Sciences et génie des matériaux
Modal Analysis For Composite Sandwich Plates Of Honeycomb Core
.The purpose of this work is to realize a vibratory study on panel’s sandwiches established by the honeycomb core and aluminum skins, used in the conception of the aerospace structures; all the analyses are based on conditions in the embedded free limits (E-L-L-L). The aim is to compare the natural frequencies of the two plates with those obtained from the two simulation models. Two methods are used in modeling, 3D drawing of the sandwich structures and calculating an equivalent structure using the homogenization method based on representative elementary volume (REV) using ANSYS software. The modal resolution of these two configura-tions is performed by the finite element method. The comparison of numerical results shows excellent agreement. Voir les détails
Mots clés : Sandwich plate, homogenization, FRF's, modal analysis, Finite element method.
Corrosion of AISI4130 in différents électrolytiques solution
This article discusses the electrochemical behavior of AISI 4130 alloy steel in various electrolyte solutions H2SO4, HCl and NaCl. Corrosion tests were carried out on a potentiostat / galvanostatat room temperature in the various electrolytes, under an Ag / AgCl reference electrode with .Electrochemical Impedance Spectroscopy (EIS) measurement. The results obtained through the tafel curves show that the corrosion process can be divided in two parts highlighting the aggressivity of Cl- ions. The impedance which is characterized by a large semicircle in the Nyquist graph increases under H2SO4.Equivalent circuits have been determined to represent the corrosion processes at differente ectrolytes. Voir les détails
Mots clés : AISI 4130, electrolytes H2SO4, HCl and NaCl
Image compression of Surface defects of the hot-rolled steelstrip using discrete Cosine Transform and Discrete Wavelet Transform
Automatic quality control of surface of hot rolled steel using computer vision systems is a real timeapplication, which requires highly efficient Image compression techniques in order to improve the data transmissionand storage capacity.In this work, two image compression methods are simulated. They are Discrete Cosine Transform(DCT) and Discrete Wavelet Transform (DWT).The results of simulation are shown that The Discrete WaveletTransform (DWT) technique given improved result compared with Discrete Cosine Transform (DCT). Voir les détails
Mots clés : Automatic quality control, Computer vision, image compression, Cosine transform, wavelets transform
Image compression of Surface defects of the hot-rolled steelstrip using discrete Cosine Transform and Discrete WaveletTransform
Automatic quality control of surface of hot rolled steel using computer vision systems is a real timeapplication, which requires highly efficient Image compression techniques in order to improve the data transmissionand storage capacity.In this work, two image compression methods are simulated. They are Discrete Cosine Transform(DCT) and Discrete Wavelet Transform (DWT).The results of simulation are shown that The Discrete WaveletTransform (DWT) technique given improved result compared with Discrete Cosine Transform (DCT). Voir les détails
Mots clés : Automatic quality control, Computer vision, image compression, Cosine transform, wavelets transform.
Investigation of WC decarburization effect on the microstructure and wear behavior of WC-Ni hardfacing under dry and alkaline wet conditions
The performance of drilling tools hardfacing in different conditions is strongly related to microstructural aspect of the coating and to the adhesion with the substrate. In the present investigation, the manual oxy-acetylene brazing process was employed for AISI 1020 steel hardfacing using WC-Ni. The substrate/hard facing interface was particularly studied which was a Ni-Cr-Al-Mo interlayer prepared by flame thermal spray method. The microstructural results exhibit a good embedding of WC particles into the Ni matrix, where the inter-diffusion of Ni, Cr, and Fe elements at the interface is enhanced using the interlayer. The dissolution and decarburization phenomena of WC particles with the formation of W2C eutectic phase and their effect on the decohesion and pull out of the particles during the wear test were studied. The hardness (HIT) and Young's modulus (EIT) of different parts of the hardfacing were investigated by instrumented nanoindentation. The wear resistance of the surface coatings under alkaline condition using sodium hydroxide (NaOH) basic solution of pH?=?12 is two times higher than under dry condition. Furthermore, the formation of SiO2 third body stripes along the wear track promotes the decrease of the friction coefficient and the volume loss. On the other side, the wear mechanism is adhesive with severe plastic deformation of the Ni matrix in dry condition and oxidative/abrasive wear in alkaline wet condition. Voir les détails
Mots clés : Interface, WC dissolution, Hardfacing, inter-diffusion, Decarburization
Simplified Modelling of Tandem Cold Rolling
In this paper, a calculation technique for solving the problem of regulatinginter-stand tension in a tandem cold rolling is proposed. Based on the slicesmethod, the proposed technique develops a computational model for a singlestand, and then generalizes it for five stands. The effectiveness of this technique is evaluated using experimental data acquired from tandem rolling millof IMittal steel complex of El-Hadjar-Algeria. By taking into account theelasticity of the rolls and using Newton’s method; the developed model can beused to calculate, successfully, the tensions correction of the five stands.Compared with the LAM3 software, the obtained results indicated that theproposed technique is effective and can be used to produce better performance of tandem cold rolling. Voir les détails
Mots clés : modelling, tandem cold rolling, slices method, elasticity, Newton’s method.
Thermal spray metallisation of carbon fibre reinforced polymer composites Effect of top surface modification on coating adhesion and mechanical properties
Thermal Spray TS processes are used to enhance the surface properties of Polymer Matrix Composites. However, poor adhesion and mechanical degradation are usually experienced. The main objective of this work is to investigate the effect of the modification of the top surface of Carbon Fibre Reinforced Polymer CFRP substrate on the TS deposition of metallic coatings. CFRP composite panels were manufactured with different upper layers I pure epoxy overflow layer, II pure copper powder filler layer, III mixture copper and stainless steel powder filler layer, and IV aluminium mesh layer. The top layers of the CFRP substrates were manufactured during the forming process. Arc Spray, one of the TS processes, was used to deposit zinc coating onto the manufactured CFRP panels. The substrates were sandblasted before the TS process to enhance the adhesion of the deposited zinc to the substrate. The quality of the coatings including adhesion and mechanical properties was investigated using tensile adhesion and bending test, respectively. The porosity, microstructure, morphology and surface fracture of the metallised CFRP coupons were characterized using optical and electronical microscopy techniques. The results obtained revealed that pure epoxy top layer did not resist to sandblasting prior to TS process, contrary to the substrates with fillers and mesh top layer. Moreover, the aluminium based mesh layer improved the adhesion strength by about 50 percent. Bending test results indicated that coating on CFRP composites decreased their mechanical properties. However, the use of a metallic mesh layer reduced the degradation effect of spraying. Voir les détails
Mots clés : CFRP composite, Zn coating, Arc spray, Filler layer, Adhesion strength
Experimental investigation of the polymer material (HDPE) behavior welded by FSW
This work contributes in the knowledge of the process of friction stir welding, and its use for the first time in a polymer material, it is the high-density polyethylene material widely used in gas transport and other applications. Welding and friction stir is a rapid and a controlled process to achieve strong and sustainable mechanical connection plates welded on. Simple Tensile tests were conducted in order to characterize the parameters of HDPE welded and not welded. We found that the FSW can be used in the welding of this material. Voir les détails
Mots clés : HDPE, welding, FSW
Dephosphorization of Western Algerian Oolitic iron ore
A Combination of roasting and acid leaching processes was tested for the dephosphorisation of Gara Djebilet oolitic iron ore (Algerian Western Sahara) that contains a high phosphorus content of 0.91% which exceed-acceptable limits. A laboratory scale, this process involving a chemical attack after roasting of the raw sample of iron ore that mixed with alkaline additives (CaCl 2 or NaCl) followed by an acid leaching using nitric acid, perchloric acid, hydrochloric acid and sulfuric acid. 89% of phosphorus is removed by the addition of the salt (NaCl) then attacked by nitric acid. The laboratory tests carried out for a dephosphorisation show that the combination of roasting with alkaline additives, followed by an acid leaching makes it possible to obtain high quality iron concentrate. Despite the phosphorus content decreases from 0.91 to 0.1%. Voir les détails
Mots clés : Oolitic iron ore, acid leaching, dephosphorisation, alkaline additive.
Exploitation des sous-produits sidérurgiques du complexe Elhadjar -Annaba-.
Le présent travail de recherche se base sur l'exploitation du sous-produit sidérurgique (calamine) et sa transformation en produit utilisable dans le domaine des peintures anticorrosion. Ces oxydes de fer ont été examinés comme pigment et inhibiteur de corrosion dans deux types de peintures à concentrations différentes (1%, 3%, 7%, 15%) pour déterminer la meilleure formulation. Le meilleur temps de broyage de calamine est 2 minutes avec une distribution volumique D(0,9) des particules à une taille inférieure de 32 micromètre et une surface spécifique égale à 1.6 m2/g. L’analyse chimique montre une teneur en fer total moyenne de 72 % et des faibles teneurs en des oxydes de manganèse et de silice. L’analyse électrochimique a prouvé que les propriétés anticorrosives ou plutôt le rendement d’inhibition augmentent avec l’augmentation de concentration de la calamine dans les peintures testées (15% pour Glylac et 7% pour Glycar). Voir les détails
Mots clés : calamine, agent anticorrosif, analyse granulométrique, analyse électrochimique.