Liste des documents
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
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
Phenol photodegradation process assisted with Wells–Dawson heteropolyacids
This work aims to investigate the catalytic properties of the heteropolyacids (HPAs) withinphotocatalytic process. Photocatalytic degradation of phenol in aqueous solution was performedusing Wells–Dawson HPAs as catalysts under UV-illuminated condition at 254 nm.The effects of various parameters such as, concentration of catalyst, initial pH, and initialphenol concentration on the performance of photocatalytic process have been investigatedto obtain the efficient and durable catalysts and determine the better reaction conditions.The kinetics and the efficiency of phenol degradation were determined by various analyticaltechniques, such as HPLC and TOC. The results show that the photocatalytic degradationefficiency increases with decreasing pH and the optimum pH is 2 for both catalysts. Thephotodegradation follows pseudo-first-order kinetics with rate constants k = 8.56 × 10−2 and 9.94 × 10−2 min−1 for iron- and vanadium-substituted HPAs, respectively. Voir les détails
Mots clés : Well-Dawson HPA, Homogeneous catalysis, Phenol photodegradation, UV irradiation
Pillared clays as catalysts for methyl parathion removal by advanced oxidation processes
A natural bentonite from Mostaganem in Algeria was modified by intercalation with polyoxocationic solutions (Al•Fe, Al•Co, Al•Cu, Al•Fe•Cu or Al•Fe•La). The modification of the bentonite occurred via pillaring by ionic exchange with these solutions. The addition of these solutions led to the formation of pillared clays with important catalytic properties in environmental impact reactions. The structural and textural properties of materials calcined at 500 °C were determined by several techniques: X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and N2 adsorption–desorption analysis. The pillared clays were then used as a Fenton-type heterogeneous catalyst for the heterogeneous sono-Fenton process for the oxidation of methyl parathion in water. The catalytic tests revealed the activity of the introduced iron species and the promoter effect of lanthanide or copper on the catalytic activity of these species. The sono-Fenton method showed promising results for the degradation of methyl parathion when compared with the Fenton method. Therefore, the sono-Fenton method can be a viable alternative technology to the existing methods for treating methyl parathion in wastewater. Voir les détails
Mots clés : Advanced oxidation process, Pillared clay, Sono-Fenton, Methyl parathion pesticide, Wastewater treatment
Phenol photodegradation process assisted with Wells- Dawson heteropolyacids
This work aims to investigate the catalytic properties of the heteropolyacids (HPAs) within photocatlytic process. Photocatalytic degradation of phenol in aqueous solution was performed using Wells-Dawson HPAs as catalysts under UV-illuminated condition at 254 nm. The effects of various parameters such as, concentration of catalyst, initial pH and initial phenol concentration on the performance of photocatalytic process have been investigated to obtain the efficient and durable catalysts and determine the better reaction conditions. The kinetics and the efficiency of phenol degradation were determined by various analytical techniques, such as HPLC and TOC. The results show that the photocatalytic degradation efficiency increases with decreasing pH and the optimum pH is 2 for both catalysts. The photodegradation follows pseudo first-order kinetics with rate constants k = 8.56×10−2 min-1 and 9.94x10-2 min-1 for iron and vanadium substituted - HPAs, respectively. Voir les détails
Mots clés : Wells-Dawson HPA, Homogeneous catalysis, Phenol photodegradation, UV irradiation
Pillared clays as catalysts for methyl parathion removal by advanced oxidation processes
A natural bentonite from Mostaganem in Algeria was modified by intercalation with polyoxocationic solutions (Al•Fe, Al•Co, Al•Cu, Al•Fe•Cu or Al•Fe•La). The modification of the bentonite occurred via pillaring by ionic exchange with these solutions. The addition of these solutions led to the formation of pillared clays with important catalytic properties in environmental impact reactions. The structural and textural properties of materials calcined at 500 °C were determined by several techniques: X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and N2 adsorption–desorption analysis. The pillared clays were then used as a Fenton-type heterogeneous catalyst for the heterogeneous sono-Fenton process for the oxidation of methyl parathion in water. The catalytic tests revealed the activity of the introduced iron species and the promoter effect of lanthanide or copper on the catalytic activity of these species. The sono-Fenton method showed promising results for the degradation of methyl parathion when compared with the Fenton method. Therefore, the sono-Fenton method can be a viable alternative technology to the existing methods for treating methyl parathion in wastewater. Voir les détails
Mots clés : Advanced oxidatio process, Sono-Fenton, heterogeneous catalysis, Methyl parathion pesticide, Wastewater treatment
Adsorption d’un mélange binaire «plomb-nickel» par le kaolin
Le kaolin a été utilisé comme adsorbant pour éliminer le nickel et le plomb en mono adsorption et en mélange binaire. Le processus envisagé en régime statique et en mono adsorption a montré qu’un gramme de kaolin peut fixer 43,2 mg/g de nickel et 35,69 mg/g de plomb selon le modèle de Langmuir avec une cinétique de pseudo 1er ordre où le temps du pseudo équilibre est de 16 minutes pour Ni++ et de 14 minutes pour Pb++. Le rapport d’affinité RL a montré que le kaolin présente une bonne capacité d’adsorption. Pour le mélange binaire, l’expérience a montré que l’adsorption du nickel est la plus importante et le pseudo équilibre est plus lent que celui de l’ion seul. Toutefois, nous avons représenté approximativement le mélange avec le modèle de Langmuir généralisé et Langmuir généralisé modifié, en utilisant à la fois des données en mono constituant et en mélange. De ces deux représentations, nous avons constaté une inversion de sélectivité pour le modèle de Langmuir généralisé et une isotherme proche de celle de l’expérimentale pour le modèle de Langmuir généralisé et modifié. Voir les détails
Mots clés : Eau -dépollution- plomb- nickel- adsorption- kaolin
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
A numerical investigation of both thermal and texturing surface effects on the journal bearings static characteristics
Journal bearing characteristics modellization has been investigated in this paper for both cases of texture presence or absence onto the bearing surface. The thermal effect has been studied. The used numerical approach in this analysis is finite difference method. The textured bearing performance enhancement passes essentially by a minimum film thickness and a friction torque improvement through an appropriate surface texture geometry and right texture distribution on the bearing surface. It is found that the simulations results are in good concordance with those issued from the literature. The obtained results by considering the temperature effect are more realistic. Voir les détails
Mots clés : Journal bearings, Reynolds equation, Hydrodynamic lubrication, Stribeck curve, texture