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Nombre total de résultats : 1840
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Conception of a friction stir welding tool

M. AISSANI, S. Gachi, D.H. BASSIR, F. Boubenider, Y. Benkedda  (2008)
Article de conférence

Friction stir welding is a new process that allows a solid-state joining technology of metallic components. Applications and development within this approach has incr eased during the last decade. In this process, the geometry of friction tool plays a fundamental role to obtain suitable microstructures in the weld and the heat affected zones, thus it will be then possible to improve the strength and fatigue resistance of the joint. Among the articles related to the friction process, only few have treated the manufacturing process of the tool. In this work, we will focus on this last point. To increase the welding quality and the process reliability, the design of the tool includes a shaft-spring-based system aimed at avoiding premature damage, furthermore to allow the measure of applied friction pressure. Our improved friction tool has then been tested for applied this welding technique on Al-2024 and Al-7075 aluminium alloys sheets. The weld quality has been evaluated by means of a microstructure analysis and micro-hardness measurements. The ability to increase the welding speed, the changes of the crystalline plans orientation in the mixed part of thermo-mechanically affected zone and grains sizes observed in micrographics underline the effect of the pin geometry and its displacement. The micro-hardness curve shows good mechanical properties. Finally, the obtained results show a su ccessful welding with accep table quality and open new interesting perspectives. Voir les détails

Mots clés : Aluminium, conception, Friction Stir Welding, tool, Micro-hardness

Microstructural Study of Thin Films CuFe Obtained by ThermalEvaporation of Nanostructured Milled Powde

H. Mechri, A. Haddad, M. Zergoug, M. Azzaz  (2017)
Publication

Commercial copper and iron powders were used as starting materials. These powderswere mechanically alloyed to obtain Cu(100-x) Fex supersaturated mixture. The milling duration waschosen in such a way as to obtain a nanostructured mixture and to form a supersaturated solidsolution of CuFe; the powder mixture was used to deposit CuFe on a glass substrate.The elaboration of our films has been carried out using thermal evaporation process (physical vapordeposition) under 1 × 10-6 mbar vacuum from an electrically heated tungsten boat, using thesupersaturated solid solution Cu(100-x) Fex powder obtained by mechanical alloying. The filmsdeposition has been done on glass substrates. In this study, we present the composition effect on thestructural and magnetic proprieties of Cu(100-x) Fex powder and thin films. The chemicalcomposition, structural and magnetic proprieties of milled powders and thin films were examinedby SEM, TEM, XRD, XRF and VSM. Voir les détails

Mots clés : thin film, CuFe Solid Solution, microstructure, DRX, MET, VSM

Caractérisation morphologique et mécanique deu polyéthylène semi cristallin extrudé

LAABED Abdellatif (2012)
Mémoire de magister

La tuyauterie en polyéthylène a haute densité (PEHD) sont utilisés pour la conduite d'eau potable marqué par un trait bleu, et la conduite du gaz naturel de ville marqué par un trait jaune. Le but de cette étude et de caractérisé ces matériaux morphologiquement et surtout mécaniquement, due a un taux de crisallinté remarquable, qui sera quantifié par plusieurs méthodes de caractérisations. cette cristallinité est causé par son historique de fabrication qui est l'extrusion.  Voir les détails

Mots clés : Polymere, PEHD, extrusion, Cristallinité, DSC

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

Hicham Ferroudji, Ahmed Hadjadj, Titus Ntow Ofei, Mohammad Aziz Rahman, Ibrahim Hassan, Ahmed HADDAD  (2019)
Publication

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

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)
Publication

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

Adaptive backstepping control using combined direct and indirect σ-modification adaptation

Y. Soukkou, S. Labiod  (2017)
Publication

In this paper, by using the dynamic surface control technique, an adaptive backstepping controller using combined direct and indirect σ-modification adaptation is proposed for a class of parametric strict-feedback systems. In this approach, a σ-modification parameter adaptation law that combines direct and indirect update laws is proposed. At first, the x-swapping identifier with a gradient-type update law is presented for a class of parametric strict-feedback nonlinear systems. Next, the main steps of the controller design for a class of nonlinear systems in parametric strict-feedback form are described. The closed-loop error dynamics is shown to be globally stable by using the Lyapunov stability approach. Finally, simulation results for a single-link flexible-joint robot manipulator are given to illustrate the tracking performance of the proposed adaptive control scheme. Voir les détails

Mots clés : Backstepping control, direct and indirect adaptive control, adaptive dynamic surface control, Lyapunov stability, flexible joint manipulators

Composite adaptive dynamic surface control of nonlinear systems in parametric strict-feedback form

Y. Soukkou, S. Labiod, M. Tadjine  (2018)
Publication

In this paper, a composite adaptive dynamic surface control scheme is developed for a class of parametric strict-feedback nonlinear systems. The proposed composite adaptation law uses both the surface error and the estimation error to update the parameters. In addition, by using the dynamic surface control technique, the problem of the explosion of complexity in the adaptive backstepping design is avoided. It is proved that the proposed scheme guarantees uniform ultimate boundedness of all signals in the closed-loop system with arbitrary small surface error by adjusting the design parameters. Simulation results demonstrate the effectiveness of the proposed approach for an electrohydraulic actuator system. Voir les détails

Mots clés : Composite adaptation law, direct and indirect adaptive control, dynamic surface control, Lyapunov stability, parametric strict-feedback nonlinear systems

Design of a Voltage Controller for a DC-DC Buck Converter Using Fractional-Order Terminal Sliding Mode Control Strategy

B. Babes, A. Boutaghane, N.Hamouda, M. MEZAACHE  (2019)
Article de conférence

This paper suggests a fractional-order terminal sliding mode control (FO-TSMC) method for the output voltage regulation of a DC-DC buck converter influenced by disturbances, such as the variations of load resistance and input voltage. A this kind of a new fractional-order (FO) dynamic sliding surface is designed to avoid the drawback on integer-order (IO) terminal sliding mode control (IO-TSMC) method and guarantee the converter reach steady-state quickly without chattering even if it undergoes arbitrary random disturbances. The proposed FO-TSMC controller’s performance is compared against to both IO-TSMC and traditional SMC control approaches. Computer simulation results display that the novel FO-TSMC approach results in evenhanded output voltage regulation performance under widely input voltage variations and load changes. Voir les détails

Mots clés : Sliding Mode Control (SMC), terminal sliding mode control (TSMC), fractional-order (FO), DC-DC buck converter

A Robust Adaptive Fuzzy Fast Terminal Synergetic Voltage Control Scheme for DC/DC Buck Converter

B. Babes, A. Boutaghnae, N. Hamouda, M. MEZAACHE, S. Kahla  (2019)
Article de conférence

In this paper, an adaptive fuzzy fast terminal synergetic voltage control scheme for DC/DC buck converter is proposed based on recently developed synergetic theory and a terminal attractor method. The advantages of presented synergetic control include the characteristics of finite time convergence, insensitive to parameters variation and chattering free phenomena. Rendering the design more robust, fuzzy logic systems are used to approximate the unknown parameters in the proposed controller without calling upon usual model linearization and simplifications. Taking the DC/DC buck converter in continuous conduction mode as an example, the algorithm of proposed synergetic control is analyzed in detail. All the simulation results demonstrate the effectiveness and the high dynamic capability of the proposed AF-FTSC control technique over the FTSC strategy. Voir les détails

Mots clés : synergetic control, fuzzy logic system, terminal technique, finite time convergence, DC/DC buck converter

Software Features Extraction From Object-Oriented Source Code Using an Overlapping Clustering Approach

Imad Eddine ARAAR, Hassina SERIDI  (2016)
Publication

For many decades, numerous organizations have launched software reuse initiatives to improve their productivity. Software product lines (SPL) addressed this problem by organizing software development around a set of features that are shared by a set of products. In order to exploit existing software products for building a new SPL, features composing each of the used products must be specified in the first place. In this paper we analyze the effectiveness of overlapping clustering based technique to mine functional features from object-oriented (OO) source code of existing systems. The evaluation of the proposed approach using two different Java open-source applications, i.e. “Mobile media” and “Drawing Shapes”, has revealed encouraging results. Voir les détails

Mots clés : feature model, software product line, overlapping clustering, reverse engineering, program analysis