Liste des communications
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.
Study of nickel silicide by X- ray diffraction
In order to understand fully the results from X-ray diffraction oscattering analysis, it is benefecial to understand the interactionsbetween X-rays and matter. X-ray methods are generally nondestructive, in that sample preparation is not required, and they canprovide a very appropriate route to obtain structural information onthin films and multilayers. Analysis can be performed across thewhole spectrum of material types from perfect single crystals toamorphous materials.In this work, X-ray diffraction was involved to study the formationof crystalline nickel silicide phases. For this purpose, Ni nanometricthin films were deposited on Si (100). XRD technique have shownthat the NiSi silicide is the predominant phase at 350°C. For theannealed samples at 500°C, only NiSi monosilicide is detectedWhen the annealing temperature increases to 750°C the NiSi2disilicide is the main formed phase. The obtained samples wereanalyzed using scanning electron microscopy (SEM), it show asurface morphology depending strongly on the substrateorientation. Voir les détails
Mots clés : thin film, nickel silicides, X-ray, XRD
Effect of roller burnishing parameters on roughnesssurface and hardness of steel S355J0 specimens byusing response surface methodology
Burnishing is a cold working process with superficialplastic deformation, which is to exert an external pressurethrough a very hard and smooth roller or ball on a surface tooccurs a uniform and work-hardened surface, makes it possibleto reduce roughness, to increase the hardness and to produceresidual stresses of compression The steel S 355 J0 specimenswere machined on a conventional lathe to the proper dimensions,these machined specimens were then burnished by a simplelocally designed and fabricated roller-burnishing tool. The mainobjective in this work is to determine a mathematical modelsstatistically based on experimental design (response surfacemethodology) using central composite second-order rotatabledesign which allows to give the relationship between the two outparameters surface roughness and hardness representative of thesuperficial layer surface caused by the four internal rollerburnishingparametersnamely:burnishingspeed,force,feedandnumberof passes of the tool. The experimental results indicatethat feed, burnishing force and speed are the most important andsignificant parameters to improve roughness surface and feed,speed, burnishing force and number of passes are the mostimportant and significant parameters to improve superficialhardness of steel S 355 J0 specimens. The surface roughness andhardness were improved to 0.15µm from about 2.5µm and to 226Hv from 176 Hv respectively. Voir les détails
Mots clés : roller-burnishing, steel S355J0, surface roughness, superficial hardness, response surface methodology
Influence of sintering temperature on thedensification of copper matrix composite reinforcedwith CoAl particle developed by SHS
This work focuses on the influence of the sinteringtemperature of a copper matrix composite and CoAl particlesproduced by SHS (Self Propagating High temperatureSynthesis).In a first step, Co-50at.%Al mixture is sintered at 950°C to obtainthe CoAl compound that will be milled for 24 hours and sinteredin presence of copper in order to a preparation of a metal matrixcomposite. Then, the CoAl-50wt. %Cu mixtures are compressedunder a pressure of 350MPa and sintered at two differenttemperatures (solid and liquid phase) under argon.The SEM examination of the composite sintered in solid phaseshows the ramifications of copper in CoAl particles, whichhighlights a diffusion of Cu through the nano pores particles.Some particles present a phase contrast, which reveals theinhomogeneity of diffusion. The EDS-X analysis confirms thisresult since we find an important quantity of copper inside aparticle. The Cobalt and aluminum are also found in the matrix.Moreover, the discontinuity is observed with the interface CoAlCu. It seems that liquid sintering phase would leads to ahomogeneous diffusion, better wetting of particles and higherdensification. A sphering of CoAl particles is also observed in thecase of the composite sintered in liquid phase, which reflects thephenomenon of dissolution-precipitation at the edges of CoAlparticles.To a complementary results, X-ray diffraction analysis (XRD)was also performed. The diffractogram of CoAl-Cu compositesintered in liquid phase reveals the presence of Cu and CoAl withshift of the Cu peaks to the left, reflecting an increase in theparameter. This swelling of the mesh of copper is due to thesubstitution of copper atoms by those of aluminum and cobalt.After the calculation of the open porosity in the compositessintered in liquid and solid phase, we found a better densificationof the composite sintered in liquid phase with a rate porosity of2%. Voir les détails
Mots clés : composite materials, intermetallics, SHS, SEMEDS X, XRD
Behaviour of dislocations near phaseboundaries in the anisotropiclinear elasticity theory
The image force undergone by amatrix dislocations close and parallel to aninterphase boundary is studied in Ag-X bicrystalswith X : Pb, Cu and Ni for disorientations rangingbetween 0° and 90°. The elastic energy of dislocationboundaryinteraction is calculated within theframework of anisotropic linear elasticity. It isrelated to the difference of the two metals shearmoduli. It is about a few hundred pico Joule permeter. The image force can be repulsive or attractiveaccording to the sign and the intensity of shearmoduli difference. The isoenergy maps have varioussymmetries according to the disorientation. Voir les détails
Mots clés : nterphase Boundary, Dislocation, Elastic Interaction, Image Force, Anisotropic elasticity, CFC Structure.
Study Ni70al20Si10prepared by mechanical alloying
Alloys based on nickel, aluminum and siliconhave been extensively studied because they are of great interestfor high temperature structural applications (low density, highspecific strength, greater resistance to oxidation, hightemperature resistance). The properties of these materials can beimproved by mechanical alloying. In this work we havedeveloped and studied intermetallic Ni70al20Siprepared bymechanical alloying. The powder mixtures were crushed in aplanetary ball mills for synthesizes shades off balance, the millingtime was a factor in the study of structural changes of thiscompound to 50 hours of milling. Characterizations by SEM andXRD are used to derive the properties of this compound. Voir les détails
Mots clés : intermetallic alloy, Mechanical Alloying, Aluminum- Nickel-Silicon, SEM, XRD
Fatigue properties estimation based on hardnessmeasurements and tensile properties of a dissimilar weldjoint
This work aims to estimate the high cycle fatigue properties of a dissimilar weld joint madeof 2205 duplex and 13% Cr supermartensitic stainless steels. The filler metal used is the2507 superduplex stainless steel. Two methods were used; one is a direct method thatconsists of experimental fatigue tests conducted under rotating bending conditions. Theother method is an indirect method where the fatigue properties are estimated by means ofempirical expressions based on hardness measurements and tensile properties such asYoung modulus and tensile strength. Results show that for high cycle fatigue regime, theoverall behavior of the dissimilar weld joint is controlled by the weld metal that has thelowest fatigue limit. The two base materials have the same level of fatigue limit which isslightly higher than that of the weld metal. A good agreement was obtained between thetwo used methods for the two base materials in contrast with the weld metal. Voir les détails
Mots clés : Dissimilar weld joint, fatigue, duplex, Supermartensitique, superduplex