Liste des documents
Simulation & Expérimentation en Soudage Etude du Comportement Thermique et Mécanique des Métaux à Usage Aéronautique.
La mise en œuvre de nouvelles techniques d’assemblage, en remplaçant le rivetage par le soudage, permet l’allègement des structures et des appareils à usage aéronautique. Dans le présent travail, l’intérêt est porté sur l’étude de deux procédés de soudage importants et récents qui sont le soudage par friction malaxage FSW et par l’arc électrique TIG. Dans un premier temps, une étude du comportement thermique de quelques métaux soudés par le procédé TIG, est menée. Une modélisation et des simulations numériques du transfert thermique sont réalisées, mettant en évidence l’apparition des zones à risques et l’effet des différents paramètres de soudage. Une étude expérimentale du soudage est ensuite présentée permettant une validation des résultats numériques. Dans un second temps, la conception et la réalisation d’un outil de soudage par friction malaxage FSW (Brevet 2007) sont effectuées. Des essais de soudage ont été menés par la suite avec succès. Les cordons de soudure obtenus par ces deux procédés ont été caractérisés par différentes techniques et leurs propriétés mécaniques ont été déterminées. Voir les détails
Mots clés : thermique, 3D, Essais mécaniques, acier, MEF, soudage TIG, soudage FSW, source de chaleur, alliage d’Aluminium
Etude Comparative des Techniques de Filtrage Actif Sélectif par le Référentiel Synchrone de Park d-q et l’Approche FMV
To minimize the total harmonic distortion (THD) and improve the power factor (PF), this paper presents a comparative study between two techniques of shunt power active filter (SPAF) by a selective action of harmonics. These two techniques are based on the SAPF of certain low frequency harmonics (5th and 7th) whose identification of the harmonics of references of the first is made by the axis synchronous d-q of the Park, and the second is done by the approach of self-tuning filter (STF) Thereafter, The active simultaneously filtering of the 5th and 7th harmonics of the current of load catches. The shapes of the signals and the THD values resulting from the results of digital simulations (Matlab-Simulink) elaborate the effectiveness and the best technique of this type of filtering. Voir les détails
Mots clés : PF, THD, Harmonics, SAPF, STF, d-q Park Synchronous Axis
Acoustic emission signal denoising to improve damage analysis in glass fibre reinforced composites
In this contribution, continuous wavelet denoising technique is developed to enhancethe signal to noise ratio of acoustic emission (AE) signals. The time– frequency characteristics of the recorded noise are first determined by calculating the noisewavelet coefficients. Then, an algorithm able to proceed denoising by extracting noise features from those corresponding to AE signals is developed. The denoising procedure is applied to get meaningful signals when the detection threshold is decreased from 30 dB to 25 dB. Furthermore, the spectral flatness measure was applied to eliminate signals originating from noise. Experiments were conducted on cross-ply composite specimens [±45°]6S to examine the efficacy of the proposed technique. The denoised signals were analysed using the continuous wavelet transform and were also analysed in terms of the dominant frequency band which was processed by a fast Fouriertransform. Results show that denoised low-amplitude AE hits are well correlated withhigh-amplitude AE hits (A≥30 dB) in terms of damage characterisation. Voir les détails
Mots clés : acoustic emission, polymer-based composite, Denoising, Signal processing, damage characterisation
Analysis and Mitigation of the Interference Between High Voltage Power Line and Buried Pipelines
Analysis of electromagnetic interference between high voltage overhead power transmission lines and nearby gas/oil pipeline has been a topic of growing interest for many years. When pipelines are located in shared row with power lines, the pipeline can incur high induced voltages and currents due the AC interference. The induced voltage on pipeline can be dangerous for operator to touch the pipeline as well as pipe corrosion can result from AC discharge. This research evaluates and analyzes the electromagnetic interference effects on oil and gas buried pipelines created by the nearby high voltage transmission lines. The aim is to evaluate the AC corrosion likelihoods of pipelines and suggest proper mitigation solutions. Voir les détails
Mots clés : AC interference, Induced Voltages, Electric Power Transmission Lines, pipeline, AC Corrosion, cathodic protection, soil resistivity
Propagation of Lamb waves in an immersed periodically grooved plate: Experimental detection of the scattered converted backward waves
Guided waves propagation in immersed plates with irregular surfaces has potential application to detection and assessment of the extent, depth and pattern of the irregularity. The complexity of the problem, due to the large number of involved parameters, has limited the number of existing studies. The simplest case of irregularities of practical interest is the two-dimensional corrosion profile. Even this case is in general so complex, that one can extract several amplitude dominant periodic surfaces only by using a Fourier spectrum of the surface. Guided waves in plates, with one or both free surfaces having periodic perturbations of different shapes, have been presented in specialized literature. In this paper is studied the propagation of Lamb waves in an aluminum plate with a periodic grooved surface on only one side and immersed in water. The interaction between an incident Lamb wave and the grating gives rise to retro-converted waves. Preliminary numerical simulation by the finite element method is performed in order to obtain key parameters for the experiments. It is shown that retroconverted waves radiating into the water are detectable although their amplitudes are small. The phonon relation is verified for the leaky Lamb modes. The damping coefficients of the leaky Lamb modes in the grooved immersed plate are evaluated. Voir les détails
Mots clés : Liquid–solid interfaces, Rough plate, Periodic grating, Lamb waves, Converted modes
Numerical simulation for cracks detection using the finite elements method
The means of detection must ensure controls either during initial construction, or at the time of exploitation of all parts. The Non destructive testing (NDT) gathers the most widespread methods for detecting defects of a part or review the integrity of a structure. In the areas of advanced industry (aeronautics, aerospace, nuclear …), assessing the damage of materials is a key point to control durability and reliability of parts and materials in service. In this context, it is necessary to quantify the damage and identify thedifferent mechanisms responsible for the progress of this damage. It is therefore essential to characterize materials and identify the most sensitive indicators attached to damage to prevent their destruction and use them optimally.In this work, simulation by finite elements method is realized with aim to calculate the electromagnetic energy of interaction: probe and piece (with/without defect).From calculated energy; we deduce the real and imaginary components of the impedance which enables to determine the characteristic parameters of a crack in various metallic parts. Voir les détails
Mots clés : Eddy Current, Non-destructive testing (NDT), Cracks, Finite Element Method
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
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
Condition Monitoring of Casting Process using Multivariate Statistical Method
Growing demand for higher performance, safety and reliability of industrial systems has increased the need for condition monitoring and fault diagnosis. A wide variety of techniques were used for process monitoring. This study will mainly investigate a technique based on principal component analysis in order to improve the accuracy for fault diagnosis of casting process. The process faults are identified using the following statistical parameters: Q-statistic, also called squared prediction error, and Q-residual contribution. The proposed method is evaluated using real sensor measurements from a pilot scale. The monitoring results indicate that the principal component analysis method can diagnose the abnormal change in the measured data. Voir les détails
Mots clés : Fault Diagnosis, process monitoring, principal component analysis, Q-statistic, Q-residual contribution
Influence of niobium on the hardening phenomenon and wear in the manganese steel \(12% Mn\) destined for the railway
This study relates to the manufacture of austenitic manganese steel for the heartswitching crossings of railways in all industrial countries where heavy loads are movedby rail. This steel is characterized by a high surface hardness service yard caused by thephenomenon of hardening. According to the microstructure formed after quenching, thetransformation of austenite into martensite during working, determine the operating life.The rate of transformation of austenite into martensite can force a compromise betweenductility and wear resistance of the steel in order to withstand large forces without breaking.The objective of this study is to improve the resistance to abrasion and friction to cast stateand after heat treatment by the addition of niobium. This study permitted to develop a newshade of manganese steel can be integrated into the production of heart of railway switcheswith better lifecycle. Voir les détails
Mots clés : manganese steel, effect of niobium, hardening, wear.