Sciences des matériaux

Nombre total de résultats : 417
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Influence de la répartition des textures sur les performances d’un palier lisse

N. Tala-ighil, P. Maspeyrot, M. Fillon, A. Bounif  (2009)
Publication

Un intérêt progressif est accordé aux surfaces texturées dans les paliers lisses. L’utilisation desurfaces avec certaines géométries et dispositions de textures peut être une approche efficace pouraméliorer la performance d’un palier hydrodynamique.Cet article présente l’approche numérique utilisée pour analyser l’effet des textures de formesphérique sur les caractéristiques d’un contact hydrodynamique. Les résultats obtenus montrent que lescaractéristiques les plus importantes du contact comme l’épaisseur minimale du film, la pressionmaximale dans le contact, le débit axial et le couple de frottement peuvent être améliorés à travers unchoix approprié de la répartition des textures sur la surface du contact. Voir les détails

Mots clés : lubrification hydrodynamique, Lubrification à fluide non Newtonien, Tribologie des revêtements, Contact sous sollicitation de Freting, Tribologie sous champ électrique et magnétique, Méthodologie et caractérisation tribologique

Numerical simulation for cracks detection using the finite elements method

Salim Bennoud, Mourad ZERGOUG, Abderrazak Allali  (2014)
Publication

The means of detection must ensure controls either during initial construction, or at the time of exploitation of all parts. The Non destructive testing (NDT) gathers the most widespread methods for detecting defects of a part or review the integrity of a structure. In the areas of advanced industry (aeronautics, aerospace, nuclear …), assessing the damage of materials is a key point to control durability and reliability of parts and materials in service. In this context, it is necessary to quantify the damage and identify thedifferent mechanisms responsible for the progress of this damage. It is therefore essential to characterize materials and identify the most sensitive indicators attached to damage to prevent their destruction and use them optimally.In this work, simulation by finite elements method is realized with aim to calculate the electromagnetic energy of interaction: probe and piece (with/without defect).From calculated energy; we deduce the real and imaginary components of the impedance which enables to determine the characteristic parameters of a crack in various metallic parts. Voir les détails

Mots clés : Eddy Current, Non-destructive testing (NDT), Cracks, Finite Element Method

Numerical Simulations of Eddy Current Testing For Plated Aluminum Parts

Salim Bennoud, Mourad ZERGOUG  (2014)
Publication

Eddy current testing is a non-destructive inspection method applied to conductive materials. Its effects on aluminum are more effective than other materials. Modeling is a good tool for understanding and analyzing impedance responses due to flaws. In this paper, discretization by finite element method is used to solve the electromagnetic field equations in terms of magnetic vector and electric scalar potentials in order to calculate the probe impedance. Simulation by finite elements method was realized to calculate the electromagnetic energy of the interaction between coil and tested part. The real and imaginary components of the probe impedance were deduced from calculated energy that allows determining the characteristic parameters of a crack in aluminum parts. Voir les détails

Mots clés : Non destructive testing, Eddy Current, Finite Element Method, aluminum parts, numerical simulations

FEM Techniques Comparison for SIF Computing of Cracked Plate

Elkahina Sari, M. Zergoug  (2015)
Publication

The main purpose of this paper is to perform a computation comparison of stress intensity factor ‘SIF’ evaluation in case of cracked thin plate with aluminum alloy 7075-T6 and 2024-T3 used in aeronautics structure under uniaxial loading. This evaluation is based on finite element method with a virtual power principle through two techniques: the extrapolation and G−θ . The first one consists to extrapolate the nodal displacements near the cracked tip using a refined triangular mesh with T3 and T6 special elements, while the second, consists to determine the energy release rate G through G−θ method by potential energy derivation which corresponds numricaly to elastic solution post-processing of a cracked solid by a contour integration computation via Gauss points. The SIF obtained results from extrapolation and G−θ methods will be compared to analytical solution in particular case. To illustrate the influence of the meshing kind and the size of integration contour position, simulations are presented and analyzed. Voir les détails

Mots clés : stress intensity, energy release rate G

Solid state amorphization transformation in the mechanically alloyedFe27.9Nb2.2B69.9 powders

S. Alleg a, ∗, A. Hamouda a, S. Azzaza a, R. Bensalem a, J.J. Sun˜ ol b, J.M. Greneche c  (2010)
Publication

Mössbauer spectrometry and Rietveld analysis of X-ray diffraction patterns were used to follow the solid state amorphization transformation during the milling process of the Fe27.9 Nb2.2 B69.9 powders. The reaction between elemental Fe, Nb and B powders leads to the formation of the Nb(B) and Fe(B) solid solutions after 1 and 10 h of milling, respectively. A mixture of -Fe, Nb(B) and highly disordered Fe(Nb, B) solid solution is found after 25 h of milling. An amorphous structure is obtained on further milling time (100 h). From the Mössbauer spectrometry results, it is observed that the total mixing of the elemental powders, at the atomic level, is achieved after 50 h of milling and a stationary state corresponding to a full paramagnetic amorphous phase is reached after 100 h of milling. The amorphization process can be described by an Avrami parameter close to n = 1. Voir les détails

Mots clés : Nanostructures Powder metallurgy X-ray diffraction Mössbauer effect

SOLID STATE AMORPHISATION OF A Fe-Co-Nb-B POWDER MIXTURE BY MECHANICAL ALLOYING

YOUNES Achour (1) ; BENSALEM Rachid (1) ; ALLEG Safia (1) ; HAMOUDA Assia (1) ; AZZAZA Sonia (1) ; SUNOL Juan Joseph (2) ;GRENECHE Jean Marc (  (2010)
Publication

L'alliage Fe61Co21Nb3B15 a été préparé à partir d'un mélange de poudres par broyage mécanique haute énergie. Les changements structuraux et microstructuraux ont été suivis par diffraction des rayons X (DRX), spectrométrie Môssbauer, et calorimétrie différentielle programmée (DSC). Une structure amorphe, hautement désordonnée dans laquelle sont logés des grains de taille nanométrique de borure de fer, a été décelée, après un broyage de 48 h, par DRX et par spectrométrie Môssbauer. Un processus de recristallisation mécanique mène à la formation de nano-grains de α-Fe et α-FeCo, après un temps de broyage prolongé. Le désordre dans les poudres broyées a été confirmé par DSC où plusieurs courbes exothermiques se chevauchent sur un large domaine de température. Ce comportement provient de la relaxation des contraintes et du grossissement des grains. Voir les détails

Mots clés : Recristallisation ; Poudremétallique ; Etatamorphe ; Microstructure ; Amorphisation ;Alliage base fer ;Alliage mécanique ;Métallurgie poudre ; Broyage ;

Influence of heat treatment condition on passivity of titaniumaluminum-vanadium alloy in sodium chloride solution

M.Mokhtari, A.ZIOUCHE, M.Zergoug, S.Bouhouche, A.Boukari  (2013)
Publication

Corrosion of Ti6Al4V was study with different heat treatments in3,5% NaCl solution by electrochemical measurements, includedpotenthiodynamic polarization curves, linear polarization resistance(LPR) measurements and electrochemical impedance spectroscopy(EIS), in order to focus on exploring the effect of annealing on theelectrochemical response in a quantitative manner. The samples wereprepared in the state of the art; heat treatments were applied at fourdifferent temperatures of 550, 750, 950 and 1100°C. Themicrostructure of samples has been studied using the opticalmicroscopy and the mechanical properties have been evaluated suchas microhardness HV. The electrochemical test show that the corrosionrates of treated samples at temperature equal or more then 750 ° C;are much better for the untreated sample. Although, the corrosionproduct on the surface is identified as titanium dioxide by XRD in allsamples. Voir les détails

Mots clés : Ti6Al4V, corrosion, heat treatment, Corrosion product, XRD

Properties of Co-doped ZnO thin films grown by pulsed laser deposition on glass substrates

Adel TAABOUCHE, Abderrahmane BOUABELLOU, Fouad KERMICHE, Faouzi HANINI, Yacine BOUACHIBA, Azzedine Grid, Tahar KERDJA  (2014)
Publication

Undoped and cobalt-doped zinc oxide (CZO) polycrystalline piezoelectric thin films (Co: 3,5 at.%) using a series of high quality ceramic targets have been deposited at 4501C ontoglass substrates using a pulsed laser deposition method. The used source was a KrFexcimer laser (248 nm, 25 ns, 2 J∕cm2). X-ray diffraction patterns showed that the Codoped ZnO films crystallize in a hexagonal wurtzite type structure with a strong (002) orientation, and the grain sizes calculated from these patterns decrease from 37 to 31 nmby increasing Co doping. The optical waveguiding properties of the films were characterized by using a prism-coupling method. The distinct M-lines of the guided transversemagnetic (TM) and transverse electric (TE) modes of the ZnO films waveguide have beenobserved. With the aim of study the optical properties of the ZnO films, an accuraterefractive index and thickness measurement apparatus was set up, which is called M-linesdevice. An evaluation of experimental uncertainty and calculation of the precision of therefractive index and thickness were developed on ZnO films. The optical transmittancespectra showed a good transparency in the visible region. Calculated optical band gapvarying from 3.23 to 3.37 eV when the content of Co doping increases from 0 to 5 at.%. Voir les détails

Mots clés : Thin films, ZnO, pulsed laser deposition, Piezoelectric, Waveguiding properties, Optical transmittance

Influence de la précipitation secondaire sur les propriétés d'usure d'une fonte au chrome alliée

K.BOUHAMLA, A. HADJI, H. MAOUCHE  (2011)
Publication

La résistance à l'usure des fontes au chrome est fonction du type d'éléments d'addition. Notre approche consiste à étudier l'effet combiné des éléments d'alliage (Ti, Mo, Mn et Nb) sur le comportement à l'usure des fontes au chrome. plusieurs techniques sont employées ( microscopie optique et MEB, DSC et DRX). Des essais d'usure par frottement et par abrasion ont complété cette étude. Les résultats obtenus montrent que l'addition des éléments d'alliage a eu un effet affinant sur la matrice. Un changement microstructural est enregistré au niveau de la matrice sous forme de précipitations proeutectiques et secondaires. Les éléments carburigènes introduits dans la fonte ont favorisé une nette augmentation de la résistance à l'usure par frottement après traitement thermique, comparativement à leur effet sur la résistance à l'abrasion. Voir les détails

Mots clés : fonte au chrome, usure, précipitations

STYDY OF MECHANICAL PROPERTIES OF MOLYBDENUM COATINGS DEPOSITED BY THERMAL FLAME SPARYING ON GRAY CAST IRON

Samira.TLILI, Mohamed Zine TOUHAMI, Nacereddine. ZEGHIB, Abdelkader.KHETTACHE  (2012)
Publication

Thermal spraying coatings are used to meet the most stringent industrial requirements in the wider of application. The molybdenum coatings present a good wear resistance which used several mechanical applications. In this work, we studied the mechanical properties of molybdenum coating deposited using thermal flame spraying on gray cast iron with lamellar graphite. After optimization of the spraying parameters, the microstructure was investigated using optical microscopy, scanning electron microscopy and X-ray diffraction. The mechanical properties obtained by microhardness and nanoindentation tests were evaluated on a polished cross section. The mass loss was measured using the abrasive wear test at varying the normal load. The results showed an improvement the mechanical properties of gray cast iron after deposition of molybdenum with wire-flame spraying. Voir les détails

Mots clés : Thermal Spraying, Molybdenum Coating, mechanical properties, Nanoindentation, wear.