References of "Habraken, Anne"
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See detailAnalytical formulation for actual mechanical properties of stainless steel structural members
Rossi, Barbara ULg; Degée, Hervé ULg; Habraken, Anne ULg

in Steel Research International (2008), 79(2), 265-272

One of the fastest growing market segments for stainless steel is its use for cold-formed profiled structural members. It is wellknown that the forming process is likely to significantly enhance the ... [more ▼]

One of the fastest growing market segments for stainless steel is its use for cold-formed profiled structural members. It is wellknown that the forming process is likely to significantly enhance the mechanical properties of the profile by strainhardening. This leads to increased resistance compared to a resistance assessment based on nominal properties, even if this effect is partly counterbalanced by the introduction of residual stresses. It is thus necessary to be able to accurately determine its actual mechanical properties. For this purpose, experimental data and theoretical investigations aiming at determining the material behaviour of coldformed stainless steel profiles including the effects of the forming process are reported in this paper. [less ▲]

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See detailMulti-Step toolpath approach to overcome forming limitations in single point incremental forming
Verbert, J.; Belkassem, B.; Henrard, Christophe ULg et al

in Boisse, P. (Ed.) Proceedings of the 11th International ESAFORM Conference on Material Forming (2008)

Although Incremental Forming offers distinct advantages over traditional forming processes, such as short lead times and low setup costs, the process still has some drawbacks. Besides the obtainable ... [more ▼]

Although Incremental Forming offers distinct advantages over traditional forming processes, such as short lead times and low setup costs, the process still has some drawbacks. Besides the obtainable accuracy, one of the main challenges of the process are the process limits. Many workpiece geometries cannot be manufactured due to the fact that the maximum wall angle that can be formed is limited for a certain sheet material and thickness to a given angle. Different solutions to this approach have been proposed and this paper further investigates one of those solutions, the multi step approach for single point incremental forming. Experiments were performed and compared with simulations to better understand the phenomena underlying the improved process performance. [less ▲]

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See detailAdaptive remeshing for incremental forming simulation
Lequesne, Cédric ULg; Henrard, Christophe ULg; Bouffioux, Chantal ULg et al

in Pavel, H. (Ed.) Proceedings of the 7th International Conference and Workshop on Numerical Simulation od 3D Sheet Metal Forming Processes (NUMISHEET 2008) (2008)

Incremental forming of aluminium sheets has been modelled by finite element simulations. However the computation time was prohibitive because the tool deforms every part of the sheet and the mesh along ... [more ▼]

Incremental forming of aluminium sheets has been modelled by finite element simulations. However the computation time was prohibitive because the tool deforms every part of the sheet and the mesh along the tool path must be very fine. Therefore, an adaptive remeshing method has been developed. The elements that are close to the tool are divided into smaller elements in order to have a fine mesh where high deformations occur. Consequently, some new nodes become inconsistent with the non-refined neighbouring elements. To overcome that problem, their displacements are constrained, i.e. dependent on their master nodes displacements. The data concerning these new nodes and elements are stored in a linked list, which is a fundamental data structure. It consists of a sequence of cells, each containing data fields and a pointer towards the next cell. The goal of this article is to explain the developments performed in the finite element code, to validate the adaptive remeshing technique and to measure its efficiency using the line test simulation. During this test, which is a simple incremental forming test, a clamped sheet is deformed by a spherical tool moving along a linear path. [less ▲]

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See detailComparison of the tests chosen for material parameter identification to predict single point incremental forming forces
Bouffioux, Chantal ULg; Henrard, Christophe ULg; Eyckens, P. et al

in Asnafi, Nader (Ed.) Proceedings of the International Conference of International Deep Drawing Research Group (IDDRG 2008) (2008)

Single Point Incremental Forming is a sheet forming process that uses a smooth-ended tool following a specific tool path and thus eliminates the need for dedicated die sets. Using this method, the ... [more ▼]

Single Point Incremental Forming is a sheet forming process that uses a smooth-ended tool following a specific tool path and thus eliminates the need for dedicated die sets. Using this method, the material can reach a very high deformation level. A wide variety of shapes can be obtained without specific and costly equipment. To be able to optimize the process, a model and its material parameters are required. The inverse method has been used to provide material data by modeling experiments directly performed on a SPIF set-up and comparing them to the experimental measurements. The tests chosen for this study can generate heterogeneous stress and strain fields. They are performed with the production machine itself and are appropriate for the inverse method since their simulation times are not too high. [less ▲]

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See detailMultiscale finite element study of Ti-555
Habraken, Anne ULg; Gerday, Anne-Françoise ULg; Duchene, Laurent ULg

in Akhtar S. Khan; Babak Farrokh; Baig, M. (Eds.) et al Proceedings of the 14th International Symposium on Plasticity & Its Current Applications, Mechanics & Mechanisms of Finite Plastic Deformation (2008)

The material parameters of the 2 phases Ti-555 alloy have to be extracted in order to perform simulations on representative microscopic cells and guide the optimization of the alloy. The identification of ... [more ▼]

The material parameters of the 2 phases Ti-555 alloy have to be extracted in order to perform simulations on representative microscopic cells and guide the optimization of the alloy. The identification of the flow parameters of the BCC β-phase is discussed, using macroscopic and microscopic constitutive laws. The validation is performed, comparing experimental and numerical tensile tests obtained for different strain rates. [less ▲]

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See detailIdentification of material parameters to predict Single Point Incremental Forming forces
Bouffioux, Chantal ULg; Eyckens, P.; Henrard, Christophe et al

in International Journal of Material Forming (2008)

The purpose of this article is to develop an inverse method for adjusting the material parameters for single point incremental forming (SPIF). The main idea consists in FEM simulations of simple tests ... [more ▼]

The purpose of this article is to develop an inverse method for adjusting the material parameters for single point incremental forming (SPIF). The main idea consists in FEM simulations of simple tests involving the SPIF specificities (the “line test”) performed on the machine used for the process itself. This approach decreases the equipment cost. It has the advantage that the material parameters are fitted for heterogeneous stress and strain fields close to the ones occurring during the actual process. A first set of material parameters, adjusted for the aluminum alloy AA3103 with classical tests (tensile and cyclic shear tests), is compared with parameters adjusted by the line test. It is shown that the chosen tests and the strain state level have an important impact on the adjusted material data and on the accuracy of the tool force prediction reached during the SPIF process. [less ▲]

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See detailModelling the vertical spincasting of large bimettalic rolling mill rolls
Studer, Léo ULg; Detrembleur, Sylvain ULg; Habraken, Anne ULg et al

in Proceedings of the Second International Conference on Advances in Solidification Processes (ICASP-2) (2008)

In order to take into account the dynamic effects of molten metal during solidification, a methodology is presented to interface a metal solidification solver with a specifically developped flow dynamics ... [more ▼]

In order to take into account the dynamic effects of molten metal during solidification, a methodology is presented to interface a metal solidification solver with a specifically developped flow dynamics solver. [less ▲]

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See detailMultiscale modeling of equal channel angular extruded aluminium with strain gradient crystal plasticity and phenomenological models
Duchene, Laurent ULg; Geers, M. G. D.; Brekelmans, W. A. M. et al

in Rollett, A. (Ed.) Proceedings of the 15th International Conference on the Texture of Materials (ICOTOM-15) (2008)

The Equal Channel Angular Extrusion process is used to modify the microstructure of an AA1050 aluminum alloy in order to produce an ultra fine grained material. Due to the severe plastic deformation ... [more ▼]

The Equal Channel Angular Extrusion process is used to modify the microstructure of an AA1050 aluminum alloy in order to produce an ultra fine grained material. Due to the severe plastic deformation undergone by the material during the ECAE process, the subsequent behavior of the material is non-conventional and difficult to model with classical constitutive laws (e.g. ECAE aluminum presents a large initial back-stress which must be adequately incorporated in the model). In this study, the evolution of the back-stress during the ECAE process is analyzed. Two different numerical models were investigated in this respect. The first one is a single crystal strain gradient plasticity model based on dislocation densities. The second model is the Teodosiu and Hu’s hardening model, which is a microstructuraly based phenomenological model at the macroscale. The results provided by the two models are obviously distinct. Nevertheless, some common trends can be pointed out, among which the amplitude of the back-stress that is similar. In agreement with the cyclic deformation mode of the studied route C ECAE process, the evolution of the predicted back-stress is also cyclic in both models. [less ▲]

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See detailStudy of bendability of steel sheets
Ben Bettaieb, Mohamed ULg; Lemoine, Xavier; Duchene, Laurent ULg et al

in Steel Research International (2008), (79/1), 225-232

In the present contribution bending tests are modeled and the bendability of steel sheets is evaluated. Bendability refers to the ratio of the minimum bend radius to the initial sheet thickness at which ... [more ▼]

In the present contribution bending tests are modeled and the bendability of steel sheets is evaluated. Bendability refers to the ratio of the minimum bend radius to the initial sheet thickness at which the bending proc-ess is successfully accomplished [1]. The metallurgic microstructure of the studied sheet consists in two principal phases: a fully dense matrix (which may be itself composed by several metallurgic phases) and spherical voids. For that purpose, the Gurson Tvergaard Needleman law ([2], [3], [4]) is used and significantly modified. The behavior of the fully dense matrix is de-fined by the anisotropic Hill 48 function and the Swift hardening law. The width of the sheet is assumed to be large enough to neglect the transversal strains and the stress component in the thickness direction is also neglected. The bending operation can thus be modelled by a plane strain-plane stress loading. The influence of mechanical pa-rameters such as the initial porosity, the Lankford coefficient and the strain harden-ing exponent on the bendability is studied herein. The failure here is defined by the onset coalescence of neighbour voids and is checked by using Thomason [5], Pardoen [6] and Brunet [7] coalescence models. So the influence of other phenomena (like the shear band development and the localized necking) on the bendability is neglected here. [less ▲]

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See detailA new finite element integration scheme. Application to a simple shear test of anisotropic material
de Montleau, P.; Habraken, Anne ULg; Duchene, Laurent ULg

in International Journal for Numerical Methods in Engineering (2008)

Finite element simulations involving large strains and large displacements imply the setting up of a precise kinematics for the integration scheme. Moreover, anisotropic mechanical behaviours have to be ... [more ▼]

Finite element simulations involving large strains and large displacements imply the setting up of a precise kinematics for the integration scheme. Moreover, anisotropic mechanical behaviours have to be expressed in an appropriate local reference frame. In the present paper, a computational procedure is derived from a particular velocity gradient definition. Its implementation in a finite element code is described. Application to a simple shear test is proposed. For anisotropic materials, a sinusoidal behaviour of the shear stress component is emphasized. This is due to the anisotropic yield locus and appears in the case of a saturated isotropic hardening law. [less ▲]

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See detailRotation of axes for anisotropic metal in FEM simulations
Duchene, Laurent ULg; Lelotte, Thomas; Flores, Paulo et al

in International Journal of Plasticity (2008), (24), 397427

For the FE simulations relying on elasto-plastic models based on anisotropic yield locus description, it is important for the simulation accuracy to follow a Cartesian reference frame, where the yield ... [more ▼]

For the FE simulations relying on elasto-plastic models based on anisotropic yield locus description, it is important for the simulation accuracy to follow a Cartesian reference frame, where the yield locus is expressed. The classical formulations like the Hill 1948 model keep a constant shape of the yield locus when other texture based yield loci regularly update their shape. However in all these cases, the rotation of the Cartesian reference frame must be known. For simple shear tests performed on steel sheets, experimental displacements provide the actual updated position of initial orthogonal grids. The initial and final texture measurements give information on the average crystals rotation. For Hill constitutive law and texture based models, this paper compares the experimental results with different ways to follow the Cartesian reference frame: the co-rotational method, an original method based on the constant symmetric local velocity gradient and the Mandel spin computed by four different methods. [less ▲]

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See detailProcess window enhancement for single point incremental forming through multi-step toolpaths
Duflou, J. R.; Verbert, J.; Belkassem, B. et al

in CIRP Annals - Manufacturing Technology (2008), (57), 253-256

Single point incremental forming (SPIF) suffers from process window limitations which are strongly determined by the maximum achievable forming angle. Forming consecutive, intermediate shapes can ... [more ▼]

Single point incremental forming (SPIF) suffers from process window limitations which are strongly determined by the maximum achievable forming angle. Forming consecutive, intermediate shapes can contribute to a significantly enlarged process window by allowing steeper maximum wall angles for a range of part geometries. In this paper an experimentally explored multi-step toolpath strategy is reported and the resulting part geometries compared to simulation output. Sheet thicknesses and strains achieved with these multi-step toolpaths were verified and contribute to better understanding of the material relocation mechanism underlying the enlarged process window. [less ▲]

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See detailOn the evaluation of the through thickness residual stresses distribution of cold formed profiles
Rossi, Barbara ULg; Habraken, Anne ULg; Pascon, Frédéric ULg

in 10th International ESAFORM Conference on Material Forming : ESAFORM, Zaragoza, 18-20 April 2007 (2007)

The aim of this research is to evaluate the through thickness residual stresses distribution in the walls and in the corners of a cold-formed open section made of a material presenting a non linear ... [more ▼]

The aim of this research is to evaluate the through thickness residual stresses distribution in the walls and in the corners of a cold-formed open section made of a material presenting a non linear hardening behaviour. To get results as close as possible to the reality, the complete process is modeled, including coiling and uncoiling of the sheet before the cold bending of the corner itself. The elastic springback after flattening as well as after final shaping are also taken into account. In order to validate the model in predicting the residual stresses distribution, the presented results are confronted to experimental measurements and FE results collected from the literature. [less ▲]

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See detailForming limit predictions for single-point incremental sheet metal forming
Van Bael, A.; Eyckens, P.; He, S. et al

in Cueto, Elías; Chinesta, Francisco (Eds.) Proceedings of the 10th International ESAFORM Conference on Material Forming (2007)

A characteristic of incremental sheet metal forming is that much higher deformations can be achieved than conventional forming limits. In this paper it is investigated to which extent the highly non ... [more ▼]

A characteristic of incremental sheet metal forming is that much higher deformations can be achieved than conventional forming limits. In this paper it is investigated to which extent the highly non-monotonic strain paths during such a process may be responsible for this high formability. A Marciniak-Kuczynski (MK) model is used to predict the onset of necking of a sheet subjected to the strain paths obtained by finite-element simulations. The predicted forming limits are considerably higher than for monotonic loading, but still lower than the experimental ones. This discrepancy is attributed to the strain gradient over the sheet thickness, which is not taken into account in the currently used MK model. [less ▲]

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See detailStrategy of material parameters identification for non linear mechanical behavior: sensitivity of FE computation
Bouvier, Salima; Alves, L.; Habraken, Anne ULg

in Cueto, Elías; Francisco, Chinesta (Eds.) Proceedings of the 10th International ESAFORM Conference on Material Forming (2007)

The purpose of the present work is to analyze several aspects related to the connection between the constitutive models, their identification and the FEM predictions. Several issues are addressed: the ... [more ▼]

The purpose of the present work is to analyze several aspects related to the connection between the constitutive models, their identification and the FEM predictions. Several issues are addressed: the experimental data base that should be used in the identification procedure, the choice of the mechanical tests involved (monotonous and/or non-proportional loading, homogeneous or heterogeneous tests...), the identification strategies (direct or inverse FE optimization, simultaneous or sequential material parameters identification...). Besides its obvious interest, such study aim to find a good balance between the number and the type of relevant involved mechanical tests in material behavior characterization. This is an important issue for industrial applications. [less ▲]

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See detailComparisons of FEM approaches modelling the metal plastic behaviour
Habraken, Anne ULg; Gerday, Anne-Françoise ULg; Diouf, B. et al

in Cueto, Elías; Chinesta, Francisco (Eds.) Proceedings of the 10th ESAFORM Conference on Material Forming (2007)

Simple phenomenological laws (e.g. classical Hill 1948 quadratic law) are compared to more complex laws based on crystal plasticity through various numerical simulations: mechanical tests of ECAE ... [more ▼]

Simple phenomenological laws (e.g. classical Hill 1948 quadratic law) are compared to more complex laws based on crystal plasticity through various numerical simulations: mechanical tests of ECAE materials, nanoindentation of titanium alloys and copper, and large strain torsion of copper bars. Taking into consideration the complexity of the investigated processes, the numerical results present rather good agreements with experimental observations. [less ▲]

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See detailInverse modelling of nanoindentation tests to identify Ti-555 behaviour
Gerday, Anne-Françoise ULg; Clement, N.; Jacques, P. J. et al

in Proceedings of the 11th world conference on titanium (2007)

Nanoindentation is commonly used to probe local plastic properties of materials [1-4]. From these nanoindentation tests, finite element (FE) modeling is currently used to identify material data. The ... [more ▼]

Nanoindentation is commonly used to probe local plastic properties of materials [1-4]. From these nanoindentation tests, finite element (FE) modeling is currently used to identify material data. The general ambition of this research is to extract the material parameters representative of the response of a new generation of Ti alloy, called Ti-555, in order to perform simulations on representative microscopic cells and guide the optimization of the alloy. In this paper, the identification of the flow parameters of the -phase of this alloy, using a microscopic crystal plasticity-based constitutive law is described. The nanoindentation tests are performed using a pyramidal Berkovich diamond indenter and the different slip systems of the b.c.c. -phase are supposed to be activated with identical critical shear stresses. The FE nanoindentation force-displacement curves obtained with the microscopic constitutive law are compared to the experimental ones. The influence of the orientation of the grains is also analysed. A previous sensivity analysis on different parameters with different constitutive laws and materials has shown a great influence of different parameters on the nanoindentation results but almost no influence of other parameters [5-6]. [less ▲]

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See detailDevelopment of an inverse method for identification of materials parameters in the single point incremental sheet forming process
Bouffioux, Chantal ULg; Henrard, Christophe ULg; Gu, Jun et al

in Tisza, M. (Ed.) Proceedings of the IDDRG 2007 International Conference (2007)

The purpose of this article is to develop an inverse method for adjusting the material parameters during single point incremental forming. The main idea consists in simulating tests performed on the same ... [more ▼]

The purpose of this article is to develop an inverse method for adjusting the material parameters during single point incremental forming. The main idea consists in simulating tests performed on the same machine as the one used for the process itself. This reduces the costs of the equipment since no specific and costly standard test equipment is needed. Moreover, it has the advantage that the material parameters are fitted for a heterogeneous stress and strain state occurring during the real process. Before using the inverse method, the numerical results must be compared with the experimental ones. Several boundary conditions will be tested. [less ▲]

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See detailMicro and macro investigation on the hardening of a titanium alloy
Lelotte, Thomas; Rossi, Barbara ULg; Habraken, Anne ULg

in 11th World conference on titanium: Ti 2007, Kyoto 3-7 June 2007 (2007)

This paper presents the experimental and numerical tests made on the Titanium based alloy Ti6A14V to identify its yield locus and the hardening behaviour. A bi-axial experimental equipment has been used ... [more ▼]

This paper presents the experimental and numerical tests made on the Titanium based alloy Ti6A14V to identify its yield locus and the hardening behaviour. A bi-axial experimental equipment has been used to perform cyclic shear tests, simple shear tests and successive simple shear tests and plane-strain tests. Coupled with classical tensile tests, these tests enable to identify the yield locus and the hardening model. Teodosiu and Hu’s hardening law and isotropic Swift type hardening and kinematic Armstrong Frederick hardening models have been investigated. [less ▲]

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See detailModelling the vertical centrifugal casting of large bimetallic rolling mills
Studer, Léo ULg; Habraken, Anne ULg; Pirotton, Michel ULg et al

in Onate, E.; Papadrakis, M.; Schrefler, B. (Eds.) Proceedings of the Conference of Computational Methods for Coupled Problems in Science and Engineering 2 (2007)

In order to take into account the dynamical effects of molten metal during solidification, we want to interface a metal solidification solver with a flow dynamics solver.

Detailed reference viewed: 78 (6 ULg)