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Nombre total de résultats : 1831
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A Simple Efficient Finite Element for the Sandwich Plates Analysis

K. BELKAID, B. BOUBIR, N. BOUTASSETA, H. Aouaichia, N. Fergani, D. GAAGAIA  (2019)
Article de conférence

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

Effect of cold rolling on the recrystallization of 904L austenitic stainless steel

Lyacine RABAHI, Brahim MEHDI, Idir HADJI, Riad BADJI, Nabil KHERROUBA  (2019)
Article de conférence

The aim of this work is to study the recrystallization in the 904L austenitic stainless steel, which underwent a cold rolling with two different deformation amounts (50 and 90%). DSC tests have been conducted to determine the temperature range of the recrystallization. It was found that reducing the deformation amount slightly delays the recrystallization. The microstructure of the as-received alloy consists of austenitic grains recognized by the twins they contain. The deformation induced a corrugated microstructure with the presence of ribs. The XRD analysis confirmed that only γ phase peaks were present in the as-received alloy and showed that the deformation induced the extinction of γ phase peaks and the apparition of α phase peaks. Voir les détails

Mots clés : recrystallization, 904L, Cold rolling, DSC

Tomographic Image Reconstruction in the Case of Limited Number of X-Ray Projections Using Sinogram Inpainting

a.allag, a.benammar, R.Drai, T.BOUTKEDJIRT  (2019)
Publication

In many medicine and industry applications, a precise X-ray tomography reconstruction of the internal objects structure is of great importance for reliable interpretation data. The tomography allows obtaining a spatial distribution of the internal materials structure. In certain experiments conditions, the projection data acquisition is guided by angle limitations or a restricted angle, this requires a subsampling of the projections number or a partial data absence. Accordingly, the reconstructed images may suffer from severe artefacts especially with the presence of noise. In this context, the purpose of this paper is to propose a tomographic image reconstruction method based on FBP associated to sinogram inpainting. The studied inpainting technique is based on first order variational methods such as the Chambolle-Pock algorithm. This method allows the quality improvement of the reconstruction images tomographic with reduced number of projection. The PSNR is improved by 7 to 10 dB in the reconstructed image compared to the classical FBP reconstruction. Voir les détails

Mots clés : x-ray tomographic, image reconstruction

Investigation of the Effect of Aluminum Alloy Position on ResidualStresses in Dissimilar fsw Weld by Using the Ultrasonic Method

I.Hadji, R.Badji, M.Gaceb, N.Kherrouba, L.Rabahi  (2019)
Publication

The main goal of this study is to show the effect of the advancing side (AD) and theretreating side (RT) position on the Residual stresses and local mechanical behaviour ofdissimilar friction stir welds of aluminum alloys AA2024-T3 and AA7075-T6. Different sampleswere produced by varying the rotational speed of the tool (1200 and 1400 rpm) and the alloyposition regarding the advancing side of the tool. Ultrasonic Method has been used to evaluateResidual Stresses. This method is based on the acoustoelastic effect, which measures the velocityvariation of the elastic waves according to the stress state of the material. This can be achievedthrough a calibration test, which permits the determination of the acoustoelastic coefficient (K).The results show a tensile stress in the Nugget (N), the heat affected zone (HAZ) and acompression stress in the base metal (BM). Increasing the rotational speed reduces the amplitudeof the longitudinal residual stresses with a high reduction in the case where AA7075 - T6 is inthe advancing side whit 1400 rpm. This has been directly associated to the increase in the heatinput and the reduction of the thermal mismatch between different areas of the weld. Themicrostructure effect of aluminum alloy position acts on the acoustoelastic constant K. Thechoice of t0 corrects the overestimated residual stresses in the (HAZ) and (N). Voir les détails

Mots clés : FSW, contraintes résiduelles, microstructure, comportement mécanique, corrélation d'image numérique

Modélisation Numérique du comportement à l’endommagement d’un matériau composite

Hassani Mohamed (En préparation)
Thèse de doctorat

In this thesis, we focused on the development of micromechanical model specific to plain woven composite in order to predict their progressive damage , where the law of material behavior is considered as nonlinear elasto-plastic (this depend on tensile test results) . The first part of the work will be conducted to elaborate plain woven composite specimen and perform tensile test. After that micromechanical model would be developed in order to determine the initial effectives elastic modulus from homogenization techniques, of RVE, which can be used to relate between Mico scale and Macro scale. Subsequently, an incremental formulation of the unit cell  method will be considered taking into account the evolution of plasticity and damage. The implementation of investigated approach will be achieved through finite element code and the validation of the model will be considered in the case of a quasi-static loading. Voir les détails

Mots clés : Woven composite, damage, plasticity

Détermination des contraintes lors de l’interactionfluide Conduite avec prise en compte du phénomène de cavitation.

Hassani Mohamed (2012)
Mémoire de magister

A mathematical model has been developed to calculate the transient flow in elastic pipes. This model takes into account the interaction beetwin structure of the pipe and the fluid behavior and the cavitation phenomenon. When the liquid pressure falls below the vapour pressure, a bubbly cavitation occurs and grows in different location of the pipeline. This cavitation can produce sever damage to structure .the application of mass,momentum and energy conservation laws yields to a system of hyperbolic partial differential equations resolved by a MOC with finite differences scheme. The model is tested with experimental data. Voir les détails

Mots clés : Water hammer, transient flow, Cavitation

VISCOELASTIC EFFECTS IN ELASTIC MODULUS MEASUREMENT USING DEPTH-SENSING INDENTATION

A. Mokhtari, N.Tala-ighil, A. Brick Chaouche, Y. A. MASMOUDI  (2019)
Article de conférence

The nanoindentation test is used to determine the viscoelastic parameters of a thermoplastic polymer at ambient temperature. The aim of the study is to obtain a mean representative value taking into account the influence of the viscosity on the elastic modulus of the poypropylene. For that, Berkovich indenter has been chosen and applied load equal to 100mN. We used poypropylene as a prototype of viscoplastic material, having a creep more important than the others thermoplastic polymers. It was found that, during nanoindentation, the Young's modulus estimated by the Oliver-Pharr method is several times higher than that which is suitable. The Pile-up and viscoelasticity are usually at the cause of this failure and an analysis of their influences is attempted in this work. The loading and unloading curve obtained from FE simulation results by the nanoindentation test is then undertaken to complete the work. The various results have enabled to analyze the influence of viscosity on the elastic modulus of the polypropylene matrix. Voir les détails

Mots clés : thermoplastic polymer, Nanoindentation, constitutive behaviour, Finite Elements

Comportement à l'usure des boulets de broyage moulés et forgés Caractérisation et comparaison

K. BOUHAMLA, A. HADJI, A. GHARBI, O. GHELLOUDJ, H. MAOUCHE, F.Z. DERRADJI, S. REMILI  (2019)
Article de conférence

Les secteurs miniers sidérurgiques et cimentiers utilisent de grandes installations pour préparer la matière première et la rendre aussi fine que possible pour répondre à des exigences de process bien définies. Généralement deux types de boulets sont utilisés, les boulets de fonderie et les boulets forgés. Les boulets de fonderie sont en fonte au chrome par contre les boulets forgés sont en acier. Ces derniers sont fournis en différentes granulométrie et composition chimique. En cours de broyage, les boulets subissent des sollicitations différentes qui se résument en un impact une abrasion une friction ainsi que d’autres types d’usure. La tenue à l’usure de ces deux types de boulets est différente du fait qu’ils ne présentent pas le même type de microstructure. Les boulets en fonte au chrome sont constitués d’une microstructure mixte composée d’un réseau de carbure contenu dans une matrice à prédominance martensitique par contre les boulets en acier, la phase carbure existe en proportion très minime. La microstructure est constituée d’un mélange de martensite et bainite.Dans ce travail, nous présentons une étude comparative sur le comportement à l’usure les boulets en fonte au chrome et les boulets en acier forgé. Des caractérisations chimique, métallographique et microstructurales par DRX sont effectuées pour définir la composition chimique, le type de microstructure, la nature et la proportion des phases microstructurales existantes. Des mesures de dureté et des essais d’abrasion et de frottement sont aussi réalisés afin d’évaluer le comportement à l’usure des deux matériaux étudiés. Les résultats obtenus révèlent une large différence du point de vue composition chimique et composants microstructuraux. Les essais d’usure ont montré que les boulets en fonte au chrome et les boulets en acier forgé manifestent un comportement à l’usure qui diffère selon le type d’usure subit. Les boulets en fonte au chrome résistent mieux au frottement par contre les boulets forgés ont une meilleure résistance à l’abrasion. Voir les détails

Mots clés : Boulets moulés;, boulets forgés;, microstructure;, usure;

Etude des propriétés mécaniques et électrochimiques d'un multi-matériau  fonctionnel obtenu par  rechargement dur base Ni-Cr-Fe

ALLOU Djilali (En préparation)
Thèse de doctorat

La corrosion et l’usure dans un milieu de refroidissement complexe et agressif étant très compliqué, ce travail a pour objectif, en plus du fait de réaliser deux  bi- matériaux  (25CD4/ Inconel 182) par deux modes de rechargement dur  différent , Shielded Metal Arc Welding (SMAW) et le Tungstène Inerte Gaz (TIG Pulsée), de caractériser l’assemblage sous trois formes différentes : Microstructurale,  Mécaniquement et par des mesures électrochimiques en mettant l’accent sur la protection cathodique et les critère de protection du couplage galvanique 25CD4/Inconel 182. Deux étapes essentielles ont été réalisées, à savoir ; La réalisation des bi-matériaux par rechargement SMAW et TIG Pulsée et la caractérisation mécanique et physico-chimique des composés, particulièrement, l’étude électrochimique en milieu marin (3,5% de NaCl) à la température ambiante en tenant compte de l’un des moyen de protection le plus utilisé dans l’industrie : la protection cathodique. Voir les détails

Mots clés : tig pulsée, inconel182, rechargement, corrosion, Protection cathodique

Corrosion E?ects on the Magnetic Behavior of Magnetic Circuitof an Induction Machine

ALLOU Djilali, KHORCHEF Mohamed, M’hamed Ouadah, Omar TOUHAMI, Rachid IBTIOUEN  (2018)
Publication

In This paper, the e?ect of corrosion on the magnetic behavior of a magnetic material usedas a magnetic circuit in the induction machines is studied. With this objective, the magnetic propertiesof the samples with corrosion and without corrosion were evaluated by the study of hysteresis loopsusing a homemade vibrating sample magnetometer (VSM). The magnetic parameters extracted from thehysteresis loops such as saturation magnetization, coercive, remanent magnetization, squareness ratio,magnetic permeability, and hysteresis area were analyzed. It was shown that more energy is required todemagnetize the sample with corrosion than the sample without corrosion, and the hysteresis loss in thecase of the sample with corrosion is more than the case of the sample without corrosion. These meanthat when the corrosion is presented in the magnetic circuits of the induction machine, the hysteresisloss increases, consequentially reducing the machine e?ciency. Voir les détails

Mots clés : corrosion, magnetic behavior, hysteresis loops