Mécanique
A Simple Efficient Finite Element for the Sandwich Plates Analysis
In this work, a numerical simulation has been considered of a sandwich composite panel subjected to a mechanical uniaxial load in order to study the buckling behaviors. In this study, we used the finite element Abaqus software and a simple efficient finite element model available in the literature [1] in order to: 1- Describe the fundamental buckling modes of a sandwich composite panel. 2- Understand the buckling behavior on this type of structure. 3- Validate the reply of the developed element on buckling behavior for the sandwich composite structure with the finite element ABAQUS software. Voir les détails
Mots clés : composite, sandwich, buckling modes, finite element
CFD method for analysis of the effect of drill pipe orbital motion speed and eccentricity on the velocity profiles and pressure drop of drilling fluid in laminar regime
Due to the axial and lateral loads applied to the drill pipe during the drilling process, this last may loseits stability and begins to make complicated motions like the orbital one. In the present paper, thisorbital motion of the drill pipe is modelled using CFD method to investigate its effect on the axial andtangential velocity profiles in the wide and narrow regions of the eccentric annulus (E=0.2, E=0.4,E=0.6 and E=0.8), as well as, effect of the orbital motion speed on pressure drop gradient of drillingfluid is studied. Our results show that increment of the orbital motion speed from 100 to 400 rpmcauses an increase of 913% of the maximum axial velocity, however, this increment is estimated atabout 100% in the case where the drill pipe makes pure rotation for the eccentric annulus (E=0.8),Moreover, orbital motion of the inner pipe prevents the secondary flow to appear in the wide region ofeccentric annulus. For all eccentricities, the tangential velocity of the orbital motion case in the narrowregion for 400 rpm speed is 120% higher than pure rotation one Voir les détails
Mots clés : Orbital motion, eccentricity, velocity profiles, pressure drop, drilling fluid, laminar flow
AN EXPERIMENTAL STUDY ON MECHANICAL OF A COMPOSITE MATERIAL FOR ORTHOPEDIC USE
This study consists in the mechanical characterization of a composite material used in the fabrication of orthopedic prostheses by ONAAPH (Annaba- Algeria). The studied composite is the result of a combination of a polymethyl methacrylate (PMMA) resin, fiberglass reinforcements and an absorbent of the resin, namely Perlon. The method adopted for obtaining specimens is the same as that used in the manufacture of prostheses. except that the shape of the mold used in our study is rectangular, allowing to obtain composite plates. The three-point bending tests were carried out on a MTS43 universal machine in the Advanced Materials Research Unit (URMA / CRTI, Annaba/Algeria). The identification of the damage mechanisms according to the mechanical loading conditions as well as the degradation of the constitutive elements, will be discussed. Voir les détails
Mots clés : composite, mechanical tests, mechanical behavior, Finite Elements
Characterization of local mechanical behavior of TA6V weld sheet
The present work aims to study the local mechanical behavior of TA6V weld sheet. To this purpose, X-ray Diffraction (XRD), optical microscopy and nano-indentation measurements have been employed. The results highlight strong relationship between the hardness (HIT), Young’s modulus (EIT) values and the microstructure of each zone and phase present along the weld joint. The HIT of the molten zone (MZ) is greater than that of the Heat affected zone (HAZ) and the base metal (MB) in the α phase, whereas it shows small values in the HAZ than that of MB in β phase. Voir les détails
Mots clés : TA6V, Nanoindentation, Microhardness, microstructure.
The influence of scale yielding conditions in the determination of the fracture load using both analytical and numerical approaches for the study of the elasto-static anti-plane problem of a crack in a semi-infinite strip containing a non-homogeneous zone
The elasto-static anti-plane problem of a crack in a semi-infinite strip containing a non-homogeneous zone was studied using two approaches. The first one consist on an analytical approach based on the solution of a Singular Integral Equation (SIE formulation) using the Dugdale-Barenblatt cohesive model and the second approach is a numerical method based on a finite element analysis using a bilinear cohesive model (FEM-CZM approach). The results were expressed in term of fracture load. The length of the developing cohesive zone ahead of the crack tip was deduced at the crack initiation. This critical length size which was normalized with the crack size is taken as a characteristic length for defining the small/large scale yielding conditions of the particular studied case. For the small cohesive zone sizes (small scale yielding conditions), the computed values of the fracture load show a small difference between analytical and numerical approaches. In the other hand for the case of large cohesive zone sizes, the obtained values of the fracture load show significant discrepancy between the two approaches. Voir les détails
Mots clés : Crack, Singular Integral Equation, FEM, cohesive models, scalCrack, scale yielding conditions
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
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)
Surveillance des ventilateurs de dépoussiérage en utilisant les cartes auto-organisées
La disponibilité et le bon fonctionnement des processus et des produits sont parmi les préoccupations majeures dans l’industrie sidérurgique. Au niveau de l’unité de préparation de la matière et agglomération (PMA) du complexe sidérurgique IMETAL El-Hadjar - Annaba, l’évaluation des performances des ventilateurs de dépoussiérage est une tâche extrêmement importante pour assurer leur sûreté et leur fiabilité. Il est donc indispensable de mettre en œuvre des méthodes fiables de contrôle et de surveillance afin de détecter de façon précise l’apparition de signe de défaillance. Dans ce travail, nous proposons l’utilisation de la carte auto-organisée (SOM) (en anglais. Self-Organizing Map) pour évaluer le ventilateur de dépoussiérage sur la base de calcul des indices de détection performants. Chaque indice est évalué par l’analyse de son changement et de sa variation par rapport à l’état sain. Les différents résultats obtenus montrent que l’approche proposée donne une évaluation globale et améliore considérablement la performance des indices calculés utilisés pour l’évaluation du ventilateur. Voir les détails
Mots clés : Carte auto-organisée (SOM), Indice de détection, surveillance, Industrie sidérurgique, Ventilateur de dépoussiérage
caractérisation du kaolin (DD1) conçu pour l'élaboration des briques réfractaires
Résumé :L’objectif de ce travail est d’étudier le comportement thermomécanique d’un réfractaire élaboré à différentes : analyse chimique classique et analyse par la fluorescence RX, révèlent que notre partir d’un kaolin local. Nous avons commencé par la caractérisation de la matière première utilisée kaolin (DD1) de Djebel Debbagh-Guelma. Les résultats de la caractérisation chimique par deux méthodes échantillon a une grande teneur en Al2o3- Sio2 par rapport aux autres oxydes. L’analyse granulométrique nous a permis de connaitre les différentes tailles des grains (de 32 et sup250µm).La connaissance de la nature et de la cristallinité des phases est un préalable à l'interprétation du comportement de ces produits pendant un traitement thermique l’analyse par la diffraction des rayons X(DRX) est nécessaire. Le dépouillement des spectres de DRX est un peu difficile, car les kaolins bruts contiennent des phases minérales, des matières organique et des impuretés, le spectre représente les phases essentielles qui apparaissent dans notre échantillon qui sont : kaolinite, halloysite, gibbsite, nacrite, magnétite et dickite, la phase majoritaire qui apparais avec une proportion de 58% est la kaolinite. Voir les détails
Mots clés : Kaolin, réfactaire, thermomécanique, caractérisatio, élaboration
EFFECTS OF TOLUENE-METHANOL MIXTURE ON MECHANICAL AND STRUCTURAL PROPERTIES OF HDPE PIPE
The aging of pipes is an economic and technical challenge for drinkable water and natural gas networks. The degradation of HDPE pipes depends on factors such as age, laying and service conditions, environmental temperature, fluids and soils corrosiveness, density and traffic loads. In service, polymer structures are often exposed to aggressive environmental stresses such as UV’s, oxygen, acids, bases and solvents, affecting the nature of the material as well as its microstructure, physical status and chemical composition. Various studies have presented results on HDPE pipes embrittlement, focusing on cracking phenomena under environmental stress cracking, creeping and fatigue cracking. The weakening of the material usually resulted from mechanical behavior modifications which made it unable to withstand loads without breaking under normal service conditions. In this study, we attempted to assess the effects of an equimolar toluene-methanol mixture while considering exposure to air and water as references. Morphological properties such as crystallinity, crystalline lamellae thickness and the oxidation induction time (OIT) are studied using differential scanning calorimetry in order to establish the extent of degradation using DSC. Mechanical tests and thermal analysis show that toluene-methanol mixture is much more absorbed by the resin compared to water, i.e. the degradation is very pronounced. In terms of mechanical properties (E, σy and εf), the nominal values collapsed. In addition, the study shows the evolution of these parameters as a function of pipe thickness in order to get an idea about structural heterogeneity across pipe wall. An increase in the crystallinity together with crystalline lamellae thickness is observed which is confirmed by literature for other organic solutions. This phenomenon is known as chemical-crystallization due to the shrinkage of the amorphous phase during possible chain segmentation process. Voir les détails
Mots clés : HDPE; Environmental effect; Aging; Mechanical properties; Crystallinity; OIT