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Nombre total de résultats : 435
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Study of the effect burnishing on superficial hardness and hardeningof S355JR steel using experimental planning

M. BOUREBIA, A. Bouri, H Hamadache, S. Achouri, L. Laouar, A. GHARBI, O. GHELLOUDJ, K. BOUHAMLA (2019)
Article de journal

Surface hardness plays an important role in lifetime of a mechanical piece subjected to friction and wear. Indeed, thehardness can be improved by superficial plastic deformation processes (SDP), such as mechanical surface treatment"MST", in particular the ball burnishing. However, the treatment result of is conditioned by mastery of operationthus ensuring treated piece good mechanical and geometric properties. Experimental work was carried out byapplying the ball burnishing process on steel tensile specimens S355JR, in order to observe the influence oftreatment parameters regime on surface hardness 'Hv' and the effect of latter on tensile behavior of this steel. Twoparameters of regime were considered namely: burnishing force "Py" and number of passes "i". The relationshipbetween these parameters and microhardness measured at "Hv" surface has been highlighting using factorial plans22. Moreover a mathematical model has been obtained allowing prediction of response (Hv) as well as optimizationof parameters of treatment regime. The experimental results showed that for surface hardness Hv it is possible toreach a 45% improvement rate for a burnishing force py = 20 Kgf and a number of passages i = 3 for this material.Regarding behavior of material during tensile test, for a low burnishing force (py = 10N) and a number of passes (i= 5), the section further weakening (S = 4.14), proof than ductility of material has decreased.Voir les détails

Mots clés : Surface hardness, factorial designs, ball burnishing, Mathematical model, tensile behaviour

Preparation, structural and functional properties of PbTiO3-δ ceramics

Khiat Abd elmadjid, Felicia Gheorghiu, Mokhtar Zerdali, Mohammed Kadri, Saad Hamzaoui (2019)
Article de journal

In the present study, oxygen deficient PbTiO3-δ ceramics were prepared by solid state-reaction method. The formation of the pure perovskite phase with tetragonal structure was confirmed for the 800 °C/2 h calcined sample by using X-ray diffraction analysis at room temperature. Energy dispersive X-ray spectroscopy analyses confirm the creation of oxygen vacancies in the system for charge compensations, as demonstrated by the percentage of O atoms of ∼53%. The complex impedance data reveals important contributions of the oxygen vacancies to the total dielectric response that are homogeneous distributed within the sample. The room temperature magnetic properties show a weak ferromagnetic character in all the samples that might be attributed to the oxygen vacancies defects and to surface effects.Voir les détails

Mots clés : Ceramics, oxygen vacancies, EDX spectra, Dielectric properties, Magnetic Properties

Effect of zinc/cadmium proportion in CdS layers deposited by CBD method

R. Zellagui, H. Dehdouh, F. Boufelgha, A. Boughelout, T. Sahraoui, D. Chaumont, M. Adnane (2019)
Article de journal

Cadmium poisoning and the cost of panel recovery which is very expensive and difficult in the buffer layers of CdS in solar cell, for these two drawbacks, we do a search on the effect of proportion of zinc/cadmium in the properties layers of CdS. For this, our studies study the properties of CdxZn1-xS layers deposited by chemical bath (CBD). CdZnS thin films were synthesized by chemical bath deposition (CBD) with different deposition protocols to optimize deposition parameters such as temperature, deposition time, ion concentrations and pH. The surface morphology, structural, optical and chemical properties of the CdZnS thin films were studied by SEM, XRD, Raman and UV-visible spectrophotometer. The transmittance is 80% in the visible region 300 nm - 800 nm; the crystalline structure is hexagonal and cubic, the grain size is between 9.95 to 25.82 nm. It is observed that the transmittance and the shape change with the concentration of zinc in the solution; this result favors the application of these films in solar cells application.Voir les détails

Mots clés : CdZnS, chemical bath, SEM, Raman, solar cells, Thin films

Copper removal in solution by sawdust: kinetic and thermodynamic study

T. CHOUCHANE, A. Boukari, A. Bendjama, O. Khireddine, S. chibani (2018)
Article de journal

This study presents the results obtained when okoumé sawdust is used for the removalof copper contained in wastewater. The tests show that one gram of sawdust can fix29.56 mg of copper, according to the Langmuir model with kinetics of the pseudo firstorder where the time of the pseudo equilibrium is reached after 40 minutes of agitation.The elimination is envisaged in batch mode, at 20 ° C, a stirring speed of 200 rpm, atpH value of 4.4 and a particle size between 500 ≤ Ø < 700μm. Measured results alsoreveal that external diffusion controls the speed of the overall process of adsorption anddiffusion into the pores is not the only mechanism limiting kinetics. The thermodynamicstudy shows that this sorption is spontaneous , exothermic and that no changes havebeen made in the structure of the sawdustVoir les détails

Mots clés : Cooper, adsorption, sawdust, water, pollution

Unsupervised weld defect classification in radiographic images using multivariate generalized Gaussian mixture model with exact computation of mean and shape parameters

Nafaa Nacereddine, Aicha Baya Goumeidane, Djemel Ziou (2019)
Article de journal

In industry, the welding inspection is considered as a mandatory stage in the process of quality assurance/quality control. This inspection should satisfy the requirements of the standards and codes governing the manufacturing process in order to prevent unfair harm to the industrial plant in construction. For this purpose, in this paper, a software specially conceived for computer-aided diagnosis in weld radiographic testing is presented, where a succession of operations of preprocessing, image segmentation, feature extraction and finally defects classification is carried out on radiographic images. The last operation which is the main contribution in this paper consists in an unsupervised classifier based on a finite mixture model using the multivariate generalized Gaussian distribution (MGGD). This classifier is newly applied on a dataset of weld defect radiographic images. The parameters of the nonzero-mean MGGD-based mixture model are estimated using the Expectation-Maximization algorithm where, exact computations of mean and shape parameters are originally provided. The weld defect database represent four weld defect types (crack, lack of penetration, porosity and solid inclusion) which are indexed by a shape geometric descriptor composed of geometric measures. An outstanding performance of the proposed mixture model, compared to the one using the multivariate Gaussian distribution, is shown, where the classification rate is improved by 3.2% for the whole database, to reach more than 96%. The efficiency of the proposed classifier is mainly due to the flexible fitting of the input data, thanks to the MGGD shape parameter.Voir les détails

Mots clés : Mixture model, Multivariate GGD, radiography, weld defect, classification

Fast Adapting Mixture Parameters Schemes for Probability Density Difference-Based Deformable Model

Aicha Baya Goumeidane, Nafaa Nacereddine (2019)
Article de journal

This paper presents a new region-driven active contour using the pdf difference to evolve. The pdf estimation is done via a new and fast Gaussian mixture model (GMM) parameters updating scheme. The experiments performed on synthetic and X-ray images have shown not only an accurate contour delineation but also outstanding performance in terms of execution speed compared to the GMM estimation based on EM algorithm and to non-parametric pdf estimations.Voir les détails

Mots clés : Active contour, Adaptive mixture, GMM parameters update

Photocatalytically-assisted electrooxidation of herbicide fenuron usinga new bifunctional electrode PbO2/SnO2-Sb2O3/Ti//Ti/TiO2

Karima Barbari, Rachid Delimi, Zahia Benredjem, Samia Saaidia, Abdelhak Djemel, Toufik CHOUCHANE, Nihal Oturan, Mehmet A. Oturan (2018)
Article de journal

The degradation of the herbicide fenuron was investigated using a new porous bifunctional electrodewhere the electrooxidation takes place on one side and the photocatalysis on the other side. The characterizationof the synthetized bifunctional electrode (PbO2/SnO2-Sb2O3/Ti//Ti/TiO2) was performed byscanning electron microscopy, energy dispersive X-ray spectrometry and X-ray diffraction analysis andshowed that the anodic side (Ti/SnO2-Sb2O3/PbO2) is covered with a tetragonal b-PbO2 film and that thephotocatalytic side (Ti/TiO2) consists of an anatase phase of TiO2. The single application of electrooxidationachieved 87.8% fenuron degradation and 84.1% chemical oxygen demand (COD) removal whileheterogeneous photocatalysis resulted in only 59.2% and 39.7% fenuron concentration decay and CODremoval, respectively. On the other hand, the photocatalytically-assisted electrooxidation (photo-electrooxidation)performed on the bifunctional electrode provided higher performances of fenurondegradation (97.5%) and mineralization (97.4%). Investigation of operating parameters highlighted thepositive effect of increase in current density. Conversely, an increase in fenuron concentration led to adecrease in degradation rate and COD removal. It was also found that the COD removal and mineralizationefficiency are higher in a neutral medium.Voir les détails

Mots clés : Fenuron Bifunctional electrode Lead dioxide anode Electrooxidation Photo-electrooxidation

Core-rim structure formation in TiC-Ni based cermets fabricatedby a combined thermal explosion/hot-pressing process

S. Lemboub, S. Boudebane, F.J. Gotor, S. Haouli, S. Mezrag, S. Bouhedja, G. Hesser, H. Chadli, T. CHOUCHANE (2018)
Article de journal

TiC-Ni-based cermets were obtained by thermal explosion from different elemental mixtures(Ti, C, Ni and X, where X = Cr, Mo or W) and subsequently densified by hot-pressing under acyclic load. The whole process was performed in a single stage in the same experimentaldevice according to the following thermal and pressure procedure: a heating rate ramp up to1573 K without applying any load followed by an isothermal dwelling under a compressivecyclic load of 32 MPa. The thermal explosion synthesis occurred during the heating ramp at atemperature close to 1273 K that was practically independent of the starting nominalcomposition. The influence of different refractory elements on the chemical composition andmicrostructure of cermets was studied. SEM characterization showed that only with Mo andW, the cermets developed the characteristic core-rim structure. A high densification wasachieved, but decreased when the refractory elements were added. Nevertheless, in thesecases higher hardness values were obtained.Voir les détails

Mots clés : Cermets, Thermal explosion, Core-rim microstructure, Solid-solution carbides

Inhibition Efficiency of Cinnamon Oil as a Green Corrosion Inhibitor

Mohamed Monder Bouraoui · Samia Chettouh · Toufik Chouchane · Nabila Khellaf (2019)
Article de journal

The corrosion inhibition efficiency of cinnamon oil for stainless steel 304 L in 0.1 and 1.0 M HCl solutions was investigatedusing electrochemical study and surface electronic observation. The potentiodynamic polarization curves showed that, independentlyof the time of immersion in 1.0% HCl, a reaction to the anode occurred, which was explained by the dissolutionof the metal due to the strong aggressiveness of the medium; the addition of 1% cinnamon oil led to a corrosion efficiencyof 84%. Furthermore, in 0.1 M aggressive medium the tests with addition of inhibitor showed that the inhibition efficiencyincreases (86.6–96.0%) with an increase in the cinnamon oil concentration from 0.5 to 5%. Scanning electron microscopeobservations of metal surface confirmed the existence of a protective adsorbed film of the inhibitor on the steel surface. Cinnamonoil can be proposed as an efficient green inhibitor of corrosion of stainless steel exposed to hydrochloric acid mediums.Voir les détails

Mots clés : Aggressive medium · Cinnamon oil · Corrosion inhibitor · Stainless steel

Effet du niobium sur la résistance à l’usured’une fonte au chrome traitée thermiquement

K. BOUHAMLA, A. HADJI, H. MAOUCHE, H. MERRADI (2011)
Article de journal

Chromium cast irons are well known for their wear properties. They are widelyused in engineering practices such as mining, cement industries and many others. Theirwear properties are mainly due to their microstructure which is constituted by netted M7C3type eutectic carbide held in an austenitic or martensitic matrix. Several researchers investigatedthe possibility of improving the wear properties of these cast irons by acting onthe microstructure, the morphology of the microstructural constituents as well as on theirdistribution. The present work consists in studying the effect of the niobium on the wearbehaviour of a heat treated chromium cast iron. Characterizations by optical microscopy,abrasion and friction tests are realized in order to establish the wear resistance of this castiron and also the type of microstructure having been at the origin of this improvement. Theobtained results show that the studied material is a 15% chromium white cast iron. Niobiumaddition had an effect on the microstructure as well as on the abrasion and frictionresistances of the heat treated high chromium white cast iron samples. The wear resistanceincreases with the increase of the niobium content.Voir les détails

Mots clés : Chromium cast iron, wear, eutectic carbides, alloying elements