Liste des publications
Study of the effect burnishing on superficial hardness and hardening of S355JR steel using experimental planning
Surface hardness plays an important role in lifetime of a mechanical piece subjected to friction and wear. Indeed, the hardness can be improved by superficial plastic deformation processes (SDP), such as mechanical surface treatment "MST", in particular the ball burnishing. However, the treatment result of is conditioned by mastery of operation thus ensuring treated piece good mechanical and geometric properties. Experimental work was carried out by applying the ball burnishing process on steel tensile specimens S355JR, in order to observe the influence of treatment parameters regime on surface hardness ‘Hv’ and the effect of latter on tensile behavior of this steel. Two parameters of regime were considered namely: burnishing force "Py" and number of passes "i". The relationship between these parameters and microhardness measured at "Hv" surface has been highlighting using factorial plans 22. Moreover a mathematical model has been obtained allowing prediction of response (Hv) as well as optimization of parameters of treatment regime. The experimental results showed that for surface hardness Hv it is possible to reach a 45% improvement rate for a burnishing force py = 20 Kgf and a number of passages i = 3 for this material. Regarding behavior of material during tensile test, for a low burnishing force (py = 10N) and a number of passes (i = 5), the section further weakening (S = 4.14), proof than ductility of material has decreased. Voir les détails
Mots clés : Surface hardness, factorial designs, ball burnishing, Mathematical model, tensile behaviour
Effect of microstructure and precipitation phenomena on the mechanical behavior of AA6061-T6 aluminum alloy weld.
In the present study, the effect of microstructure and precipitation phenomena on the micro hardness, tensile strength, impacttoughness, and electrochemical behavior of tungsten inert gas (TIG)-welded AA6061-T6 aluminum alloy are investigated. Themicrostructure features showed mainly the grains of aluminum solid solution with the presence of some precipitates at the grainboundaries. Scanning electron microscope micrographs exhibited the presence of Fe-based intermetallic and B-equilibriumprecipitates throughout a-Al grains. In the heat-affected zone (HAZ), the dissolution, over-aged, and coalescence of precipitatesare observed; their hardening effects disappear and a decrease in strength and hardness are noticed. The fracture toughness valuesof each zone at different temperatures using Charpy V-notch test remained constant where the HAZ presents the highest absorbedenergy. However, the temperature did not have a significant effect on the absorbed energy for each zone. In addition, the fracturedsurface of base metal (BM) and HAZ are characterized by dimple-like structure and they are larger in the HAZ. The electrochemicalbehavior of each zone of the weld evaluated in NaCl + H2O2 solution revealed that the corrosion current density of BMand HAZ is lower than that of molten zone (MZ), which displays high corrosion current density in this electrolyte and would befastest to corrode. Voir les détails
Mots clés : Aluminum alloys, TIG welding, precipitates, microstructure, Fractography, Electrochemical behavior
Numerical study of parameters affecting pressure drop of power-law fluid in horizontal annulus for laminar and turbulent flow
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
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
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
SnS THIN FILMS DEPOSITION BY SPRAY PYROLYSIS: SOLVENT INFLUENCE
Tin monosulfide (SnS) films are a new generation of absorber layers for thin ?lm heterojunction solar cell. The goal of the present study is the investigation of the role of the solvent on SnS thin films properties. Films were synthesized by ultrasonic spray pyrolysis technique. The used solution is a mixture of SnCl2.2H2O and thiourea (SC(NH2)2 precursors prepared with two different solvents: methanol and distilled water. X-ray diffraction (XRD) analysis reveals the SnS orthorhombic polycrystalline phase in different films. Using methanol as solvent leads to Sn2S3 secondary phase formation. While, film prepared with distilled water contains SnS2 as secondary phase. Scanning electron microscopy (SEM) observations reveal that films deposited with the methanol are rough with the presence of craters bubbles on the surface due to gas exo-diffusion during film growth. However, the film deposited with distilled water has a smooth, uniform, homogeneous and pinholes free surface. The electrical measurements reveal that films are p-type semiconductors, the dark conductivity increases from 3.07×10-4 (W.cm)-1 in film prepared with methanol to 5.15×10-3 (W.cm)-1 when using distilled water. We inferred that using distilled water leads to films with better quality than methanol as solvent. Voir les détails
Mots clés : Tin monosulfide, Spray pyrolysis, Thin films, solar cells
Thermo-physico-chemical and statistical mechanical properties of Washingtonian filifera new lignocellulosic fiber. Engineering Solid Mechanics
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
Quantitative and qualitative analyses of intermolecular interactions in neutral/deprotonated aspirin@β-CD inclusion complexes: QTAIM and NBO analyses
Most of the researches in supramolecular chemistry area are focused on the conventional hydrogen bonds without taking into account unconventional intermolecular interactions. The nature and strength of the conventional and unconventional interactions in inclusion complexes formed between neutral aspirin (ASA) and its deprotonated form (ASA−) with β-cyclodextrin (β-CD) have been studied. It was conducted through combining atoms in molecules (AIM) theoretical criteria suggested by Koch and Popelier and natural bond orbital (NBO) analyses by means of dispersion-corrected density functional theory (DFT-D3) with the functional B3LYP using cc-pvdz basis set in the gas phase. We have found fve intermolecular closedshell interaction groups responsible for neutral ASA:β-CD and deprotonated ASA−:β-CD inclusion complexes stability: One is conventional O–H···O bond group. The four C–H···O, C–H···C, O–H···H–C and C–H···H–C groups are nonconventional. Also, with respect to the Koch and Popelier criteria, some of them present the properties of a hydrogen bond, while others do not. The non-covalent interaction energies are calculated using Espinosa approach. Finally, according to the AIM and NBO analyses, the topological parameters (electron density ρband its Laplacian ∇2ρb), estimated interaction energies (Eint), and the stabilization energy E(2)of both complexes were correlated with the intermolecular bond lengths Voir les détails
Mots clés : β-Cyclodextrin, Aspirin, Inclusion complex, DFT-D3, QTAIM, NBO
Droplet Breakup Regime in a Cross-Junction Device with Lateral Obstacles
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.
Analytical Modeling of Dual-Junction Tandem Solar Cells Based on an InGaP/GaAs Heterojunction Stacked on a Ge Substrate
An analytical model is used to describe the electrical characteristics of a dual?junction tandem solar cell performing with a conversion efficiency of 32.56%under air mass 1.5 global (AM1.5G) spectrum. The tandem structure consistsof a thin heterojunction top cell made of indium gallium phosphide (InGaP) ongallium arsenide (GaAs), mechanically stacked on a relatively thick germa?nium (Ge) substrate, which acts as bottom cell. In order to obtain the bestperformance of such a structure, we simulate for both the upper and lowersub-cell the current density–voltage, power density–voltage, and spectral re?sponse behaviors, taking into account the doping-dependent transportparameters and a wide range of minority carrier surface recombinationvelocities. For the proposed tandem cell, our calculations predict optimalphotovoltaic parameters, namely the short-circuit current density (Jsc), open?circuit voltage (Voc), maximum power density (Pmax), and fill factor (FF) areJsc = 28.25 mA/cm2, Voc = 1.24 V, Pmax = 31.64 mW/cm2, and FF = 89.95%,respectively. The present study could prove useful in supporting the design ofhigh efficiency dual junction structures by investigating the role of differentmaterials and physical parameters. Voir les détails
Mots clés : Analytical modeling, tandem solar cell, Spectral response, conversion efficiency
Tribological investigation of carbon fiber-epoxy composite reinforced by metallic filler layer
This work aims to develop a carbon fiber/epoxy composite reinforced by metal fillers (Copper/Stainless steel) in order to improve the tribological properties. For this, a tribological study has been conducted using a ball-on-disc configuration. The surface of the material has been modified by deposing a layer of metal powder during manufacturing. For a better understanding of the wear mechanisms, the worn surface characteristics have been examined using a scanning electron microscope (SEM). The coefficient of friction and the wear rate under different normal loads have been determined for the filled and unfilled composite. The results obtained revealed an increase of the wear rate with the increase of the applied load. Metallic filled carbon–epoxy showed better wear resistance and friction behaviour under different loads. In fact, microhardness measurement showed that the surface hardness has been greatly influenced by the metal filler. The overall results illustrate the impact of metal powders in the modification of polymer matrix composites surfaces. This method is promising to improve the tribological properties. Voir les détails
Mots clés : Polymer matrix composites, Metallic fillers, wear, Coefficient of friction