Liste des documents
Design and simulation of Pyramidal Horn Antenna for NDT Applications
This paper describes a pyramidal horn antenna design which it works in a microwave domain. His operating frequency is 4.7 GHz. The parameters of the antenna were measured through its numerical modeling using HFSS (High Frequency Structure Simulator) electromagnetic simulation software. HFSS has the capability to calculate and plot a 3D image depicting the real beam of the gain. The obtained results show that an antenna gain of 12.90 dB was obtained at the frequency of 4.7 GHz, which means that the antenna is properly adapted to the transmission systems. This antenna will be used for non destructive testing (NDT) application, such as detection of cracks in different materials, materials characterization. Voir les détails
Mots clés : Pyramidal horn antenna, Finite Element Method, HFSS, Radiation Pattern, gain, non destructive testing (NDT).
Design and Real Time Implementation of Three-PhaseThree Switches Three Levels Vienna Recti?er Based onIntelligent Controllers
This paper treats the control of multilevel rectifier by applying the soft computing technique represented by the fuzzy logic. This latest, provides an inexpensive solution for controlling the ill-known complex systems, while relying on the imitation of human reasoning. In our case, the proposed intelligent controller aims at eliminating the current line harmonics, guaranteing an improved power factor, reducing the output voltage ripple and ensuring the balance between the two voltages across the two capacitors of Vienna rectifier. In order to evaluate the performance of the proposed control for Vienna rectifier, a comparative study in real time via the dSPACE card 1104 has been carried out between the traditional approach based on the conventional controllers and the new method using an intelligent controller. The experimental results confirm that the modified control approach has guaranteed a good quality of source currents in phase with the grid voltages and operation of the studied system with a power factor very close to unity. Furthermore, only one fuzzy controller used has ensured the regulation of the DC bus voltage, the minimization of the undulations for the two partial voltages and the improvement of the error of the voltage balance for the Vienna rectifier. Voir les détails
Mots clés : Vienna rectifier, Fuzzy logic controller, DC bus voltage ripple, Total harmonic distortion, Power factor correction
Diagnosis and classification using ANFIS approach ofstator and rotor faults in induction machine
Three-phase squirrel cage induction motors are one of the importantelements of the industrial production system, and are mostly used because oftheir robustness, reliability, relatively simple construction and their low cost.Nevertheless, during their function in different process, this machine types aresubmitted to external and internal stresses which can lead to several electricalor mechanical failures. In this paper, we proposed a reliable approach fordiagnosis and detection of stator short-circuit windings and rotor broken barsfaults in induction motor under varying load condition based on relative energyfor each level of stator current signal using wavelet packet decompositionwhich will be useful as data input of adaptive neuro-fuzzy inference system(ANFIS). The adaptive neuro-fuzzy inference system is able to identify theinduction motor and it is proven to be capable of detecting broken bars andstator short-circuit fault e with high precision. The diagnostic ANFIS algorithmis applicable to a variety of industrial process based on the induction machinefor detection and classified the any faults types. This approach is applied underthe MATLAB software®. Voir les détails
Mots clés : Induction machine, Detection, diagnosis, neuro-fuzzy, Monitoring
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
EVOLUTION OF THE MICROSTRUCTURAL PARAMETERS OF COLD WORK Ti-6-Al-4V ALLOY.
AbstractThe aim of this work is to investigate cold worked Ti-6Al-4V (α+β) alloy. The alloy was examined by X-ray diffraction using Rietveld refinement method. MAUD software (Materials Analysis Using Diffraction) was used to analyze the microstructural parameters evolution (crystallite size, root mean square strain (r.m.s) and dislocation density. The Crystallite size is smaller in the β-phase compared to the α-phase. Microstrain and dislocation density are higher in the α-phase than those found in the β-phasefor the as received material. The microstructural parameters of Ti-6Al-4V alloy exhibit typical values of cold deformation state. The results show that the deformation process reducesthe crystallite size (coherent diffraction domains) from 520 to 210 ? in the α-phase. Consequently, the r.m.s increases from 5 E-4to 32 E-4and the dislocation density increases from 2.92 E+10to 4.6 E+11m-2after 85 % thickness reduction. Voir les détails
Mots clés : Ti-6Al-4V alloy, cold working, crystallite size, dislocation density
Reliability Index of HDPE Pipe Based on Fracture Toughness
his work presents a contribution to evaluate the reliability of a high density polyethylene (HDPE) pipe using the PHIMECA Software. The critical stress intensity factor (KIC) is adopted as a criterion to the maximum limit of a numerically calculated KI. The reliability index β is obtained using failure probability and a mechanical model. It is found that at lower KIC, no safe domain for actual service pressures existed while for moderate and higher values of KIC (above 3.5 MPa.√m); the β design index is reached and even exceeded. In terms of increasing crack length, β decreased systematically for all toughness cases supporting the idea that reliability and fracture toughness designate similar properties for service life or material resistance to cracking. For a KIC=5 MPa.√m, the pipe is considered safe when crack length is below 370μm. Finally, it is shown that SDR basis is a reasonable and conservative design approach for plastic pipes. Voir les détails
Mots clés : HDPE pipe, critical stress intensity factor, crack length, SDR, reliability index, PHIMECA software
Micrographic Image Segmentation using Level SetModel based on Possibilistic C-MeansClustering
Image segmentation is often required as afundamental stage in microstructure material characterization.The objective of this work is to choose hybridization betweenthe Level Set method and the clustering approach in order toextract the characteristics of the materials from thesegmentation result of the micrographic images. Morespecifically, the proposed approach contains two successivenecessary stages. The first one consists in the application ofpossibilistic c-means clustering approach (PCM) to get thevarious classes of the original image. The second stage isbased on using the result of the clustering approach i.e. oneclass among the three existing classes (which interests us) asan initial contour of the level set method to extract theboundaries of interest region. The main purpose of using theresult of the PCM algorithm as initial step of the level setmethod is to enhance and facilitate the work of the latter. Ourexperimental results on real micrographic images show thatthe proposed segmentation method can extract successfully theinterest region according to the chosen class and confirm itsefficiency for segmenting micrographic images of materials. Voir les détails
Mots clés : Level set, clustering approach, micrographic images;, image segmentation.
Pulsed eddy current signal analysis of ferrous and non-ferrous metals under thermal and corrosion solicitations
Most metals endure in contact with ambient air, liquids or other metals the phenomena of oxidation. The kinetics of the corrosion can be significant and destroy the metal. The marine corrosion or soil affects many materials, more than ever if it touches the pipeline, ship hulls or buried pipes. The investigation of NDT methods to predict corrosion behavior can be a rational solution to prevent from this kind of industrials problems.Eddy current and pulsed eddy current (PEC) are proposed as a powerful Nondestructive Testing and Evaluation (NDT&E) technique. The application of this kind of technique in the industrial domain is used in detection of the defects, particularly in the determination of corrosions information contained in the received signal gives the possibility allow to use the PEC in the Non Destructive Evaluation of materials that can be analysed. The work in this papers explain the behaviour of the eddy current, pulsed Eddy Currents and various electromagnetic parameters in the analysed samples. We have showed in this work that all microstructure modifications of the samples were detected and can be quantified by Pulsed eddy current measurements. Modifications of the microstructure obtained by air cooled, quenched and corroded samples in aluminium, heat treatment changement in mild steel were evaluated by PEC. Voir les détails
Mots clés : pulsed eddy current (PEC), ), lift off variation, corrosion
Electrocatalytic oxidation of ascorbic acid at polypyrrole thin film incorporating palladium particles
In this paper, we report a simple sensing strategy for electrochemical determination of ascorbicacid (AA) using a combination of polypyrrole (PPy) thin film and palladium particles composites deposited onto n-doped silicon (Si) substrate. A two-step electrochemical process was employed to synthesize the composite films: At first, PPy film (average thickness 200 nm) was electro-generated on Si substrate from an organic solution of the pyrrole under galvanostatic conditions. Secondly, palladium particles were electrodeposited on PPy/Si surface from a separate solution by chronoamperometry technique. The surface morphology analysis of the obtained composites shows a uniform dispersion of palladium particles onto the polymer matrix and reveals that the electrodeposition time has a significant effect on the amount and size of the incorporated palladium particles. The electrochemical reactivity of the Pd–PPy/Si-modified electrodes towards the oxidation of AA was studied by cyclic voltammetry method in 0.1 M, pH 7.0 phosphate buffer solution. The oxidation current was proportional to the concentration of AA in the range of 0.5–10 mM with a detection limit of 0.2 mM. Voir les détails
Mots clés : ascorbic acid, composite, electrocatalysis, Electropolymerization, palladium, Polypyrrole
Estimated life time in an HDPE pipe with a semi-elliptical defect under internal pressure
High density polyethylene has been widely used in marine and gas transportation, storm sewers, culverts and city drainage system. Compared with other conventional pipes, it has its own advantages, such as, chemical and corrosion resistance, toughness, flexibility, easy splicing and consequent easy handling and installation. In this paper, and in order to predict the remaining lifetime of a pipe having a defect and subjected to internal pressure, it is necessary to estimate KI stress intensity factor during the propagation of the crack. The finite element method is used to assess the values of the stress intensity factor of an axially oriented semi-elliptical crack located at the inner surface of an HDPE pipe. The crack configuration is described by the relative wall thickness (t/R), the relative crack depth (a/t) and the crack aspect ratio (a/c). The lifetimes presented are discussed according to the size of the crack and the stress intensity factor in each case. Voir les détails
Mots clés : HDPE pipe, Crack, rupture, Finite Element Method FEM, stress intensity factor, Lifetime