Liste des documents
A summary of Vibration analysis techniques forfault detection and diagnosis in bearing
Bearing is one of the most critical components ofrotating machinery .They are employed to support and rotate theshafts in rotating machinery. Therefore; any fault in the bearingscan lead to losses on the level of production and equipments aswell as the creation of an unsafe working environment forhumans. For that reason, the bearing fault diagnosis has receivedconsiderable attention from the research and engineeringcommunities in recent years. The purpose of this study is toreview the Vibration analysis techniques and explore theircapabilities, advantages and disadvantage in monitoring rollingelement bearings. Voir les détails
Mots clés : Vibration analysis, bearing Fault diagnosis, Fast Fourier Transform (FFT), Envelope Analysis (EA), Short Time Fourier Transform (STFT), Empirical Mode Decomposition (EMD)
EFFECT OF MULTI-PASS HOT ROLLING ON RECRYSTALLISATION BEHAVIOUR OF FERRITIC STAINLESS STEEL TYPE 409
The aim of this research is to study the effect of interrupted deformation on the recrystallisation behaviour of ferritic stainless steel type 409. Hot rolling schedules have been performed on an experimental rolling mill using rectangular slabs of this ferritic stainless steel.The research has been carried out using material of ferritic stainless steel type 409, which contains precipitates, initially using experimental rolling of small slabs and quantitative optical metallographic techniques with one pass only. Stainless steel type 409 displays a slower rate of recrystallisation than other ferritic stainless steels and this is attributed to the presence of titanium.The effects of static recovery and full static recrystallisation between two passes on subsequent recrystallisation kinetics have been investigated. In this stainless steel, when recovery occurs between the passes, subsequent recrystallisation is retarded compared with that for a single pass of the combined strain. Increasing the recovery time increases the retardation of recrystallisation even more. Also it has been found that when recrystallisation is complete between the two passes, the rate of subsequent recrystallisation after the second deformation was considerably accelerated. Voir les détails
Mots clés : ferritic stainless steel type 409, precipitates, hot rolling, dynamic recovery, static recovery, static recrystallization.
APPLICATION DES TECHNIQUES MICRO-ONDES DANS LE DOMAINE DE CND : APPLICATION SUR LES ANTENNES IMPRIMES
Résumé : Dans ce travail nous avons effectué une analyse numérique d’une antenne imprimée en utilisant le logiciel de simulation électromagnétique HFFS (High Frequency Structure Simulation). On s'est intéressé à l’excitation d’un matériau par la technique Micro-ondes, En outre la détermination des paramètres hyperfréquences de cette antenne (fréquence de résonance, bande passante, diagramme de rayonnement, gain, etc.), les paramétres diélectriques du matériau (la permittivité diélectrique et la tangente des pertes), L’analyse par le logiciel est basée sur la méthode des éléments finis. Nous avons caractérisé les antennes imprimées à l’aide du logiciel d’Ansoft-HFSS pour les structures 3D ou Ansoft Designer pour les structures planaires 2D. La représentation de tous les éléments de base dans la structure est appelée « maillage ». Le logiciel calcule une solution à certaines positions du maillage puis reconstitue une solution globale sous forme de matrice. Le logiciel HFSS a été conçu pour étudier l’évolution des champs électromagnétiques dans des structures 3D. Les éléments de base de ce logiciel sont des tétraèdres. Dans notre travail on a effectué deux applications, la première à l’aide d’une antenne à patch rectangulaire alimentée par une sonde coaxiale à l’entrée d’un micro ruban fonctionnant à une fréquence de 2.35 GHz et la seconde est alimentée par une sonde coaxiale au milieu du patch fonctionnant à 2.4 GHz. Les résultats de simulation numérique obtenus concernent le champ électrique, la densité de courant, le coefficient de réflexion, le diagramme de rayonnement. Ils sont en général en bon accord avec ceux trouvés dans la littérature. Voir les détails
Mots clés : Antennes imprimées, Caractérisation micro ondes, matériaux, hfss.
Experimental study of metal transfer of CMT welding
The CMT welding process was investigated in this work. The transfer of Al-4043 filler metal during welding was visualized using a high-speed camera with a green laser as an illumination source. Three phases was identified during the transfer cycle. A hot phase during which a molten droplet is formed on the end of the wire electrode under a high current. A cold phase corresponds to the move of the wire toward the weld pool. The contact between the droplet and the weld pool create a short circuit during which the material transfer is initiated and the arcing current reduced. After a set time (in the middle of the short circuit phase), the wire is retracted mechanically to contribute to the droplet detachment without increasing in current welding. The effect of the current waveform on the metal transfer is investigated too. The reduction in the hot phase duration of the current waveform decreases the volume of liquid droplets at the wire tip and allows to increase the short-circuit frequency. Voir les détails
Mots clés : CMT welding; waveform; current; transfer; phase; droplet
Effect of resistance spot welding parameterson mechancial behavior of thin sheet
Different welding methods have been developedfor joining stainless steels; however, resistance spot welding is thepromising method for welding of thin sheets of these steels.Resistance spot welding is a non-solder process that uses thecombined effect of mechanical pressure and an electric currentpassing through the parts. In this study, commercially 304Lstainless steel sheets were welded by resistance spot welding atvarious welding parameters (welding effort, welding times andintensity of current welding. The results showed that theparameters, effort and welding time have little effect onmechanical properties compared with respect to the effect of theintensity of the current welding. The experimental results showalso that the welding current is an important parameter forjoining structures and its mechanical strength. The hardness andexternal aspects of spot were carried out in order to examine theinfluence of welding parameters on the welded joints. Hardnessmeasurement results indicated that welding nugget had thehighest hardness and this was followed by the heat-affected zoneand the base metal. Voir les détails
Mots clés : resistance spot welding, hardness, mechanical strength, stainless steel, electric current, welding time
Impact of the heat treatments on the microstructure of the aluminum alloys 7075 T6 welded by the friction stir welding process
The welding process of the aluminum alloys 7075 T6 is increasingly used in the aeronautical industry. The use of the friction stir welding process (FSW) requires a good understanding of the microstructure generated by the rapid temperature rise in the heat affected zone and the thermomechanically affected zone of the used alloy. By applying the process of welding FSW, the characterization of the microstructure, because of the diversity of its components in terms of size and nature, requires the use of multiple techniques of investigations such as the use of optical microscopy and scanning electron microscopy for local approaches. It also requires the use of the impact strength test to assess the quality of the weld, to characterize the interaction between the material and the welding process, and to provide quantitative data on the welded joints behavior. Voir les détails
Mots clés : Aluminum alloys 7075 T6, Friction stir welding process (FSW), heat treatment, microstructure, Impact strength test.
Comparaison entre le soudage FSW et le soudageBout a Bout pour le polyéthylène à haute densité(PEHD)
L'objectif de cette étude est la maîtrise de la technique duSoudage par Friction Malaxage (Friction Stir Welding - FSW) etloptimisation des paramètres sur un polyéthylène à haute densité(PEHD). Ce procédé d'assemblage est basé sur le phénomène demalaxage provoqué par le passage de l'outil (pion), élémentessentiel de cette technique. Létude consistera à : 1. Réaliser dessoudures par le procédé FSW. 2. Étudier le comportementmécanique à la rupture des joints soudés. Afin de maîtriser etoptimiser le procédé en maitrisant la vitesse de rotation, lavanceet la plongée de l'outil.3. Réaliser des soudages bout à bout etfaire une comparaison entre les deux soudages Voir les détails
Mots clés : comparaison, soudage, FSW, bout a bout, PEHD
SEM/ DRX / EBSD charaterization of electricsubmerged arc welded of an industrial mow carbonsteel
In this study, we tried to understand the impact ofevolution of thermal deformation during the electric submergedarc welding process used to assembling parts. This weldingprocess is applied on an industrial low carbon steel of %C 0.19Wt, %Si 0.25 Wt, %Mn 0.40 Wt, %P 0.025 Wt, %S 0.015 Wt, %Al 0.09 Wt, %Mo 0.009 Wt, %Nb 0.05 Wt and % Ti 0.03 Wt.The plates with thickness of 2.6 mm, it is called BS2. And used bythe company SNS BAG destined for making gas storagecylinders.To highlight the present work, different areas of our specimenswere investigated especially fusion zone and heat affected zone.Characterizations performed are SEM, DRX and EBSD andshow the appearance and texture development during the weldprocess. Note that in this working part, the behavior of thermal Voir les détails
Mots clés : Low Carbon Steel, Electric arc welding, mechanical parameters, textural character formatting
Determination ofresidual stressby X-ray diffractionin a weld cordon
In this study, the implementation of the method fordetermining residual stresses by X-ray diffraction andapply it to the case of a bead of solder. Weldingprocesses induce changes in the microstructure andresidual deformations and stresses that it is so difficultto control that important To study this phenomenonof welding two pieces and low alloy low carbon, werewelded to the electrical arc with coated electrode ofmild steel. The morphology of the samples wascharacterized by optical and electron microscopy,showing the significant change in the microstructurein the different area of the cord. The hardness profilesobtained show that the hardness is stable (200 Hv) inthe base metal and increases in the cord (230 Hv). Inthis work, the X-ray diffraction was used to analyzethe residual stresses. The results of measurements onthe crude sample show that the constraints are allcompression, with a higher level in the side region tothe cord and in the base metal. The relief annealed at650 ° C relaxes the constraints to a lower level whileremaining compressive. These results show that thepresent solder interesting mechanical and structuralcharacteristics, having regard to the present ofresidual compressive stresses, the absence ofstructural defects and cracks. Which promotes goodperformance and long life of the part in its operation. Voir les détails
Mots clés : soudage, contraintes résiduelles, diffraction de rayon X, microscopie.
Study of intermetallic compounds of X182CrN11-1steel hot dipped into molten aluminum
Aluminum coating technique has been applied toimprove high temperature oxidation resistance of steels. Thismethod is adopted widely due to the low cost and goodperformance. The principle of hot-dip aluminizing isaccomplished by immersing materials into molten aluminumbath to form multiple aluminized layers on the surface ofmaterial by atomic inter-diffusion between dipped materials andaluminum. This work focuses on the study of intermetallic layersformed during the hot dip aluminizing of steel with 1.82 %carbon strongly combined with chromium (10.8 %) into a moltenaluminum bath. The X182CrN11-1 steel specimens wereimmersed into molten aluminum at 750°C for 1h, 2h and 3h.Intermetallic compounds were analyzed by optical microscopeand scanning electron microscope (SEM) coupled with energydispersive X-ray spectroscopy (EDS). This study is complementedby microhardness testing.The results showed that hot dip aluminized layer was dividedinto an outer pure aluminum topcoat and an intermetallic layer.This intermetallic layer consisted of an outer FeAllayer and aninner Fe2Al53layer with tongue/finger-like morphology and themicrohardness testing records high values of the intermetallicformed (through the) up to 800Hv0 Voir les détails
Mots clés : aluminizing, intermetallic, diffusion, steel, Microhardness