References of "Habraken, Anne"
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See detailExperimental and numerical study of an AlMgSc sheet formed by an incremental process
Bouffioux, Chantal ULg; Lequesne, Cédric ULg; Vanhove, H. et al

in Journal of Materials Processing Technology (2011), 211(11), 1684-1693

A recently developed AlMgSc alloy is studied since this material, which is well adapted to the aeronautic domain, is poorly known. The first objective is to reach a better knowledge of this alloy to ... [more ▼]

A recently developed AlMgSc alloy is studied since this material, which is well adapted to the aeronautic domain, is poorly known. The first objective is to reach a better knowledge of this alloy to provide the missing useful information to the aeronautic industry and to help research institutes who want to simulate sheet forming processes by Finite Element (FE) simulations. A set of experimental tests has been performed on the as-received sheets, material laws have been chosen and the corresponding material parameters have been adjusted to correctly describe the material behaviour. The second objective is to study the applicability of the Single Point Incremental Forming process (SPIF) on this material. Truncated cones with different geometries were formed and the maximum forming angle was determined. A numerical model was developed and proved to be able to predict both the force evolution during the process and the final geometrical shape. Moreover, the model helps reaching a better understanding of the process. The characterisation method described in this research and applied on the AlMgSc alloy can be extended to other alloys. In addition, the numerical simplified model, able to accurately describe the SPIF process with a reduced computation time, can be used to study more complex geometries. [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 detailNumerical modeling of damage evolution of DP steels on the basis of X-ray tomography measurements
Ben Bettaieb, Mohamed ULg; Lemoine, Xavier; Bouaziz, O. et al

in Mechanics of Materials (2011), 43(3), 139-156

In order to couple the damage evolution and the stress state of DP steel grades, a new advanced GTN (Gurson-Tvergaard-Needleman) model was developed and implemented into a finite element code. This model ... [more ▼]

In order to couple the damage evolution and the stress state of DP steel grades, a new advanced GTN (Gurson-Tvergaard-Needleman) model was developed and implemented into a finite element code. This model is an extension of the original one. It takes into account the plastic anisotropy and the mixed (isotropic+ kinematic) hardening of the matrix. Two different methods to compute the void volume fraction were developed and used within the constitutive equations. The first method is new and allows the accurate modeling of the observations of damage initiation and growth in DP steels measured using high-resolution X-ray absorption tomography (Bouaziz et al., 2008; Maire et al., 2008). The second method is classic and assumes the additive decomposition of the total void volume fraction into a nucleation and a growth part. A parametric study is carried out to assess the effect of the kinematic hardening on some mechanical parameters such as the equivalent plastic strain, the triaxiality and the porosity. The numerical predictions are favorably compared to the experimental results. [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 detailNew Solid-Shell Finite Element Based on EAS and ANS Concepts for Sheet Metal Forming
Ben Bettaieb, Amine ULg; Duchene, Laurent ULg; Zhang, Lihong ULg et al

in AIP Conference Proceedings (2011), 1383

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See detailMaterial behavior of the hexagonal alpha phase of a titanium alloy identified from nanoindentation tests
Gerday, Anne-Françoise ULg; Ben Bettaieb, Mohamed ULg; Duchene, Laurent ULg et al

in European Journal of Mechanics A : Solids (2011), 30

This article focuses on the numerical modeling of nanoindentation tests performed on the hexagonal a phase of Ti-5553 alloy in order to identify its mechanical behavior. The main goal consists in ... [more ▼]

This article focuses on the numerical modeling of nanoindentation tests performed on the hexagonal a phase of Ti-5553 alloy in order to identify its mechanical behavior. The main goal consists in determining the relative strength of the slip modes in the a phase of Ti-5553. This work was performed using an elastoviscoplastic crystal plasticity-based constitutive law. The difficulties in determining the slip systems that can be activated and their corresponding critical resolved shear stresses (CRSS) are discussed. Numerical predictions are compared to experimental nanoindentation curves. [less ▲]

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See detailNotched Specimens Fracture Prediction with an Advanced GTN Model
Fansi Tchonko, Joseph ULg; Ben Bettaieb, Mohamed ULg; Balan, Tudor et al

in Key Engineering Materials [=KEM] (2011), 488-489

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See detailA partial hybrid stress solid-shell element for the analysis of laminated composites
Rah, Kamran; Van Paepegem, Wim; Habraken, Anne ULg et al

in Computer Methods in Applied Mechanics and Engineerinrg (2011), 200(49-52), 35263539

In this paper a low order partial hybrid stress solid-shell element based on the composite energy functional for the analysis of laminated composite structures is presented. This solid-shell element has ... [more ▼]

In this paper a low order partial hybrid stress solid-shell element based on the composite energy functional for the analysis of laminated composite structures is presented. This solid-shell element has eight nodes with only displacement degrees of freedoms, and three-dimensional constitutive models can be directly employed in the present formulation without any additional treatment. The assumed interlaminar stress field provides very accurate interlaminar stress calculation through the element thickness. These elements can be stacked on top of each other to model multilayer structures, fulfilling the interlaminar stress continuity at the interlayer surfaces and zero traction conditions on the top and bottom surfaces of the laminate. The present solid-shell does not show the transverse shear, trapezoidal and thickness locking phenomenon. [less ▲]

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See detailForming forces in single point incremental forming: prediction by finite element simulations, validation and sensitivity
Henrard, Christophe; Bouffioux, Chantal ULg; Eyckens, P. et al

in Computational Mechanics (2011), 47

The aim of this article is to study the accuracy of finite element simulations in predicting the tool force occurring during the single point incremental forming (SPIF) process. The forming of two cones ... [more ▼]

The aim of this article is to study the accuracy of finite element simulations in predicting the tool force occurring during the single point incremental forming (SPIF) process. The forming of two cones in soft aluminum was studied with two finite element (FE) codes and several constitutive laws (an elastic–plastic law coupled with various hardening models). The parameters of these laws were identified using several combinations of a tensile test, shear tests, and an inverse modeling approach taking into account a test similar to the incremental forming process. Comparisons between measured and predicted force values are performed. This article shows that three factors have an influence on force prediction: the type of finite element, the constitutive law and the identification procedure for the material parameters. In addition, it confirms that a detailed description of the behavior occurring across the thickness of the metal sheet is crucial for an accurate force prediction by FE simulations, even though a simple analytical formula could provide an otherwise acceptable answer. [less ▲]

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See detailStrain Evolution in the Single Point Incremental Forming Process: Digital Image Correlation Measurement and Finite Element Prediction
Eyckens, P.; Belkassem, B.; Henrard, Christophe et al

in International Journal of Material Forming (2011)

Incremental Sheet Forming (ISF) is a relatively new class of sheet forming processes that allow the manufacture of complex geometries based on computer-controlled forming tools in replacement (at least ... [more ▼]

Incremental Sheet Forming (ISF) is a relatively new class of sheet forming processes that allow the manufacture of complex geometries based on computer-controlled forming tools in replacement (at least partially) of dedicated tooling. This paper studies the straining behaviour in the Single Point Incremental Forming (SPIF) variant (in which no dedicated tooling at all is required), both on experimental basis using Digital Image Correlation (DIC) and on numerical basis by the Finite Element (FE) method. The aim of the paper is to increase understanding of the deformation mechanisms inherent to SPIF, which is an important issue for the understanding of the high formability observed in this process and also for future strategies to improve the geometrical accuracy. Two distinct large-strain FE formulations, based on shell and first-order reduced integration brick elements, are used to model the sheet during the SPIF processing into the form of a truncated cone. The prediction of the surface strains on the outer surface of the cone is compared to experimentally obtained strains using the DIC technique. It is emphasised that the strain history as calculated from the DIC displacement field depends on the scale of the strain definition. On the modelling side, it is shown that the mesh density in the FE models plays a similar role on the surface strain predictions. A good qualitative agreement has been obtained for the surface strain components. One significant exception has however been found, which concerns the circumferential strain evolution directly under the forming tool. The qualitative discrepancy is explained through a mechanism of through-thickness shear in the experiment, which is not fully captured by the present FE modelling since it shows a bending-dominant accommodation mechanism. The effect of different material constitutive behaviours on strain prediction has also been investigated, the parameters of which were determined by inverse modelling using a specially designed sheet forming test. Isotropic and anisotropic yield criteria are considered, combined with either isotropic or kinematic hardening. The adopted constitutive law has only a limited influence on the surface strains. Finally, the experimental surface strain evolution is compared between two cones with different forming parameters. It is concluded that the way the plastic zone under the forming tool accommodates the moving tool (i.e. by through-thickness shear or rather by bending) depends on the process parameters. The identification of the most determining forming parameter that controls the relative importance of either mechanism is an interesting topic for future research. [less ▲]

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See detailTowards the Prediction of Damage Of Peritectic Steels During Continuous Casting Process
Keller, Clément ULg; Schwartz, Renée; Bobadilla, Manuel et al

in AIP Conference Proceedings (2011), 1353

In the Continuous Casting process, products are sometimes rejected or called defective due to the presence of transversal cracks. This type of macroscopic damage is expected to be due to a ductility loss ... [more ▼]

In the Continuous Casting process, products are sometimes rejected or called defective due to the presence of transversal cracks. This type of macroscopic damage is expected to be due to a ductility loss during cooling in the bending and unbending areas of the CC line. In order to study this damage, a 2D model has been developed to predict at the mesoscopic level the intergranular crack event taking into account the creep and diffusion of voids. Already validated for a microalloyed steel, the model is identified and used in this study to predict the crack formation for three different grades of peritectic steels. Results show encouraging predictions of the damage. [less ▲]

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See detailA finite element analysis of the bending and the bendability of metallic sheets
Ben Bettaieb, Mohamed ULg; Lemoine, Xavier; Bouaziz, O. et al

in International Journal of Material Forming (2011), 4(3), 283-297

The main objective of this paper is to study the bendability of metallic sheets by using the finite element method. In this aim, two variants of an advanced Gurson-Tvergaard-Needleman model [1, 2] are ... [more ▼]

The main objective of this paper is to study the bendability of metallic sheets by using the finite element method. In this aim, two variants of an advanced Gurson-Tvergaard-Needleman model [1, 2] are implemented in the home made FE code LAGAMINE [3, 4] and coupled with the Thomason model to predict the coalescence of voids. This advanced model is an extension of the original one to take into account of the plastic anisotropy and the mixed (isotropic + kinematic) hardening of the matrix. The difference between the two variants is related to the modeling of the damage evolution. As the advanced model is used to study the bending process, its yield function is slightly modified in order to take into account the loadings with negative triaxiality ratios. These present implementations are used to simulate the pure bending process and to predict the bendability of dual phase (DP) steel. The combined effect of an initial geometrical imperfection and damage evolution on the bendability is also studied. [less ▲]

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See detailOn the numerical integration of an advanced Gurson model
Ben Bettaieb, Mohamed ULg; Lemoine, Xavier; Duchene, Laurent ULg et al

in International Journal for Numerical Methods in Engineering (2011), 85(8), 1049-1072

This article is focused on a new extended version of Gurson's model (J. Eng. Mater. Technol. 1977; 99:2–15), its numerical integration scheme and its consistent tangent matrix being within an FE code ... [more ▼]

This article is focused on a new extended version of Gurson's model (J. Eng. Mater. Technol. 1977; 99:2–15), its numerical integration scheme and its consistent tangent matrix being within an FE code. First, this new advanced Gurson model is proposed, which is an extension of the original to take into account plastic anisotropy and mixed (isotropic+kinematic) hardening. In this paper, only the growth phase of cavities is considered (the nucleation of new voids is ignored). Second, a new numerical algorithm for the integration of this new Gurson model is presented. The algorithm is implicit in all variables and is unconditionally stable. This algorithm is generic and could be used for other anisotropic yield functions and other hardening laws. Third, the consistent tangent matrix is computed in an explicit way by exact linearization of the constitutive equations. To check its efficiency and robustness, the proposed integration algorithm is compared, under some simplified assumptions and choices, with the algorithms of Aravas (Int. J. Numer. Meth. Engng 1987; 24:1395–1416) and Kojic (Int. J. Numer. Meth. Engng 2002; 53(12):2701–2720). The performance of the developed consistent modulus, compared to other techniques for the computation of the tangent matrix is assessed. The paper ends with numerical simulations of tensile tests on homogeneous and notched specimens. [less ▲]

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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 detailInvestigation of the Efficiency of the Ti555 Compared with TA6V Alloy in the Case of an Aeronautic Application
Ben Bettaieb, Mohamed ULg; Van Hoof, T.; Zhang, Lihong ULg et al

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

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See detailRoller Pressure Quench Process of Steel Plate Modelling
Lequesne, Cédric ULg; Pensis, O.; Renard, M. et al

in Proceedings of Esaform 2011 (2011)

In this study, the roller pressure quench process is applied on a low-alloy steel plate with significant thickness. The aim is to obtain martensitic high strength steel without modifying the flatness. In ... [more ▼]

In this study, the roller pressure quench process is applied on a low-alloy steel plate with significant thickness. The aim is to obtain martensitic high strength steel without modifying the flatness. In order to optimize the process parameters, a finite element model is developed. The analysis couples the mechanical, thermal and metallurgical fields. This model provides results about the final microstructure, the residual stresses and the flatness at the end of the cooling process. It has been noticed that a two dimensional plane strain simulation is not accurate because it does not predict physical transversal residual stresses. A three dimensional simulation improves the results and enables to compute the thickness variation of the plate at the end of the quench process. [less ▲]

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See detailInvestigation of the efficiency of the Ti555 compared with TA6V alloy in the case of an aeronautic application
Ben Bettaieb, Mohamed ULg; Van Hoof, T.; Zhang, Lihong ULg et al

in The 12th World Conference on Titanium Ti-2011 (2011)

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See detailExperimental characterization and constitutive modeling of TA6V mechanical behavior in plane strain state at room temperature
Gilles, Gaëtan ULg; Tuninetti Vásquez, Victor ULg; Ben Bettaieb, Mohamed ULg et al

in AIP Conference Proceedings (2011), 1383

This paper presents an experimental and theoretical study of the quasi-static behavior of TA6V titanium alloy in plane strain state. In order to quantify the anisotropy of the material, tests were carried ... [more ▼]

This paper presents an experimental and theoretical study of the quasi-static behavior of TA6V titanium alloy in plane strain state. In order to quantify the anisotropy of the material, tests were carried out at room temperature on specimens cut out from a sheet along three loading directions. The initial yield locus is described by the phenomenological CPB06ex3 criterion and Voce’s type isotropic hardening is used. Finite element simulations are performed and compared with the experiments. [less ▲]

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See detailExperimental investigations of the material behavior of Ti6Al4V titanium alloy
Rossi, Barbara ULg; Gilles, Gaëtan ULg; Zolotas, Eric et al

Report (2011)

Computer models are widely used to support the development of conventional design methods based on expensive full-scale tests or trial and error methods. Nevertheless, in order to accurately model metal ... [more ▼]

Computer models are widely used to support the development of conventional design methods based on expensive full-scale tests or trial and error methods. Nevertheless, in order to accurately model metal forming processes as well as structural behavior of load carrying elements, it is necessary to afford an accurate knowledge of the material properties. Titanium is one of the material for which various industrial sectors such as aerospace or biomedical are showing an increasing interest. This paper presents the experimental tests performed on the titanium based alloy Ti6Al4V to investigate on its mechanical behavior, especially in terms of its anisotropy and hardening. For that purpose, a classical uniaxial and a non-standard biaxial experimental equipments designed by Florès in the Materials and Structures Mechanics Laboratory of the University of Liège have been used to perform tensile, simple shear and cyclic shear tests as well as successive simple shear and plane strain tests, which provide the main contribution of this paper in the form of stress-strain curves. [less ▲]

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