References of "Duchene, Laurent"
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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 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 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 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 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 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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See detailParametric study of metal/polymer multilayer coatings for temperature wrinkling prediction
Zhang, Lihong ULg; Habraken, Anne ULg; Ben Bettaieb, Amine ULg et al

in Journal of Materials Engineering & Performance (2013), 22(9), 2437-2445

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See detailNumerical simulation of a pyramid steel sheet formed by single point incremental forming using solid-shell finite elements
Duchene, Laurent ULg; Guzmán Inostroza, Carlos Felipe ULg; Behera, Amar Kumar et al

in Key Engineering Materials [=KEM] (2013)

Single Point Incremental Forming (SPIF) is an interesting manufacturing process due to its dieless nature and its increased formability compared to conventional forming processes. Nevertheless, the ... [more ▼]

Single Point Incremental Forming (SPIF) is an interesting manufacturing process due to its dieless nature and its increased formability compared to conventional forming processes. Nevertheless, the process suffers from large geometric deviations when compared to the original CAD profile. One particular example arises when analyzing a truncated two-slope pyramid. In this paper, a finite element simulation of this geometry is carried out using a newly implemented solid-shell element, which is based on the Enhanced Assumed Strain (EAS) and the Assumed Natural Strain (ANS) techniques. The model predicts the shape of the pyramid very well, correctly representing the springback and the through thickness shear (TTS). Besides, the effects of the finite element mesh refinement, the EAS and ANS techniques on the numerical prediction are presented. It is shown that the EAS modes included in the model have a significant influence on the accuracy of the results. [less ▲]

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See detailNumerical modeling and digital image correlation strain measurements of coated metal sheets submitted to large bending deformation
Duchene, Laurent ULg; Ben Bettaieb, Amine ULg; Tuninetti Vásquez, Victor ULg et al

in Proceedings of the 16th ESAFORM conference on Material Forming (2013)

The recently developed SSH3D solid-shell element, which is based on the Enhanced Assumed Strain (EAS) and the Assumed Natural Strain (ANS) techniques, is utilized for the modeling of a severe bending ... [more ▼]

The recently developed SSH3D solid-shell element, which is based on the Enhanced Assumed Strain (EAS) and the Assumed Natural Strain (ANS) techniques, is utilized for the modeling of a severe bending sheet forming process. To improve the element's ability to capture the through thickness gradients, a specific integration scheme was developed. In this paper, the performances of this element for the modeling of the T-bent process were assessed thanks to comparison between experimental and numerical results in terms of the strain field at the outer surface of the sheet. The experimental results were obtained by Digital Image Correlation. It is shown that a qualitative agreement between experimental and numerical results is obtained but some numerical parameters should be optimized to improve the accuracy of the simulation predictions. In this respect, the influence of the penalty coefficient of the contact modeling was analyzed. [less ▲]

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See detailExperimental and numerical study of TA6V mechanical behavior under different quasi-static strain paths at room temperature
Gilles, Gaëtan ULg; Habraken, Anne ULg; Cazacu, Oana et al

in AIP Conference Proceedings (2013), 1532

This paper presents an experimental study of the quasi-static mechanical behavior of TA6V titanium alloy. Different monotonic tests were carried out in several orientations in the plane of the sheet in ... [more ▼]

This paper presents an experimental study of the quasi-static mechanical behavior of TA6V titanium alloy. Different monotonic tests were carried out in several orientations in the plane of the sheet in order to characterize the anisotropy and the tension-compression asymmetry exhibited by the material. Initial yielding is modeled by the phenomenological CPB06 criterion and Voce's isotropic hardening is used to describe its evolution. The simulation of a deep-drawing process is performed using the proposed constitutive modeling and compared with experimental data. [less ▲]

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See detailNumerical simulation of T-bend of multilayer coated metal sheet using solid-shell element
Ben Bettaieb, Amine ULg; Tuninetti Vásquez, Victor ULg; Duchene, Laurent ULg

in Steel Research International (2012)

The main aim of this paper is to model the T-bend test performed on multilayer coated metal sheets in order to measure the coating flexibility. Because of important uses of polymer coatings in many ... [more ▼]

The main aim of this paper is to model the T-bend test performed on multilayer coated metal sheets in order to measure the coating flexibility. Because of important uses of polymer coatings in many industrial applications and higher requirement on the quality of products, an accurate modeling of the T-bend process is therefore essential. During the modeling with the finite element method, the large thickness ratio between the different layers is likely to produce elements with an unfavorable aspect ratio. Therefore, to avoid obtaining inaccurate results linked to the shape of the elements, solid-shell elements are used in this study. These elements are based on the Enhanced Assumed Strain (EAS) technique and the Assumed Natural Strain (ANS) technique. These techniques permit to avoid locking problems even in very bad conditions (nearly incompressible materials, very thin elements conducting to large aspect ratios, distorted element geometry…). The EAS technique artificially introduces additional degrees of freedom (DOFs) to the element. They permit to increase the flexibility of the element which is very efficient for several locking issues. On the other hand, the ANS technique modifies the interpolation scheme for particular strain components. The ANS technique proved to eliminate the transverse shear locking from the element in bending dominated situations. Besides, a numerical integration scheme dedicated to Solid-Shell elements was implemented. It uses a user-defined number of integration points along the thickness direction, which permits to increase the element accuracy with a mesh containing a reduced number of elements along the thickness direction. The results obtained from numerical simulations are compared with some analytical results in order to check the strain predicted in the coated layer by FEM. This information helps to investigate the coating layer ductility in the real process. [less ▲]

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See detailFinite element investigation of size effects on the mechanical behavior of nickel single crystals
Keller, Clément; Habraken, Anne ULg; Duchene, Laurent ULg

in Materials Science & Engineering : A (2012), 550(30), 342-349

The influence of dimensions on the mechanical behavior of f.c.c. single crystals with dimensions larger than a few micrometers has been the topic of many experimental investigations and controversies ... [more ▼]

The influence of dimensions on the mechanical behavior of f.c.c. single crystals with dimensions larger than a few micrometers has been the topic of many experimental investigations and controversies during the 1970s and this question is still open. The objective of this article is to shed new light on this point by performing finite element simulations thanks to a strain gradient crystal plasticity model. Based on the model identification for nickel, several single crystal samples with various thicknesses and orientations were tested numerically in tension. The effect of dimensions was then analyzed considering the spatial distribution of dislocation densities. Near loading boundaries, dislocation density gradients appeared perpendicular to the Burgers vector direction of the primary activated slip system which modified the mechanical behavior. These gradients are discussed in terms of boundary conditions, crystal orientation and dislocation interactions with surfaces. [less ▲]

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See detailOn the numerical integration of rate independent single crystal behavior at large strain
Ben Bettaieb, Mohamed; Débordes, Olivier; Dogui, Abdelwaheb et al

in International Journal of Plasticity (2012), 32-33

This paper presents a new numerical algorithm for the integration of the constitutive equations of a single crystal for finite rate-independent elastoplastic strains. The algorithm addressed in this paper ... [more ▼]

This paper presents a new numerical algorithm for the integration of the constitutive equations of a single crystal for finite rate-independent elastoplastic strains. The algorithm addressed in this paper is dedicated to face-centered-cubic (FCC) crystal structures. Its first feature is a much more efficient and more accurate integration scheme of the constitutive equations compared to previous attempts. This scheme is based on a fully implicit integration procedure, yet it may be transformed easily into an explicit scheme. Determining the set of active slip systems is performed by the use of a combinatorial search procedure, and the determination of the slip rates of the different active slip systems is based on the fixed point method. The second feature of this algorithm stems from the original method used to solve the ambiguity of the possible non-uniqueness of the set of active slip systems. A robust method, based on a small positive perturbation of the critical shear stresses, is proposed to overcome this difficulty. It is worth mentioning that the algorithm developed in this paper is not limited to one particular hardening law or to FCC crystal structures. Rather, it can be used and extended to various hardening laws and crystal structures (e.g. BCC or HCP. . .) in a straightforward manner. The authors demonstrate the performance of the proposed algorithm and illustrate its accuracy and efficiency through various numerical simulations at the single crystal and polycrystal scales. The predicted results obtained from those simulations were compared with those obtained using other numerical techniques and algorithms (i.e., a pseudo-inversion technique and an explicit algorithm). Our numerical predictions are also compared with some numerical and experimental results from other papers. The response of the polycrystal was computed by using the proposed algorithm combined with Taylor’s homogenization scheme, which is used to compute the overall polycrystalline behavior. The paper ends with a statistical study of the influence of the perturbation technique on the response prediction for a single crystal and a polycrystal. [less ▲]

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See detailEvaluation of the Enhanced Assumed Strain and Assumed Natural Strain in the SSH3D and RESS3 Solid Shell Elements for Single Point Incremental Forming Simulation
Guzmán Inostroza, Carlos Felipe ULg; Ben Bettaieb, Amine ULg; Velosa de Sena, José Ilidio et al

in Key Engineering Materials [=KEM] (2012), 504-506

Single Point Incremental Forming (SPIF) is a recent sheet forming process which can give a symmetrical or asymmetrical shape by using a small tool. Without the need of dies, the SPIF is capable to deal ... [more ▼]

Single Point Incremental Forming (SPIF) is a recent sheet forming process which can give a symmetrical or asymmetrical shape by using a small tool. Without the need of dies, the SPIF is capable to deal with rapid prototyping and small batch productions at low cost. Extensive research from both experimental and numerical sides has been carried out in the last years. Recent developments in the finite element simulations for sheet metal forming have allowed new modeling techniques, such as the Solid Shell elements, which combine the main features of shell hypothesis with a solid-brick element. In this article, two recently developed elements -SSH3D element [1, 2] and RESS3 element [3]- implemented in Lagamine (finite element code developed by the ArGEnCo department of the University of Liège) are explained and evaluated using the SPIF line test. To avoid locking problems, the well-known Enhanced Assumed Strain (EAS) and Assumed Natural Strain (ANS) techniques are used. The influence of the different EAS and ANS parameters are analysed comparing the predicted tool forces and the shape of a transversal cut, at the end of the process. The results show a strong influence of the EAS in the forces prediction, proving that a correct choice is fundamental for an accurate simulation of the SPIF using Solid Shell elements. [less ▲]

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See detailApproches multi-échelles et éléments finis Solid-Shell
Duchene, Laurent ULg

Speech (2012)

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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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