Liste des publications

Nombre total de résultats : 538
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Microstructural Study of Thin Films CuFe Obtained by ThermalEvaporation of Nanostructured Milled Powde

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

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

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)

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)

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)

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)

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

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

Imad Eddine ARAAR, Hassina SERIDI  (2016)

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

Correlation Between the Pitting Potential Evolution and σσ Phase Precipitation Kinetics in the 2205 Duplex Stainless Steel

Mustapha DJAMA, Djaffar Saidi, Abdelaziz Kadri, Nabil KHERROUBA, Brahim MEHDI, Stéphane Mathieu, Thierry Schweitzer, IDIR Brahim  (2018)

The aim of this work is to correlate the pitting potential (Epit) evolution with the kinetics ofrphaseprecipitation in the 2205 duplex stainless steel aged at 850°C after solution treatment at 1150°C. Thepotentiodynamic polarization curves indicate a reduction of the pitting corrosion resistance with the agingtime, which is revealed by a decrease in theEpitvalues from 0.65 to 0.40 VSCE. Thus,Epitvalues are used todetermine the kinetics parameters of therphase precipitation. The experimental transformed fractionagrees well with the one calculated by using the modified Kolmogorov–Johnson–Mehl–Avrami equationwith an impingement parameterc= 0.6. Voir les détails

Mots clés : kinetic, KJMA, Pitting corrosion, otentiodynamic polarization, r phase precipitation

Isothermal and non-isothermal precipitation kinetics in Al–Mg–Si-(Ag) alloy

Oussama.Djema, Mabrouk.Bouabdallah, Riad.Badji, Amr.Saadi, Nabil.Kherrouba, Amane.Sahli  (2019)

In the present work, isothermal and non-isothermal precipitation kinetics in a 6063 aluminium alloy containing a small silver (Ag) addition have been investigated using Vickers microhardness and Differential Scanning Calorimetry (DSC) measurements respectively. Isothermal kinetics analysis showed that β'' phase precipitation obeyed the Johnson-Mehl-Avrami (JMA) model. The DSC analysis revealed that Ag addition modified the precipitation sequence in the investigated 6063 aluminium alloy through the formation of an additional metastable pre-β'' phase. An approach based on the additivity concept has been applied to the heating DSC diagrams to investigate the β'' phase precipitation. The obtained Avrami exponent values from this approach led to suggest that the β'' phase precipitation proceeded through two processes during continuous heating. The Avrami exponent value obtained at the final stage of the transformation was consistent with that obtained from the isothermal analysis, whereas the corresponding activation energy was higher than the one calculated from the isothermal analysis and Kissinger's method. It was also established that the precipitation kinetics of the β'' phase was enhanced by the formation of the precursor phase pre-β''. Voir les détails

Mots clés : 6063 aluminium alloy, Ag addition, Precipitation kinetics, JMA model, Additivity concept

Effect of solution treatment on the microstructure, micromechanical properties, and kinetic parameters of the β → α phase transformation during continuous cooling of Ti-6Al-4V titanium alloy

Nabil KHERROUBA, Denis CARRON, Mabrouk BOUABDALLAH, Riad BADJI  (2019)

The aim of this study is to examine the effect of solution treatment temperature (STT) on the microstructure, the micromechanical properties, and the kinetic parameters of the β → α phase transformation during continuous cooling of the dual phase titanium alloy Ti-6Al-4V. Increasing the STT from 1050 °C to 1200 °C delays the formation of the α phase during cooling and increases the value of its activation energy. The microstructural analysis reveals the emergence of αW platelets from protuberances on the αGB / αW interface. The investigation of the morphology of the αW platelets reveals the presence of ledges on their longest side showing a sharp extremity. The micromechanical properties determined by nanoindentation and microhardness tests are almost insensitive to the cooling rate but are strongly affected by the STT; the higher the STT, the lower the overall microhardness of the Ti-6Al-4V alloy. In addition, the STT affects the microhardness and the Young’s modulus of both α and β phases differently; when the STT increases, the microhardness and the Young’s modulus of the α phase decrease whereas those of the β phase increase. Voir les détails

Mots clés : Ti-6Al-4V, solution treatment, ledge mechanism, interface instability, Nanoindentation, partitioning

Structural, Electronic and Mechanical Properties of C14-Mg 2 RE(RE=Eu, Er, Tm, Yb and Lu) Laves Phases: A DFT Study

A. Zahague, B. Lagoun, A. Legris, R. Besson, L. Rabahi, D. Bradai  (2019)

The Pseudo-Potential Density Functional Theory (PP-DFT) method is applied to investigatethe structural, electronic and mechanical properties of C14-Mg 2 RE Laves phases, with RE being Eu,Er, Tm, Yb and Lu. The predicted cell parameter and c/a ratio of each compound are in good agreement with experimental and theoretical results. Moreover, the studied alloys exhibit a metalliccharacter, which is attributed to the presence of Mg atoms in the C14 Laves phase. Also, theformation of C14-Mg 2 RE is found to be controlled by the hybridisation between Mg p states and RE-d and f states. From a mechanical property analysis, the studied alloys are found to be mechanicallystable. The Mg 2 Lu compound exhibits higher ductility, while Mg 2 Er exhibits the smallest one.Finally, Mg 2 Yb is found to be more anisotropic than other phases. Voir les détails

Mots clés : A DFT calculations, B Magnesium based Laves phases, C Density Functional Theory (DFT), D Mechanical properties, E Electronic properties