Sciences des matériaux
The effect of successive repairs on the weldment quality of API 5L X-70 pipeline steel H.S.L.A
The effect of successive repairs on the weldment quality of API 5L X-70 pipeline steel H.S.L.A Voir les détails
Mots clés : welding, Heat affected zone, Thermal cycles, DRX, HSLA
Mechanical properties and characterization of metallic bond coat used in hardfacing of petroleum drill bits
Tungsten carbides are widely used as weld hardfacing deposits in petroleum drill bits. To assure proper bonding of the hardfacing to the substrate, several choices of bond coating layers are offered. In this study, tow different commercial powders A and B and mixtures of both them were thermal sprayed onto a carbon steel XC18 substrate used in petroleum drill bits. The micro hardness respectively, of the hardfacing surface and bond coating layers was measured. The microstructure was observed by optical microscopy and field emission scanning electron microscope equipped with energy-dispersive X-ray spectrometry. It has been observed that the mixture of 75% of A and 25% of B produces an uniform coating metallurgically bonded to the substrate with a little heat affected zone and a little amount of porosity. Voir les détails
Mots clés : Thermal spray coating, drill bit, Bond coat layer, weld hardfacing, adhesion.
Microstructural and mechanical characterization of dissimilar weldedjoint between 2205 duplex stainless steel and API X52 HSLA steel
In this work we study the evolution of the microstructure and phase transformations along the welded joint and the mechanical properties of dissimilar metals weld between duplex stainless steel and HSLA steel. Welds are produced by shielded metal arc welding (SMAW) using a duplex grade filler metal (E2209). The welds obtained in this study, have good mechanical properties, despite the appearance of a hard zone at the interface between the weld metal and the heat affected zone of the HSLA steel Voir les détails
Mots clés : duplex stainless steel, API 5L X52, Dissimilar welding, Heat affected zone
Finite element modeling and analysis of electromagnetic field distribution for different shapes of metallic materials
In aeronautical industry, diversity of used materials, dimensions and complexity of the parts require a specific treatment in order to fulfilling the requirements of safety and reliability.In this paper, electromagnetic problem modeling is developed in order to realize a data-processing application able to calculate electromagnetic field distribution in different mediums especially those used in aeronautics.The finite element method is successfully applied since it adapts for any selected section. The numerical results enable to determinate the field values in any point of the chosen geometry and to determine thereafter the system parameters as well as the distribution of energy. Geometry dimensions, material properties and used frequency influence on results. And for the special cases these results are compared with those given by FEMLAB code. The results are very similar with a good precision which enables usage of the developed code to carry out simulations for other geometries of materials with different proprieties. Voir les détails
Mots clés : Electromagnetic interaction, Maxwell's equations, aeronautical materials, Finite Element Method, field distributions, FEMLAB
Etude ab initio des propriétés Structurales, Magnétique etStabilité du système Fe2(Zr,Nb) dans les trois phases de Laves:C14 C15 et C36.
The pseudopotential method (PP) Based on Density Functional Theory (DFT), using theGeneralized Gradient Approximation (GGA) was applied to investigate the Fe2(Zr,Nb)system within the three Laves phases structures: Cubic C15, Hexagonal C14 and C36. Theeffects of Nb concentration on structural, magnetic and stability of the system were studied.The lattice parameters, bulk modulus and magnetic moments of the three phases werepredicted and showed a significant dependence on Nb concentration. We evidenced therigidity of the Fe2Nb was higher than the Fe2Zr one for C15, C14 and C36. The energeticphase diagram of the systems was also established by determining the heat formation and thestability of the alloys was discussed accordingly. The obtained results showed that the Lavesphase have close formation energies which suggests that the C15, C14 and C36 phases canco-exist at low-temperature. In addition, the magnetic behavior was also established and themagnetic moments were found to be on Fe atoms. Consequently, these alloys were predictedto be ferromagnetic for all phases. The obtained results were in good agreement with availabletheoretical and experimental ones. Voir les détails
Mots clés : Laves Phases, Pseudopotential Method, DFT, Heat of Formation, Stability
Etude Microstructurale de l’Alliage nanostructuré (Fe65Co35)70Al30 obtenu par mécanosynthése
Des poudres nanostructurés de l’alliage (Fe65Co35)70Al30 sont obtenues par un broyeur à haute énergie sous une atmosphère d’argon. Des variations morphologiques et microstructurale au cours du broyage sont observées par microscopie électronique à balayage (MEB) et par diffraction des rayons X (DRX). La réduction de la taille des cristallites (16–7 nm) est accompagnée par une augmentation des microdéformations du réseau. Une phase ternaire est obtenue après 8 heures de broyage. Voir les détails
Mots clés : Poudres Fe-Co, alliage nanostructuré, Mécanosynthèse, Diffraction des rayons X
Elaboration et caractérisation d'un multimatériau WC-W-Ni obtenu par infiltration: Effet du nickel sur la consolidation du W
En pratique, l’infiltration spontanée de mélanges de poudres libres sous gravité est la plus adéquate à la réalisation des outils de forage. Les pores interconnectés des poudres libres (non compactées) sont remplis avec un métal ou alliage ayant un bas point de fusion. L’attraction capillaire constitue la force motrice de l’infiltration causant la réduction de l’énergie surfacique interfaciale. Le liquide recouvre la phase solide des poudres de la matrice. Les propriétés du consolidé final dépendent étroitement de la composition du mélange de poudres et de sa réactivité avec le liant infiltrant au cours du cycle de frittage imposé. Nous nous intéressons dans cette étude, pour mieux comprendre les phénomènes qui peuvent se manifester dans le multiconstituant WC-W-Ni (matrice d’outil de forage), àl’élaboration et à la caractérisation du consolidé W-Ni en mettanten évidence l’effet du nickel sur la consolidation de W. Voir les détails
Mots clés : Consolidation, frittage, infiltration, poudres libres, PDC
Dynamic mechanical analysis of hybrid composite laminate reinforced with glass/carbon fiber
Composite materials possess the characteristics of high stiffness and high fatigue strength, which are desirable for advanced aircraft components. However, the mechanical behavior of such materials depends upon a variety of factors such as fiber volume fraction, percentage of voids, lay-up order and reinforcement type, the effects of which are difficult to establish individually. As the damage initiates in composite materials and grows during static and cyclic loading, material properties such as modulus, residual strength and strain would vary and, in many cases, they may be significantly reduced because of the progressive accumulation of cracks and delaminations. The objective of the current study was to gain a better understanding of mechanical and dynamic mechanical properties of hybrid composite laminate reinforced with glass woven fabric, carbon woven fabric and epoxy matrix, manufactured using vacuum assisted resin molding process. Quasi-static flexural and dynamic mechanical analysis (DMA) tests were conducted on hybrid composites samples prepared according to ASTM standards. Responses of carbon/epoxy and glass/epoxy laminates were also investigated to compare with that of hybrid samples as a function of fiber content. The storage modulus (E’) was found to decrease with temperature in all cases at an oscillating frequency of 1 Hz, and hybrid composite had showed better values of E’ at glass transition temperature (Tg=96°C). Microscopic examinations indicated that flexural failure was mainly due to matrix cracking, shear failure of fiber/matrix interface and delamination. Voir les détails
Mots clés : Composite laminate, hybridation effect, glass transition temperature, dynamic mechanical analysis (DMA)
simulation et étude de la corrosion de la ZATM du procédé FSW d’alliage d’Aluminium 6082 T651
Ce travail est un plus à l'étude de la soudabilité de l'aluminium par le procédé FSW. Il présente les microstructures obtenues après la simulation de la zone affecté thermo mécaniquement de la soudure dans un équipement de simulation spécifique. Des observations métallographiques et des mesures de microduretés sont employées comme techniques de caractérisation et ainsi des essais de corrosion. Voir les détails
Mots clés : FSW, ZATM, AA 6082 T651, corrosion
Mechanical Properties of Fumed Silica/Epoxy Nanocomposite
The addition of nanoparticles has proven to exhibit a high potential for significantly improving mechanical properties of polymers. This paper aims at the manufacturing and characterization of nanocomposites based on epoxy resin modified with fumed silica nanoparticles. The particles were dispersed into epoxy resin with mechanical mixing and ultrasonic instrument which gave a very well-dispersed phase of nanosilica particles. The resulting degree of dispersion and the interfacial adhesion were investigated by scanning electronic microscopy SEM. Such fumed silica was suspended in an epoxy resin and their rheological properties were measured. Uniaxial Tensile tests under quasi-static and impact conditions performed to evaluate some mechanical characteristics (stress-strain curves, Young’s modulus, yield stress, strain at rupture) of the nanocomposite. Voir les détails
Mots clés : Epoxy, fumed silica, nanocomposite, dispersion of nanoparticles.