Génie mécanique

Nombre total de résultats : 207
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M. BENTTOUMI  (2020)
Mémoire de Master

Aluminum has very low mechanical properties. To significantly increase them, we actedon three main modifying factors of the microstructure. Addition to aluminum of a very lowdensity element including 13% silicon which facilitates the flowability of the metal, gravitysand molding and structural hardening treatments.Al-Si alloys are highly indicated by their lightness, their high tensile and corrosionresistance. The study focuses on the influence of maturation on the evolution of the elasticproperties determined by the tensile and ultrasound tests of the Al-13% mass eutectic alloy. Iffor six states: raw casting noted - F and maturation in 6h steps noted - M0h, M6h, M12h,M18h and M24h. The parts produced from this alloy are part of the components used invarious projects by SNVI Rouïba and Electro-Industries de Fréha (covers, pump casing,motor pistons, etc.).All the results of the mechanical and structural properties gathered in Part III of our thesisshow us that we should recommend for the molding of parts whatever the series: the grossreference state designated - F. Voir les détails

Mots clés : Al-Si, sand, ripening, mechanical properties

Effet des traitements thermiques sur le comportement microstructural et mécanique de l’acier inoxydable Lean duplex 2101 lors du vieillissement

R. Bourahla, A. Labadlia  (2019)
Mémoire de Master

As part of this project of memory we propose by this work a study on the microstructural and mechanical behavior of a stainless steel Lean Duplex LDSS 2101 during heat treatments realized in two stages: a treatment of dissolution at a temperature of 1050 ° C for one hour then water quenching, followed by an aging treatment at 720 ° C at different holding times (T = 10min, 60min, 10h, 24h, 120h, 240h) followed by quenching to water.The different samples are metallurgically characterized by optical microscopy and scanning electron microscopy (SEM). XRD analysis was used to identify the phases and precipitates formed during the treatments. Thermal treatments have significantly affected the phase equilibrium of stainless steel, caused by nitrides and carbides precipitation phenomena.Micromechanical characterization was performed by nano-indentation tests for the measurement of hardness and Young's modulus for each phase for the different samples. Voir les détails

Mots clés : stainless steel Lean Duplex LDSS 2101

Influence de l’énergie de soudage sur la microstructure et la résistance à la corrosion de l’acier inoxydable Lean duplex UNS S32101

Mémoire de Master

Duplex stainless steels are widely used in industry, because their two-phase structure with equivalent fractions in austenite and ferrite gives them very interesting mechanical properties and high resistance to different types of corrosion. However, the use of these steels is limited by their sensitivity to the formation of hazardous intermetallic phases with adverse effects on hardness and corrosion resistance. It is a weakening of the material that is visible under certain welding conditions. The subject deals with the study of a welding process applied Lean duplex stainless steel, LDX 2101 to a nickel-reduced stainless steel and aims to show the influence of the experimental parameters (03 energies) on the microstructural and stress corrosion resistance properties ( CSC) of the weld joint Voir les détails

Mots clés : Lean duplex stainless steel, LDX 2101, welding energy, stress corrosion cracking (SCC)

Optimization of the number of layers for a fixed thickness of a composite material subjected to compression loading

D. ZELMATI, O. GHELLOUDJ, R. Graine, N. Sehab, F. Sehab, W. RICHI  (2020)
Article de conférence

In this paper, the effect of varying the number of layers for a fixed total thickness is investigated. In order to conserve the integrity and the safety of a multilayers composite structure, the search of the optimal number of layers in the cross section, induced the low stress-strain field intensity, is strongly recommended. Meanwhile, this study aims to show how the mechanical response of a multilayers composite plate loaded on a compression in the axial direction, changes when the number of layers increases from for a fixed total thickness. Voir les détails

Mots clés : security factor, stress-strain field, Composite material, Compression loading


Zitouni Abdelhalim (2020)
Thèse de doctorat

Ce travail de thèse a pour objectif d’étudier le comportement thermohydraulique du bain fondu lors du soudage à l’arc électrique. Cette étude a été menée dans le but de concevoir un modèle mathématique et de développer un programme FORTRAN qui permet de résoudre les équations gouvernant le bain de fusion pendant le soudage. Les résultats issus de ce programme peuvent contribuer à la prédiction de la distribution de température pendant le soudage, l’élargissement de la ZAT, le champ de vitesse ainsi que la forme et la taille du bain de fusion. En modélisation mathématique du soudage, l’apport d’énergie modélisé par une source de chaleur surfacique donne de bons résultats lorsque l’épaisseur des pièces à souder est faible. Dans la simulation numérique du comportement thermique du bain de fusion par les méthodes des différences finies et éléments finis, les cycles thermiques calculés par la méthode des éléments finis sont plus proches de ceux mesurés pendant la période de refroidissement. Le modèle du comportement thermohydraulique du bain de fusion basé sur la formulation courant-tourbillon des équations de Navier – Stokes nous a permis de les simplifier par l'élimination de l’équation de la conservation de masse et de champ de pression. Les résultats du calcul montrent que la force de tension superficielle domine les forces motrices dans le bain de fusion et favorise un bain de fusion mouillant. Les résultats du calcul concernent le champ de température, les cycles thermiques, le champ de vitesse et la taille du bain de fusion sont en bon accord avec ceux rapportés dans la littérature. Voir les détails

Mots clés : Modélisation thermohydraulique, soudage TIG, formulation courant tourbillon, simulation numérique

Analytical Modeling of the Behavior of Composite Structure Subjected to Combined Tensile and Moment Loading

D. ZELMATI, R. Graine, O. Guelloudj, N. Sehab and F. Sehab  (2020)
Article de conférence

The present work is a contribution in assessment of the security factor of the structures made from composites materials in order to work within safe conditions. In the first step, a Matlab code is developed in order to develop a mechanical model able to predict the mechanical behavior of the high performance composite material without necessity to the expensive experimental test. In the second step, an analytical modeling is performed for the composite structure subjected to a tensile load in the longitudinal direction and a moment in the transversal direction in order to assess the strain and the stress fields in all layers of the composite material and evaluate the security factor in all plies. Meanwhile, the new mechanical model can be used as a tool decision in design and maintenance in order to check the integrity of the composite structure. Voir les détails

Mots clés : composite, laminate, integrity, security factor, moment loading

Droplet Breakup Regime in a Cross-Junction Device with Lateral Obstacles

Tawfiq Chekifi  (2019)

Numerical simulation using Ansys Fluent code is performed, to investigate droplet generation in cross-junction based VOF method. Droplets of water are generated by the shear stress applied by continuous phase (oil), two configurations of cross-junction are suggested; the first is a simple model no modification is performed at the outer channel, while the second model is characterized by a lateral obstacle. we study the effect of velocity ratio, viscous parameter, interfacial tension, flow condition on droplet size and frequency, the effect of lateral obstacles on droplets generation is also focused and analysed. The numerical simulations showed that the velocity ratio and interfacial tension play a significant role in determining the droplet breakup and non-breakup. On the other side, the increase of flow rate ratio can be effectively used to decrease the droplet size. In addition, droplets produced in cross-junction with lateral obstacles are generally found to be larger than that produced with the first model. Moreover, the frequency of droplet production was increasing by increasing of flow rate ratio. The numerical results show very good agreements with previous numerical and experimental works for the growth of droplet breakup, size and frequency. Voir les détails

Mots clés : Water droplet, cross-junction, CFD, VOF, microchannel.

Effect of heat treatment on surface hardness and tribologicalbehavior of XC38 steel—approach by the experiments plans

Bourebia Mounira (2019)
Thèse de doctorat

This work aims at predicting the micro-hardness of XC38steel using the experiments plans as well asstudy of tribological behavior of thissteel. The heat treatments were considered by adopting thefactorial plans 22 methodology at two factors (temperature ‘T’ and holding time ‘t’), each at two levels(-1, +1). The results obtained allowed lead to a mathematical model predicting the micro-hardness‘Hv’ in every point of the study field. Moreover, the curves of the responses surfaces clearly show theinfluence of two factors studied (T, t) on ‘Hv’. Mechanical characterization of treated samples showedasignificant increase in the micro-hardness, which achieve to 76% for the treated sample at 850 °Cduring 2 h compared to untreated state. An investigation of wear tracks morphology shows thatfriction under a load of 10 N results in predominant adhesive wear, while a load of 2 N favorabrasive wear. Voir les détails

Mots clés : heat treatment, factorial plans, prediction, superficial hardness, tribological behavior

Thermo-physico-chemical and statistical mechanical properties of Washingtonian filifera new lignocellulosic fiber. Engineering Solid Mechanics

Djamel Edinne Gaagaiaa, Mustapha Bouakba, Abdelheq Layachi  (2019)

In this work, novel cellulosic fibers are extracted from Washingtonia Filifera (WF) plant using an environment-friendly technique. Morphological, Physico-chemical, thermal and mechanical properties are reported in this paper. Micro graphical SEM shows the presence of cells in the fiber.FTIR and XRD experimental analyzes show a cristinality index of 48.88%, and the WF fibers are found to be thermally stable until 201°C by using TGA and DTG thermographic analyzes with an appropriate activation energy of 72.46 kJ/mol, where Young modulus and tensile strength of strain were determined using tensile tests of single fiber at 2.17 GPa, 134 MPa and 26.55%, respectively. Mechanical properties are analyzed using a statistical method. Voir les détails

Mots clés : WF fibers, mechanical properties, FTIR, XRD, TGA, Statistical methods

Numerical study of parameters affecting pressure drop of power-law fluid in horizontal annulus for laminar and turbulent flow

Hicham Ferroudji, Ahmed Hadjadj, Ahmed HADDAD, Titus Ntow Ofei  (2019)

Efficient hydraulics program of oil and gas wells has a crucial role for the optimization of drilling process. In the presentpaper, a numerical study of power-law fluid flow through concentric (E = 0.0) and eccentric annulus (E = 0.3, E = 0.6 andE = 0.9) was performed for both laminar and turbulent flow regimes utilizing a finite volume method. The effects of innerpipe rotation, flow behavior index and diameter ratio on the pressure drop were studied; furthermore, the appearance anddevelopment of secondary flow as well as its impact on the pressure drop gradient were evaluated. Results indicated thatthe increment of the inner pipe rotation from 0 to 400 rpm is found to decrease pressure drop gradient for laminar flow inconcentric annulus while a negligible effect is observed for turbulent flow. The beginning of secondary flow formation in thewide region part of the eccentric annulus (E = 0.6) induces an increase of 9% and a slight increase in pressure drop gradientfor laminar and turbulent flow, respectively. On the other hand, the variation of the flow behavior index and diameter ratiofrom low to high values caused a dramatic increase in the pressure drop. Streamlines in the annulus showed that the secondary flow is mainly induced by eccentricity of the inner pipe where both high values of diameter ratio and low values of flowbehavior index tend to prevent the secondary flow to appear. Voir les détails

Mots clés : Computational fluid dynamics (CFD) · Power-law fluid · Pressure drop · Secondary flow