Génie mécanique
FRACTURE BEHAVIOR AND MECHANICAL CHARACTERIZATION OF A COMPOSITE ORTHOPEDIC USE IN THE TWO DIRECTION OF FLOW MOLDING
A standard tensile test was carried out on prismatic specimens of glass-perlon reinforced acrylic resin laminate composite material of orthopedic use, developed by the National Office Equipments and Accessories for People with Disabilities, ONAAPH Annaba (Algeria). The measurement results of the Young's modulus and the fracture strength show a large scatter characteristic of these materials and are influenced by the cutting direction of the samples compared to the direction of molding. The use of the probabilistic two parameters Weibull's model made it possible to characterize brittleness and the fracture behavior of these materials and quantitatively to describe the probabilistic aspect of the latter. A report of the principal mechanisms responsible of the fracture is drawed up according to microscopic observations of the fracture topographies of the broken samples.weibull, glass, perlon,acrylic, orthopedic. Voir les détails
Mots clés : Weibull, glass, perlon, acrylic, orthopedic
Étude numérique de l’influence des mélanges gazeux dans un four de réchauffage
Ce travail s’inscrit dans le cadre d’une étude visant l’optimisation des paramètres de fonctionnement des brûleurs industriels à flamme de diffusion. L’exemple développé ici s’intéresse particulièrement à l’étude de l’effet des mélanges gazeux sur les caractéristiques dynamique et thermique de l’écoulement ainsi que leurs impacts sur la stabilité de la flamme et la composition du mélange. L’étude est menée sur un brûleur industriel à gaz de 250kilowatt. Les simulations numériques sont effectuées à l’aide du code de calcul FLUENT, en utilisant le modèle de turbulence k-ε standard couplé au modèle de combustion turbulente ED (Eddy Dissipation).les résultats obtenus pour un combustible considéré un mélange méthane-hydrogène. La proportion volumique d’hydrogène varie de 0 à 100%, montrent que la structure de l’écoulement et la forme de la flamme dans la chambre de combustion dépendent de la composition du combustible. Voir les détails
Mots clés : Brûleur industriel, mélanges gazeux, Simulation numérique, Modèle κ −ε Standard, Combustion Turbulente
Effect of powder addition and welding process on microstructure and mechanical properties of Ferritic Stainless Steel welds
Ferritic stainless steels are classified as such because the predominant metallurgical phase present is ferrite. These steels are characterized by good resistance to stress corrosion cracking (SCC), pitting corrosion, crevice corrosion (particularly in chloride environments), higher thermal conductivity, low coefficient of heat dilation and lower cost, when compared to austenitic stainless steels. The combination of low cost and good properties has made ferritic stainless steel more and more attractive in various application fields, such as, heat exchangers, petroleum refining equipment, storage vessels, protection tubes, solar water heaters, and exhaust manifold applications.However, ferritic stainless steel steels are associated with many problems during the welding process. These problems are the martensite formation and grain growth, causing a reduction of ductility and toughness. For these reasons, until recently, the application of this group steels is limited in welded structures. The aim of the present study is to investigate the influence of the Ti and Al on the microstructure and mechanical properties of AISI 430 ferritic stainless steel welds produced by GTA welding. The details of tensile tests, optical microscopic observations, microhardness, and Scanning electron microscopy (SEM) fractography, are discussed. Voir les détails
Mots clés : GTA welding, ferritic stainless steel, powder addition, welding process, microstructure, mechanical properties, fracture surface
Microstructure and mechanical behavior of TIG bimetallic joints
Bimetallic weld techniques have progressed a great deal in the last decade. In this work, the effect of the filler metal composition on microstructure and mechanical behavior of dissimilar HSLA-X70/304L stainless steels weld joint is investigated. The dissimilar weld joints are fabricated using austenitic, duplex and low Carbone filler metal. The mechanical behavior is investigated through microhardness, charpy impact and tensile test.The results show that, the weld metal composition has a great influence on mechanical properties and microstructure of weldments, in particular the grain size and phases nature, changes with filler metal composition. In addition presence of martensitic slats in the FZ when using the low Carbone filler metal, detailed microstructure examination is carried out and related to the mechanical behavior of the dissimilar joints. Voir les détails
Mots clés : TIG welding, Bimetallic weld, HSLA, DSS, HAZ, microstructure, Microhardness
Study of the evolution of the mechanical properties of the steel pipe coatings in controlled environments
In this study, the experimental results are present the evolution of mechanical properties according to some aggressive environments with a coating of high-density polyethylene, steel pipe used for transporting hydrocarbons. The standard specimens tested in dumbbell shaped were prepared according to ISO 527. The mechanical properties are measured in traction using a computer-driven testing machine. The environments have shown that they have a real influence on the behavior of specimens subjected to uniform traction. The results are discussed in terms of curves (σ, ε). The tensile strength is generally between the values 19.5 and 25.5 MPa, this property comes after the total stretch of the specimen where it has been under severe strain that strongly influence the original structure of the material. In the synthetic oil, the elastic modulus is reduced by 42% and the yield strength collapsed completely in the case of 50% of the crude oil. Voir les détails
Mots clés : Pipe, agressive environnement, polyethylene, mechanical properties, degradation.
ETUDE DU COMPORTEMENT CINEMATIQUE DES MACHINES A 5 AXES
Les surfaces complexes peuvent être trouvées dans de nombreuses applications industrielles telles que les pièces d’automobile, les coques de bateaux ou les pièces d’aérospatial. L’usinage de telles surfaces nécessite une machine à 5 axes.Vu le compromis entre la variété des configurations cinématiques de ces machines et le large domaine d’usinage des surfaces complexes existe un problème majeur qui est l’orientation d’outil pour le suivi sans contrainte du chemin non linéaire d’outil, parmi ces contraintes en site : l’interférence, et la collusion. L’objectif de cette travail est de corrigé le comportement d’orientation relatif entre pièce /outil pour les machines à 5 axes et ceci par l’analyse approfondie des différentes cinématiques des MO 5axes, par l’application des algorithmes de génération du chemin d’outil en position (CL) et en contact (CC). Voir les détails
Mots clés : Usinage des surfaces complexes, les machines à 5 axes, orientation d’outil, interférence et collusion.
Numerical study of thermal Effects in the hydrodynamic Behavior of textured journal bearings
The journals bearing characteristics with texture presence on the bearing surface are investigated. The thermaleffect has been studied. The used numerical approach in this analysis is Finite Difference Method. The textured bearingperformance enhancement passes essentially by a minimum film thickness and a friction torque improvement through anappropriate surface texture geometry and right texture distribution on the bearing surface. It is found that the simulationresults are in good concordance with those issued from the litterature. The obtained results by considering thetemperature effect are more realistic. Voir les détails
Mots clés : Hydrodynamic lubrication, journal bearing, texturation, dimple
Surface texturing effect comparative analysis in the hydrodynamic journal bearings
The journal bearing is a complex system with high film convergence and with cavitation hydrodynamicphenomena. The surface texturation influence study on journal bearing performances requiresunavoidably experimental investigations followed by a numerical modelling of the problem. This work consistsin modellization and understanding of the journal bearing characteristics in both cases of presence orabsence of textures onto the bearing surface. The finite difference method is used as numerical approachin the analysis. The textured bearing performance enhancement passes essentially by an improvement of aminimum film thickness, a maximum pressure and a friction torque through an appropriate surface texturegeometry and appropriate texture distribution on the contact surface. It is found that the simulationsresults are in good concordance with litteratures. The texture area position on the bearing surface is theprimary endpoint for journal bearing performance enhancement. The best design of textured area dependsstrongly on the geometrical parameters and the journal bearing operating conditions. Voir les détails
Mots clés : Journal bearings, Reynolds equation, Hydrodynamic lubrication, Stribeck curve, texture
Damage modelling in thermoplastic composites reinforced with natural fibres under compressive loading
In this work, the compression failure of thermoplastic composites made of jute/polypropylene is investigatedby experimental and numerical studies. Two laminate specimen’s lengths with different fibre orientations have been considered to analyse this composite type response to a compressive solicitation. The applied numerical model permits to understand the mechanisms of damage and evolution in the laminate.The interlayer damage (delamination) and the intra-layer damage (matrix cracking) have been modelled bythe combined use of the Cohesive Zones model (CZM) and the Matzenmiller, Lubliner and Taylor (MLT)mechanical model. It was found that the loading conditions of laminates and the fibres orientation affect the compression failure load of the thermoplastic composites. Voir les détails
Mots clés : Jute/polypropylene, mechanical behaviour, damage, laminates, modelling
A numerical investigation of both thermal and texturing surface effects on the journal bearings static characteristics
Journal bearing characteristics modellization has been investigated in this paper for both cases of texture presence or absence onto the bearing surface. The thermal effect has been studied. The used numerical approach in this analysis is finite difference method. The textured bearing performance enhancement passes essentially by a minimum film thickness and a friction torque improvement through an appropriate surface texture geometry and right texture distribution on the bearing surface. It is found that the simulations results are in good concordance with those issued from the literature. The obtained results by considering the temperature effect are more realistic. Voir les détails
Mots clés : Journal bearings, Reynolds equation, Hydrodynamic lubrication, Stribeck curve, texture