Liste des documents
Tamanrasset’s Clay Characterization and Use as Low Cost, Ecofriendlyand Sustainable Material for Water Treatment: Progress and Challengein Copper Cu (II)
In this study, the adsorption of copper Cu (II) from aqueous solution, on Tamanrasset’sclay which is low cost adsorbent, was studied using batch experiments. The adsorption study includesboth equilibrium adsorption isotherms and kinetics. The characterization of the adsorbent necessitatedseveral methods such as X-Ray Diffraction, Scanning Electron Microscopy coupled with EnergyDispersive X-ray, BET for specific surface area determination, Fourier transform infraredspectroscopy and thermogravimetric analysis. Indeed, various parameters were investigated such ascontact time, initial metal ion concentration, mass of solid, pH of the solution and temperature. Theadsorption process as batch study was investigated under the previews experimental parameters. Theresults revealed that the adsorption capacity of Cu2+ is maximized at naturel pH of metal 5.5. Removalof copper by the clay of Tamanrasset (kaolinite) achieved equilibrium within 50 minutes; the resultsobtained were found to be fitted by the pseudo-second order kinetics model. The equilibrium processwas well described by the Langmuir model and the maximum adsorption capacity was found to be26.59 mg/g. Voir les détails
Mots clés : adsorption, Clay, copper, kinetic, Isotherms
Segmentation of x-ray image for welding defects detection using an improved Chan-Vese model
The welding defects detection in industries is becoming an important area and is attracting the attention of many researchers. Radiography is one of the most widely used techniques for inspecting weld defects. X-ray images are generally characterized by low contrast, poor quality and uneven illumination, so the extraction of weld defects could become a difficult task. Among the techniques most used in this field, it is the active contour and the main problem of this technique is the initial contour selection. To solve this problem and obtain reliable and efficient detection of welding defects, we propose in this work a new approach for welding defects detection from x-ray image based on an improved Chan-Vese model. This improved model is based on three stages. The first stage is the detection the region of interest. In the second stage, we apply the Fuzzy C-Mean (FCM) algorithm to select one of the clusters as the initial contour. In the third stage, we use the Chan-Vese model and the selected initial contour to segment the acquired images and obtain the boundaries of the weld defects. Experiments are carried out on different x-ray welding images of the GDxray database in order to extract the characteristics of the welding defects. The results obtained show the effectiveness of the proposed approach compared to conventional techniques. Voir les détails
Mots clés : Chan-Vese model Fuzzy, C-means clustering, X-ray image, Welding defects
Scale space Radon transform
An extension of Radon transform by using a measure function capturing the user need isproposed. The new transform, called scale space Radon transform, is devoted to the casewhere the embedded shape in the image is not ?liform. A case study is brought on a straightline and an ellipse where the SSRT behaviour in the scale space and in the presence of noiseis deeply analyzed. In order to show the effectiveness of the proposed transform, the exper-iments have been carried out, ?rst, on linear and elliptical structures generated syntheticallysubjected to strong altering conditions such blur and noise and then on structures imagesissued from real-world applications such as road traf?c, satellite imagery and weld X-rayimaging. Comparisons in terms of detection accuracy and computational time with well-known transforms and recent work dedicated to this purpose are conducted, where theproposed transform shows an outstanding performance in detecting the above-mentionedstructures and targeting accurately their spatial locations even in low-quality images. Voir les détails
Mots clés : radon transform, line, ellipse, scale space, noise
Investigation ?n Dry Sliding Wear Performance and Corrosion Resistance of 13Cr5Ni2Mo Supermartensitic Stainless Steel
This work aimed to study the microstructure, wear and corrosion resistance of supermartensitic stainless steel (SMSS). Heat treatment applied to samples consists of quenching after austenitization at elevated temperature (1250 °C) followed by a double tempering at 650 °C. Conventional mechanical properties, scanning electron microscopy (SEM/EDS) analysis and X-ray diffraction methods (XRD) are used to analyze the microstructure and to evaluate the wear mechanisms. The potentiodynamic polarisation and the electrochemical impedance spectroscoopy (EIS) methods are used to evaluate the corrosion resistance in both the 0.5M H2SO4 and 0.5M NaCl aggressive media. The microstructure is mainly composed with tempered lath martensite, small quantity of retained austenite and carbides. Oxidative and abrasive wear dominated the wear process in dry condition. During the corrosion process, the same mechanism of degradation was found in both the 0.5M NaCl and 0.5M H2SO4. Voir les détails
Mots clés : Supermartensitic steel, microstructure, friction, Wear Corrosion
Plastic Deformation Effect on Wear and Corrosion resistance of Super Martensitic Stainless Steel
The microstructure and the mechanical properties of a super martensitic stainless steel (SMSS) were investigated in this study. Test specimens were taken from seamless tube generally used in oil and gas industries. The specimens were plasti- cally deformed by tension from its as-received state to different levels of elongation at 2%, 10%, and 15%, respectively. The focus was to study the influence of plastic deformation on the tribological behavior against alumina balls in dry conditions and the corrosion resistance in 3.5% NaCl solution. Analysis results showed an abrasive wear as the main wear mechanism. Plastic deformation prior to sliding wear test increases wear resistance as the deformation rate increases. Based on the elec- trochemical experiments, all of the specimens showed an increase in their corrosion resistance i.e., the corrosion potential Ecorr (vs. Ag/AgCl) tends to move toward more noble values with respect to the initial potential. The greatest polarization resistance was displayed by the specimen with 10% of deformation rate. Voir les détails
Mots clés : Super Martensitic Stainless Steel, Cold deformation, wear, corrosion
Arc Welding Current Control Using Thyristor Based Three-Phase Rectifiers Applied to Gas Metal Arc Welding Connected to Grid Network
The purpose of the welding operation is to ensure the continuity of the materials to be assembled in large industrial sectors. This study aims to suggest a topology of the Thyristor based three-phase rectifiers applied to the Gas Metal Arc Welding (GMAW) process connected to the grid network, the output currents are controlled and using various pulsed forms such as square, annealing, and spike pulse operations and investigate and compare between the effects of the three references welding currents structures on the welding current, welding voltage, droplet diameter, and welding quality. To have the best pulse operation, the amplitude and frequency are kept the same for all operations, the application of meshing graphs in the references of welding currents structures, welding current, welding voltage, and droplet diameter can illustrate a clear comparison between them. The simulation results show that the square pulse operation is the best among them. The Single-Sided Amplitude Spectrum (SSAS) method is also applied to the welding current and droplet diameter of the three operations under slow and rapid droplet detachment rates to estimate the droplet detachment frequency. The results show the great success of the SSAS in estimating the precise frequency. Voir les détails
Mots clés : Gas Metal Arc Welding, three-phase rectifier, grid network, SSAS method, welding current, welding voltage, droplet diameter, detachment frequency
DNS using CLSVOF method of single micro-bubblebreakup and dynamics in ?ow focusing
Numerical simulations are performed to investigate the breakup of air bubble in ?ow focusingcon?guration; the CLSVOF (coupled level set with volume of ?uid) method is employed to track theinterface, which allows a better identi?cation of the liquid–gas interface via a function called level set. TheCFD simulations showed that the velocity ratio, the interfacial tension, the outer channel diameter, thecontinuous phase viscosity, the ori?ce width and length play an important role in the determination of the airbubble’s size and shape. However, at low capillary number, increasing the ?ow velocity ratio gives a smallerbubble size in shorter time, while the increase in interfacial tension leads to a bigger bubble. Moreover, thecarrier ?uid is found to slightly affect the bubbling mechanism, while the smallest bubbles were obtainedwith the smallest ori?ce size. In addition, three breakup regimes are observed in this device: disc-bubble(DB), elongated bubble (EB) and the slug bubble (SB) regime ?ows. This work also demonstrates that theCLSVOF is an effective method to simulate the bubbles breakup in ?ow focusing geometry. In addition, acomparison of our computational simulations with available experimental results reveals reasonably goodagreement. Voir les détails
Mots clés : Bubbling, Multiphase ?ow, CLSVOF, CFD and ?ow focusing
Effects of Boundary Conditions and Operating Parameters on Temperature Distribution during the Friction Stir Welding Process
This work deals with a numerical simulation of the friction stir welding FSW process of alloy material AA2195-T8. A 3D transient thermal model for simulating the heat transfer phenomena in the welding phase is applied. In this model, the FSW tool is considered as a circular heat source moving in a rectangular plate having a cooling surface and subjected to nonuniformandnon-homogeneousboundaryconditions.ThethermalproblemissolvedusingthefiniteelementmethodaspartofaLagrangianformulation.TheobtainedresultsallowustodeterminethemaximumvalueofthetemperatureintheNuggetzoneoftheweldedjoint.Duringthisprocess,thethermalcycleandthetemperaturedistributionweredeterminedfordifferentvaluesoftheweldingprocessparameters.Theobtainednumericalresultsareingoodagreementwiththeoneavailableintheliterature. Voir les détails
Mots clés : Frictio n Stir Welding, Heat transfer, AA2195-T8
Thermal analysis of the friction stir welding process based on boundary conditions and operating parameters
Modelling of friction stir welding (FSW) remains a complicated task, as it is crucial to predict the mechanical properties of the final welded part. This research focuses on the numerical simulation aspect of the alloy material AA2195-T8. 3D transient thermal model was applied to simulate the heat transfer phenomena in the welding phase. In this model, the FSW tool is considered as a circular heat source moving in a rectangular plate having a cooling surface and subjected to non-uniform and non-homogeneous boundary conditions. To solve the thermal problem, the finite element method was used as part of a Lagrangian formulation. The obtained results allow us to determine the maximum value of the temperature in the Nugget zone of the welded joint. Sensitivity analysis of the operating parameters was also investigated to determine the thermal cycle and the temperature distribution during this welding process. Our results were successfully compared with the ones available in the literature with good agreement. Voir les détails
Mots clés : Friction Stir Welding, Heat transfer, AA2195-T8, alloy material, parameter characterisation
Chemical sensor array modeling. Quartz crystal microbalance sensors.
The primary objective of the paper is to develop Gibbs- Duhem like equations for the interactions between Quartz Crystal Microbalance (QCM) based sensor array and a mixture of vapors. These differential equations connect the variations of the sensors partial sensitivities or the sensors response with the gas mixture components concentrations. Furthermore, Thermodynamic models in the case of conducting polymer sensors, whose multi-component adsorption follows the generalized adsorption model of Langmuir have been deduced, these are differential equations that connect the adsorption entropies to the selectivities of the sensors and coefficients of standardization at constant temperature Voir les détails
Mots clés : chemical sensor array, Quartz Crystal Microbalance sensors, gas mixture, modeling, equations of Gibbs-Duhem, adsorption entropy