Sciences et génie des matériaux
Comportement mÈcanique et microstructural de soudure hétérogène.
Cette étude vise à étudier l'effet du métal fondu sur la microstructure et les propriétés mécaniques des soudures en utilisant un procédé de soudage TIG avec deux courants différents entre un alliage d'acier inoxydable AISI430 et un alliage de cuivre. Les joints de soudure ont été performé à l'aide de métal de soudure Ok 60, E316L, E2209L et Cu, Cu-Sn et E6010. Les propriétés mécaniques obtenues à partir des corrélations de dureté, de traction et d'image ont été corrélées à la microscopie optique et MEB, pour établir une relation entre la composition du métal soudé et les microstructures dans différentes régions de soudure. Il est conclu que le métal fondu conduit à une amélioration des caractéristiques mécaniques et de la ténacité avec une légère réduction de la résistance à la traction et de la dureté. Voir les détails
Mots clés : soudage TIG, comportement mécanique, microstructure, corrélation d'image.
Characterization and analysis of novel natural cellulosic fiber extracted from Strelitzia reginae plant
The purpose of this study is to evaluate in detail the usability of new cellulosic fibers extracted from the stem of the plant Strelitzia reginae, as a potential reinforcement for polymer composites. The morphological, physical, thermal, and mechanical properties of fibers were addressed for the first time in this paper. Both untreated and alkali-treated fibers were characterized, using scanning electron microscopy (SEM), Fourier-transform infrared, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), optical microscope, and X-ray diffraction (XRD) and applying tensile test for determining the mechanical behavior. For both fiber treated at one hour (T1H) and at four hours (T4H), the stem anatomy and fiber SEM micrographs showed a strong presence of fiber cells. Thermogravimetry and DSC showed that the fiber was thermally stable up to 233°C for untreated fiber, 254 and 240°C, respectively, In single-fiber tensile tests, it was observed that the fibers extracted from the stem of Strelitzia reginae were strong. The mean values of Young’s modulus exhibited by untreated fibers and treated (T1H) and (T4H) are, respectively, 9.89 GPa, 12.08, and 18.39 GPa. Also mean values of tensile strength are 271.79, 306.23, and 421.39 MPa. The XRD reveals the presence of cellulose with a Crystallinity Index of 70% for raw fiber and 72% for the treated one. Fourier-transform infrared analysis well demonstrated the effect of chemical treatment. It can be concluded from the results of all above experiments that the Strelitzia reginae fibers (SR) could serve as a possible reinforcement in composite materials. Voir les détails
Mots clés : natural fibers, Biocomposite, Surface analysis, SEM, FT-IR, thermal analysis, TGA, XRD, DSC
Etude D’efficacité D’inhibiteur NALCO E1154A Sur L’acier A36 Utilisé Dans Les Bacs De Stockage Des Hydrocarbures Du Site GTFT-ILIZI
The corrosion of the condensate and LPG storage tanks in the GTFT zone presents a major problem that leads to a degradation of the storage tanks where huge sums are spent annually to protect the structures against corrosion, The maintenance and repair of the storage tanks. storage systems go through a detailed inspection program in order toobtain the data necessary to be properly adapted, today corrosion protection includes treatments such as cathodic protection, surface treatments or even the modification of the corrosive environment by addition of corrosion inhibitors. These constitute an original means of combating corrosion.In order to test the effectiveness of NALCO 115 EC 1154A inhibitor on A36 steel for use in the protection against corrosion of storage facilities for hydrocarbon products inthe GTFT zone, we were interested in this study to seek the optimal concentration in order to perform electrochemical tests. Voir les détails
Mots clés : corrosion, storage bins, inhibitors, A36 steel
Elaboration et Caractérisation des Cuprates Supraconducteurs de type YBCO
In this work, we prepared YBCO samples by sol-gel process and the gel decomposition studied by TG/DSC, which shows the X-ray diffraction due to the fact that the samples contained a preponderant phase (YBa2Cu3O7). SEM images showed the polycrystalline structure of samples with grain size between 2 and 3 µm and high porosity rate. Longitudinal and transverse ultrasonic velocity and attenuation measurements were performed on 3 mm thick samples. The experiments were performed at room temperature (300 K). The objective of this technique is ultrasonic characterization. Voir les détails
Mots clés : YBCO, sol-gel, XRD, DTA, Ultrasound
Effect of WC-Co cermet positioning and NiCr interlayer on the microstructure and mechanical response of the dissimilar WC-Co / AISI 304 L rotary friction joint
In this work, incompatible properties of WC-Co cermet and AISI 304 steel were combined in the same component using rotary friction welding (RFW) process. The dissimilar joints were performed using a ductile NiCr interlayer with the change in the WC-Co cermet positioning i.e., fixed rotary side and feeding side. Similar microstructure across the weld joints was obtained of the different welding configurations that produced similar behavior in hardness and elastic modulus. A diffusion zone was formed at the weld interface as a result of the mutual inter-diffusion of both cermet (W and Co) and steel elements (Fe, Cr and Ni) that enhanced with the insertion of the interlayer when the cermet was fixed in rotary side. The introduction of the NiCr interlayer was beneficial to relax the residual stresses and improving the shear strength of the WC-Co cermet/AISI 304L steel joints, which is promising technology for drilling tools industries. Voir les détails
Mots clés : Rotary friction welding, WC-Co cermet, mechanical properties, NiCr interlayer, Interface
Effect of WC-Co cermet positioning and Ni-Cr interlayer on the microstructure and mechanical response of the dissimilar WC-Co / AISI 304 L rotary friction joint
In this work, incompatible properties of WC-Co cermet and AISI 304 steel were combined in the same component using rotary friction welding (RFW) process. The dissimilar joints were performed using a ductile NiCr interlayer with the change in the WC-Co cermet positioning i.e., fixed rotary side and feeding side. Similar microstructure across the weld joints was obtained of the different welding configurations that produced similar behavior in hardness and elastic modulus. A diffusion zone was formed at the weld interface as a result of the mutual inter-diffusion of both cermet (W and Co) and steel elements (Fe, Cr and Ni) that enhanced with the insertion of the interlayer when the cermet was fixed in rotary side. The introduction of the NiCr interlayer was beneficial to relax the residual stresses and improving the shear strength of the WC-Co cermet/AISI 304 L steel joints, which is promising technology for drilling tools industries. Voir les détails
Mots clés : Rotary friction welding WC-Co cermet NiCr interlayer Interface Microstructure Mechanical properties
Dissimilar FSW of AA2024 and AA7075: Effect of materials positioning and tool deviation value on microstructure, global and local mechanical behavior
In this work, the effect of material location and tool deviation on the global and local mechanical behavior of dissimilar AA2024/AA7075 friction stir weld joints was investigated. The results showed that increasing the tool deviation value up to 1mm towards the AA2024, fixed in advancing side, improved the material mixing quality and enhanced the grain refinement in the stir zone. It was found that the highest ultimate tensile strength was obtained when the AA2024 alloy was fixed in the advancing side for 1mm tool deviation towards this material. Above this deviation value, a gradual decrease of the global mechanical properties of the weld joints was noticed. Digital image correlation (DIC) technique coupled to tensile testing revealed an improvement of local strain in the stir zone and the heat affected zones of the dissimilar joints when AA2024 alloy was positioned in the advancing side. Voir les détails
Mots clés : Dissimilar friction stir welding, tool deviation, DIC, mechanical properties, microstructure
Rotary friction welded C45 to 16NiCr6 steel rods: statistical optimization coupled to mechanical and microstructure approaches
In the present work, the dissimilar joints between C45 carbon steel and nickel-chromium 16NiCr6 steel rods were produced usingrotary friction welding process. Statistical analysis based on response surface methodology (RSM), microstructural examinationusing scanning electron microscopy with backscattered electron diffraction (EBSD) and mechanical tests were performed toinvestigate the friction weld joints. The results showed that friction time and rotation speed were the most effective parameters onthe weld joint quality with the highest t-ration of − 4.27, where the maximum bending strength of 1406.9 MPa was obtained at2000 rpm for 13 s friction time. Increasing friction time to 13 s resulted in remarkable decrease in grain size (about 35%) at theweld interface, which increased the hardness (350HV0.1) and elastic modulus (260 GPa). Voir les détails
Mots clés : Rotary friction welding . RSM methodology . Microstructure
Mise en œuvre de l’essai de fatigue sur des alliages d’aluminium
The problem of fatigue of structures is commonly present in all sectors of the maritime, aeronautical, and mechanical and many other industries. In order to fully understand this harmful phenomenon, tests of different types of stresses are carried out at the laboratory level. This requires a good mastery of the test protocol. The analysis of the results obtained by these tests allows to study the behavior of the material. Our study consists in the implementation and the determination of the operating conditions of a uniaxial fatigue test with two types of specimens made of aluminum alloys of different thicknesses are tested. A tensile test is carried out to determine the mechanical behavior of the specimens and to have the necessary parameters to carry out a fatigue test, a metallographic study to characterize the specimens before carrying out the fatigue test. All the results obtained from the test are in the form of curves and a hysteresis loop. Voir les détails
Mots clés : Fatigue test, fatigue of aluminum, aluminum’s alloys
Préparation et caractérisation des nanoparticules de ferrite de nickel dopée au Cérium par la méthode de coprécipitation
Nanocrystalline powders of cerium-doped nickel ferrite were synthesised by the coprecipitation method and the effect of the non-magnetic cerium content on the structural and magnetic properties was studied. X-ray diffraction (XRD) was used to determine the structure of NiFe2O4 nanoparticles. The surface morphology and chemical composition of the NiFe2O4 nanoparticles were obtained by scanning electron microscope analysis. The magnetic properties were studied by Vibrating Sample Magnetometry (VSM). Magnetic hysteresis cycles were measured with a maximum applied magnetic field of ≈ 1000Oe Voir les détails
Mots clés : NiFe2O4, cerium, co-precipitation, Magnetic Properties, DRX, SEM, VSM