Sciences des matériaux

Nombre total de résultats : 417
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Thermally affected characterization region by Barkhausen noise

M. Zergoug, N. Boucherou, A. Haddad, A. Benchaala, B. Moulti, H. Tahraoui, F. SELLIDJ, A. Hammouda  (2000)

The controlling of some industrial components require the development of new and particular nondestructive testing techniques. The testing method using Barkhausen noise (BN) is a particular one which can be applied to ferromagnetic materials. It is a magnetic nondestructive evaluation method and can provide very important information about the material structure. The aim of our work is to study the material structure using this technique to characterize the region submitted to thermal processing. Samples of steel have been heated at temperatures between 650°C and 1200°C with variable parameters (time processing, maintenance time, etc.). Acoustic BN processing allows an easy interpretation of results. Micrographs of samples have been obtained to confirm the results obtained by BN. Voir les détails

Mots clés : Non-Destructive testing, Barkhausen noise, Fast Fourier transformer, Magnetic field, welding, microstructure

Etude et simulation du comportement des matériaux polymères soudé par le FSW

Sid Ahmed AMEUR (2012)
Mémoire de magister

Ce travail apporte une contribution à la connaissance de procéder de soudage par friction-malaxage, et son utilisation pour la première fois pour un matériau polymère il s’agit du polyéthylène à haute densité, se matériau largement utiliser dans le transport de gaz et d’autres applications. Le soudage par friction-malaxage et un procédé rapide et contrôlé afin d'obtenir une liaison mécanique forte et durable sur les plaques soudes. Les essais de traction simple ont été réalisés dans le but de caractériser les paramètres du PEHD soudé et non souder. Nous avons constaté que le FSW peu être utiliser dans le soudage de matériau Voir les détails

Mots clés : Polymères, PEHD, soudage, FSW.

Study of physico-chemical properties of diatomiteAlgeria: Application to the thermal insulation ofliquid steel bath

H. MERADI, L. Bahloul, K. Bedoud, S. BENAYACHE  (2017)

The purpose of this paper is to characterize and to evaluate the diatomite powder of Sig region (West Algeria) withoutfluorine by powder generally used in tundish to thermal insulation of steel bath contain fluorine, that affecting the environment andhealth of workers. Thermal and physicochemical characterization showed different endothermic and exothermic peaks. Thescanning microscopy method was used and a large porosity was observed, which is very beneficial for improving the thermalconductivity of the product. The trial industrial in steelwork with diatomite powder, showed a weak loss temperature of steel (10 °Cmax), and filled fully function in thermal insulation of the steel bath. Voir les détails

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

Effect of Immersion Time and Cooling Mode on the Electrochemical Behavior of Hot-Dip Galvanized Steel in Sulfuric Acid Medium

Choukri Lekbir, Nessrine Dahoun, Asma Guetitech, Abdenour Hacid, Aicha ZIOUCHE, Kamel Ouaad, Amar Djadoun  (2017)

In this work, we investigated the influence of galvanizing immersion time and cooling modes environments on the electrochemical corrosion behavior of hot-dip galvanized steel, in 1 M sulfuric acid electrolyte at room temperature using potentiodynamic polarization technique. In addition, the evolution of thickness, structure and microstructure of zinc coatings for different immersion times and two cooling modes (air and water) is characterized, respectively, by using of Elcometer scan probe, x-ray diffraction and metallography analysis. The analysis of the behavior of steel and galvanized steel, vis-a-vis corrosion, by means of corrosion characteristic parameters as anodic (βa) and cathodic (βc) Tafel slopes, corrosion potential (Ecorr), corrosion current density (icorr), corrosion rate (CR) and polarization resistance (Rp), reveals that the galvanized steel has anticorrosion properties much better than that of steel. More the immersion time increases, more the zinc coatings thickness increases, and more these properties become better. The comparison between the two cooling modes shows that the coatings of zinc produced by hot-dip galvanization and air-cooled provides a much better protection to steel against corrosion than those cooled by quenching in water which exhibit a brittle corrosive behavior due to the presence of cracks. Voir les détails

Mots clés : cooling mode, hot-dip galvanization, Metallography, Potentiodynamic polarization, steel, X-ray diffraction, zinc coating

Simplified modeling to avoid breakage of sheet metal during tandem rolling

K. SLIMANI, M. ZAAF, S. TLILI, C.E. Ramoul .  (2017)
Article de conférence

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

Caractérisation structurale et tribologique de l’acier A105N

Article de conférence

La caractérisation structurale et le comportement tribologique de l’acier A105N, avant et après traitement thermique, ont été étudiés, en utilisantla microscopie optique, la microcopie électronique à balayage et le test d’usure par frottement sur un dispositif pion/disque. Les résultats obtenus montrent qu’à l’état brut, l’acier A105N présente une structure biphasée, composée de ferrite et perlite. Le traitement de mise en solution à 900°Crend la structure martensitique et améliore la résistance à l’usure par la diminution du coefficient de frottement. Voir les détails

Mots clés : A105N, usure, frottement, trempe, martensite

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


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

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

Contribution to the minimization of vibration ofrotating machines

Merazi Sayah  (2016)
Article de conférence

Rotating machines are used in areas as diverse as transport (trainsmotorized vehicles, etc.) Production industry, or appliances. Thevibrations from them may êtregênantes; they are the source of somenoise radiated by this machine and are therefore undesirable forusers, they can be transmitted to neighboring structures andaccelerate deterioration or aging, can also damage the rotatingmachines-they mê is therefore of interest to develop methodsto reduce the vibration level of the machines, as well as that of theirenvironment direct.Ces optimization methods (minimization) canminimize the natural vibrations using against vibration generatedby actuators requiring external power. The objective of this work isto develop a method of minimizing vibrations of a rotating machine,which aims to reduce the vibrational level of an area of its outercasing. This field can then be used for attachment of this machineand so help to minimize the amount of vibration it transmits to itsdirect environment. A new method also converge to the globaloptimum (minimum vibration value), and take into account possiblevariations of vibrational disturbances to eliminate. It allows asignificant reduction of vibrations, without changing thecharacteristics of the system. Voir les détails

Mots clés : Rotating machines, vibration sensors, optimization.

Acoustic Emission Monitoring of high risk installation in industrial environment

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

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