Liste des communications
ÉTUDE DES PROPRIÉTÉS THERMIQUES DES BATTITURES DU LAMINOIR À CHAUD COMPLEXE SIDERURGIQUE El-HADJAR-ANNABA
Les battitures de laminoir à chaud du complexe sidérurgique d’El-Hadjar-Annaba représentent 0,1% de la production annuelle des produits plats laminés causant des pertes qui peuvent être valorisées dans certains domaines d’application.A priori, nous avons étudié les propriétés thermiques des battitures provenant du laminoir à chaud. La formation de ces battitures au cours de laminage dépend de plusieurs facteurs métallurgiques, en particulier la température dans le four de réchauffage, la pression partielle des gaz dans les différentes zones du four poussant, le temps de séjour à l’intérieur du four etc…L’analyse thermique par DSC et TGA montre des pics exothermiques synonyme d’une déshydratation et déshuilage de la calamine et des pics endothermiques indiquant une éventuelle recristallisation des oxydes de fer en l’occurrence FeO qui est stable au-delà d’une température de 570°C. Voir les détails
Mots clés : Battitures, oxydation, Laminage, Propriétés thermiques, DSC-TGA
Electronic and magnetic properties of Ba2CoWO6: First principal investigation
We report an investigation of the structural; electronic and magnetic properties of a new double perovskite Ba2CoWO6 by means of density functional calculations (DFT); within the generalized gradient approximation (GGA). The lattice constants of Ba2CoWO6 was obtained and found toagree very well with published experimental reports. The total and partial density of state are calculated and discussed. The results reveal that the Ba2CoWO6 has stable antiferromagnetic character. Our results predicts that Ba2CoWO6 have metallic nature. Voir les détails
Mots clés : ab initio, FP-LAPW, Electronic structure, Double perovskite
Theoretical and numerical study of the reflection ofan ultrasonic pulse radiated by a linear phased array transducer at a fluid-fluid interface
This study is devoted to the calculation, in transient mode, of the ultrasonic field emitted by a linear array and reflected from a fluid-fluid interface thanks to a finite element package widely used in computer simulations for solving partial differential equations describing such physical phenomena. The results obtained show the various waves emerging at the interface: direct and edge waves, specular reflection and the appearance of radiating surface waves at critical angle. The various waves are identified by their arrival times calculated using the ray method. Voir les détails
Mots clés : Transient ultrasonic, liquid-liquid interface, reflection, phased array
Measurement of thickness of thin metal sheets by the A0 Lamb mode at low frequency.thickness products
Industrial structures undergo significant stresses during their life and can destroy the environment. This can, in many cases, cause serious damage, often imperceptible. Several methods are used to detect and locate such early stage damage.Lamb waves, which are guided by both surfaces of a planar structure, are good candidates to inspect the plate in a non invasive manner. These waves have the advantage to travel long distances without significant attenuation in the direction of propagation, which allows control quickly, permanently and inreal time, large areas of difficult access. In this work, we present a method to measure the thickness of thin sheets using the propagation of the first anti-symmetric A0 Lamb mode, generated by a piezoelectric transducer. The principle is based on the existing proportionality relationship between the group velocity and thickness of thin metal sheets, at low frequencies. We test this relation on various metallic sheets of thicknesses: 25; 75; 100; 160 and 200 microns. Voir les détails
Mots clés : Lamb waves, group velocity, thickness, Transducer.
SPATIO-TEMPORAL ASPECTS OF THE DOMAIN PROPAGATION IN A SPIN-CROSSOVER LATTICE WITH DEFECT
We study the spatiotemporal formation and spreading of the high-spin state (HS) during the cooperative relaxation of the photo-induced metastable high spin (HS) state at low temperature of anelastic lattice, in the presence of a defect injected in the center of the lattice. For that, we designed a 2D rectangular-shaped lattice with discrete spins coupled by springs. The distances between the sites are spin-dependent which prevents any analytical resolution of the present problem. The elastic coupling between the spin-crossover (SCO) sites results in a long-range effective interactions between the spin states from which originates the complexity and the richness of this problem. The numerical resolution of the problem is performed using Monte Carlo simulations on the spin states and theatomic positions. The simulations are restricted to a lattice with a hole (simulating the defect) with afixed size. The presence of the defect shows the dynamics of the spin-crossover transformations startsfrom one corner of the rectangular lattice and propagates along the width (shortest distance to thesurface).Then a second regime of longitudinal propagation takes place, whose velocity slows down significantly in the vicinity of the defect. Then the interface leaves the defect, where it was pinned atlow velocity and accelerates when it approaches the border of the lattice. We have also investigated the spatial dependence of the displacement field, from which we derived the spatial distribution of the divergence, which directly connects to the distribution of the internal strain and elastic energy. Valuable information is derived from the time-dependence of the total elastic energy in particular around the defect. Voir les détails
Mots clés : Spin Crossover, phase transition, interface propagation, Defects, elasticity, Monte Carlo Simulations
Using Multivariate Statistics & Multi-Scale Entropy to Monitor Gears Degradation and Signal Denoising Strategy using Wavelet Decomposition
This paper focuses on fault diagnosis in gears transmissions driven by induction machines. A new tool of anomaly detection based on multi-scale entropy (MSE) algorithm in conjunction with multivariate statistical approach of the motor current signature analysis (MCSA) is proposed. Simulation results show that the proposed methods are able to detect tooth surface decay in the permanent regime of MCSA. Voir les détails
Mots clés : gear Fault diagnosis, Multi-scale entropy, Induction machine, Wavelet decomposition and principal component analysis.
Stress and temperature effects study on anhysteretic curves behavior of magnetostrictive materials
The present work deals with the effect of stress and temperature on the effective magnetic field which occurs in magnetostrictive materials when it is subjected to external applied field. The magnetostriction is then computed for changes made onstress and temperature respectively. The anhysteretic curves representing the magnetization behavior with applied magnetic field are deduced. The results obtained are comparable with those provided in literature. Voir les détails
Mots clés : Stress, Magnetostrictive materials, Magnetization, Temperature, Stress field, Anhysteretic curve
Defects dispersion studies in composite structures has polymer matrix
The performance / weight composite materials with polymer matrix reinforced by fibers makes them a material of choice for structural applications in many fields such as aerospace and civil engineering. Among these materials, the epoxy matrix composites reinforced carbon fibers are often referred to as having the most interesting mechanical properties due to the remarkable properties of the carbon fibers. The epoxy resin is also involved in obtaining these exceptional properties thanks to its ability to impregnate the fibers well, its chemical and electrical resistance and low retraction during polymerization.Analysis of measurement results of the three pointbending on the composite materials epoxy matrix reinforced with different layers of carbon fibers using Weibull statistics allow us to the highlight the probabilistic aspects of the fracture and the dispersion defects in structures. Voir les détails
Mots clés : composite, fiber, polymer, probability default.
Innovative Eddy Current Probes Characterization Of Micro Defects
In this paper, we designed Eddy Current probes based on two different technologies, depending on the application. The first one is based on traditional probes based on classical winding coils, the second one takes advantage of the small size and high sensitivity of micro-coils etched on a flexible kapton film. Those probes are very efficient in the detection of defects located in complex geometries or in small curvature radius components. The simulation also provides the ability to compare upstream performance of a new probe relative to a conventional sensor and thus guide the choice of investment in innovative technology. Voir les détails
Mots clés : Eddy curren, Defect characterization, Finite Element Method, micro coil, arrayed eddy current sensor
Physical and chemical analysis of the material cast of a prosthesis for tibia (morphology and DSC).
In this approach, we have shown the results of Scanning Electron Microscope characterization (SEM), Optical Microscopy and Differential Scanning Calorimetry (DSC). The prosthesis is a composite material consisted of an organic matrix reinforced by a glass fiber and perlon, prepared by a standard casting method under vacuum. All our results show us: -The microscopic analysis has a porous structure. -Furthermore, the optical micrography chows the arrangement of the fiber in the matrix. -The result of Differential Scanning Calorimetry shows a glass transition (Tg). Voir les détails
Mots clés : physical analysis, prosthesis for tibia, MEB, DSC, optical microscopy.