Liste des communications
Effect of welding process and filler metal on microstructure and mechanical behavior of dissimilar stainless steel welds
Dissimilar weldments have been widely used in the industry and there are many applications in which weldments are made from metals of different compositions, because of economic benefits. However dissimilar is often more difficult than joining the same metals, due to the differences in the physical, mechanical, and metallurgical properties of the metals to be joined.In this work the effect of welding process parameters and filler metal types on microstructure and mechanical properties of dissimilar stainless steel welds joints are studied. Microstructure, microhardness and tensile strength of the welds joints have been evaluated and the results are compared. The fracture surfaces of the tensile specimen were examined by scanning electron microscopy (SEM). From this investigation it is observed that we can used austenitic and duplex filler if the welding process parameters are optimized. Voir les détails
Mots clés : GTA welding, dissimilar stainless steel, welding process, microstructure, mechanical properties, fracture surface
Effect of powder addition and welding process on microstructure and mechanical properties of Ferritic Stainless Steel welds
Ferritic stainless steels are classified as such because the predominant metallurgical phase present is ferrite. These steels are characterized by good resistance to stress corrosion cracking (SCC), pitting corrosion, crevice corrosion (particularly in chloride environments), higher thermal conductivity, low coefficient of heat dilation and lower cost, when compared to austenitic stainless steels. The combination of low cost and good properties has made ferritic stainless steel more and more attractive in various application fields, such as, heat exchangers, petroleum refining equipment, storage vessels, protection tubes, solar water heaters, and exhaust manifold applications.However, ferritic stainless steel steels are associated with many problems during the welding process. These problems are the martensite formation and grain growth, causing a reduction of ductility and toughness. For these reasons, until recently, the application of this group steels is limited in welded structures. The aim of the present study is to investigate the influence of the Ti and Al on the microstructure and mechanical properties of AISI 430 ferritic stainless steel welds produced by GTA welding. The details of tensile tests, optical microscopic observations, microhardness, and Scanning electron microscopy (SEM) fractography, are discussed. Voir les détails
Mots clés : GTA welding, ferritic stainless steel, powder addition, welding process, microstructure, mechanical properties, fracture surface
Fast Algorithm to Minimize model CombiningDynamically Local and Global Fitting Energy for Image Segmentation
Segmentation by using region-based deformable models has known a great success and large domain of applications. In this paper, we propose a fast algorithm to minimisemodel which combines local fitting energy and global fitting energy. The minimisation via the proposed algorithm avoids solving any Partial Differential Equation PDE. Consequently, there is no need to any stability conditions. Furthermore, owing to the fast convergence we don’t need to the re-initialisation step and the term that keeps Level Set LS as Signed Distance Function SDF. In addition, we have used a dynamic function to adjust between the local and global energies. Successful segmentation results are obtained on synthetic and real images with a great saving of CPU time compared to the minimisation via gradient descent method. Voir les détails
Mots clés : image segmentation, region-based model, Level set, hybrid models, sweeping, fast convergence
Tomographic Image Reconstruction Using Filtered Back Projection (FBP) And Algebraic Reconstruction Technique (ART)
This paper presents comparative study and experimentation of Algebraic Reconstruction Technique (ART) and Filter Back Projection (FBP). The ART and FBP methods are used to reconstruct the object from the X-ray projection. The process of creating back the object image from the Radon Transform of the object is known as Image Reconstruction. Image reconstruction is a famous and interesting field which comes under computed tomography. Computed Tomography is used for identifying the hidden or inner defects of objects. In this paper Algebraic Reconstruction technique and Filter Back Projection methods are implemented and the experimented results are compared using performance parameters for various test cases. Projections for the image reconstruction are calculated analytically by defining two phantoms: Shepp-Logan phantom head model and the standard medical image of abdomen. The original images are grayscale images of size 128 × 128, 256 × 256, respectively. Voir les détails
Mots clés : Computed tomography, X-ray projection, Filter Back Projection, Algebraic Reconstruction Technique
Density functional approach to study structural and electronic properties of III-Sb semi-conductors by modified Becke-Johnson Potential
In this work, we present the structure and electronic properties of the semiconductors III-Sb binaries, using a first principles calculations have been performed, using the FullPotential Linearized Augmented Plane Wave (FP-LAPW) calculations based on Density Functional Theory (DFT) [1-2].The local density approximation (LDA) and the revised Perdew-Burke-Ernzerhof generalized gradient approximation (GGA-PBEsol) were used only in calculating structural properties, the modified Becke–Johnson (mBJ-GGA) approach were used to calculate the electronic properties. Our calculations are in good agreement with the theoretical works and experimental data, deducing the possibility of these materials to be used in the optoelectronics devices. Voir les détails
Mots clés : FP-LAPW, mBJ-GGA, wien2k, structural parameters, electronic properties
Theoretical investigation of optical properties of zinc blende III-Antimony materials
A first-principles calculations have been performed, using the Full Potential Linearized Augmented Plane Wave (FP-LAPW) calculations based on Density Functional Theory (DFT) method as implemented in Wien2k code, to evaluate the optical properties of III-Antimony binary compounds AlSb, GaSb and InSb, using the new semi-local modified Becke–Johnson potential (TB-mBJ) developed by Tran and Blaha. The real and the imaginary parts of the dielectric function, absorption coefficient, reflectivity and optical conductivity versus photon energy were presented to discuss optical properties of III-Sb. The results obtained were compared with experimental data and other computational works, suggesting our compounds as suitable materials for optoelectronic device applications. Voir les détails
Mots clés : FP-LAPW, DFT, mBJ-BT, Optical parameters.
Study and control of PWM arc welding inverter based on a microcontroller
This paper presents an arc welding inverter, based on a microcontroller device for generate PWM pulse. An IGBT inverter was established by applying several control techniques. This system improves the power factor of welding machine and reduce the harmonics. Simulations results are presented to show the operation of proposed system. Voir les détails
Mots clés : are welding inverter, microcontroller, PWM, IGBT inverter
Asymmetric Generalized Gaussian Mixturesfor Radiographic Image Segmentation
In this paper, a parametric histogram-based image segmentation methodis used where the gray level histogram is considered as a finite mixture of asymmetricgeneralized Gaussian distribution (AGGD). The choice of AGGD is motivated byits flexibility to adapt the shape of the data including the asymmetry. Here, themethod of moment estimation combined to the expectation–maximization algorithm(MME/EM) is originally used to estimate the mixture parameters. The proposedimage segmentation approach is achieved in radiographic imaging where the imageoften presents an histogram with a complex shape. The experimental results providedin terms of histogram fitting error and region uniformity measure are comparableto those of the maximum likelihood method (MLE/EM) with the advantage thatMME/EM method reveals to be more robust to the EM initialization than MLE/EM. Voir les détails
Mots clés : AGGD, MME/EM, MLE/EM, Radigraphy
Microstructure and mechanical behavior of TIG bimetallic joints
Bimetallic weld techniques have progressed a great deal in the last decade. In this work, the effect of the filler metal composition on microstructure and mechanical behavior of dissimilar HSLA-X70/304L stainless steels weld joint is investigated. The dissimilar weld joints are fabricated using austenitic, duplex and low Carbone filler metal. The mechanical behavior is investigated through microhardness, charpy impact and tensile test.The results show that, the weld metal composition has a great influence on mechanical properties and microstructure of weldments, in particular the grain size and phases nature, changes with filler metal composition. In addition presence of martensitic slats in the FZ when using the low Carbone filler metal, detailed microstructure examination is carried out and related to the mechanical behavior of the dissimilar joints. Voir les détails
Mots clés : TIG welding, Bimetallic weld, HSLA, DSS, HAZ, microstructure, Microhardness
Asymmetric Generalized Gaussian Mixtures for Radiographic Image Segmentation
In this paper, a parametric histogram-based image segmentation methodis used where the gray level histogram is considered as a finite mixture of asymmetricgeneralized Gaussian distribution (AGGD). The choice of AGGD is motivated byits flexibility to adapt the shape of the data including the asymmetry. Here, themethod of moment estimation combined to the expectation–maximization algorithm(MME/EM) is originally used to estimate the mixture parameters. The proposedimage segmentation approach is achieved in radiographic imaging where the imageoften presents an histogram with a complex shape. The experimental results providedin terms of histogram fitting error and region uniformity measure are comparableto those of the maximum likelihood method (MLE/EM) with the advantage thatMME/EM method reveals to be more robust to the EM initialization than MLE/EM. Voir les détails
Mots clés : AGGD, MME/EM, MLE/EM, Radigraphy