Browsing by Author "Zedira Hamma"

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    Characterization of precipitates in a 7.9Cr–1.65Mo–1.25Si–1.2V steel during tempering
    (Materials Characterization(Elsevier), 2009-09-01) Djebaili Hamid; Zedira Hamma; Djelloul Abdelkader
    In this paper, the precipitates formed during the tempering after quenching from temperature 1150 °C for 7.90Cr–1.65Mo–1.25Si–1.2V steels are investigated using an analytical transmission electron microscope (A-TEM).The study of this tempering is carried out in isothermal and anisothermal conditions, by comparing the results given by dilatometry and hot hardness. Tempering is performed in the range of 300–700 °C. Coarse primary carbides retained after heat treatment are V-rich MC and Cr–Mo-rich M7C3 types. In turn, it gives a significant influence on the precipitation of fine secondary carbides, that is, secondary hardening during tempering. The major secondary carbides are Cr–Mo–V-rich M′C (and/or) Cr–Mo-rich M2C type. The peak hardness is observed in the tempering range of 450–500 °C. In the end, we observe between 600 and 700 °C, that this impoverished changes the phase. At these high temperatures of tempering, we observe that there is a carbide formation of the types M6C developing at the expense of the fine M7C3 carbides previously formed
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    Modélisation de la rupture d’un pli unidirectionnel perforé
    (Revue des Composites et des Matériaux Avancés, 2009) BREK Samir; Manaa Rabah; Zidani Kamel; Zedira Hamma; Djebaili Hamid
    The Composite materials are the subject of several studies because of their high specific characteristics and advantages of the latter to adapt to mechanical stress from a judicious preparation of matrix and reinforcement, particularly laminates of Unidirectional Carbon / Epoxy, are increasingly used for the realization of structures. However, the holding of composite structures can be greatly reduced by the addition of geometric singularitie. This work is to determine the critical distance between two holes in one ply unidirectional carbon / epoxy, tensional and study the effect of the factor of stress concentration on the total ruin and brutal (that is to say wide mixture of fiber and matrix for a unidirectional ply).
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    One Dimensional Modeling of the Shape Memory Effect
    (Modeling and Numerical Simulation of Material Science, 2013-03-24) Meddour Belkacem; Zedira Hamma; Djebaili Hamid
    This paper aims to build a constitutive model intended to describe the thermomechanical behavior of shape memory alloys. This behavior presents many facets, among them we have considered the simple way of shape memory, which is one of most important properties of shape memory alloys. Because of numerous stages of this effect, the subject was divided into three independent parts. For each part, we built the corresponding thermodynamic potential and we deduced the constitutive equations. To make this model workable, we have developed an algorithm. The simulation was performed using the NiTi as shape memory alloy.
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    One Dimensional Modeling of the Shape Memory Effect
    (Modeling and Numerical Simulation of Material Science, 2013-03-24) Meddour Belkacem; Zedira Hamma; Djebaili Hamid
    This paper aims to build a constitutive model intended to describe the thermomechanical behavior of shape memory alloys. This behavior presents many facets, among them we have considered the simple way of shape memory, which is one of most important properties of shape memory alloys. Because of numerous stages of this effect, the subject was divided into three independent parts. For each part, we built the corresponding thermodynamic potential and we deduced the constitutive equations. To make this model workable, we have developed an algorithm. The simulation was performed using the NiTi as shape memory alloy.
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    Prévision de la ruine des composites stratifiés perforés sous chargement thermomécanique
    (Revue des composites et des matériaux avancés, 2011) BREK Samir; Zidani Kamel; Djebaili Hamid; Manaa Rabah; Zedira Hamma
    The laminated composite structures in the form of plates are increasingly used for the design of mechanical structures. These are generally resistant structures, capable of withstanding mechanical loading and thermo mechanical important. Although the analysis of composite structures is required to a key point in the design of structures, there is lack of studies for laminated composite perforated, especially for high gradient structures are sought by monotonic or cyclic thermo mechanical loading, the transverse cracking is usually the first damage observed in the matrix as a fold disoriented relative to the axis of solicitation. In this work we propose a numerical study to calculate the critical distances between two holes in the plates laminated carbon / epoxy loaded by thermomechanical loadings, we used a software structural analysis by finite element method (Castem2009).
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    Three Dimensional Modeling and a Simulation of the Shape Memory Effect
    (Scientific Technical Review,, 2014) Meddour Belkacem; Zedira Hamma; Djebaili Hamid
    The paper deals with modeling and simulating the shape memory effect , one of many behaviors of shape memory alloys. The effect was first divided into three stages. Every stage has its own thermodynamic potential and constitutive equations. The martensite fraction is the only internal variable to be considered: in the first stage, it represents the fraction of detwinned martensite; in the second stage, it represents the fraction of transformed martensite into austenite, and in the last stage, it represents the fraction of the produced martensite from the austenite transformation. For every stage, we deduced the constitutive equations using the principles of thermodynamics and a simple formalism. When the model was defined, we simulated it using the experimental data obtained by analyzing a cube specimen subjected to triaxial traction and thermal load. The obtained results of this simulation reflect the behavior of this kind of materials when thermomechanical load is applied. The main finding of this paper is that the proposed constitutive model can be used to simulate the shape memory effect.
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    Three-dimensional modeling of pseudoelastic effect of the shape memory alloys
    (Journal of the Serbian Society for Computational Mechanics, 2015-01-10) Meddour Belkacem; Zedira Hamma; Djebaili Hamid
    The present work aims to develop a 3D constitutive model to describe pseudoelastic effect on the behavior of memory shape alloys. This phenomenological constitutive model is based on a set of variables: temperature and stress as control variables, and the fraction of the martensite as an internal variable. By using the first and the second principle of thermodynamics and with a simple formalism, we have developed constitutive equations followed by criteria of transformations. This developed model has parameters intended to be determined by a tensile pseudoelastic test. We have introduced an algorithm to simulate the response of the model with respect to experimental data. Three cases were considered: one dimensional, biaxial and triaxial loading.