Liste des publications
Numerical Simulations of Eddy Current Testing For Plated Aluminum Parts
Eddy current testing is a non-destructive inspection method applied to conductive materials. Its effects on aluminum are more effective than other materials. Modeling is a good tool for understanding and analyzing impedance responses due to flaws. In this paper, discretization by finite element method is used to solve the electromagnetic field equations in terms of magnetic vector and electric scalar potentials in order to calculate the probe impedance. Simulation by finite elements method was realized to calculate the electromagnetic energy of the interaction between coil and tested part. The real and imaginary components of the probe impedance were deduced from calculated energy that allows determining the characteristic parameters of a crack in aluminum parts. Voir les détails
Mots clés : Non destructive testing, Eddy Current, Finite Element Method, aluminum parts, numerical simulations
La Méthode Descente De Gradient Pour La ReconstructionTomographique Des Images 2D A Rayon-X
Cet article concerne la reconstruction tomographique 2D d’images à rayon-x. Le problème dereconstruction tomographique est un problème inverse c.-à-d. Estimer l’objet à partir de ses projections. Dans cetravail, nous avons établi une étude détaillée sur la méthode de descente de gradient, qui s’inscrit dans le cadredes méthodes itératives de reconstruction tomographique. Ces méthodes consistent à exprimer le problèmedirectement sous une forme discrète. Grâce aux résultats de simulation, nous avons montré que l’algorithme degradient offre une bonne qualité de reconstruction en termes des critères d’évaluation en plus la qualité visuelledes images reconstruites. Voir les détails
Mots clés : Reconstruction Tomographique, problème inverse, projections, Descente de Gradient
Effect Of Impurities On Microstructure And Structural Propertiesof The As-Cast And Treated Al-Zn
The microstructure of two Al-Zn alloys (with 10 and 30 wt.%Zn content) produced by melting in the high frequency induction furnace were investigated by means of scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD) analysisand themicrohardness tests. The results indicate that the presence of iron impurity causes the formation of eutectic (Al,Zn)3Fe in both alloys. The presence of the silicon impurity results in the formation of the phase separation in the Al-10%Zn as-cast alloy. The columnar to equiaxed transition was produced only in the Al-30%Zn as-cast alloy. The Vickers microhardness is higher in the equiaxed zone than in the columnar to equiaxed transition (CET) zone. The presence of iron causes intermetallic phase formation (Al, Fe, Si) 3,6Zn in the Al-30%Zn as-cast alloy enabling an increase in the lattice parameter. After a homogenization treatment, the microstructure of Al-Zn treated alloys consists only of αdendrites and stable eutectic phase. Voir les détails
Mots clés : Al-Zn, HF melting, Dendrites, CET, Impurities, Structural properties.
Modeling and Simulation for 3D Eddy Current Testing in Conducting Materials
The numerical simulation of electromagnetic interactions is still a challenging problem, especially in problems that result in fully three dimensional mathematical models. The goal of this work is to use mathematical modeling to characterize the reliability and capacity of eddy current technique to detect and characterize defects embedded in aeronautical in-service pieces. The finite element method is used for describing the eddy current technique in a mathematical model by the prediction of the eddy current interaction with defects. However, this model is an approximation of the full Maxwell equations. In this study, the analysis of the problem is based on a three dimensional finite element model that computes directly the electromagnetic field distortions due to defects. Voir les détails
Mots clés : Eddy Current, Finite Element Method, Non destructive testing, numerical simulations
Allotropic transformation of cobalt in magnetic induction melted
In contrast to the abundance of studies in Fe -Al and Fe-Co, those in the Fe-Al-Co ternary system arescarce. Consequently, the phase separation and phase diagram of this system remain still ambiguous. Ternary Fe0.6Al1-x Cox(x values in a molar ratio of 0.05, 0.1, 0.15, and 0.2) have been elaborated by high frequency magnetic induction fusion, in order to study the effect of cobalt ternary addition on the structural behavior such as phase separation, thermal and mechanical properties of Fe-based alloy system, by means of x-ray diffraction, thermal analysis (DSC) and Vickers microhardness. An unexpected allotropic phase transformation from stable HCP to metastable FCC Cobalt has been observed in all alloys. Voir les détails
Mots clés : Fe-Al-Co, phase transformation, phase separation, lattice parameter.
Robustness of Radon transform to white additive noise: General case study
A detailed study is presented on the robustness of the Radon transform to additive white noise for the general case of a rectangular grey-level image. Voir les détails
Mots clés : radon transform, white additive noise
NONDESTRUCTIVE EVALUATION OF THE CARBON CONTENT IN STEEL
The aim of this work is to propose an experimental method to evaluate the steel carbon content by ultrasound. The sample is immersed in a water tank in order to analyze it under various incidences of sound waves. Longitudinal wave velocities are measured by immersion by using a 5-MHz frequency probe. Transverse wave velocities are measured in a contact mode by using a 4-MHz transverse wave transducer. The attenuation coefficients of ultrasonic longitudinal and transverse waves are deduced from three successive basic echoes through the sample. The effects of some heat treatments on ultrasonic parameters are also studied. The measurement of ultrasonic parameters in steel offers an interesting possibility of tracing the carbon content and, at the same time, provides information on the steel structure and its elasticity Voir les détails
Mots clés : carbon content, steel, ultrasonic waves.
CHARACTERIZATION OF THE CRITICALLY REFRACTED LONGITUDINAL (LCR) WAVES AND THEIR USE IN DEFECT DETECTION
The critically refracted longitudinal (LCR) waves are used in various domains of nondestructive evaluation, especially for residual stress measurements. However, few works have characterized the associated ultrasonic beam. In this article, the characterization of the LCR ultrasonic beam, both numerically and experimentally, is first clarified in order to provide some answers to questions that arise about its behavior in elastic solids. The aim of the second part of this work is to investigate the use of the LCR waves for the detection of surface defects of different sizes in aluminum. For that, the effect of defects at fixed depth (5 mm) with various diameters (2, 4, 6, and 8 mm) and fixed diameter (8 mm) with various depths (5, 7, and 10 mm) in an aluminum sample have been investigated at frequencies around 1 MHz. It has been experimentally found that the amplitude of the (LCR) wave decreases and its frequency spectrum changes with a given defect. The rate of the decrease of the amplitude and the change in the spectrum is related to the increase of the defect depth. The study shows that the effect on the propagating of the LCR waves is larger as the defect depth increases.The critically refracted longitudinal (LCR) waves are used in various domains of nondestructive evaluation, especially for residual stress measurements. However, few works have characterized the associated ultrasonic beam. In this article, the characterization of the LCR ultrasonic beam, both numerically and experimentally, is first clarified in order to provide some answers to questions that arise about its behavior in elastic solids. The aim of the second part of this work is to investigate the use of the LCR waves for the detection of surface defects of different sizes in aluminum. For that, the effect of defects at fixed depth (5 mm) with various diameters (2, 4, 6, and 8 mm) and fixed diameter (8 mm) with various depths (5, 7, and 10 mm) in an aluminum sample have been investigated at frequencies around 1 MHz. It has been experimentally found that the amplitude of the (LCR) wave decreases and its frequency spectrum changes with a given defect. The rate of the decrease of the amplitude and the change in the spectrum is related to the increase of the defect depth. The study shows that the effect on the propagating of the LCR waves is larger as the defect depth increases. Voir les détails
Mots clés : critical angle, critically refracted longitudinal (LCR) wave, main lobe, NDE, NDT, surface defect
Kinetics study and neural network modeling of degradation of Naphtol Blue Black by electro-Fenton process: effects of anions, metal ions, and organic compound
In the present work, the degradation of azo dye Naphtol Blue Black (NBB) in aqueous solution by electro-Fenton process was investigated. The results indicated that the degradation of NBB by electro-Fenton process followed the second-order reaction kinetics. The experimental results were also modeled by artificial neural network (ANN) with mean squared error of 10-5. This model was developed in Matlab using a feed forward back propagation network; multilayered perceptron. The input variables to the feed-forward neural network were as follows: initial Fe3+ concentration, initial pH, concentration of Na2SO4, temperature, applied current, and initial dye concentration. The degradation efficiency and rate constant were chosen as the experimental responses or output variables. The findings indicated that ANN provided reasonable predictive performance (R2 > 0.99). Effects of additives such as anions, metal ions, and organic compound on the efficiency and on the rate constant of NBB degradation were also studied under optimum conditions. Voir les détails
Mots clés : degradation, Electro-Fenton, Naphtol Blue Black, Artificial neural network
Automatic detection of articulations disorders from children’s speech preliminary study
Automatic detection of articulations disorders from children’s speech preliminary study Voir les détails
Mots clés : GMM-UBM SVM Model fusion Articulations disorders Speech disorders