References of "Hammami, Walid"
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See detailTwinning in pure Ti subjected to monotonic simple shear deformation
Tirry, Wim; Bouvier, Salima; Benmhenni, Najoua et al

in Materials Characterization (2012), 72(October 2012), 2436

Two different textures of pure Ti were subjected to monotonic simple shear and this for three different orientations of the texture versus the shear direction. EBSD and TEM observations reveal the ... [more ▼]

Two different textures of pure Ti were subjected to monotonic simple shear and this for three different orientations of the texture versus the shear direction. EBSD and TEM observations reveal the presence of {10-12} and {11-22} twins. A statistical relevant analysis of the morphology of these twins combined with a resolved shear stress (RSS) analysis was performed. This analysis reveals that {10-12} and {11-22} twins have a similar average thickness, but the {10-12} twins show a far larger spread on their thickness compared to {11- 22} twins and can grow to almost the size of the original parent grain. Correlation of the twin fractions with the RSS analysis shows that this RSS technique is an acceptable method explaining the difference in twin fractions for different textures and orientations. A detailed analysis shows that {11-22} twins occur in average with a smaller volume fraction but with a higher RSS, indicating they are more difficult to nucleate or grow compared to {10-12} twinning. In general a higher RSS value on the twin plane is not connected with a higher twin thickness; only in case of {10-12} twins the highest RSS values show clearly thicker twins. [less ▲]

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See detailExperimental and numerical study of TA-6V mechanical behavior in different monotonic loading conditions at room temperature
Gilles, Gaëtan ULg; Cazacu, Oana; Hammami, Walid ULg et al

in Procedia IUTAM (2012), 3

This paper presents an experimental characterization of the quasi-static mechanical response of a TA-6V titanium alloy in sheet form. Monotonic tests, such as uniaxial tension and compression, plane ... [more ▼]

This paper presents an experimental characterization of the quasi-static mechanical response of a TA-6V titanium alloy in sheet form. Monotonic tests, such as uniaxial tension and compression, plane strain and simple shear, were conducted along several orientations in the plane of the sheet in order to investigate the plastic anisotropy and the tension-compression asymmetry displayed by the material at the macroscopic scale. It was observed a moderate anisotropy in yielding while the anisotropy in r-ratios is very pronounced. Initial yielding is described using criteria that account for both plastic anisotropy and strength differential effects. Comparison between experimental data and FE simulation results illustrates the ability of the model to predict the mechanical response of TA-6V. [less ▲]

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See detailPhenomenological and crystal plasticity approaches to describe the mechanical behaviour of Ti6Al4V titanium alloy
Hammami, Walid ULg; Gilles, Gaëtan ULg; Habraken, Anne ULg et al

in International Journal of Material Forming (2011), 4(2), 205-2015

This paper presents a multiscale study of the quasi-static behaviour of a Ti6Al4V titanium alloy sheet. Tensile and compressive tests were carried out on specimens along several orientations from the ... [more ▼]

This paper presents a multiscale study of the quasi-static behaviour of a Ti6Al4V titanium alloy sheet. Tensile and compressive tests were carried out on specimens along several orientations from the rolling direction in order to characterise the material anisotropy. In parallel, X-Ray diffraction texture measurements were performed before and after deformation in tension. A phenomenological model (CPB06exn) and a multiscale crystal plasticity model (Multisite) were investigated to describe the mechanical behaviour of the tested material. The identification of the material parameters provides good predictions of the plastic anisotropy using both tensile and compressive data. The crystal plasticity model is in good agreement with the experiments in tension but it was observed that some improvements should be done to take into account the tension-compression asymmetry displayed by the material. Moreover both models lead to a good prediction of the Lankford’s coefficients and yield strength. [less ▲]

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See detailTi6A14V Anisotropy and Texture Evolution Predictions Using Multisite and Self Consistent Crystal Plasticity Models
Hammami, Walid ULg; Tirry, Wim; Coghe, Frederick et al

in Proceedings of the 12th World conference on Titanium (2011)

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See detailExperimental characterization and elasto-plastic modeling of the quasi-static mechanical response of TA-6 V at room temperature
Gilles, Gaëtan ULg; Hammami, Walid ULg; Libertiaux, Vincent ULg et al

in International Journal of Solids & Structures (2011), 48(9), 12771289

The paper presents an experimental study of the quasi-static deformation behavior of a TA-6V in sheet form. To quantify the plastic anisotropy and the tension-compression asymmetry of this material at ... [more ▼]

The paper presents an experimental study of the quasi-static deformation behavior of a TA-6V in sheet form. To quantify the plastic anisotropy and the tension-compression asymmetry of this material at room temperature, monotonic tensile and compressive tests were carried out on specimens cut out along several orientations in the plane of the sheet. It was observed that although the tensile flow stress anisotropy is very mild, the Lankford coefficients’ anisotropy is very pronounced. To describe the observed mechanical response an elastic/plastic approach was used. Yielding was described using a family of yield criteria that account for strength differential effects and allow an improved description of the anisotropy and its evolution through multiple linear transformations. Comparisons between uniaxial monotonic data and FE simulations using the model show a very good agreement. [less ▲]

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See detailA deformation based blank design method for formed parts
Hammami, Walid ULg; Padmanabhan, R.; Oliveira, M. C. et al

in International Journal Mechanics and Materials in Design (2009), 5(4), 303-314

Blank design is an important task in sheet metal forming process optimization. The initial blank shape has direct effect on the part quality. This paper presents a deformation based blank design approach ... [more ▼]

Blank design is an important task in sheet metal forming process optimization. The initial blank shape has direct effect on the part quality. This paper presents a deformation based blank design approach to determine the initial blank shape for a formed part. The blank design approach is integrated separately into ABAQUS, and DD3IMP, a research purpose in-house FEA code, to demonstrate its compatibility with any FEA code. The algorithm uses FE results to optimize the blank shape for a part. Deep drawing simulation of a rectangular cup geometry was carried out with an initial blank shape determined empirically. The blank shape was iteratively modified, based on the deformation history, until an optimal blank shape for the part is achieved. The optimal blank shapes predicted by the algorithm using both FEA softwares were similar. Marginal differences in the shape error indicate that the deformation history based push/pull technique can effectively determine an optimal blank shape for a part with any FEA software. For the shape error selected, both procedures estimate the optimal blank shape for the part within five iterations. [less ▲]

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See detailCrystal Plasticity Modelling of Monotonic Shear Tests on Pure Titanium
Hammami, Walid ULg; Bouvier, S.; Duchene, Laurent ULg et al

in Oñate, E.; Owen, D. R. J. (Eds.) Computational plasticity X. Fundamentals and applications (2009, September)

This study consists in the modelling of shear tests performed on pure titanium using a polycrystalline model. Numerical and experimental results are presented.

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See detailCrystal plasticity prediction of Lankford coefficient using the MULTISITE model: influence of the critical resolved shear stresses
Hammami, Walid ULg; Delannay, Laurent; Duchene, Laurent ULg et al

in International Journal of Material Forming (2009, August), 2(Supplément 1), 65-68

The MULTISITE model [1] is based on polycrystalline plasticity and the underlying hypotheses of the model are (i) that the deformation of each grain is significantly influenced by the interaction with a ... [more ▼]

The MULTISITE model [1] is based on polycrystalline plasticity and the underlying hypotheses of the model are (i) that the deformation of each grain is significantly influenced by the interaction with a limited number of adjacent grains, and (ii) that local strains deviate from their macroscopic average according to specific “relaxation modes”. The LAMEL model [2] is reformulated into the more general elastic-viscoplastic MULTISITE model permitting various relaxation modes. This model has been validated for cubic materials but hexagonal close-packed (HCP) crystals usually demonstrate larger anisotropy than cubic crystals. The model was used to simulate uniaxial tensile tests performed on rolled sheets made of Ti-6Al-4V. The Lankford coefficients (r) calculated in various directions in the plane of the sheet were analysed. In this study, different grain interaction hypotheses were tested. Besides, it appeared that the value of the critical resolved shear stresses (CRSS) of the different slip system families of the HCP metal had significant effects on the results. Their influence as well as the influence of the strain rate sensitivity parameter was examined. [less ▲]

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