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Nombre total de résultats : 1176
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Influence of manufacturing process on wear resistance Of grinding balls

BOUREBIA.MOUNIRA, BOUHAMLA Khedidja, MAOUCHE Hichem, Gherbi Amel, Chaour Mouhamed, Laouar.Lakhder (2017)

Abstract The grinding balls are widely used in cement works, they are often manufactured by the molding process, but the problem faced by major cement plants in Algeria is that these balls wear out quickly and broken. The objective of this work is to test wear resistance of grinding balls made by molding and grinding balls produced by forging. The tests of characterization of samples will be made thus that wear tests. The results indicate that grinding balls made by forging resist longer than molded balls by fact this method offers by fiber-forming phenomenon a solid texture which allows increases service life, wear resistance and impact strength.Voir les détails

Mots clés : Grinding ball, forging, molding, texture, wear


A.Younes, N.Dilmi, A.BOUAMER, H.Amar, Z.GUEZOUI, M.amir, M.Zergoug (2016)

Nanostructured materials are current topics in research and development in recent years because of the good mechanical and physical properties compared to crystalline materials. The nanocrystalline coatings may show increased hardness, good mechanical strength [1], good corrosion resistance and the oxidation resistance, and / or good behavior to friction and wear [1,2]. In particular, nanostructured materials have good properties in tribology, motor vehicles, heavy machines and cutting tools, etc. that require advanced materials functioning with minimum energy loss. Nanostructured coatings such tribological surfaces for use in contact with harsh conditions were searched intensively for the past decade. PVD and CVD are well-known methods for depositing such [3] coatings. However, the drawbacks associated such that the deposition sector size, substrate geometry, cost and complexity of the process often limit their use. In this perspective, the deposit by thermal spraying gives much attention. The different materials Metal, ceramics or cermet [4], nanostructured coatings were deposited by thermal spraying processes such as HVOF. In addition, the properties of these coatings have been found to strongly depend on the porosity, of the phase distribution, and the residual stress [5-6]. Voir les détails

Mots clés : Nanostructured materials, alumina, Mechanical Alloying, MEB, EDX, DRX, VSM

Structural, Mechanical, Electronic, Elastic and Chemical Bonding Properties of the Complex K2PtCl6-Structure Hydrides Sr2RuH6 First-Principles Study

O.Boudrifa, A.Bouhemadou (2016)

We report a systematic study of the structural, electronic and elastic properties of the ternary ruthenium-based hydrides Sr2RuH6 within two complementary first-principles approaches. We describe the properties of the Sr2RuH6 systems looking for trends on different properties. Our results are in agreement with experimental ones when the latter are available. In particular, our theoretical lattice parameters obtained using the GGA-PBEsol to include the exchange-correlation functional are in good agreement with experiment. Analysis of the calculated electronic band structure diagrams suggests that these hydrides are wide nearly direct band semiconductors, with a very slight deviation from the ideal direct-band gap behaviour and they are expected to have a poor hole-type electrical conductivity. The TB-mBJ potential has been used to correct the deficiency of the standard GGA for predicting the optoelectronic properties. The calculated TB-mBJ fundamental band gap is about 2.99eV. Calculated density of states spectra demonstrate that the topmost valence bands consist of d orbitals of the Ru atoms, classifying these materials as d-type hydrides. Analysis of charge density maps tells that these systems can be classified as mixed ionic-covalent bonding materials. The single-crystal and polycrystalline elastic moduli and their related properties have been numerically estimated and analysed for the first time.Voir les détails

Mots clés : Ruthenium-based hydrides; first-principles calculations; elastic constants; electronic structure

Fundamental properties of the rocksalt ZnO and MgO: an ab-initio prediction

Moufdi Hadjab, Smail BERRAH, Hamza ABID (2016)

The one of the most accurate first-principales methods is the Full Potential Linearized Augmented Plane Wave (FP-LAPW) formalism, based on Density Functional Theory (DFT), has been exploited to study theatrically, the fundamental properties of the both ZnO and MgO rocksalt binary compound using 16 atoms rocksalt supercell which corresponds to (1×1×2) conventional cell. The Local Density Approximation (LDA) was used only for the structural properties, to treat the exchange-correlation terms. In order to explore the wanted properties. The recently modified semi-local Becke-Johnson potential within LDA correlation in the form of (mBJ) was used to predict the optoelectronic properties of ZnO and MgO binary materials. As results, our computed lattices parameters equal to: 4.22 Å and 4.16 Å respectively, showed satisfactory agreements with experimental values (4.27 Å and 4.2 Å) for ZnO and MgO respectively again. in order to understand the changeability between relaxed and un-relaxed of the electronic structures, The calculated band structures reveal that ZnO posses indirect band gap (Г-M) while for MgO have an indirect band gap (Г-Г) which agree well with the experiment and other theoretical calculations. Optical dielectric function, refractive index, absorption coefficient and optical conductivity, are well described in a wide range of the incident photon energy. The acquired results are used to give an significant guideline to the material's design for optoelectronic applications.Voir les détails

Mots clés : ZnO, MgO, FP-LAPW, Electronic materials, Optical parameters, ab initio calculations.


Abdeldjalil BENFOUGHAL, Khaled BOUBENDIRA, Nasira SASSANE, Mohamed BOULKRA, Skander Boukhezar, Noureddine BOUGHDIR, Nihel HAMZAOUI (2016)

The tribological and thermal behavior of dry sliding contact steel composite carbone/carbone and steel-organic matrix composites are studied according to the parameters normal load, sliding speed, friction coefficient and test time. In the case of automotive braking, using a mathematical model, the surface temperature of contact was determined. Four normal forces, four sliding speeds and four friction coefficients were applied in this study. These parameters have a significant influence on the variation of average contact temperature. The results illustrate the evolution of the contact temperature according to the braking time.Voir les détails

Mots clés : Temperature, friction, steel, composite, Disc, Trim.

Modélisation et simulation numérique du reformage catalytique du n-hexane sur un catalyseur bi-fonctionnel en régime transitoire


Ce travail est une tentative de modéliser et simuler mathématiquement le comportement, en régime transitoire, d’un réacteur catalytique isotherme a lit fixe avec résistance au transfert et dispersion axiale.Le modèle est appliqué à la réaction de reformage catalytique du n-hexane sur un catalyseur bi-fonctionnel (métal - acide). Cette réaction est d’une grande importance à l’échelle industrielle pour avoir des essences de haute qualité, ces calculs ont été faits en régime transitoire. L’objectif du travail était de suivre l’influence sur l’installation du régime stationnaire d’un certain nombre de paramètres à savoir : temps de séjour, concentration moyenne des sites actifs, la position des particules catalytique dans le lit. Les résultats obtenus nous ont éclairés sur le mécanisme d’installation du régime stationnaire dans le réacteur.Voir les détails

Mots clés : Reformage catalytique, réacteur a lit fixe, catalyseur bifonctionnel, résistance au transfert, Régime transitoire

Study of physico-chemical properties of diatomite Algeria Application to the thermal insulation of liquid steel bath

Hazem MERADI, L’hadi ATOUI, Lynda BAHLOUL, Khouloud BEDOUD, Sihem BENAYACHE (2016)

The purpose of this paper is tocharacterize and to evaluate the diatomitepowder of Sig region (West Algeria) withoutfluorine by powder generally used in tundish tothermal insulation of steel bath contain fluorine,that affecting the environment and health ofworkers. Thermal and physicochemicalcharacterization showed different endothermicand exothermic peaks. The scanning microscopymethod was used and a large porosity wasobserved, which is very beneficial for improvingthe thermal conductivity of the product. The trialindustrial in steelwork with diatomite powder,showed a weak loss temperature of steel (10 °Cmax), and filled fully function in thermalinsulation of the steel bath.Voir les détails

Mots clés : diatomite, fluorine, Tundish, steelwork, thermal insulation, DSC

Study of structural and thermal properties of SiO2 and Al2O3 in the Diatomite

K.Boubendira, K.LABIOD, S.BENAYACHE, F.AOUADJA, H.Meradi (2016)

Diatomite is a light colored rock formed entirely or substantially of "backbones" of diatoms. These unicellular algae are surrounded by a "shell" in silica, frustule, the accumulation of the substance can lead to the formation of a rock.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

Simulation des propriétés électriques d'une cellule solaire hétérojonction à base de InGaP/GaAs

F. Bouzid, M. HADJAB, A. HADJ LARBI (2016)

Dans ce travail, en se basant sur le model idéal pour décrire la caractéristique courant-tension et en utilisant des paramètres matériels réalistes, nous avons optimisé la performance d'une cellule solaire hétérojonction à base de composés semi-conducteur (InGaP/GaAs), en optimisant simultanément plusieurs paramètres de la couche InGaP. Notre calcul indique que le rendement énergétique maximal de la cellule étudiée peut atteindre 33.73% sous illumination 1-Soleil AM1.5 et une température ambiante. Ce dernier montre le potentiel d’une telle structure qui pourrait être une alternative aux structure traditionnelles.Voir les détails

Mots clés : simulation, Cellule solaire, couche mince, Hétérojonction, Rendement.

Acoustic Emission Monitoring of high risk installation in industrial environment

Hamid HAFID, Alain PROUST, Richard DUNOYER, Omar AL HAJ (2016)

Acoustic Emission (AE) technology is widely used to control in service pressure vessel in a wide range of industry. Acoustic emission monitoring and its benefits have long been known and utilized by many industries to optimize the use of structures, increase operational safety, and to save money through effective condition assessment and maintenance. The application and acceptance of AE monitoring within the civil engineering industry has greatly expandedin the past few years [1]. Among the technological progress of AE it is possible to apply the technology in Atex environment with industrial process giving some genuine information on propagating defects even in refining and petrochemical plants.The monitoring of critical equipment allows an early detection of significant defects and the ability of following their severity in serviceto give an alarm to improve the safety of equipments and particularly piping systems. Some industrial examples are given in this paper to shed into thelight the return of experience on AE long term monitoring. AE technology is used: to give an in situ diagnostic, to prevent catastrophic ruptures, to help to reduce maintenance costs, and to avoid shutdown with assessing risk based inspection.Voir les détails

Mots clés : Accoustic Emission, Monitoring