 aluminum alloys sheets. The weld quality has been evaluated by means of a microstructure analysis and micro-hardness measurements. The capacity to increase the welding speed, the changes of the crystalline plans orientation in the mixed part of thermo-mechanically affected zone and grains sizes observed in micrographics underlines the effect of the pin geometry and its displacement. The micro-hardness curve shows good mechanical properties. Finally, obtained results show welds of very good qualities. This study opens new interesting perspectives. Voir les détails

Mots clés : Aluminium, Design, Friction Stir Welding, Metallography, Micro-hardness

Simulation & Expérimentation en Soudage Etude du Comportement Thermique et Mécanique des Métaux à Usage Aéronautique.

AISSANI Mouloud  (2014)

La mise en œuvre de nouvelles techniques d’assemblage, en remplaçant le rivetage par le soudage, permet l’allègement des structures et des appareils à usage aéronautique. Dans le présent travail, l’intérêt est porté sur l’étude de deux procédés de soudage importants et récents qui sont le soudage par friction malaxage FSW et par l’arc électrique TIG. Dans un premier temps, une étude du comportement thermique de quelques métaux soudés par le procédé TIG, est menée. Une modélisation et des simulations numériques du transfert thermique sont réalisées, mettant en évidence l’apparition des zones à risques et l’effet des différents paramètres de soudage. Une étude expérimentale du soudage est ensuite présentée permettant une validation des résultats numériques. Dans un second temps, la conception et la réalisation d’un outil de soudage par friction malaxage FSW (Brevet 2007) sont effectuées. Des essais de soudage ont été menés par la suite avec succès. Les cordons de soudure obtenus par ces deux procédés ont été caractérisés par différentes techniques et leurs propriétés mécaniques ont été déterminées. Voir les détails

Mots clés : thermique, 3D, Essais mécaniques, acier, MEF, soudage TIG, soudage FSW, source de chaleur, alliage d’Aluminium

Analog Circuit Implementation of FractionalOrder Damped Sine and Cosine Functions

H. Nezzari, A. Charef, and D. Boucherma  (2013)

This paper introduces for thefirst time analog circuitimplementations of two fundamental linear fractional order systems whose impulse responses called fractional order damped sineand cosine functions are the inverse Laplace transform of their irrational transfer functions. These analog circuit implementationsare derived through rational function approximations of their irrational transfer functions. Voir les détails

Mots clés : Analog circuit, fractionalorder differential equation, fractional order system, irrational function, rational function.

Effect of Substrates on the Properties of ZnO ThinFilms Grown by Pulsed Laser Deposition

Adel TAABOUCHE, Abderrahmane BOUABELLOU, Fouad KERMICHE, Faouzi HANINI, Sarah MENAKH, Yacine BOUACHIBA, Tahar KERDJA, Chawki BENAZZOUZ, Mohamed BOUAFIA, Saad AMARA  (2013)

Polycrystalline zinc oxide (ZnO) thin films have been deposited at 450˚C onto glass and silicon substrates by pulsedlaser deposition technique (PLD). The used source was a KrF excimer laser (248 nm, 25 ns, 5 Hz, 2 J/cm2). The effectsof glass and silicon substrates on structural and optical properties of ZnO films have been investigated. X-ray diffraction patterns showed that ZnO films are polycrystalline with a hexagonal wurtzite—type structure with a strong (103)orientation and have a good crystallinity on monocrystalline Si(100) substrate. The thickness and compositional depthprofile were studied by Rutherford Backscattering spectrometry (RBS). The average transmittance of ZnO films deposited on glass substrate in the visible range is 70%. Voir les détails

Mots clés : ZnO, Thin films, PLD, Silicon, X-ray diffraction, Optical transmittance, RBS