Jamal Fajoui
University of Nantes
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Publication
Featured researches published by Jamal Fajoui.
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science | 2015
David Gloaguen; Guy Oum; Vincent Legrand; Jamal Fajoui; Marie-José Moya; Thilo Pirling; W. Kockelmann
Intergranular strains due to tensile plastic deformation were investigated in a commercially pure Ti. Neutron diffraction has been used to characterize the evolution of residual elastic strain in grains with different crystallographic orientations. Experimental data have been obtained for the macroscopic stress–strain curve and the intergranular strain evolution in the longitudinal and transverse direction relative to the uniaxial loading axis. The elasto-plastic self-consistent (EPSC) approach was used to model the deformation behavior of the studied material. Comparison between the neutron measurements and the model predictions shows that in most cases the EPSC approach can predict the lattice strain evolution and capture the plastic anisotropy observed in the experiments.
Journal of Applied Crystallography | 2010
David Gloaguen; Jamal Fajoui; Emmanuel Girard; Ronald Guillén
Texture and residual stress analysis using X-ray diffraction have been carried out on zirconium alloy cladding tubes after cold pilgering, an industrial mechanical process. The final rolling pass has been completely characterized by X-ray diffraction. An interpretation of the effect of intergranular stresses on the development of analysed stress has been made using a modified elastoplastic self-consistent model in order to account for the effect of the high intrinsic plastic anisotropy of hexagonal close-packed crystals. The contribution and magnitude of the first- and second-order residual stresses were correctly evaluated using information from the model. The main features of the rolling sequence were qualitatively reproduced by the simulations, considering prismatic slip as the main active deformation mode in this alloy under large strain.
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science | 2016
Jamal Fajoui; David Gloaguen; Vincent Legrand; Guy Oum; Joe Kelleher; Winfried Kockelmann
The generation of internal stresses/strains arising from mechanical deformations in single-phase engineering materials was studied. Neutron diffraction measurements were performed to study the evolution of intergranular strains in austenitic steel during sequential loadings. Intergranular strains expand due to incompatibilities between grains and also resulting from single-crystal elastic and plastic anisotropy. A two-level homogenization approach was adopted in order to predict the mechanical state of deformed polycrystals in relation to the microstructure during Bauschinger tests. A mechanical description of the grain was developed through a micro–meso transition based on the Kröner model. The meso–macro transition using a self-consistent approach was applied to deduce the global behavior. Mechanical tests and neutron diffraction measurements were used to validate and assess the model.
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology | 2018
Mohamed Kchaou; Amira Sellami; Jamal Fajoui; Recai Kus; Riadh Elleuch; Frédéric Jacquemin
This article describes and explains the tribological tests and methods for the evaluation of the performance of the brake friction materials. It starts by discussing the particularities of these materials and the variation of characterization tests, which can experimentally simulate many aspects of brake situation but with a large field of tribo-test, from standard to specific protocol. Examples of preparation, procedures, instrumentation, and analysis results for the tribological aspect testing ranging from the scale of vehicle braking performance (by methods including inertia dynamometers, Krauss testing, friction assessment screening test, and Chase testing) to simplified test using reduced-scale prototypes for small-sample friction, are explained. A particular attention is attributed to the discussion of the viability of the friction coefficient report in relation to the material properties and brake compound performance. At the end of this article, the guarantee of the performance output or ranking evaluated by such experimental methods is discussed.
Journal of Sandwich Structures and Materials | 2018
Fahmi Alila; Jamal Fajoui; Raphael Gerard; Pascal Casari; Mohamed Kchaou; Frédéric Jacquemin
In the first part of this paper, a viscoelastic model is used to numerically study the cellular foam core fatigue behaviour. Material’s temperature evolution is quantified with a numerical/experimental confrontation. In the second part, the slamming phenomenon is discussed by measuring the panel flexural strain on a racing sailboat during navigation. Making use of these results, a new slamming test rig was developed to evaluate the fatigue of sandwich structure under realistic loading. Four-point bending and slamming tests were performed on sandwich beams in order to compare their fatigue life and to discuss the physical parameters.
Materials Science Forum | 2017
David Gloaguen; Baptiste Girault; Jamal Fajoui; Vincent Klosek; Marie José Moya
A theoretical and experimental study was carry out to investigate deformation mechanisms in a textured titanium alloy. In situ neutron diffraction measurements were performed to analyze different {hk.l} family planes ({10.0}, {10.1}, {11.0} and {00.2}) and determine the corresponding internal strain pole figures. This method was applied to a pure titanium (a-Ti) submitted to a uniaxial tensile load up to 2 %. The experimental data was then used to validate the EPSC model in order to predict the distribution of lattice strains determined by neutron diffraction for various diffraction vector directions. This comparison reveals that the model results were in good agreement with the experimental data and the simulations reproduced the lattice strain development observed on the strain pole figures determined by neutron diffraction.
Journal of Sandwich Structures and Materials | 2016
Raphael Gerard; Jamal Fajoui; Pascal Casari; Frédéric Jacquemin
In this work, we demonstrate that current fatigue characterization tests with high density foam suffer from edge effects within the specimen, probably leading to early failures. Then a new specimen is designed to avoid this artifact. With this developed geometry, the stress is concentrated in the center of the specimen and not in the edge as given by the ASTM D1623-78 standard one. This allows getting the optimal fatigue life of PVC 4e-5 ℃-1 foam during tensile–tensile fatigue test.
Materials Science Forum | 2006
David Gloaguen; Jamal Fajoui; Bruno Courant; Ronald Guillén
A two-level homogenisation approach is applied to the micro-mechanical modelling of the elasto-plasticity of polycrystalline materials during various strain-path changes. The model is tested by simulating the development of intragranular strains during different complex loads. Mechanical tests measurements are used as a reference in order to validate the model. The anisotropy of plastic deformation in relation to the evolution of the dislocation structure is analysed. The results demonstrate the relevance of this approach for FCC polycrystals.
Acta Materialia | 2013
David Gloaguen; Guy Oum; Vincent Legrand; Jamal Fajoui; Samuel Branchu
Computational Mechanics | 2009
Jamal Fajoui; David Gloaguen; Bruno Courant; Ronald Guillén