Liste des publications
Notch detection in copper tubes immersed in water by a compressional guided waves
Tube- or pipe-like structures are used to convey fluids such as gas, oil or water. These fluids can be transported on land, in sea or in industrial buildings. Hence, tubes can suffer from mechanical, thermal and chemical stresses. The latter, can severely damage these structures due to the oxidation phenomena. This damage weakens the structure and reveals cracks and inhomogeneities. The objective of this work is to detect and characterise damage in tubes immersed in water by a non-destructive method. This research work is devoted to the development of an experimental device. This device can detect and locate axy- and nonaxy-symmetric circumferential small notches located on the outer surface of a filled tube and immersed in water using guided waves. Different sizes of notches are milled into copper tubes with a thin wall are considered. A single transducer is used for emission and reception of leaky guided waves by using the pulse-echo technique. The compressional L(0,2)mode is launched at relatively high frequency using oblique incidence of the transducer into the fluid. By using the wave leakages, notches of small sizes are detected and located. In addition, the sensitivity of the L(0,2) mode to the radial depth and circumferential extent of notches is evaluated. A roughly linear behaviour of the amplitude reflection coefficients is revealed which is in accordance with research works found in the literature. Voir les détails
Mots clés : guided waves, Immersed tubes, Circumferential notches, Experimental device
Élimination du manganèse en solution par le kaolin« Étude cinétique et thermodynamique »
Le kaolin purifié et traité par HCl 0,4 M, a été utilisé comme adsorbant pour éliminer lemanganèse contenu dans les eaux de rejets. La caractérisation physico-chimique a montré quele kaolin de Guelma est constitué en majorité de silice et d’alumine. Sa surface spécifiquemesurée est plus importante pour un kaolin purifié et activé. Le processus envisagé en régimestatique, montre qu’un gramme de kaolin peut fixer selon le modèle de Langmuir premièreversion, jusqu’à 38,23 mg de manganèse avec une cinétique de pseudo 1er ordre. Le temps depseudo équilibre est de 20minutes. Rapport RL montre une bonne affinité du kaolin vis-à-visà l’adsorbat. Le transport externe des ions métallique considérés de la solution versl’adsorbant semble une étape contrôlant la vitesse du processus globale. Cependant, letransport interne dans les pores n’est pas le seul mécanisme limitant de la cinétique desorption. Les paramètres thermodynamique montrent que cette adsorption est spontanées,exothermique et qu’aucun changement n’a été effectue au niveau de sa structure (ΔS<0).L’énergie d’activation est de l’ordre de 27,79 kj/mole Voir les détails
Mots clés : Kaolin, manganèse, adsorption, eau, pollution
Inverse problem for material analysis by ultrasound
Internal defects detection by ultrasound non destructive testing is widely used in industry. Ultrasonic time signal data are diffi cult to interpret since they require continuous signal analysis for each point of the piece. Inverse problem in materials analysis puts some challenges because the composition variables are both discrete and continuous and because the engineering properties are highly nonlinear functions. In this paper we address the non linear features of back scatted ultrasonic waves from steel plate, for understanding its micro structural behaviour. The experiments show a challenging interface between material properties, calculations and ultrasonic wave propagation modelling Voir les détails
Mots clés : PACS: 43.25.Hg ; 43.35.Zc ; 43.60.Hj ; 43.60, Multiscale analysis • Structural noise • Ultrasonic NDT/NDE • Wavelet
Amélioration de la qualité de surface par le procédé de brunissage
La vie d'un matériau en service dépend non seulement de la combinaison des facteurs de charge et d'environnement auxquels il est soumis mais aussi de l'état de surface. Donc la caractérisation de la surface (rugosité, et défauts de surfaces) est importante pour relier le processus de fabrication aux propriétés en service, ainsi le procédé de traitement mécanique "brunissage" peut améliorer les caractéristiques de surface. La qualité du fini de la surface dépend de la maitrise des paramètres de régime de traitement lors de la réalisation. Cette étude a pour objectif, l’application de ce procédé pour un alliage d'aluminium du commerce et l'optimisation du régime de traitement. Les paramètres considérés sont : l'effort appliqué " Py ", l'avance " f " et le diamètre de bille " Db ". La relation entre ces paramètres et la rugosité de surface" Ra " a été mise en évidence à l'aide des plans d’expériences de " Box-Behnken ". Au moyen d'un programme sous Matlab, un régime optimal a été déterminé en vue d'obtenir un maximum d’effet " Ramin". Les résultats expérimentaux ont montré que l'application de ce type de traitement offre des améliorations vis-à-vis de l'aspect de surface pour ce matériau, soit Ra = 0,19 ÷ 0,23 µm. Voir les détails
Mots clés : Mots clés : Brunissage, rugosité, optimisation, plans d'expériences, traitement de surface
Local Segmentation via an Implicit Region-Based Deformable Model Applied To Weld Defects Extraction
This paper is devoted to present and discuss a model that allows a local segmentation by using statistical information of a given image. It is based on Chan-Vese model, curve evolution, partial differential equations and binary level sets method. The proposed model uses the piecewise constant approximation of Chan-Vese model to compute Signed Pressure Force (SPF) function, this one attracts the curve to the true object(s)’s boundaries. The implemented model is used to extract weld defects from weld radiographic images in the aim to calculate the perimeter and surfaces of those weld defects. Encouraged resultants are obtained on synthetic and real radiographic images. Voir les détails
Mots clés : Active contour, Chan-Vese Model, binary Level set, local segmentation, weld radiographic images
Experimental and Numerical Study of Polypropylene Composite Reinforced with Jute Fibers
This paper is devoted to the study of the mechanical response of polypropylene (PP) thermoplastic composite reinforced with jute fibers. In order to use these composites in structural applications it is necessary to understand the mechanisms governing their mechanical behavior and damage. For this purpose, we have fabricated two kinds of PP/jute laminates: [0°/90°]2S and [+45/-45°]2S with the fibers direction, using the molding technique under compression. The mechanical properties of the material are then characterized by tensile and compressive tests. The numerical part of this work concerns the incorporation of the Matzenmiller, Lubliner, and Taylor (MLT) damage model to take into account the post-elastic-peak and the post-peak strain softening responses observed in the PP/jute composite. This is possible by using formulation with two criterions. The 3D constitutive law has been implemented into the finite code Abaqus using an explicit scheme. In order to assess the capability of this model to describe the material behavior, comparisons are made between numerical and experimental results. Excellent agreements are found between numerical predictions and experimental observations. The model also captures correctly the zones where damage occurs in the two kinds of laminates. Voir les détails
Mots clés : PP/jute, mechanical behavior, damage, laminate, modeling
Inspection of laminated composite materials by two ultrasonic techniques
This paper presents some ultrasonic methods to detect and to characterize defects, possibly obtained after damage caused in composite materials. Firstly, artificial defects are located by two piezoelectric transducers. A two-dimensional ultrasonic cartography C-scan, performed section by section, at different positions which took part through the thickness of acarbon fiber-reinforced plastic composite beam, to be analyzed. Next, fundamental symmetric S0 mode of Lamb waves is used to measure the size of the delamination by scanning over the surface beneath which a delamination lies. A remarkable decrease in the arrival time due to the delamination is detected, and the delamination length can be calculated based on a simple model for Lamb-wave propagation. Furthermore, the delamination edge is located as a sudden decrease in the amplitude. The rate of decrease in amplitude of an individual pulse cycle was detected to vary with the depth of the delamination, being most sensitive to delaminations near the surface of the plate. This is particularly useful when sizing for defects close to the surface, where a normal-incidence pulse-echo ultrasonic method has problems, particularly when the depth of the defect or the back-wall echoes lie within the length of the transmitted ultrasonic pulse. The technique has potential for faster c-scanning of a complete plate than the usual normal-incidence pulse-echo method. Voir les détails
Mots clés : Ultrasonic C-scan, laminate plate, delamination, Lamb wave
Local and Global Statistics-Based Explicit Active Contour for Weld Defect Extraction in Radiographic Inspection
Welding is a process of utmost importance in the metal industry. With the advances in computer science and artificial intelligence techniques, the opportunity to develop computer aided technique for radiographic inspection in Non Destructive Testing arose. This paper deals with the weld defects detection in radiographic films. A greedy active contour model is used exploiting global and local statistics to drive the model to the boundaries. Moreover, and to decrease the computation cost, the local statistics computation is done only for pixels in a selected band. Results seem to be promising ones. Voir les détails
Mots clés : Radiographic inspection, weld defects, Active contours
Growth and characterization of electrodeposited Cu2O thin films
This work demonstrates the electrodeposition of cuprous oxide (Cu2O) thin films onto a fluorine-doped tin oxide (FTO)-coated conducting glass substrates from Cu(II) sulfate solution with C6H8O7 chelating agent. During cyclic voltammetry experiences, the potential interval where the electrodeposition of Cu2O is carried out was established. The thin films were obtained potentiostatically and were characterized through different techniques. From the Mott–Schottky measurements, the flat-band potential and the acceptor density for the Cu2O thin films are determined. All the films showed a p-type semiconductor character with a carrier density varying between 2.41 × 1018 cm−3 and 5.38 × 1018 cm−3. This little difference is attributed to the increase of the stoichiometric defects in the films with the deposition potential. Atomic force microscopy analysis showed that the Cu2O thin films obtained at high potential are more homogenous in appearance and present lower crystallites size. X-ray Voir les détails
Mots clés : Cu2O, electrodeposition, Mott–Schottky, optical properties, Thin films, XRD
Investigation properties of Au – Porous a-Si0.60C0.40as Humidity sensor
In this letter, we report the study of a humidity sensor based on porous amorphous silicon carbide (PASiC) as a function of exposure time and relative humidity (RH). Resistive humidity sensors Au–PASiC/Si(p) were fabricated through evaporating coplanar interdigital gold electrodes. The PASiC was formed by anodization of a-Si0.70C0.30 in HF/ethylene glycol (ETG) solution at current density of 50 mA/cm2 for 30 s. The structural properties of a-Si0.70C0.30 thin films deposited by DC magnetron co-sputtering using single silicon crystal, 6H-SiC targets and the PASiC films were investigated by FT-IR and Raman spectroscopy. Hygroscopicity was studied by measuring the resistance of the PASiC under various RH. The results show that the measured resistance highly depends on the applied bias voltage. Moreover, the response signal against RH is found linear for an applied voltage of 2 V. Finally, the response and recovery times were determined around 13 s and 20 min, respectively. Voir les détails
Mots clés : Porous SiC, Electrochemical etching, RH sensors, Au electrodes