Liste des documents
Characterization of the deformation texture after tensile test and cold rolling of a Ti-6Al-4Vsheet alloy
The deformation texture after cold rolling and tensile test of an industrial Ti-6Al-4V sheet alloy was studied using X-ray diffraction. The alloy was subjected to a cold rolling to different thickness reductions (from 20% to 60%) and then tensile tests have been carried out along three directions relatively to the rolling direction (0°, 45° and 90°). The experimental results were compared to the existing literature and discussed in terms of active plastic deformation mechanisms. Voir les détails
Mots clés : TA6V, deformation texture, Anisotropy, Lankford
First-principles calculations of the structural, electronic and optical properties of In1−xBxAsyP1−y quaternary alloys lattice matched to InP and BeS
The structural, electronic, and optical properties of the cubic In1−xBxAsyP1−y quaternary alloys lattice matched to InP and BeS have been investigated by using the full-potential linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT). The generalized gradient approximation (GGA) of Wu and Cohen was used as the exchange correlation potential to calculate the structural and electronic properties. In addition, the alternative GGA proposed by Engel and Vosko and the modified Becke–Johnson potential are utilized to calculate the electronic properties. The computed structural and electronic properties of the binary compounds are in good agreement with the available experimental and theoretical data. For the alloys, non-linear variations of composition x and y with the lattice constant, bulk modulus, direct, indirect band gap, dielectric constant and refractive index are found. All the compounds are direct band gap excluding BP and BAs. The energy band gap of In1−xBxAsyP1−y quaternary alloys lattice matched to InP and BeS substrates is computed. Finally, the band gap of our materials is less than 3.1 eV. Thus the In1−xBxAsyP1−y quaternary alloys may possibly be used in visible light devices. Voir les détails
Mots clés : FP-LAPW, DFT, In1−xBxAsyP1−y quaternary alloys, Lattice matched
First-principle calculations of the structural, electronic, thermodynamic and thermal properties of ZnS x Se1−x ternary alloys
First-principle calculations were performed to study the structural, electronic, thermodynamic and thermal properties of ZnS x Se1−x ternary alloys using the full potential-linearized augmented plane wave method (FP-LAPW) within the density functional theory (DFT). In this approach the Wu–Cohen generalized gradient approximation (WC-GGA) and Perdew–Wang local density approximation (LDA) were used for the exchange–correlation potential. For band structure calculations, in addition to WC-GGA approximation, both Engel–Vosko (EV-GGA) generalized gradient approximation and recently proposed modified Becke–Johnson (mBJ) potential approximation have been used. Our investigation on the effect of composition on lattice constant, bulk modulus and band gap for ternary alloys shows a linear dependence on alloy composition with a small deviation. The microscopic origins of the gap bowing were explained using the approach of Zunger and co-workers. Besides, a regular-solution model was used to investigate the thermodynamic stability of the alloys which mainly indicates a phase miscibility gap. Finally, the quasi-harmonic Debye model was applied to see how the thermal properties vary with temperature at different pressures Voir les détails
Mots clés : FP-LAPW, DFT, energy band structure, Thermal Properties, Debye model, critical temperature
Inferential Sensor - Based Adaptive Principal Components Analysis of Mould BathLevel for Breakout Defect Detection and Evaluation in Continuous Casting
This paper is concerned with a method for breakout defect detection and evaluation in a continuouscasting process. This method uses Adaptive Principal Component Analysis (APCA) as a predictor of inputs -outputs model, which are defined by the mould bath level and casting speed. The main difficulties that causebreakout in continuous casting are, generally, phenomenon related to the non-linear and unsteady state of themetal solidification process. PCA is a modeling method based on linear projection of the principal components;the adaptive version developed in this work uses the sliding window technique for the estimation of the modelparameters. This recursive form updates the new model parameters; it gives a reliable and accurate prediction.Simulation results compare PCA, APCA, nonlinear system identification using neural network (NN) and supportvector regression (SVR) methods showing that the APCA gives the best Mean Squared Error (MSE). Based onthe MSE, the proposed approach is analyzed, tested and improved to give an accurate breakout detection andevaluation system. Voir les détails
Mots clés : Soft sensor, continuous casting, Adaptive principal component analysis, breakout detection and evaluation.
Uncertainty estimation of mechanical testing properties using sensitivity analysis and stochastic modelling
This paper is concerned with a method for uncertainty evaluation of mechanical propertiesin metal testing. This method uses a combined approach based on Monte Carlo simulationand Markov Chain (MCMC) as a computing procedure of different uncertainties of mechanicaland metallurgical parameters such as stress, and elongation. The MCMC is a stochasticmethod that computes the statistical properties of the considered states such as the probabilitydistribution function (PDF) according to the initial state and the target distributionusing Metropolis-Hasting (MH) algorithm. Conventional approach is based on the Guide ofUncertainty Measurement (GUM), the uncertainty budget is established for the stress andelongation parameters respectively. A comparative study between the conventional procedureand the proposed method is given. This kind of approaches is applied for constructingan accurate computing procedure of uncertainty measurement of mechanical and metallurgicalparameters. Voir les détails
Mots clés : Markov Chain Monte Carlo (MCMC) Metropolis-Hasting (MH) algorithm Mechanical and metallurgical testing Stress, elongation and hardness measurement Guide of Uncertainty Measurement (GUM)
Contribution to Inverse Kinematic Modeling of a Planar Continuum Robot Using a Particle Swarm Optimization
According to the literature, research on modeling continuum robots isfocused on ways to develop the kinematic models, because of the lack of analyticalmodels for these robots and the complexity of the problem which reside in thecoupling of operational variables and infinite of possible solutions for a desiredconfiguration. This paper presents a numerical approach for solving the inversekinematic model of a planar continuum robot (PCR), assuming that each sectionof the manipulator is curved as a circular arc, with an inextensible central axis ofthe structure. At first, this paper presents an inverse kinematic model solution forone bending section, whereas the extreme points, of each section, used in calculatingthe inverse kinematic model for multi-sections is calculated numerically usinga particle swarm optimization (PSO) technique. Finally, Simulation examples ofthis method are carried to validate the proposed approach. Voir les détails
Mots clés : Planar continuum robot, modeling, Inverse kinematic model, optimization, Particle Swarm Optimization
Computer aided weld defect delineation using statistical parametric active contours in radiographic inspection
A perfect knowledge of a defect shape is determinant for the analysis step in automatic radiographic inspection. Image segmentation is carried out on radiographic images and extract defects indications. This paper deals with weld defect delineation in radiographic images. The proposed method is based on a new statistics-based explicit active contour. An association of local and global modeling of the image pixels intensities is used to push the model to the desired boundaries. Furthermore, other strategies are proposed to accelerate its evolution and make the convergence speed depending only on the defect size as selecting a band around the active contour curve. The experimental results are very promising, since experiments on synthetic and radiographic images show the ability of the proposed model to extract a piece-wise homogenous object from very inhomogeneous background, even in a bad quality image. Voir les détails
Mots clés : Welded joint, Radiographic inspection, Active contours, local statistics-based model, band region selection
Optimization of Optical Gain in Inx Ga1-xSb/GaSb unstrained quantum well structures
In this paper we study the effects of In concentration, temperature, quantum well width and carrier density on optical gain for GaSb/InxGa1-xSb/GaSb untrained quantum well structures. This system was chosen as it is useful in infrared emission, finally, we introduce the optimum structure of quantum well to obtain the maximum optical gain, at room temperature and infrared emission particularly 2.3 (μm), for the use this structure in application of spectroscopic analysis of the gases specially CH4. This structure can be used for light absorption to increase the solar cell efficiency a based on a quantum well and multi-junction. Voir les détails
Mots clés : Quantum well, In1-x Gax Sb, optical gain, laser, Detection
Bayesian Networks-Based Defects ClassesDiscrimination in Weld Radiographic Images
Bayesian (also called Belief) Networks (BN) is a powerfulknowledge representation and reasoning mechanism. Based on probabilitytheory involving a graphical structure and random variables, BN iswidely used for classification tasks and in this paper, BN is used as aclass discrimination tool for a set of weld defects radiographic imagesusing suitable attributes based on invariant geometric descriptors. Testsare performed on a database of few hundred elements where the resultsare outstanding and very promising, since they outperform those givenby powerful SVM classifiers. Voir les détails
Mots clés : Bayesian networks, weld defects, Geometric descriptors, radiography
Joining Ti3SiC2 MAX Phase with 308 Stainless Steel and Aluminum Fillers by Tungsten Inert Gas (TIG)-Brazing Process
Herein we report on the Tungsten Inert Gas (TIG) brazing of Ti3SiC2 to 308 stainless steel and Al brazing fillers materials. The microstructures of the interfaces were investigated by scanning electron microscopy and energy dispersive spectrometry. Intensive interactions including dissolution and diffusion simultaneously occurred within the Ti3SiC2 and at the Ti3SiC2/308 stainless steel interface during TIG-Brazing. The interfacial region between Ti3SiC2 and 308 stainless steel filler is comprised of a decomposed Ti3SiC2 zone, an interaction layer zone and a modified 308 stainless steel zone. When the Ti3SiC2 comes into contact with the 308 SS molten filler during TIG-brazing, it starts decomposing into a TiCx+SiLiquid +Sigas, and simultaneously, deep penetration of the molten 308 SS into the Ti3SiC2 occurred to form a complex bright phase containing [Fe, Cr, Ni, Ti, C, Si] and TiCxphase. The loss of Si is attributed to its evaporation during the TIG-brazing process. Thermally induced residual stress due to thermal expansion mismatches create interfacial cracks between the decomposed Ti3SiC2 and the interaction layer zone. The phases that most likely form when Ti3SiC2 is joined with Al brazed filler material are Al in which some Si is dissolved, TiAl3 and Ti4AlC3. No cracks were observed during TIG joining of Ti3SiC2 with Al brazing filler material. Voir les détails
Mots clés : Tungsten Inert Gas (TIG) brazing, Ti3SiC2