Liste des communications
Determination of the elastic parameters of thermoplastic composites using the indentation technique
this work deals with the application of the macroindentation technique to the determination of the elastic parameters of composite with polypropylene matrix and reinforced with ductile and brittle fibers. The aim is to obtain a representatives average values taking into account the influence of the holding time and type of the used reinforcement (ductile or brittle reinforcement) on the overall elastic modulus of the studied polymers. To do this, the diameter of the indenter used ischosen relatively large (diameter of 16 mm) and the load equal to 6 kN. The various results obtained made it possible to see the effects of the holding time and the type of reinforcements used on the evolution of the elastic modulus of the reinforced composite Voir les détails
Mots clés : thermoplastic composites, macro-indentation test, viscoplastic behavior
Description of the solid method of BaTiO3 ceramics elaborations
Abstract— There are two major methods of the barium titanate ceramic BaTiO3 elaboration, the solid and the liquid methods (Hydrothermal, sol-gel processing, and Coprecipitation) [1, 2, 3].In this work, we present a theoretical study to describe the solid method of BaTiO3 elaboration, it is the most method used in the industry, because it is very economical, inexpensive and easier to implement. Voir les détails
Mots clés : component formatting; style; styling; insert
Modal Analysis For Composite Sandwich Plates Of Honeycomb Core
.The purpose of this work is to realize a vibratory study on panel’s sandwiches established by the honeycomb core and aluminum skins, used in the conception of the aerospace structures; all the analyses are based on conditions in the embedded free limits (E-L-L-L). The aim is to compare the natural frequencies of the two plates with those obtained from the two simulation models. Two methods are used in modeling, 3D drawing of the sandwich structures and calculating an equivalent structure using the homogenization method based on representative elementary volume (REV) using ANSYS software. The modal resolution of these two configura-tions is performed by the finite element method. The comparison of numerical results shows excellent agreement. Voir les détails
Mots clés : Sandwich plate, homogenization, FRF's, modal analysis, Finite element method.
Corrosion of AISI4130 in différents électrolytiques solution
This article discusses the electrochemical behavior of AISI 4130 alloy steel in various electrolyte solutions H2SO4, HCl and NaCl. Corrosion tests were carried out on a potentiostat / galvanostatat room temperature in the various electrolytes, under an Ag / AgCl reference electrode with .Electrochemical Impedance Spectroscopy (EIS) measurement. The results obtained through the tafel curves show that the corrosion process can be divided in two parts highlighting the aggressivity of Cl- ions. The impedance which is characterized by a large semicircle in the Nyquist graph increases under H2SO4.Equivalent circuits have been determined to represent the corrosion processes at differente ectrolytes. Voir les détails
Mots clés : AISI 4130, electrolytes H2SO4, HCl and NaCl
Puzzle of c-WN phase stabilization
In this paper, we present first-principles calculationsthat compare structural and electronic properties of WN inthe NaCl and NbO phases. Our results predict that the NbOstructure of WN is more stable than the NaCl structure withoutdefects, where the enthalpy of formation per formula unit Hf =-0.872eV and 0.616eV for NbO and NaCl structures, respectively.Moreover, the calculated lattice parameters of c-WN are a=4.35A°and a=4.11A° for NaCl and NbO phases, respectively. It is veryclear that the lattice parameter obtained for c-WN in NbO is invery good concordance with that reported experimentally of a =4.14A° . Although the formation energy calculations support thehypothesis of the stability of the NbO phase, the experimental xrayphotoelectron spectroscopy (XPS) electron density of statesfor valence band spectra corresponds to that density of statescalculated for c-WN in NaCl phase. Based on this comparison,more consideration must be taken into account to elucidate thisissue. Voir les détails
Mots clés : Cubic Tungsten nitride ceramics, Firstprinciples calculations, Formation energy
Experimental study of the thermo-mechanical behaviour of alumina-silicaterefractory materials elaborated from Algerian kaolinitic clays
This work aims to study the thermomechanical behavior of an algerian kaolinitic clay. We started with the characterization of the raw material (DD1) of Djebel Debbagh -Guelma, in order to obtain a deep information about the microstructure of the material before and after a heat treatment, notably its crystallographic nature and the grains size and shape. The chemical composition and physical properties are reported. The mineralogical and chemical characteristics, based on X-ray diffraction (XRD) and scanning electron microscopy (SEM), were also carried out. The general behavior of the material with increasing temperature was analyzed through the various microstructure investigations and thermal analysis. Voir les détails
Mots clés : Thermo-mechanical properties, aolinitic clays, elaborate
Characterizations of joints HDPE welded by FSW
The aim of this work is the characterization of high density polyethylene (HDPE) joints welded by the Friction Stir Welding (FSW) technique. The characterization is done by destructive testing (mechanical tensile tests) for welded joints.To do this work, a series of experimental tests were made by taking in account of several parameters: - the geometry of the welding tool (pin), the axial force Fz applied to the tool along its axis of rotation, to compensate for the pressure formed in the weld zone, the speed of rotation of the tool, the speed of advance of the tool,in this work, we only take in account of the last two parameters.The results obtained were satisfactory and show the influence of these parameters on the quality of the joint. Voir les détails
Mots clés : FSW, HDPE, polymers, welding
ANALYSE PHYSICO-CHIMIQUE DE LAITIER DE HAUT FOURNEAU PAR SPECTROSCOPIE INFRAROUGE (IR) ET DIFFRACTION DE RAYON X (DRX)
L’industrie sidérurgique génère une production fatale de matières secondaires constituées de produits de réactions résultant de son activité de production d’acier. Ces matières secondaires sont désignées communément par les coproduits sidérurgiques tels que : les laitiers de haut fourneau. Les principales propriétés physiques de laitier de haut fourneau (La densité et la surface spécifique). Les échantillons ont été caractérisés par différentes techniques d’analyses parmi nous citons : la diffraction des rayons X et la spectrométrie infrarouge à transformée de Fourrier. Les diffractogrammes obtenus sur les échantillons des laitiers caractérisent la phase vitreuse et quelques raies de faible intensité représentant les composés cristallisés. Lors de l’analyse des poudres par spectrométrie infrarouge IR, Le spectre a montré des bandes identifiées, telles que le les liaisons Al-O, Ca-O, et Si-O qui se caractérisent par les bandes de vibration à environs 634, 1793, 956 cm-1 plus la présence des carbonates caractérisés par la bande 879 cm-1. Voir les détails
Mots clés : Déchets sidérurgiques, Caractérisation chimique, DRX, IR, laitier
Comparative study between EKF and Geometrical methods for theAcoustic Emission source localization.
The purpose of this paper is to optimize and apply probabilistic methods and compare the obtained results to geometric method for locating acoustic emission (AE) source in a plate-like structure. The time of arrival (TOA) of the AE waves in each sensor taking into account the uncertainties, was determined by the continuous wavelet transform (CWT). Then the group wave's velocity was calculated by Monte Carlo simulation. As a probabilistic method, the extended Kalman filter (EKF) is used to iteratively estimate the location of AE sources. Experimental results have shown that the probabilistic method estimates thelocation of the pencil lead break better than the geometric method.Experimental tests were performed on a copper plate to validate the comparison of the two approaches performances. Voir les détails
Mots clés : Acoustic Emission (AE), Time of arrival (TOA), Continuous Wavelet Transform (CWT), Monte Carlo simulation, Geometrical method, Extended Kalman Filter (EKF)
Classification des défauts mécaniques par les machines à vecteurs de support (SVM).Application aux machines tournantes
Cet article présente l’utilisation de la méthode des machines à vecteurs de support SVM (en anglais. Support Vector Machine) pour le diagnostic et la classification des défauts des machines tournantes. La classification par SVM utilise le concept de discrimination par apprentissage machine qui s’appuie sur la notion de généralisation à partir d’un ensemble de données. Le choix des paramètres de classification, tels que le principe de vaste marge, fonction Kernel ainsi que l’hyperplan jouent un rôle important pour une bonne séparation des données et l’aboutissement à des taux de classification adéquats. La séparation a été développée, et appliquée en utilisant des indicateurs temporels et fréquentiels obtenus à partir des signaux vibratoires recueillis à partir d’un banc d’essai installé au niveau de « L’unité de recherche appliquée en sidérurgie métallurgie URASM-CRTI Annaba». Les signaux acquis correspondent à deux modes de fonctionnements; fonctionnement sain et fonctionnement défectueux matérialisé par des défauts d’engrenage et de balourd. L’application de la technique proposée sur des signaux de vibration réels a montré son efficacité en termes de séparation et de classification multi-défauts. Voir les détails
Mots clés : machines tournantes, vibration, classification, Machines à vecteurs de support (SVM)