Liste des communications
Segmentation of the Weld Radiographic Images by the Level Set Method using the Kernel Fuzzy C-Means Clustering.
In this paper, we are interested to segment weld radiographic images using the level set method (LSM) based on kernel fuzzy c-means clustering (KFCM) in order to extract the region of interest (weld defects) and to improve the precision of segmentation. The proposed approach contains two successive necessary stages. The first one consists in the application of kernel fuzzy c-means algorithm to get a clustered image. The second stage is based on the using of the appropriate class of the clustered image as an initial contour of the level set method to extract the defects boundaries. The experimental results have shown that the proposed model can extract successfully the interest region from image and confirm its efficiency for welding defects segmentation. Voir les détails
Mots clés : Level set, kernel fuzzy c-means, weld defects, weld radiographic images, image segmentation
NDT CHARACTERIZATION OF NANOCOMPOSITE
Nanostructured materials are current topics in research and development in recent years because of the good mechanical and physical properties compared to crystalline materials. The nanocrystalline coatings may show increased hardness, good mechanical strength [1], good corrosion resistance and the oxidation resistance, and / or good behavior to friction and wear [1,2]. In particular, nanostructured materials have good properties in tribology, motor vehicles, heavy machines and cutting tools, etc. that require advanced materials functioning with minimum energy loss. Nanostructured coatings such tribological surfaces for use in contact with harsh conditions were searched intensively for the past decade. PVD and CVD are well-known methods for depositing such [3] coatings. However, the drawbacks associated such that the deposition sector size, substrate geometry, cost and complexity of the process often limit their use. In this perspective, the deposit by thermal spraying gives much attention. The different materials Metal, ceramics or cermet [4], nanostructured coatings were deposited by thermal spraying processes such as HVOF. In addition, the properties of these coatings have been found to strongly depend on the porosity, of the phase distribution, and the residual stress [5-6]. Voir les détails
Mots clés : Nanostructured materials, alumina, Mechanical Alloying, MEB, EDX, DRX, VSM
PRISE EN COMPTE DE L’ASPECT NON LINÉAIRE DANS L’ANALYSE MODALE DES STRUCTURES MÉCANIQUES
La connaissance des caractéristiques modales est primordiale dans l’étude du comportement dynamique des structures. L’application de l’analyse modale a été souvent réservée au domaine linéaire. Cependant, la plupart des structures mécaniques, rencontrées dans la pratique, présentent un comportement plus ou moins non linéaire. L’aspect non linéaire est d’origines diverses, dépend de plusieurs facteurs et peut se manifester globalement (géométrie, propriétés mécaniques,…) ou localement (conditions aux limites, joints, …).Dans ce travail, nous avons applique l’analyse modale a des systèmes vibratoires discrets (masse-ressort) non linéaires d’aspect géométrique.Plusieurs méthodes ont été utilisées pour déterminer les paramètres modaux, a savoir :- Balance harmonique (analytique).- Variété de l’invariant de Shaw-Pierre (numérique).- Range Kutta d’ordre 4.Des programmes ont été établis sous matlab pour exploiter ces méthodes. Les résultats obtenus nous ont permis de préciser :- la limite entre les systèmes linéaires et non linéaires.- l’effet des conditions initiales et le paramètre non linéaire.- domaine d’application des méthodes permettant l’étude des systèmes non linéaires. Voir les détails
Mots clés : analyse modal, Non linéarité, vibration, Paramètres modaux (Fréquences et Modes propres)
ANALYSE DU PIGMENT DE FER ROUGE ET LA CALAMINE POUR LA FABRICATION D’UNE PEINTURE
Ce travail a un double objectif. D’une part la valorisation des matières premières naturelles et d’autre part le recyclage des sous-produits sidérurgiques (calamine). L’objectif étant la synthétisation d’une peinture anticorrosive.Dans cette première partie, nous étudierons la caractérisation de ces deux composants par leurs broyabilités (finesse), leurs analyses chimique, leurs analyses thermique (ATG, DSC), leurs structures morphologique et leurs cycles d’hystérésis. L’analyse chimique a montré que le pigment contient 53,18 % de fer total et une gangue dominée par la silice. La calamine quant à elle contient 73,83 % de fer sous forme d’oxydes de fer (FeO, Fe3O4 et Fe2O3). Les essais d’aimantation ont montrés que la calamine est ferrimagnétique du fait qu’elle contient de la magnétite. Le pigment de fer est composé principalement d’hématite avec très peu de goethite est classé dans la catégorie des antiferromagnétiques. Des essais de broyabilités ont montré que la calamine est beaucoup plus apte au broyage que le pigment. L’analyse granulométrique mesurée par un granulométre laser (Hydro 2000MU), nous a donné une distribution volumique des particules avec une taille comprise entre 0.7 et 32 µm pour la calamine et entre 0,6 et 40µm pour le pigment.Ainsi les diamètres moyens sont de 3,75 µm et 4,01 µm pour la calamine et le pigment broyés respectivement à 01 et 05 minutes. Leurs surfaces spécifiques sont de 1,6 et 1,5 m2/g.L’analyse thermogravimétrique (ATG) et la variation thermique de flux (DSC) ont montré que le pigment de fer perd du poids avec dissolution de phase en consommant de l’énergie quand la température augmente. La calamine gagne en poids par la formation de nouvelle phase avec dégagement de chaleur. Voir les détails
Mots clés : Pigment de fer, calamine, oxydes de fer, broyage, granulométrie, thermogravimétrie
Comparative study of optical properties of In0.25Ga0.75As and In0.75Ga0.25As in zinc-blende phase by first-principles calculations
The full-potential linearized augmented plane wave method (FP-LAPW) within Density Functional Theory (DFT) framework as implemented in the WIEN2K computational code is used in order to study the structural, electronic and optical properties of In0.25Ga0.75As and In0.75Ga0.25As ternaries alloys. The structural parameters such as lattice parameters, bulk modulus, and its pressure derivative were extracted using the Local Density Approximation (LDA)3, and the one of Wu and Cohen (GGA-WC) for the exchange-correlation (XC) functional. In addition, the electronic and the optical properties of our compounds were obtained by using the new semi-local modified Becke–Johnson potential (TB-mBJ) developed by Tran and Blaha. The performed results were compared with experimental data and other computational works. Consequently, our computations of the equilibrium lattice parameter and bulk modulus generally give a good agreement with the experimental measurements. For electronic and optical properties, we deduced that the TB-mBJ approach is relatively more suitable for the properties of our both ternaries alloys. Voir les détails
Mots clés : DFT, FP-LAPW, InGaAs, Optical parameters
Mean Scatterer Spacing For Human Liver Tissue Characterization Using Backscattered Ultrasound Signals
We studied the periodicity of in vitro healthy and pathological liver tissue using the backscattered ultrasound signals. Lot of signal processing methods are used to mean scatterer spacing (MSS) as a parameter of tissue characterization, we cite: Spectral Auto-Correlation (SAC), Spectral Correlation of the autoregressive model (AR-SAC) and others. We used the Discrete Wavelet Technique (DWT) to MSS estimate, in comparison, the DWT with Fourier Transform together (DWT with FT) can provide a very effective tool to extract the MSS from such structure and characterize the tissue Voir les détails
Mots clés : Periodicity, Liver tissue, Mean scatterer spacing, Backscattered Ultrasound Signals
Faults Diagnosis of Rolling Bearing Based on Empirical Mode Decomposition: Optimized Threshold De-noising Method
The faults of rolling bearings frequently occur in rotary machinery, therefore the rolling bearings fault diagnosis is a very important research project. The vibration signal is usually noisy and the information about the fault in the early stage of its development can be lost. A threshold de-noising method based on Empirical Mode Decomposition (EMD) is presented in this paper. Firstly, the signal is decomposed into a number of IMFs using the EMD decomposition .Secondly the algorithm based on the energy to determine the trip point is designed for IMF selection, then, by comparing the energy of the selected IMFs with excluded IMFs, singular selected IMFs are dealt with soft threshold function, and finally the de-noised signal is obtained by summing up the selected IMFs, it is proved that the best IMFs can be summed up and properly de-noised by the proposed method .The results show the effectiveness of the proposed technique in revealing the bearing fault impulses and its periodicity for both simulated and real rolling bearing vibration signals. Voir les détails
Mots clés : bearing fault detection, EMD, threshold De-noising, IMF selection, Singular IMF
Study of microscopic and thermal properties of iron-based powders obtained by high-energy ball milling of Calamine
Abstract:This study was carried out with an intention to prepare iron-based powders from metallurgy industry waste called Calamine. The latter consists of oxides scale formed on the surface of hot rolled steel. The mechanical alloying process used in this work is high-energy planetary ball mill.Morphological and thermal shifts of the milled oxides scale powders were characterized by optical microscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The results showed that the oxide scale contains more than 98% of iron. Voir les détails
Mots clés : calamine, iron-based powders, mechanical alloying scanning electron microscopy, thermal analysis
Study of physico-chemical properties of diatomite Algeria: Application to the thermal insulation of liquid steel bath
The purpose of this paper is to characterize and to evaluate the diatomite powder of Sig region (West Algeria) without fluorine by powder generally used in tundish to thermal insulation of steel bath contain fluorine, that affecting the environment and health of workers. Thermal and physicochemical characterization showed different endothermic and exothermic peaks. The scanning microscopy method was used and a large porosity was observed, which is very beneficial for improving the thermal conductivity of the product. The trial industrial in steelwork with diatomite powder, showed a weak loss temperature of steel (10 °C max), and filled fully function in thermal insulation of the steel bath. Voir les détails
Mots clés : diatomite, fluorine, Tundish, steelwork, thermal insulation, DSC
Condition Monitoring and Fault Diagnosis of Bearing Using Hybrid Method Based on EEMD and Minimum Entropy Deconvolution
The application of vibration signals is power tool for diagnostic of bearing defect, however this signal is usually noisy and the information about the fault can be lost.This paper presents a novel method based on ensemble empirical mode decomposition EEMD and the minimum entropy deconvolution (MED) . MED technique is used to denoise the vibration signals, and the filtered signal is decomposed into a number of IMFs using the EEMD decomposition. The selection of the relevant modes is dependent on the correlation coefficient between the IMFs and the filtered signal. The experimental results show that the roller bearing fault features can be extracted effectively by this method Voir les détails
Mots clés : Empirical Mode Decomposition, minimum entropy deconvolution, bearing faults, correlation coefficient