Liste des documents
Amélioration des caractéristiques mécaniques dessurfaces par nitruration-procédé technologique du plasma à froid
Les propriétés mécaniques de surface jouent un rôleessentiel dans tout système mécanique ainsi que dans toutprocessus ou la surface dun composant est impliquée en tantquinterface. Dans le but daméliorer certain nombre de cespropriétés mécanique il est possible de modifier la compositionchimique superficielle dun matériau métallique par diffusiondun ou plusieurs éléments, Il sagit donc de la filière detraitement thermochimique par diffusion métalloïdes et demétaux tels que (la cémentation, la nitruration, lanitrocarburation, la boruration, laluminisation etchromisation...)La réalisation dun traitement de durcissement superficiel parnitruration assisté par plasma de quatre nuances différentesdacier, [A33, A60, XC48 et linoxydable], est présentée danscette étude. Ainsi lanalyse des propriétés mécaniques de surfacetelles que la micro-dureté et la microstructure ont été examinées, Voir les détails
Mots clés : traitement de surfaces, nitruration, plasma, micro-dureté.
Structural and electrical properties of the ceramicmanganite Pr0.6Sr0.4Mn1-xCuxO3
The ceramics that are the focus of this paper ,have a Perovskite structure (ABO),with the general chemicalformula Pr0.6Sr0.4Mn1-xCuxO33(x=0.05) .The compounds areprepared by solid state reaction. The X-ray diffraction data areanalyzed and it has been found that all the compoundscrystallize in the orthorhombic structure. The observations bySEM show that the grain size decreases by copper doping. Thetemperature of magneto-resistivity curves are registered fromroom temperature down to 50K under a magnetic field up to 5Tesla and showed that the undoped sample present a metalinsulatortransition (I-M) at a temperature T 210,23 K.Some physical parameters are extracted and their evolutionwith magnetic field are presented and discussed. Voir les détails
Mots clés : manganite, ceramic, Doping, resistivity
Thermal, rheological and morphological propertiesof biodegradable blends based on poly (lactic acid)and polycarbonate blends
Biopolymers are expected to be an alternative forconventional plastics due to the limited resources and soaringpetroleum price which will restrict the use of petroleum basedplastics in the near future. In this context, poly(lactic acid) (PLA)has attracted the attention of polymer scientists as a potentialbiopolymer to substitute the fossil fuel based polymers.Even the huge advancements in PLA research, there is stillmany drawbacks that continue to limit its employment in somesectors which require particular mechanical and thermalproperties. For this reason, blending with other polymersappears as an attractive strategy to overcome the PLAsshortcomings and enlarge its application domains. Amongpossible PLA blends, its combination with polycarbonate (PC)presenting a high inherent thermal stability and an importanttensile strength appears the more suitable path to overcome PLAbrittleness and poor thermal resistance. Consequently, PLA/PCblends have received considerable attention in research becauseof their potential applications as friendly to the environmentadvanced packaging materials and for industrial applications.The objective of this study was to prepare biodegradablematerials based on a bio-based polymer, which is the PLA and anengineering thermoplastic, PC. The properties of the blends werecharacterized by differential scanning calorimetry (DSC),thermogravimetric analysis (TGA)and scanning electronmicroscopy (SEM).The study showed that the blends kneadingtorque are between those of the homopolymers and areproportional to the rate of PLA. Thermogravimetric analysisshowed that PC improved notably the thermal stability of theblends. DSC results pointed out significant changes on thethermal behavior of the PLA phase into the blends. Voir les détails
Mots clés : Blends, Biopolymer, Poly (lactic acid ), Polycarbonate, Thermal stability.
A Three-Dimensional Solution for Bending Analysis ofFunctionally Graded CeramicMetal Sandwich Plates withStretching Effect
In this research, a simple but accurate sinusoidalplate theory for the thermomechanical bending analysis offunctionally graded sandwich plates is presented. The mainadvantage of this approach is that, in addition to incorporatingthe thickness stretching effect, it deals with only 5 unknowns asthe first order shear deformation theory (FSDT), instead of 6 asin the well-known conventional sinusoidal plate theory (SPT).The material properties of the sandwich plate faces are assumedto vary according to a power law distribution in terms of thevolume fractions of the constituents. The core layer is made of anisotropic ceramic material. Comparison studies are performed tocheck the validity of the present results from which it can beconcluded that the proposed theory is accurate and efficient inpredicting the thermomechanical behavior of functionally gradedsandwich plates. The effect of side-to-thickness ratio, aspect ratio,the volume fraction exponent, and the loading conditions on thethermomechanical response of functionally graded sandwichplates is also investigated and discussed. Voir les détails
Mots clés : Sandwich plate, thermomechanical, analytical modelling, unctionally graded material, stretching effect.
Effet du traitement Thermique (Trempe libre )sur lesproprietes thermiques et thermo-dynamique dupolypropylene(PP)
This work deals on the study of the thermalproperties of polypropylene (PP) in the presence of residualstress (CR). A laboratory scale, two valid methods forintroducing residual stresses in the polymer, which are nonuniformcooling (thermal quenching), and the non-uniformplastic deformation (cold rolling) is known. The results obtainedby the DMA analysis result presentation of two relaxations , 'for all the samples studied. DSC results show a decrease in thecrystallinity of the polymer at free quenching temperature of20°C. Voir les détails
Mots clés : Polypropylene, Quenching, Thermal history.
Analysis of Free Vibration of Sandwich BeamsConsider Normal Deformation Effect
A new refined hyperbolic shear and normaldeformation beam theory is developed to study the free vibrationof functionally graded (FG) sandwich beams under variousboundary conditions.The effects of transverse shear strains as well as the transversenormal strain are taken into account. Material properties of thesandwich beam faces are assumed to be graded in the thicknessdirection according to a simple power-law distribution in termsof the volume fractions of the constituents. The core layer is stillhomogeneous and made of an isotropic material. Equations ofmotion are derived from Hamiltons principle.Analytical solutions for the bending, free vibration andbuckling analyses are obtained for simply supported sandwichbeams. Illustrative examples are given to show the effects ofvarying gradients, thickness stretching, boundary conditions, andthickness to length ratios on the bending, free vibration offunctionally graded sandwich beams. Voir les détails
Mots clés : refined shear deformation theory, Stretching effect, free vibration, boundary conditions., functionally graded sandwich beam
Elastic interaction between dislocation and interface:Force image effect in the ceramic bimaterials (Al2O3-AlN)
The Al2O3and AlN materials are often used as electricalinsulators (electronic substrates) also the case of pressure sensorswhere the aluminum nitride (AlN) is selected as the piezoelectriclayer and the alumina (Al2O3) as a solid substrate insulating.In the absence of the effects of temperature, deformation andexternal stress, we are interested in this work to study themobility of dislocations near the heterophase interface ofbimaterials based alumina (Al2O3)under the effect of the imageForce. These dislocations having a Burgers vector b = 1/3 [11-20],. The interface is defined by its planeparallel to the dislocation line and disorientation varies between 0they are located in Al2O3and 180 ° around the axis [10-10]. The image force must becalculated in the context of the anisotropic linear elasticity usingthe theorem of Barnett and Lothe and the Stroh formalism. Fi = - E / d, E is the elastic interaction energy.The results show that dislocation motion under the image forceeffect depends on the elastic and crystallographic properties ofthe materials constituting the bicrystals and even disorientationof the interface which has an effect on the intensity of the elasticinteraction energy. The dislocations are repelled to the interfaceif the difference in shear modulus between the two materials ispositive 1>0), they are attracted to the interface in theopposite case 1<0). Voir les détails
Mots clés : dislocations, Image Force, Peierls stress, elastic anisotropy
Elaboration and characterization of a piezoelectricceramic resonator
In this work. We Synthesized PbTiOfrom PbO and TiOoxides from Solid state reaction and westudied the development and manufacture of solidpiezoelctrique resonator of PT .We played on parameter assintering time. We used XRD and SEM for morphologicalcharacterization and Analyzer for impedance piezoelectriccharacterization. Voir les détails
Mots clés : PT, ferroelectric, resonator, impedance, XRD, SEM
Reliability-simulation of composite tubular structure by finites elements method–Mechanical loading
The diversified use of filamentary composites in harsh marine environments, recorded in recent years has prompted researchers to focus their work on the reliability prediction. Owing to differences between the properties of the materials used for the composite, the manufacturing processes, the load combinations and types of marine environment, the prediction of the reliability of composite materials has become a primary task. Through failure criteria, TSAI-WU and the maximum stress, the reliability of multilayer tubular structures under mechanical loading is the subject of this first part of our research project, where Monte Carlo method estimated the failure probability. A sensitivity analysis was performed in order to identify the influence of the deferent parameters as : materials properties, geometry, manufacturing and loading, on the reliability of the composite cylindrical structure studied. To achieve a high accuracy of the results, we have carried out 10 simulations. The results showed great influence of radius ratio (Ply thickness); than internal pressure loading and finally winding angle. Voir les détails
Mots clés : Multilayer Tubular Structures, Marine structure, Design, Reliability, Monte Carlo.
Elaboration and structural study of Ni/SiOCo/SiO2and Ni-Co/SiO2nanocomposites2
The present work examines the structural properties of Ni, Co and Ni-Co supported on silica. The samples areprepared by impregnation, followed by calcination and thermal H- treatment. Several techniques, such as SEM and XRD, are used forthe characterization of the samples at different steps of their elaboration. After impregnation, the X-rays diffraction reveals theformation of nickel and cobalt silicide (NiSi, Co2Si, NiCoSi and Ni20.56Co3.44Si). After calcination, the XRD pattern presents the featuresof nickel and cobalt oxides (NiO, Co3O4, NiCoO2, NiCo2O44and CoO)with an average size of 10-25 nm. After H- treatment, the metallicphases (Ni, Co and Ni0.75Co0.25) appear at T 350°C Voir les détails
Mots clés : nanocomposites, Structural properties, Co 2 Si, NiCoSi, NiO, Co 3 O 4, NiCoO 2, NiCo 2 O 4, Metal/Support interaction.