Publications Internationales
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Item Effect of the A1 to L10 transformation on the structure and magnetic properties of polycrystalline Fe56Pd44 alloy thin films produced by thermal evaporation technique(Elsevier, 2018) Bahamida, Saida; Fnidiki, A.; Coïsson, M.; Barrera, G.; Celegato, F.; Olivetti, E.S.; Tiberto, P.; Laggoun, A.; Boudissa, M.X-ray diffraction, conversion electron Mössbauer spectroscopy and superconducting quantum interference device magnetometer techniques have been used to characterize the evolution of the microstructure and of the magnetic properties of phase transformation from disordered FePd face-centred cubic (A1) phase, to an ordered phase L10 FePd of tetragonal structure. This study was carried out by isothermally annealing in vacuum at 550 °C, as a function of annealing time, a Fe56Pd44 thin film alloy deposited on silicon substrate. The structural transformations are accompanied by a decrease of the (c/a) ratio and by an increase of the coercive field as a function of annealing time. After 10 min of annealing, the (c/a) ratio is equal to 0.945, which indicates that the disordered FePd phase is completely transformed into the ordered L10 FePd phase. By increasing annealing time, the microstructure of the alloy evolves, antiphase boundaries and twin boundaries develop. In contrast to the relationship most commonly described in the literature, that the highest coercivity corresponds to a two-phase ordered/disordered mixture, in ours studies the maximum value for coercivity corresponds to the fully ordered state. Furthermore, we propose that the high coercivity in these films is due to pinning centres of magnetic domain walls by antiphase boundaries and twin boundariesItem Deep convolutional neural networks for Bearings failure predictionand temperature correlation(JVE International, 2018) Belmiloud, D.; Benkedjouh, T.; Lachi, Mohammed; Laggoun, A.; Dron, J. P.Rolling elements bearings (REBs) is one of the most sensitive components and the common failure unit in mechanical equipment. Bearings failure prognostics, which aims to achieve an effective way to handle the increasing requirements for higher reliability and in the same time reduce unnecessary costs, has been an area of extensive research. The accurate prediction of bearings Remaining Useful Life (RUL) is indispensable for safe and lifetime-optimized operations. To monitor this vital component and planning repair work, a new intelligent method based on Wavelet Packet Decomposition (WPD) and deep learning networks is proposed in this paper. Firstly, features extraction from WPD used as input data. Secondly, these selected features are fed into deep Convolutional Neural Networks (CNNs) to construct the Health Indicator (HI). This study focuses on analysing the relationships such as correlations between the HI and temperature. We develop a solution for the Connectiomics contest dataset of bearings under different operating conditions and severity of defects. The performance of the proposed method is verified by four bearing data sets collected from experimental setup called “PRONOSTIA”. The results show that the health indicator obtains fairly high monotonicity and correlation values and it is beneficial to bearing life prediction. In addition, it is experimentally demonstrated that the proposed method is able to achieve better performance than a traditional neural network based methodItem The role of siliconon the micro structure and magnetic behaviour of nanostructured (Fe0.7Co0.3)100_xSix powders(Elsevier, 2017) Hocine, M.; Guittoum, A.; Hemmous, M.; Martínez-Blanco, D.; Gorria, P.; Rahal, B.; Blanco, J.A.; Sunol, J.J.; Laggoun, A.Item The role of silicon on the microstructure and magnetic behaviour of nanostructured (Fe0.7Co0.3)100_xSix powders(Elsevier, 2017) Hocine, M.; Guittoum, A.; Hemmous, M.; Martínez-Blanco, D.; Gorria, P.; Rahal, B.; Blanco, J.A.; Sunol, J.J.; Laggoun, A.Single-phase(Fe0.7Co0.3)100 xSix nanostructured powders(x¼0,5, 10,15and20)havebeenelaboratedby mechanical alloyinginordertoinvestigatetheeffectofsilicononthemicrostructureandmagnetic properties ofthesealloys.AdisorderedFe(Co,Si)solidsolutionwithbodycentredcubic(bcc)crystal structure isformedafter72hofmillingforallthecompositions.TheadditionofSigivesrisetoapro- gressivedecreaseofthelatticeparameter,fromabout2.865ÅforthebinaryFe70Co30 compound downto 2.841Åforthepowderwith x¼20. ThesamplewiththeuppermostSicontentexhibitsthelowestvalue for themeangrainsize(E10nm)aswellasthelargestmicrostrain(above1.1%).Allthesamplesare ferromagnetic atroomtemperature,althoughthesaturationmagnetizationvaluereducesalmostlinearly by addingSitothecomposition.Asimilartrendisobservedforthehyperfine magnetic field obtained from theanalysisoftheroomtemperatureMössbauerspectra.Thehyperfine field distributionsshowa broad double-peakshapefor x40, whichcanbeascribedtomultiplelocalenvironmentsfortheFe atoms insideadisorderedsolidsolutionItem Monte Carlo investigation of magnetization switching of interacting ferromagnetic nanoclusters(American Scientific Publishers, 2014) Brinis, D.; Ledue, D.; Laggoun, A.; Patte, R.Item Microstructure and magnetic properties of nanostructured (Fe0.8Al0.2)100-xSix alloy produced by mechanical alloying(Elsevier, 2015) Boukherroub, Nadia; Guittoum, A.; Laggoun, A.; Hemmous, M.; Martínez-Blanco, D.; Blanco, J.A.; Souami, N.; Gorria, P.; Bourzami, A.; Lenoble, O.Item A comparative structural and magnetic study of Fe100-xPdx(x=15, 20 and 36) thin films deposited on Si (100) and glass substrates(Elsevier, 2015) Bahamida, Saida; Fnidiki, A.; Laggoun, A.; Guittoum, A.Various structural and magnetic characterization techniques have been used to investigate Fe100-xPdx (x=15, 20 and 36) thin films deposited onto silicon and glass substrates, by thermal evaporation technique. X-ray diffraction analysis shows the presence of supersaturated solid solution with bcc structure for Pd concentrations of 15% and 20%. However, for 36% of Pd, in addition to the supersaturated α-FePd (bcc) phase, another disordered FePd3 phase with fcc structure is present. At 20 at% Pd, the magnetic characterization shows a saturation of the bcc (α-FePd) phase and the appearance of the fcc phase. The correlation between the structure and magnetic properties allows us to compare the two substrates effects on deposited thin films. As results, the measurements indicate that the grain size D, the thin film thickness and the d(110) spacing significantly affect the magnetic coercivity HC. The Fe-Pd alloys deposited on a monocrystalline Si (100) and glass substrate show that the coercivity HC is given by the random anisotropy model. & 2015Item Monte carlo investigation of magnetization switching of interacting ferromagnetic nanoclusters(American Scientific Publishers, 2014) Brinis, D.; Ledue, D.; Laggoun, A.; Patte, R.Item Effects of dimensionality and spatial distribution on the magnetic relaxation of interacting ferromagnetic nanoclusters : a Monte Carlo study(American Institute of Physics, 2014) Brinis, D.; Laggoun, A.; Ledue, D.; Patte, R.Item Methodological approach of selecting a vibration indicator in monitoring bearings(Academic Journals, 2013) Djebili, Omar; Bolaers, F.; Laggoun, A.; Dron, J. P.A rolling bearing is an important element in a rotating machine. Whatever the operating conditions, it is subject to fatigue which causes spalling. In aiming to obtain the most possible real fatigue curve, the vibration level is shown according to different statistical indicators such as the RMS (Root Mean Square), the kurtosis, the crest value, the crest factor and the peak ratio, then to choose the best of them that is able to show the evolution of the bearing degradation. In this work, through the experimental vibratory follow up of the thrust bearing spall using different statistical indicators, we present an optimization methodology in order to find a most significant indicator that is able to characterize the damage evolution