Sciences et génie des matériaux
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.
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
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
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.
Extraction of green inhibitor and study of their antioxidant effectiveness of ecologicalcorrosion
Several methods are available to prevent or retard corrosion ofmetallic materials, the use of inhibitors is one of the besttechnique to ensure their protection in contact with aggressivemedia such as hydrochloric acid medium. The environmentaltoxicity of organic corrosion inhibitors has prompted thesearch for green corrosion inhibitors as they are biodegradable,do not contain heavy metals or other toxic compounds. As inaddition to being environmentally friendly and ecologicallyacceptable, plant products are inexpensive, readily availableand renewable. The objective of this work is the extraction oflimonene from orange peels and study their effectiveness onthe corrosion of X42 steel in HCl medium. The analysis ofinhibitor was evaluated by chemical methods, and theelectrochemical study shows that the addition of limonene tothe medium induces a reduction in the corrosion rate of thesteel in HCl medium. Other parameters may influence itsinhibitory activity such as immersion time, concentration ofinhibitor, the nature of media (acidic or basic). Voir les détails
Mots clés : Metal and alloys; Acid medium; corrosion inhibitors; Green inhibitors; limonene
EVALUATION OF MECHANICAL STRESS EFFECT ON THE PROPERTIES OFSTAINLESS STEEL SURFACES BY SECM, SKP, SVET AND LEIS
Mechanical stress or fatigue cracks originate from varioussurface imperfections, such as inclusions, pits, or residualstress. It is very important to use a method to predict thelikelihood of environment-assisted cracking or pitting corrosion.The austenitic stainless steel shows high corrosionresistance level. It knows that plastic deformation decreaseit's resistance. The corrosion form in case of this steel is veryspecial and the corrosion tests are difficult. The investigationof Scanning Kelvin Probe (SKP), s canning vibrationelectrode technique (SVET) and localized electrochemicalimpedance spectroscopy (LEIS) to evaluate the influence ofmechanical stress on the electrochemical properties ofaustenitic stainless steel 316L.We tested the selected steel about its corrosion behaviour afterhigh rate deformation. We wanted to find a relationshipbetween the corrosion resistance decreasing and the rate ofthe plastic deformation. Plastic deformation effect of thecorrosion resistance in case of austenitic stainless steel Voir les détails
Mots clés : SKP, SVET, LIES, corrosion, austenitic, plastic deformation 316
RISK OF CONTAMINATION OF ANNABA CITY LITTORAL BY THE MILL SCALE
A significant amount of scale is produced during casting of ingots and processing of hot-rolled products. In the El Hadjar steel complex, during the various rolling operations, the amount of scale produced is approximately 0.1% of the annual production of the rolling mills. The quality of the thin sheet during rolling is affected by the behavior of the iron oxide layers formed on their surfaces. For this reason,acids and oils are used for the descaling of slabs and billets by means of pressurized water. The calamine, contaminated by these various acids and used oils, is rejected and stored involuntarily on important areas and pollutes soil and groundwater. Micrographic observations as well as X-ray diffraction analysis have shown that calamine consists mainly of iron oxides. Hematite and magnetite become the main components for oxidation times greater than 1 hour. Characterization tests have shown that calamine is dense (ρ = 4.8 g cm3), its particle size is variable depending on the degree of oxidation (from 0.5 to 10 mm). Simultaneous thermal analysis showed that an increase in mass of the calamine sample with a release of heat. Studies are underway for the physico-chemical characterization of the soils of the storage areas. Voir les détails
Mots clés : Scale, Risks, soil, thermal analysis, granulometry, X-ray diffraction
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
Effect of brazing current on microstructure and mechanical behavior of WC-Co/AISI 1020 steel TIG brazed joint
In this work, the WC-Co carbide/1020 steel brazed joints which were prepared by Tungsten Inert Gas (TIG) process using different brazing currents have been studied. The peak temperature reached by increasing the brazing current caused remarkable inter-diffusion of Ni, Mn, Cu and Co elements between the braze and the base materials. The higher the brazing current was, the larger the diffusion extent of these elements became and the greater the WC rearrangement occured. As the diffusion rate of Ni towards the WC-Co was enhanced through increasing brazing current, a short range diffusion of Co element towards the braze was recorded. A Special Shear Test (SST) conducted at room temperature revealed the best bonding strength for the current of 80A. Besides, hardness (HIT) and elastic modulus (EIT) values of the interfaces were situated between those of the braze and the base materials. Voir les détails
Mots clés : WC-Co cemented carbide, TIG brazing, inter-diffusion, Interface, Nano-indentation
Valuation of mill scale as iron pigments for painting anticorrosive.
The mill scale is a steelmaking byproduct. This work focuses on the valuation of the steel waste and its transformation to a usable product in the field of anti-corrosion paints. These iron oxides have been examined as a pigment and corrosion inhibitor in two types of paints with different concentrations (1 %, 3 %, 7 %, and 15 %) to determine the best formulation. Their properties were compared to that of an anticorrosion paint trademark based on iron oxide. For this purpose various techniques of mechanical and physical-chemical analysis were used; grinding is applied to pieces of mill scale for very fine powders (< 32 μm); the particle size of the milled scale analysis, to determine their particle size distribution; a primary electrochemical method used to evaluate the performance and scale vis-à-vis the phenomenon of corrosion behavior, and a UV-Visible spectroscopic method for determining the concentration of total dissolved iron. The experimental results showed that the anti-corrosion properties or rather inhibition efficiency increases with increasing concentration of the mill scale in the tested paints. Voir les détails
Mots clés : mill scale, corrosion inhibitor, spectroscopic, electrochemical analysis