Liste des publications
FEM Techniques Comparison for SIF Computing of Cracked Plate
The main purpose of this paper is to perform a computation comparison of stress intensity factor ‘SIF’ evaluation in case of cracked thin plate with aluminum alloy 7075-T6 and 2024-T3 used in aeronautics structure under uniaxial loading. This evaluation is based on finite element method with a virtual power principle through two techniques: the extrapolation and G−θ . The first one consists to extrapolate the nodal displacements near the cracked tip using a refined triangular mesh with T3 and T6 special elements, while the second, consists to determine the energy release rate G through G−θ method by potential energy derivation which corresponds numricaly to elastic solution post-processing of a cracked solid by a contour integration computation via Gauss points. The SIF obtained results from extrapolation and G−θ methods will be compared to analytical solution in particular case. To illustrate the influence of the meshing kind and the size of integration contour position, simulations are presented and analyzed. Voir les détails
Mots clés : stress intensity, energy release rate G
Three-dimensional simulation of 304L steel TIG welding process: contribution of the thermal flux
In this study, we focus on the determination of the heat transfer properties in Tungsten-Inert-Gas welding (TIG) problem combining an experimental and a three-dimensional simulation approaches. Optimal conditions are used to weld stainless steel (304L) sheets in butt configuration. Both instrumental monitoring and metallographic investigation of the welded material are carried out. The modelling of the heat source is performed by a mobile Gaussian surface source exhibiting a bi-elliptical shape. This source is implemented in a three-dimensional finite element model to compute heat flux and temperature fields. The comparison between the experimental and numerical thermal cycles shows a fair agreement. Predicted temperature fields and heat flux distributions are discussed. Conversion of isotherms into microstructural information shows that the size of the fusion zone is four times smaller than the heat affected zone dimension. The metallographic analysis confirms the expected microstructural evolutions but highlights differences between observed and predicted extents of the heat affected zone. Voir les détails
Mots clés : Finite elements method, Three-dimensional heat fluxAjout mot clé, TIG welding, 304L steel, Heat affected zone, Fusion Zone
Similarity Transformation Parameters Recovery based on Radon Transform. Application in Image Registration and Object Recognition
The Radon transform, since its introduction in the beginning of the last century, has been studied deeply and applied by researchers in a great number of applications, especially in the biomedical imaging fields. By using the Radon transform properties, the issue is to recover the transformation parameters regarding the rotation, scaling and translation, by handling only the image projections assuming no access to the spatial domain of the image. This paper proposes an algorithm using an extended version of the Radon transform to recover such parameters relating to two unknown images, directly from their projection data. Especially, our approach deals with the problem of the estimation accuracy of the rotation angle and its finding in one step instead of two steps as it is reported in the literature. This method may be applied in image registration as well in object recognition. The results are, for the first time, exploited in object recognition where comparison with powerful descriptors shows the outstanding performance of the proposed paradigm. Moreover, the influence of additive noise on registration and recognition experiments is discussed and shows the efficiency of the method to reduce the effect of the noise. Voir les détails
Mots clés : radon transform, 2π-Based Radon transform, Rotation, Scaling and translation transforms, Parameters recovery algorithm, Additive image noise
Damage modelling in thermoplastic composites reinforced with natural fibres under compressive loading
In this work, the compression failure of thermoplastic composites made of jute/polypropylene is investigatedby experimental and numerical studies. Two laminate specimen’s lengths with different fibre orientations have been considered to analyse this composite type response to a compressive solicitation. The applied numerical model permits to understand the mechanisms of damage and evolution in the laminate.The interlayer damage (delamination) and the intra-layer damage (matrix cracking) have been modelled bythe combined use of the Cohesive Zones model (CZM) and the Matzenmiller, Lubliner and Taylor (MLT)mechanical model. It was found that the loading conditions of laminates and the fibres orientation affect the compression failure load of the thermoplastic composites. Voir les détails
Mots clés : Jute/polypropylene, mechanical behaviour, damage, laminates, modelling
An Effective Method for Bearing Faults diagnosis
The bearings are the most important mechanicalelements of rotating machinery. They are employed to supportand rotate the shafts in rotating machinery. An unexpected defectof the bearing may cause significant economic losses. For thatreason, the condition monitoring of these bearings has become afundamental axis of development and industrial research. Thefocus of this paper is to combine tow conventional methods:Hilbert Transform (HT) and Discrete Wavelet Transform (DWT)to develop a better method for detection and diagnosis the bearingfaults .This new method applied on real measurement signalscollected from an experimental vibration system. The monitoringresults indicate that the proposed method improves the bearingfaults diagnosis compared to other common techniques. Voir les détails
Mots clés : Vibration analysis, bearing Fault diagnosis, Hilbert Transform (HT), Envelope Analysis (EA), Discrete Wavelet Transform (DWT) ), Fast Fourier Transform (FFT)
EDDY CURRENT CHARACTERIZATION OF NANOMATERIALS
NDT Magnetic measurements as impedance in Eddy currents, corecitif and residual field in hysteresis loop are used to study the different stages of mechanical alloying in the Fe–Co system. In this paper, we changed the electromagnetic properties of Fe-Co, by developing their metallurgical parameters such as grain size. For this we are used a planetary ball mill, we are milled the FeCo alloy for different milling times until to obtain nanostructure, the lamellar structure with some small particles embedded inthem was observed during the first stage of mechanical alloying. XRD patterns show after 10 h of milling the formation of a disordered solid solution having a body-centered cubic (bcc) structure. After40h of milling, morphological studies indicated that the average crystallites size is around 15 nm. Voir les détails
Mots clés : nanostructured materialsx, powder metallurgy, NDT, Eddy Current, Magnetic measurement
Etude du comportement structural et mécanique d’un alliage aéronautique 2024 T3 par procédé de soudage.
Vu leurs propriétés mécaniques importantes, l’aluminium et ses alliages ont suscité beaucoup d’intérêt au cours de ces dernières années, notamment dans le domaine de la recherche et plus particulièrement pour des applications aéronautiques et aérospatiales. Néanmoins, l’assemblage de ces matériaux reste encore difficile à cause de l’existence de la couche d’alumine jouant le rôle d’une barrière empêchant ainsi leurs soudabilités. Ce travail a pour but l’étude du comportement structurale et mécanique d’un alliage aéronautique 2024 T3 obtenus par le procédé de soudage sous atmosphère protectrice TIG pulsé, cela, en optimisant les paramètres de travail afin d’avoir un bon cordon de soudure. Une étude métallographique est faite sur les différentes zones du joint soudé (Métal de base MB, Zone Affectée Thermiquement ZAT et la Zone Fondue ZF) en utilisant la microscopie optique. De plus, l’évolution des propriétés mécaniques le long du joint soudé est suivie par un profil de microdureté sur les différentes zones (MB, ZAT et ZF). Voir les détails
Mots clés : Aluminium, soudage TIG, TIG pulsé, Aluminium à durcissement structural
Contribution to characterization of the diatomite forindustrial application
Diatomite also known Kieselguhr, is a non metallic mineral composed of the skeletal remains of microscopic single-celledaquatic algae called diatoms.The aim of this study was to test and to evaluate the diatomite of Sig region (West Algeria)tosubstitute the main mold powder used in continuous casting of steel for thermal insulation and lubrication. Generally, fluorineis added to mould fluxes to improve the viscosity. But this leads to the environmental pollution and the equipment corrosion. Thelaboratory and industrial investigations of diatomite have indicated the good results obtained in continuous casting of steel forthermal insulation and environmental protection against pollution (without fluorine). Also the characterization showed the hotbehavior of this product with the various transformations and could give the possibility to other use. Voir les détails
Mots clés : diatomite, thermal insulation, lubrication, mold fluxes, fluorine
Characterization by thermal analysis of natural kieselguhr and sandfor industrial application
Kieselguhr also known diatomite is a silica-based mineral, usually light in color (white if pure). It is very finely porous and verylow in density. It is composed mainly of silica as career sand. The aim of this study was to characterize the kieselguhr and sandfor together use in industry for various applications. Both products come of Sig deposit (West Algeria).The results ofsimultaneous analyses by Thermogravimetric Analysis and Differential Scanning Calorimetry (TGA-DSC) for kieselguhr andsand sample shows almost identical peaks except for the peak which appears at 574° C which corresponds to the transformationof quartz sand that does not appear in the Kieselguhr sample because of its amorphous character and higher exothermic peak at574° C approximately. Voir les détails
Mots clés : Kieselguhr, diatomite, sand, thermal analysis, DSC, TGA
Evaluation of the Effect of Citronellol Group on Functionalized Mesogenic Materials by Capillary GC
In this paper, the effects of functionalization with terpenes on two new liquid-crystalline stationary phases for gas chromatography (GC) are described. Citronellol was used as the terminal group in the first material, and tetrahydrogeraniol was used with a second material. Inverse GC showed that the new materials have wide liquid-crystalline ranges (mesophases), 371–500 and 395–501 K, respectively. Moreover, they show good thermal stability up to 523 K and good potential as stationary phases for capillary GC. To clarify the effects of the liquid crystal structures and functional groups on retention and separation, the chromatographic behaviors of the two stationary phases were compared by eluting alkylbenzenes, polycyclic aromatic hydrocarbons, aromatic compounds, and terpenoids. The selectivities for a wide range of analytes achieved using the citronellol column were significantly better than those obtained using the tetrahydrogeraniol column. The columns showed different retention behaviors and fine resolutions for some of the main constituents of essential oils. Introduction of the double bond of citronellol greatly improved the polarization interactions involved in the shape recognition of the liquid-crystalline state for isomers. The new citronellol liquid-crystalline stationary phase, therefore, has a high affinity for natural compounds. Voir les détails
Mots clés : Capillary gas chromatography, Terpenoid liquid crystal, Stationary phase