References of "Habraken, Anne"
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See detailAnisotropy and tension-compression asymmetry modeling of the room temperature plastic response of Ti-6A1-4V
Tuninetti, Victor; Gilles, Gaëtan ULg; Pardoen, Thomas et al

in International Journal of Plasticity (2015)

The mechanical behavior of the alloy Ti-6A1-4V is characterized using uniaxial tension, uniaxial compression, simple shear and place strain tests in three orthogonal material directions. The experimental ... [more ▼]

The mechanical behavior of the alloy Ti-6A1-4V is characterized using uniaxial tension, uniaxial compression, simple shear and place strain tests in three orthogonal material directions. The experimental results reveal tension/compression asymmetry, anisotropic yielding and anisotropic strain-hardening. These features are incorporated into an elasto-plastic constitutive law based on the macroscopic orthotropic yield criterion "CPB06" adapted to hexagonal metals. A new identification method for the yield criterion parameters is proposed by inverse modeling of the axial strain field compression specimens in the three orthogonal directions of the material. The sensitivity of different sets of material parameters to the identification method is also analysed and the capacity of the model to accurately predict the forces and displacement field is discussed. A validation of the best set of identified CPB06material parameters is performed by comparing the load-displacement curves in different loading directions for tensile tests on notched round bars with different levels of stress triaxiality and for compression tests on elliptical cross-section specimens, both tests involving multiaxial strain fields and large deformations. [less ▲]

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See detailEffect of stress path on the miniaturizatio size effect for nickel polycrystals
Keller, Clement; Hug, Eric; Duchene, Laurent ULg et al

Conference (2015, January 04)

The mechanical behavior of mettalic materials deeply depends on the size of samples. For specimen dimensions de creasing from a few millimeters to a few micrometers, the general observed trend is a ... [more ▼]

The mechanical behavior of mettalic materials deeply depends on the size of samples. For specimen dimensions de creasing from a few millimeters to a few micrometers, the general observed trend is a softening of the mechanical behavior in tension which affects the stress level and the strain hardening. This effect is triggered by the derease of the number of grains across the thickness ( also called thickness"t" over grain size "d" ratio). The objective of this work is to provide new experimental results in order to analyse the miniaturization size effects for various stress paths without strain gradients across the thickness of the samples. To this aim, experimental tensil tests, large tensile tests and shear tests have been performed on Ni sheets ( 0.5mm) with various grain sizes ensuring different t/d ratios. Results show that the miniaturization softening is affected by triaxiality, the larger is this parameter, the lower is the mechanicval softening. These features seem to be linked to surface effects which are larger for low triaxiality stress paths. Attempts of numerical simulations using strain gradient crystal plasticity model are also performed to confirm the role played by surface effects. [less ▲]

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See detailEffect of stress path on the miniaturization size effect for nickel polycrystals
Keller, Clement; Hug, Eric; Habraken, Anne ULg et al

in International Journal of Plasticity (2015), 64

The mechanical behavior of metallic materials deeply depends on the size of samples. For specimen dimensions decreasing from a few millimeters to a few micrometers, the general observed trend is a ... [more ▼]

The mechanical behavior of metallic materials deeply depends on the size of samples. For specimen dimensions decreasing from a few millimeters to a few micrometers, the general observed trend is a softening of the mechanical behavior in tension which affects the stress level and the strain hardening. The objective of this work is to provide new experimental results in order to analyze the miniaturization size effects for various stress paths without strain gradients across the thickness of the samples. To this aim, experimental tensile tests, large tensile tests and shear tests have been performed on Ni sheets with various grain sizes. Results show that the miniaturization softening is affected by triaxiality, the larger is this parameter, the lower is the mechanical softening. These features seem to be linked to surface effects which are larger for low triaxiality stress paths. From an industrial point of view, it is hence possible to improve the forming of microparts using suitable stress paths. [less ▲]

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See detailNumerical investigation of cut-edge effect using the Gurson-Tvergaard-Needleman model
Lemoine, Xavier; Tudor, Balan; Habraken, Anne ULg

in Procedia Engineering (2014, October)

In this contribution, the formability of sheet metal cut edges is investigated using damage model.Classical forming limit diagrams are known not to apply properly to the cut edges. However, with mild ... [more ▼]

In this contribution, the formability of sheet metal cut edges is investigated using damage model.Classical forming limit diagrams are known not to apply properly to the cut edges. However, with mild steels the sheet edges usually behave better than the Forming Limit Diagram prédictions, so this phenomenon has not been given sufficient attention. In contrast, for Advanced High Strengh Steels the cut edges exhibit reduced formability as compared to the plain sheet;this effect is very sensitive to the quality of the cutting process. The current investigation is aimed to evaluate the ability of available damage models to predict this effect on sample applications. The Gurson-Tvergaard-Needleman model is used and the material parameters for a Dual Phase are considered [1]. The effect of the cutting process is described by means of initial fields of equivalent plastic strain and porosity. The geometrical distribution and typical values for these two initial fields are devised based on literature . Numerical simulations of flat notched tensile tests are used within the FE code Abaqus/Explicit to illustrate the impact of the initial fields on the moment and the location of the failure initiation. The influence of the mesh size in the cutting-affected area is also investigated. The hole expansion test and a flat bending test are further simulated to investigate the influence of the cut edge. [less ▲]

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See detailOn the Elasto-viscoplastic behavior of the Ti5553 alloy
ben bettaieb, Mohamed; Van Hoof, Thibaut; Pardoen, thomas et al

in Materials Science & Engineering : A (2014), 617

The elastoviscoplastic behavior of the Ti533 alloy is characterized and compared to the classical Ti-6A14V alloy. The true stress-strain curves are determined based on tensile tests performes under ... [more ▼]

The elastoviscoplastic behavior of the Ti533 alloy is characterized and compared to the classical Ti-6A14V alloy. The true stress-strain curves are determined based on tensile tests performes under different strain rates at room temperature and at 150°C, from which the elastic constants and the parameters of a Norton-Hoff viscoplastic model are identified. The strength of the Ti5553 alloy is 20-40% higherthan the strength of the Ti-6A1-4V alloy. The Ti5553 alloy constitutes thus a promising candidate for advanced structural applications. In view of modeling structural applications of forming operations, the elastic and plastic initial anisotropy of the two alloys is investigated by combining compression on cylinders with elliptical sections, uniaxial tensile tests in different material directions , plane strain and shear tests. The initial anisotropy of the different alloys is very weak which justifies the modeling of the mechanical behavior with isotropic yield surface. The identified elastoviscoplastic model is validated by comparing experimental results with FE predictions both on cylindrical specimens subjected to tensile tests and on flat specimens subjected to plane strain conditions. [less ▲]

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See detailFully implicit integration scheme for the GTN model
Guzmán Inostroza, Carlos Felipe ULg; Habraken, Anne ULg

Poster (2014, May 12)

Fully integration scheme for the GTN model, applied to some shear extensions. The model also comprises Hill type anisotropy and mixed (Isotropic/kinematic) hardening. The consistent tangent matrix is also ... [more ▼]

Fully integration scheme for the GTN model, applied to some shear extensions. The model also comprises Hill type anisotropy and mixed (Isotropic/kinematic) hardening. The consistent tangent matrix is also calculated. [less ▲]

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See detailNumerical Simulation of a Conical Shape Made by Single Point Incremental Forming
Velosa De Sena, José ULg; Duchene, Laurent ULg; Habraken, Anne ULg et al

in Incremental sheet forming (2014, May 08)

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See detailImpact of metallurgical size effects on plasticity of thin mettallic materials
Hug, Eric; keller, clement; Habraken, Anne ULg

in Materials Science Forum (2014), 783-786

Three examples involving size effects are presented witj implications concerning the formability: small Ni-20wt.%Cr resistive bridges, magnetic micro-sensors performed with (Ni,Co,Fe)based alloys and ... [more ▼]

Three examples involving size effects are presented witj implications concerning the formability: small Ni-20wt.%Cr resistive bridges, magnetic micro-sensors performed with (Ni,Co,Fe)based alloys and copper clad aluminum thin wires. The mechanical properties are directly linked to the ratio thickness over grain size (t/d ratio) of the parts.These metallurgical considerations must be taken into account when we are concerned by numerical simulation of the process of such components. It is shown that the simulations can correctly reproduce the softening effect linked to a decrease in thickness and in number of grains across the thickness. Finally the effect of a moderate increase in temperature on these results will be briefly reported. [less ▲]

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See detailNumerical Simulation of a Conical Shape Made By Single Point Incremental
Velosa De Sena, José ULg; Guzmán Inostroza, Carlos Felipe ULg; Duchene, Laurent ULg et al

in Incremental sheet forming (2014, January 06)

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See detailOn the numerical simulation of sheet metal blanking process
Canales Cardenas, Cristian ULg; Bussetta, Philippe ULg; Habraken, Anne ULg et al

Conference (2014)

One of the most widely used cutting techniques in sheet metal forming processes for mass production is the blanking process. In this process, a metallic sheet is placed between a die and a blankholder ... [more ▼]

One of the most widely used cutting techniques in sheet metal forming processes for mass production is the blanking process. In this process, a metallic sheet is placed between a die and a blankholder, and is then cut by the action of a punch which moves downward. The quality of the final product is directly linked to the resulting shape of the cut edge. Due to the complexity of the separation step, the set-up of the blanking process in practice is often driven by empirical knowledge. Thus, an accurate numerical tool is extremely desirable to optimize the setting parameters of this technique and will lead to a better understanding of the entire process. The numerical approach must be able to deal with three main issues involved in blanking: large and localized deformation, friction and contact, and ductile fracture. Furthermore, due to requirements of mass production the punch velocity is normally high and the effects of the strain rate must also be considered. Several approaches have been developed in order to model this cutting process but its accuracy still presents some numerical challenges. [less ▲]

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See detailExperimental investigation and phenomenological modeling of the quasi-static mechanical behavior of TA6V titanium alloy
Gilles, Gaëtan ULg; Habraken, Anne ULg; Duchene, Laurent ULg

in Key Engineering Materials [=KEM] (2014), 622-623

This paper proposes an experimental and numerical investigation of the quasi-static mechanical behavior of TA6V at room temperature. Different loading conditions ( tension, compression, plane strain ans ... [more ▼]

This paper proposes an experimental and numerical investigation of the quasi-static mechanical behavior of TA6V at room temperature. Different loading conditions ( tension, compression, plane strain ans simple shear) were applied on a 0.6 mm thick sheet in several in plane directions. Based on the experimental results, several identifications are performed to determinate the parameters involved in the CPB06 yield criterion and its extensions. The error/time computation ratio for the different identifications is next analysed to fix the choice of the yield criterion. The latter is finally associated with an isotropic hardening law on the one side and a formulation taking into account the evolution of the yield locus on the other side in order to describe the material. The ability of the proposed formulations to predict the TA6V response is studied int he case of a deep-drawing process. [less ▲]

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See detailStudy of residual stresses in bimetallic work rolls
Neira Torres, Ingrid ULg; Gilles, Gaëtan ULg; Tchuindjang, Jérôme Tchoufack ULg et al

in Advanced Materials Research (2014), 996

An experimental campaign of compression tests, differential thermal analysis (DTA), differential scanning calorimetry ( DSC), dilatometry and microstructure analysis has been performed, as well as the ... [more ▼]

An experimental campaign of compression tests, differential thermal analysis (DTA), differential scanning calorimetry ( DSC), dilatometry and microstructure analysis has been performed, as well as the identification of the material data set for finite element ( FE) analysis of bimetallic rolls. This article numerically investigates the stress and strain fields after the cooling stage and it checks their effect on the subsequent heat treatment step. As bimetallic rolls have a different material for core and shell, the effect of the roll size and the shell thickness on residual stresses is also studied. [less ▲]

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See detailEffect of the kinematic hardening in the simulations of the straightening of long rolled profiles
Bouffioux, Chantal ULg; Boman, Romain ULg; Caillet, Nicolas et al

in Key Engineering Materials [=KEM] (2014), 611-612

Residual stresses and lack of straightness appear during the cooling of sheet piles where the initial temperature field is not homogeneous. To meet the standards, the long hot rolled pieces are ... [more ▼]

Residual stresses and lack of straightness appear during the cooling of sheet piles where the initial temperature field is not homogeneous. To meet the standards, the long hot rolled pieces are straightened using a series of rollers placed alternately above and below the pieces with shifts which create a succession of bendings. The process is modeled to study the impact of the industrial parameters ( the duration of the cooling and the rollers positions), to improve the final geometry and to reduce the residual stresses.Tests are carried out on this structural steel to observe the material behavior, then material laws are chosen and parameters of these laws are defined using and inverse method. Two sets of material data are obtained: for the first one, the hardening is supposed to be isotropic, and for the second one, additional tests are performed to describe isotropic and kinematic hardenings.The cooling followed by the straightening is then simulated by the finite element with these two sets of date. The comparison of the rollers forces, the deformation and the residual stresses show the impact of the kinematic hardening on such a process where the material undergoes a sucession of the tensions and compressions. The real forces applied by the rollers,the real curvature of the interlocks at the end of the straightening process and the distribution of the residual longitudinal stresses measured on the web using the ring core method are used to validate the numerical model. [less ▲]

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See detailImpact of anisotropy and viscosity to model the mechanical behavior of Ti-6Al-4V alloy
Tuninetti Vásquez, Victor ULg; Habraken, Anne ULg

in Materials Science and Engineering: A (2014)

This paper compares the predictions of an isotropic-thermo-elasto-viscoplastic approach and of an anisotropic-thermo-elastoplastic one with experimental results representative of the mechanical behavior ... [more ▼]

This paper compares the predictions of an isotropic-thermo-elasto-viscoplastic approach and of an anisotropic-thermo-elastoplastic one with experimental results representative of the mechanical behavior of Ti-6Al-4V at moderate temperatures and low strain rates. The first model is the well known Norton-Hoff viscoplastic constitutive law with isotropic von Mises yield locus identified by using monotonic tension tests performed at strain rates from 10-3 s-1 to 10-1 s-1 and at temperatures up to 400°C. The second model is a thermo-elasto-plastic one defined by the orthotropic yield criterion CPB06. It takes into account the anisotropy and the strength differential (SD) effect in tension-compression of Ti-6Al-4V at RT, 150°C and 400°C. The identification of the SD effect is done by using tension and compression tests and the anisotropy behavior is identified by using shear, plane strain, tension and compression tests performed in three orthogonal material directions. The accuracy of the load and displacements predictions of the two macroscopic constitutive models are compared to experimental results obtained from tests performed on specimens with multiaxial loadings and large strain at several temperatures. [less ▲]

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See detailUsing Gmsh as a mesh generator and post-processor for LAGAMINE
Guzmán Inostroza, Carlos Felipe ULg; Mouton, Thibaud ULg; Habraken, Anne ULg

Scientific conference (2013, September 11)

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See detailAdaptive remeshing technique for the single incremental forming simulations using solid-shell elements
Velosa De Sena, José ULg; Guzmán Inostroza, Carlos Felipe ULg; Duchene, Laurent ULg et al

Scientific conference (2013, September 11)

Nowadays, conventional stamping is a well developed process. It is used for large production manufacturing which amortizes the cost of the tools. However, the possibility to use stamping processes for ... [more ▼]

Nowadays, conventional stamping is a well developed process. It is used for large production manufacturing which amortizes the cost of the tools. However, the possibility to use stamping processes for small volume production or prototypes can be still very expensive. As a result, the Single Point Incremental Forming (SPIF) emerges as a new possibility to solve the cost problem in small volume production. It is performed in a rapid and economic way without the need of expensive tooling. Its dieless nature makes the process appropriate for rapid prototypes and highly personalized pieces. Despite the progresses achieved during the last years, simulating SPIF through the Finite Element Method (FEM) continues nevertheless to be a demanding task. The constantly changing contact conditions between the tool and the sheet surface, as well as the nonlinear material model combined with non-monotonic strain paths during the forming process. In consequence, simulation time increases, even using shell hypothesis and simple geometries. Furthermore, the simulation with 3D “brick” elements in general increases the CPU time even more. To overcome this difficulty, an adaptive remeshing technique that was previously developed for the LAGAMINE code for shell elements [1] and afterwards extended to RESS (Reduced Enhanced Solid-Shell) finite element [2]. This allows that a portion of the sheet mesh is dynamically refined only in the tool vicinity, following its motion. Accordingly, this avoids the requirement of initially refined mesh and, consequently, the global CPU time is reduced. The current study will be focused in a benchmark simulation example applied to a component made by SPIF process using adaptive remeshing combined with RESS finite element. [less ▲]

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See detailAccurate Single Point Incremental Forming Simulations using Solid-Shell Elements
Guzmán Inostroza, Carlos Felipe ULg; Sena, José Ilídio; Duchene, Laurent ULg et al

Scientific conference (2013, September 11)

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See detailStudy of phase transformations within bimetallic rolling mills
Neira Torres, Ingrid ULg; Lecomte-Beckers, Jacqueline ULg; Tchuindjang, Jérôme Tchoufack ULg et al

Scientific conference (2013, September 10)

With the aim of simulating the cooling behavior after a re-austenitizing stage of bimetallic rolling mills, both materials corresponding to spheroidal graphite iron (core material) and high chrome steel ... [more ▼]

With the aim of simulating the cooling behavior after a re-austenitizing stage of bimetallic rolling mills, both materials corresponding to spheroidal graphite iron (core material) and high chrome steel (shell material) must be characterized through thermo physical and mechanical tests as well as microscopic observations. Dilatometer tests were carried out for both materials in order to determinate thermo physical properties such as thermal expansion coefficient and density. Compression tests were also performed in order to estimate the effect of mechanical stress on martensite phase transformation, especially the nature and the type of martensite and start of transformation temperature. However there are some parameters that are still unknown and that are highly difficult to determinate. Inverse simulations are performed through Lagamine code with the aim of finding an estimated value for these parameters or improved parameters, more accurate than the ones already estimated. [less ▲]

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See detailBauschinger effect in thin metallic films by Fem simulations
marandi, kianoosh; vayrette, renaud; Pardoen, Thomas et al

in XII International Conference on Computational Plasticity. Fundamentals and Application COMPLAS XII , Barcelone 3-5 septembre 2013 (2013, September)

Unpassivated free-standing gold and aluminium thin films, subjected to tensile tests show Bauschinger effect (BE) during unloading [1,2]. The focus of this work is to investigate the effect of ... [more ▼]

Unpassivated free-standing gold and aluminium thin films, subjected to tensile tests show Bauschinger effect (BE) during unloading [1,2]. The focus of this work is to investigate the effect of microsstructural heterogeneity such as grain sizes on the BE and the macroscopic deformation behavior in thin metallic films. The finite element code LAGAMINE is used to model the response of films involving sets of grains with different strenghts. The numerical results are compared with experimental results from tensile tests on aluminium thin films from the work of Rajagolapan, et al. [2] [less ▲]

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