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Nombre total de résultats : 1189
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WEAR STUDY OF SUPERMARTENSITIC STAINLESS STEEL 13Cr5Ni2Mo

S.Tlili, C.E.RAMOUL, K. SLIMANI (2017)
Communication

Due to the increasing need for more cost-effective use of materials, supermartensitic stainless steels have been developed over the past 20 years and are ever more applied in the oil and gas industries to replace highly alloyed alternatives. In practice, the supermartensitic steels are used in the quenched and tempered state. In this study, we were interested in the frictional wear behavior of a supermartensitic stainless steel 13Cr 5Ni 2Mo,this steel intended for the manufacture of pipe used in the petroleum field. Several means of investigation have been used, namely thermal analysis by DSC on samples after homogenization treatment at 1050 ° C. for 20 hours. The microstructure and the wear mechanism were studied using scanning electron microscopy. We choised a peak-disk tribometer under dry conditions against an Al2O3 alumina ball and a WC tungsten carbide ball. All the tests were carried afterquenching at 1050 °Cand tempering at 550 °C, 2 hours (treatment which gave better hardness properties obtained by micro-indentation) at ambient temperature while varyingthe applied load of 2N, 6N to 10N. A one-off analysis of wear debris by EDS at SEM was also completed.The results obtained showed that the coefficient of friction of the 13 Cr 5Ni 2Mo steel against the ball WC is greater than that of the Al2O3 ball and that the mechanism of wear by friction of this steel is different for each antagonist.Voir les détails

Mots clés : SMSS, microstructure, heat treatments, friction, Mechanism Wear

Effect of calcination for synthetesis of bioceramic hydroxyapatite powder by co-precipitation method: structural properties

M. Mokhtari, L. Bahloul, S. Guerfi, L. Lalimi, A. Azi, I. Fadel (2017)
Communication

Hydroxyapatite powders (HAp) were synthesized by a low cost method using calcium chloridedihydrate (CaCl2.2H2O) and diammonium hydrogen phosphate ((NH4)2HPO4) as calcium andphosphate ion sources, respectively. The process is carried out at two different temperatures 80 and 100 °C with calcinations at 900 and 1200 °C for 90 min.X-Ray powder diffraction confirms the effect of calcination on the crystallinity and lattice parametersof as prepared HAp.The effect of conditions on the different obtained samples by varying the synthesis parameterssuch as preparation temperature and calcinations were studied. Furthermore, the temperaturedependence on the structural properties of HAp samples was investigated.Voir les détails

Mots clés : hydroxyapatite, HAp, Bioceramic, Precipitation technique, X-ray diffraction

Kalman Filter and Markov Chain Monte Carlo Method for Uncertainty Estimation

Extended Kalman Filter (2017)
Communication

This paper is concerned with a method for uncertainty evaluation of carbon – Sulfur content using Infra red combustion method. The considered method of analysis is a comparative technique based on the infra red emission of the combustion; the calibration step assumes an obtention of an accurate chemical composition of metallic analyzed sample.It is proposed in this work a new combined approach using the Kalman Filter and Markov Chain Monte Carlo (MCMC) for uncertainty estimation of steel Carbon (C) - Sulfur (S) content analysis. The Kalman filter algorithm is extended to the model identification of the chemical analysis process using the main factors affecting the analysis results; in this case the estimated states are reduced to the model parameters. The MCMC is a stochastic method that computes the statistical properties of the considered states such as the probability distribution function (PDF) according to the initial state and the target distribution using Monte Carlo simulation algorithm. Conventional approach is based on the Guide of Uncertainty Measurement (GUM), the uncertainty budget is established for steel Carbon (C) - Sulfur (S) content respectively. A comparative study between the conventional procedure and the proposed method is given. This kind of approaches is applied for constructing an accurate computing procedure of uncertainty measurement.Voir les détails

Mots clés : Extended Kalman Filter

STUDY OF THE POLYPROPYLENE BEHAVIOR ON A LOCAL SCALE USING THE NANO-INDENTATION TECHNIQUE.

Mokhtari Ahcene, Tala-Ighil Nacer, Fillon Michel (2017)
Communication

The aim of this work is to study the polypropylene matrix behaviour of a composite glass/pp on a local scale using the nano-indentation technique. For this, a non-linear modelling of the polypropylene matrix behaviour is performed. The used model combines between an elasto-plastic response and a visco-plastic response corresponding quantitatively to the matrix response. The numerical simulations were carried out using the finite element calculation code Abaqus/Explicit. The tests of nano-indentations were carried out at ambient temperature on polypropylene specimens and the parameters of the material were identified using the inverse method. The obtained numerical results show that the developed model can accurately predict the static response obtained by experimental measurements.Voir les détails

Mots clés : Polypropylene matrix, nano-identation, inverse method, modelling

Density Functional Theory Model for the Prediction of the Adsorption Centers of Organic Corrosion Inhibitors within Acidic Medium

A. Addoun, A. Haddad (2017)
Communication

In this work, prediction of the potential adsorption centers of ascorbic acid and paracetamol compounds was carried out using density functional theory method at B3LYP/6-31G basis sets. Highest occupied and lowest unoccupied molecular orbital energy levels, energy gap, total energy and polarity of the selected organic compounds were determined and correlated to their respective inhibition efficiencies. Comparatively, higher values of energy level and polarity were noticed for ascrobic acid which predicts more reactivity; thus, a better adsorption property. Electrochemical tests were conducted for mild steel in 1 M HCl solution. The corrosion tests revealed a better inhibition efficiency with ascorbic acid against paracetamol. Hence, application of the DFT model showed a very good agreement with the experimental values.Voir les détails

Mots clés : DFT, corrosion, adsorption, organic inhibitor

Chemical sensor array modeling using multivariable partial differential equations: comparison between conducting polymer and metal oxide based resistive sensors

a.abbas, A.Badidi Bouda, a.mebtouche (2017)
Communication

In the presented paper, the interactions between a chemical sensor array and a gas mixture were investigated. A partial differential equations that contain several variables, and connects the partial sensitivities of the sensor array elements with the input variables (concentrations of the gas mixture components), have been developed. Furthermore, the solutions of the differential equations were deduced. We were especially interested for resistive sensors based on conducting polymers and metal oxide sensitive layers (or films), we made a comparison between them .Voir les détails

Mots clés : chemical sensor array, gas mixture, modeling, Metal oxide sensors, Conducting Polymer Sensors

PRISE EN COMPTE DE L’ASPECT NON LINÉAIRE DANS L’ANALYSE MODALE DES STRUCTURES MÉCANIQUES

LATEF Mohamed, Pr. AΪAD Abedelkarime (2016)
Communication

La connaissance des caractéristiques modales est primordiale dans l’étude du comportement dynamique des structures. L’application de l’analyse modale a été souvent réservée au domaine linéaire. Cependant, la plupart des structures mécaniques, rencontrées dans la pratique, présentent un comportement plus ou moins non linéaire. L’aspect non linéaire est d’origines diverses, dépend de plusieurs facteurs et peut se manifester globalement (géométrie, propriétés mécaniques,…) ou localement (conditions aux limites, joints, …).Dans ce travail, nous avons applique l’analyse modale a des systèmes vibratoires discrets (masse-ressort) non linéaires d’aspect géométrique.Plusieurs méthodes ont été utilisées pour déterminer les paramètres modaux, a savoir :- Balance harmonique (analytique).- Variété de l’invariant de Shaw-Pierre (numérique).- Range Kutta d’ordre 4.Des programmes ont été établis sous matlab pour exploiter ces méthodes. Les résultats obtenus nous ont permis de préciser :- la limite entre les systèmes linéaires et non linéaires.- l’effet des conditions initiales et le paramètre non linéaire.- domaine d’application des méthodes permettant l’étude des systèmes non linéaires.Voir les détails

Mots clés : vibration, Analyse modale, non linéarité géometrique

Electronic Properties Study, of Ni/MgO Nanoparticles by (XPS)

N. Ouafek, N. Keghouche, H. Dehdouh, C.Untidt (2017)
Communication

A lot of knowledge has been accumulated on the metal clusters supported on oxide surfaces because of their multiple applications in microelectronics, heterogeneous catalysis and magnetic devices.In this work, the surface state of Ni / MgO has been studied by XPS (X-ray Photoemission Spectroscopy). The samples were prepared by impregnation with ion exchange Ni2+ / MgO, followed by either a thermal treatment in air (T = 100 -350 ° C) or a gamma irradiation (dose 100 kGy, 25 kGy dose rate h -1). The obtained samples are named after impregnation NMI, NMR after irradiation, and finally NMC(T) after calcination at the temperature T (T = 100-600 °C). A structural study by XRD and HRTEM reveals the presence of nanoscaled Ni-Mg intermetallic phases (Mg2Ni, MgNi2 and Mg6Ni) and magnesium hydroxide. Mg(OH)2 in nanometric range (2- 4 nm). Mg-Ni compounds are of great interest in energy filds (hydrogen storage…).XPS spectra show two Ni2p peaks at energies of about 856.1 and 861.9 eV, indicating that the nickel is primarily in an oxidized state on the surface. The shift of the main peak relative to the pure NiO (856.1 instead of 854.0 eV) suggests that in addition to oxygen, nickel is engaged in another link with magnesium. This is in agreement with the O1s spectra which present an overlap of peaks corresponds to NiO and MgO, at a calcination temperature T ≤ 300 ° C.Voir les détails

Mots clés : nanoparticles, Ni-MgO, XPS, XRD

Influence of manufacturing process on wear resistance Of grinding balls

BOUREBIA.MOUNIRA, BOUHAMLA Khedidja, MAOUCHE Hichem, Gherbi Amel, Chaour Mouhamed, Laouar.Lakhder (2017)
Communication

Abstract The grinding balls are widely used in cement works, they are often manufactured by the molding process, but the problem faced by major cement plants in Algeria is that these balls wear out quickly and broken. The objective of this work is to test wear resistance of grinding balls made by molding and grinding balls produced by forging. The tests of characterization of samples will be made thus that wear tests. The results indicate that grinding balls made by forging resist longer than molded balls by fact this method offers by fiber-forming phenomenon a solid texture which allows increases service life, wear resistance and impact strength.Voir les détails

Mots clés : Grinding ball, forging, molding, texture, wear

NDT CHARACTERIZATION OF NANOCOMPOSITE

A.Younes, N.Dilmi, A.BOUAMER, H.Amar, Z.GUEZOUI, M.amir, M.Zergoug (2016)
Communication

Nanostructured materials are current topics in research and development in recent years because of the good mechanical and physical properties compared to crystalline materials. The nanocrystalline coatings may show increased hardness, good mechanical strength [1], good corrosion resistance and the oxidation resistance, and / or good behavior to friction and wear [1,2]. In particular, nanostructured materials have good properties in tribology, motor vehicles, heavy machines and cutting tools, etc. that require advanced materials functioning with minimum energy loss. Nanostructured coatings such tribological surfaces for use in contact with harsh conditions were searched intensively for the past decade. PVD and CVD are well-known methods for depositing such [3] coatings. However, the drawbacks associated such that the deposition sector size, substrate geometry, cost and complexity of the process often limit their use. In this perspective, the deposit by thermal spraying gives much attention. The different materials Metal, ceramics or cermet [4], nanostructured coatings were deposited by thermal spraying processes such as HVOF. In addition, the properties of these coatings have been found to strongly depend on the porosity, of the phase distribution, and the residual stress [5-6]. Voir les détails

Mots clés : Nanostructured materials, alumina, Mechanical Alloying, MEB, EDX, DRX, VSM