Papers by Author: El Hachemi Amara

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Authors: Karim Kheloufi, El Hachemi Amara
Abstract: A numerical analysis of the role of the gas friction force on the shape of the melt surface in laser cutting process is carried out. The liquid film shape is analyzed in the central plane of cutting for both cases with the pressure gradient force only and for the case of gas friction force contribution. It is shown that, the gas friction force has a significant role in the formation of humps in the central kerf zone and the transition from the smooth melt ejection regime to a wavy structure characterized by humps formation.
Authors: S. Aggoune, El Hachemi Amara
Abstract: We consider in the present work the fusion laser cutting of stainless steel sheets under a nitrogen laminar gas jet. The molten metal is treated as a laminar and steady viscous incompressible fluid. The mathematical model describing our problem is set in terms of Navier-Stokes equations, solved numerically using the finite differences method, where the effect of the gas jet velocity on the molten boundary layer is considered. The generated shear stress occurring on the gas-liquid interface and its contribution in the momentum is carried out, and it is found that when the skin friction and the shear stress decrease, the thickness and the velocity at the edge of the molten boundary layer increase along the kerf surface. The layer thickness reduces when the assisting gas velocity is increased.
Authors: Farida Hamadi, El Hachemi Amara
Abstract: In this paper we present a numerical modeling of a nanosecond laser pulse interaction with a titanium target. We investigate the vapor plume formation and the influence of the ambient gas pressure on plume expansion dynamics. The vapor plume formation depends on the results of the heat transfer in the solid target modeling. The solid-liquid phase change is modeled by a two dimensional approach using an enthalpy formulation. The resulting plume expansion in the argon background gas is studied using the species transport model. The algebraic equations are discretized by the finite volume method implemented by Fluent CFD software [1]. The calculation results of plume expansion velocity, density, temperature and degree of ionization in the plume are presented.
Authors: Farida Hamadi, El Hachemi Amara, Djamila Bennaceur-Doumaz, R. Boutaka, H. Kellou, Kamel Bourai, A. Noukaz, R. Beggar
Abstract: In this paper, we study the oxidation process during the heating of a titanium metallic surface by a Nd-YAG fiber pulsed laser beam under air environment. For this, we adopted an approach that considers a three-dimensional heat diffusion model coupled with an oxidation parabolic law (oxidation kinetics). The heat diffusion equation solved numerically, gives the temperature field. The oxide film growth is simulated by implementing a dynamic mesh technique. We developed computational procedures UDFs (User Defined Function) running interactively with the Fluent fluid dynamics software [ that implements the finite volume method. These UDFs are developed to insert the oxidation law, the temperature field, the specific boundary conditions and the mesh deformation into the calculation.
Authors: Toufik Tamsaout, El Hachemi Amara
Abstract: Laser forming is a technique consisting in the design and the construction of complex metallic work pieces with special shapes difficult to achieve with the conventional techniques. By using lasers, the main advantage of the process is that it is contactless and does not require any external force. It offers also more flexibility for a lower price. This kind of processing interests the industries that use the stamping or other costly ways for prototypes such as in the aero-spatial, automotive, naval and microelectronics industries. The analytical modeling of laser forming process is often complex or impossible to achieve, since the dimensions and the mechanical properties change with the time and in the space. Therefore, the numerical approach is more suitable for laser forming modeling. Our numerical study is divided into two models, the first one is a purely thermal treatment which allows the determination of the temperature field produced by a laser pass, and the second one consists in the thermo-mechanical coupling treatment. The temperature field resulting from the first stage is used to calculate the stress field, the deformations and the bending angle of the plate.
Authors: El Hachemi Amara, Toufik Tamsaout, Karim Kheloufi, Herman Berger, Sisa Pityana
Abstract: A 3-D transient modelling based on the numerical resolution of the fluid flow ant the heat transfer equations is developed for butt welding using the cladding process. The physical mechanisms included in our model concern the matter melting, and the re-solidification. The implementation of developed procedures called User Defined Functions (UDFs) working interactively with Fluent CFD code, and a dynamic mesh method, allows to treat the problem with its specific and complex boundary conditions. The fusion, resolidification, and the temperature dependence of the physical properties are taken into account. As results, clad formation and information on the temperature field are obtained.
Authors: Karim Kheloufi, El Hachemi Amara
Abstract: A three dimensional model for direct laser powder deposition process is developed to simulate the geometry and the thermal field in building a single-bead wall (thin-wall). This model was employed using the Fluent commercial code to which several modules were appended (User Defined Functions UDF). The temperature distribution, the geometrical features of the generated structure, and thermal cycles have been carried out. We show that the results analysis can provide guidance for the process parameter selection in LPD. , and develop a base for further residual stress analysis.
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