Liste des communications
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.
Comparison of IR Spectra of Five PorcelainCompositions Prepared Using Algerian RawMaterials
The interest in Infrared (IR) spectroscopy is anessential technique for the characterization of ceramic. Its mainadvantage when it comes to studying items is that it is nondestructive:the samples can be investigated without furtherpreparation. IR spectroscopy probes molecular and crystal latticevibrations and therefore is sensitive to the compositions, chemicalenvironment, bonding and crystalline/amorphous structure of asample material. Five Porcelain compositions were studied bynon-destructive infra Raman spectroscopy: kaolin was derivedfrom Debagh deposit (Guelma region), Quartz was derived fromEl Oued region and PF was derived from Ain Barbar deposit(Annaba region) and both commercial Alumina talc. Ramanintensity is a very powerful tool, which allows investigating andcharacterizing the modifications of the structure in covalentbonded compounds. Hence the observed porcelain spectralfeature at ~1050 cm-1is due to SiOfor the five compositions.From our study, as well as the literature reviewed it appears thatinvestigators uniformly confirm the benefits of IR spectroscopyconcerning identification of chemical functional groups of thedifferent chemical compositions. Voir les détails
Mots clés : porcelain, IR, quartz, alumina, talc
Modeling and optimization of the composite plateslaminated by genetic algorithm
Our study made it possible to develop and test a program ofoptimization based on a technique of optimization based on theuse of a genetic algorithm. This program moreover was appliedto the resolution of several types of problems connected to theoptimal design of laminated structures. Among these problems,orientations of the folds, the material and the number of folds asvariable which were already solved . In this work, we havepresented the principles of the genetic algorithm functioning , itsapplication to the laminated composites and to the originaltechnique of coding which allows giving an account of theindustrial constraints of composites development.The flexibility of the general structure of our software allowstreatening the various types of problems like: calculation of themodule of rigidity as well as the factors of buckling and rupture.We develop the OpStrAG software to optimize the characteristicsof rigidity of the laminates and also their constraints towardsrupture and their deformations under a given loading. Voir les détails
Mots clés : composite materials, laminated Plates, Modeling and optimizatio, genetic Algorithm.
A new and economic approach to synthesize andfabricate anorthite based ceramics using kaolin andCaCO3
This new and economic approach to fabricateresistant anorthite based ceramics consists of Algerian kaolinand calcite (CaCO3). The anorthite (CaO·Al2O3E-Mail :zaiou_21 @yahoo.fr·2SiO) basedceramics were obtained by solid state reaction. The startingpowders were sintered at different temperatures (800-1100°C) for 1 h. The optimum sintering conditions gave arelatively higher density (2.64 g/cm3). Different techniqueswere used to investigate the physical proprieties of theprepared anorthite such as: scanning electron microscopy, Xraydiffraction, Raman spectroscopy and tensile strength. Thebest obtained 3 points flexural strength value was about 202MPa for the samples sintered at 1000 °C for 1 h. Furthermore,the best value of Vickers micro-hardness of the samplessintered at 1000 °C was 7.1 GPa. Finally, a correlationbetween microstructure and mechanical properties ofelaborated supports has been discussed. Voir les détails
Mots clés : anorthite, Kaolin, calcite, Sintering, Vickers micro-hardness, tensile strength.
OPTIMIZATION OF THE BEHAVIOR OF BUCKLINGOF THE STRATIFIEES BY GENETIC ALGORITHM
The laminated composite structures which are largely usednowadays, become unstable when they are prone to loadings ofmechanical or thermal nature and flame in the elastic zone.Consequently, buckling has a very great importance whendesigning this kind of structure. In this work, we studied thephenomenon of the buckling which was devoted underinvestigation of the optimization of a composite materiallaminated by the use of a data-processing method based on amathematical theory which uses the stochastic statistics it is thetheory of the genetic algorithms (GA). The objective of this workis, the maximization of the rigidity of the plate laminated bymaximizing the critical load of buckling according to theorientations of the folds. Voir les détails
Mots clés : Composite laminated, optimization, Buckling, genetic Algorithm.