Liste des documents
Phase transition phenomena in an iron phosphateglass and thermal stability criteria
The thermal stability of an iron phosphate glassdedicated to radioactive waste confinement is a crucialcharacteristic for the integrity of the waste package. In this study,we investigate the thermal stability criteria defined by Hruby,Weinberg and Lu/Liu by measuring the glass transitiontemperature (Tg), the crystallization temperature (T), and themelting temperature (T) of an iron phosphate glass loaded withradioactive waste. These temperatures decrease when loading theglass with the waste: Tg decreases from 623.48 °C to 580.04 °C,Tcmfrom 766.34 to 679.26 °C and Tfrom 932.76 °C to 919.75 °C.Thermal stability criteria show satisfactory values, in the interval0.14 0.69. Voir les détails
Mots clés : Iron phosphate glass, Thermal stability, Radioactive waste, XRD, DTA, SEM
Bending of laminated beams using Timoshenkomodel via nonlocal elasticity
In this paper, the bending of laminated beamsusing first order shear deformation theory via nonlocal elasticityis presented. The analysis is presented for static flexure ofsymmetric and anti-symmetric cross-ply laminated beamssubjected to sinusoidal load.Governing equations and boundary conditions are obtainedby using the principle of virtual work.Analytical solutions of bending for simply supportedlaminated beams are presented using this theory to illustrate theeffect of nonlocal theory, and the influence of aspect ratio isexamined. Voir les détails
Mots clés : First-order shear deformation theory; bending, laminated beam, non local
Analytical Characterization of Nd2FeB sinteredmagnet14
The remarkable properties (magnetism andcorrosion resistance)of the Nd-Fe-B sintered magnet areassociated with the presence of other metal elements thatNeodymium-Iron-Boron like Cu, Mn, Al, V, Ni and others. Withan aim of having information on the components in the Nd-Fe-Bmatrix and on the distribution of these elements, in this work, theNAA has highlighted the presence of several metallic elements.Using a mass ratio equal to an activity ratio we can calculate theproportions of detected Elements. The results are: iron with51.30%, neodymium with 25.41% and other elements like nickelwith 1.25%. The rest from the matrix, 22.04%, represents theproportions of B and the other elements traces. In this work weare interested in neutron activation analysis (NAA) in the onlyreason is to identify the metallic Elements in trace (ppm). Voir les détails
Mots clés : NdFeB Sintered magnets, NdFeB characterization, NAA.
Elaboration of Metallic oxide nanopowder Fe dopedZnO
Among the methods of elaboration the metallicoxide nanopowders based on green chemistry,co-precipitation isa simple process used for industrial production in differentsectors .It is the preparation of an aqueous solution containingthe desired cation then mixing with a solution containing theprecipitating agent .the precipitate is then separated from theliquid by filtration, washing, drying and then thermallydecomposing to yield the desired product.Our study focused on pure and Fe doped ZnO nanopowders(Zn1-xFeO, x=0.0,0.005,0.02,0.05 and 0.15)prepared by coprecipitationmethode at room temperature with zinc acetate as azinc source. Samples were analyzed by X-ray diffraction (XRD),scanning electron microscope (SEM), infrared spectroscopy IRand UV-visible spectroscopy.xAll powders are polycrystalline with a hexagonal (wurtzite),grain powders were nanometric sizes. From a doping level thesecondary phase ZnFe2O4 appear and found a decrease in grainsize and increase internal stresses with increasing theconcentration of Fe dopant. SEM images show the existence ofsettlements powder particles in spherical form. IR infraredspectroscopy we identified in the specific vibration and the peakcharacteristic of the ZnO matrix, Zn-O binding was clearlyobserved at around 470 cm-1.the Study of the optical properties ofthe samples clearly shows the doping effect on the opticalabsorption spectra and allowed us to determine the opticalabsorption edge and the width of the gap. Voir les détails
Mots clés : ZnO, ZnFe 2 O, co-précipitation, the structural properties, nanopowder.
First principles study of the new half-metallicferromagnetic full-Heusler alloysCo2CrSi1_xGex: An ab-initio study
We have studied the structural, electronic, elastic,magnetic, thermal and thermodynamic property of thequaternary Heusler alloys Co2CrSi1-xGe(x = 0, 0.25, 0.5, 0.75, 1)with the linearized augmented plane wave method based ondensity functional theory (DFT)and implemented in wien2kcode. For exchange correlation potential we have used thegeneralized gradient approximation (GGA) of Perdew et al. Ourresults provide a theoretical study for the mixed HeuslerCo2CrSi1-xGexx(0
Mots clés : DFT, wien2k, GGA, Heusler, Debye
Effect of cold rolling on texture evolution duringprimary recrystallization of an IF steel
In the present study, we present the effect of cold rolling on texture evolution during primary recrystallization of an IF steelthat is destined to the automotive industry. From the hot rolled sheet, three deformation rates were performed by cold rolling: 25, 50and 75 % followed by several heat treatments in order to obtain the fully recrystallized states. Microhardness Vichers was used toestimate the recrystallized fraction and XRD (X-ray diffraction)for the texture characterization. The results show that texture of thehot rolled sample is near random and its evolution is very low for the 25% reduced sample. However, texture become more importantfor 50% and 75% reduces states, with the strengthening of -fiber and the appearance of -fiber. The evolution of texture duringprimary recrystallization is quite different. Recrystallization of the 25% and 50% cold rolled states shows a maximum of the ODF on{223}<110> component and texture tends generally to be random. The recrystallization texture of the 75% reduced sample ischaracterized by a -fiber more intense than - fiber and a maximum of the ODF around the component {111}<110>. It was observedalso that -fiber starts to develop during the primary recrystallization of the 50% rolled state, and becomes more pronounced duringrecrystallization of the 75% cold rolled sample. Voir les détails
Mots clés : IF steel, Cold rolling, primary recrystallization, texture, XRD, -fiber, -fiber.
Impact resolution methods of contact on themechanical behavior of structures
Contact problems are inherently non-linear due tothe instability of the contact surface. The analysis of theseproblems has a great importance in the industrial applications. Inmany industrial processes of working such as stamping, rollingand forming, the phenomena of contact play an essential role.The numerical simulation of these problems can raise seriousdifficulties on the level of modelling and computing time.There are various numerical methodsfor managing contact between two solid or between a solidand a rigid surface. Several contacting methods are used in thetreatment of contact problems. The method of penalty andlagrangian method that exists in finite element codes such asANSYS,ABAQUS,...In order to remove the advantages and disadvantages of thesemethods, a comparative analysis on the mechanical behavior ofstructure based on a case study is the subject of this study. Voir les détails
Mots clés : contact, methods, penalties, AugmentedLagrangian, mechanical behavior.
Study of the structural evolution of Ni50%atAl50%at mixture during mechanical alloying
In this study elemental powder of 50 %.at Ni and50 %.at Al mixture was mechanically alloyed in planetary ballmill Retsch PM400, for a predetermining time until 48h. Using Xraydiffraction and scanning electron microscopy (SEM) it wasobserved that milling of powder leads to the formation of NiAlphase. By the investigation of results from different techniquemicrostructural and morphology of the powder was investigatedover time of milling. Voir les détails
Mots clés : NiAl alloy, X-ray diffraction, SEM, laser granulometry
Numerical analysis of Hydrogen embrittlement ofhigh strength steels using Monte Carlo method
A probabilistic approach has been applied tohydrogen desorption phenomena in the wire rod for pre-stressedconcrete. The phenomena was treated in a deterministic study byCarneiro in 2010 , this work aims to reflect uncertainty propertyof the material of a high carbon steel such as effective diffusioncoefficient (De)and concentration parameters(C). Aprobabilistic simulation method of Monte Carlo was used todetermine the contribution of each random variable on thevariability of reduction in area in our case the limit state criteriarequired in the study is reduction in area parameter must begreater than or equal to 30% (Carneiro, 2010). Afterwards westudy the influence of parameters that govern the phenomenondesorption hydrogen and dispersion of the parameters whileoptimizing calculative time. Voir les détails
Mots clés : hydrogen embrittlement, the probabilistic simulation method of Monte Carlo, spatial variability.
Experimental study of shot peening effect onthe surface of austenitic stainless steels :roughness, residual stresses and workhardening
Shot peening is a mechanical surfacetreatment widely used in automotive and aerospaceindustries to enhance the fatigue life of mechanicalparts. In this process, many small and hard particles,called shots, are projected at high velocities on to thesample. The multiple impacts plastically deform thematerial surface and induce an in-plane compressiveresidual stress field near the surface. Roughness,compressive residual stress and work hardening of anAISI 304 austenitic stainless steel was studied toexplain it evolution according to the Almen intensityand mechanical properties. Shot peening increasessurface hardness levels. We can confirm in case ofCSP the highest microhardness observed at topmostsurface. According to these results it can beconsidered, that after CSP application, themicrohardness in depth of 0.025 mm increased fromabout 220 HV to 350 HV. Voir les détails
Mots clés : -shot peening, residual stresses, work hardening, Almen intensity, roughness, FWHM.