References of "Bouffioux, Chantal"
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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 detailBack Analysis and optimisation method with Lagamine
Levasseur, Séverine ULg; Bouffioux, Chantal ULg

Speech (2013)

Comparison of Back Analysis and Optimization Methods to characterize materials with LAGAMINE

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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 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 detailForming Forces in Single Point Incremental Forming, Prediction by Finite Element Simulations
Henrard, Christophe; Bouffioux, Chantal ULg; Eyckens, P. et al

in Computational Mechanics (2010)

The aim of this article is to study the accuracy of the nite element simulations to predict the tool force during the Single Point Incremental Forming process. The forming of two cones in soft aluminum ... [more ▼]

The aim of this article is to study the accuracy of the nite element simulations to predict the tool force during the Single Point Incremental Forming process. The forming of two cones in soft aluminum was studied with two Finite Element (FE) codes and several constitutive laws (an elastic-plastic model coupled with different hardening approaches). The parameters of these laws were identi ed using tensile and shear tests, as well as an inverse 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 in uence on the force prediction: the type of nite element, the constitutive law and the identi cation procedure for the material parameters. In addition, it con rms that a very 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 detailMaterial data identification to model the single point incremental forming process
Bouffioux, Chantal ULg; Pouteau, P.; Duchene, Laurent ULg et al

in International Journal of Material Forming (2010), 3(Suppl. 1), 979-982

In this study, the Single Point Incremental Forming process (SPIF) is applied on a specific aluminium alloy used in the aerospace industry since this technique and material combine a low specific weight ... [more ▼]

In this study, the Single Point Incremental Forming process (SPIF) is applied on a specific aluminium alloy used in the aerospace industry since this technique and material combine a low specific weight, high strength and stiffness properties and high strain levels. To be able to optimize the process, a model and its material parameters are required. It was noticed that a simple isotropic hardening model was not sufficient to provide an accurate tool force prediction [1]. Therefore an elasto-plastic law with a mixed isotropic-kinematic hardening is investigated. The inverse method coupled with the Finite Element (FE) code: "Lagamine" [2] is used to fit the material data of this complex law. In order to validate the model and the material data, a Line test and a Cone test are used. [less ▲]

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See detailOptimized Remeshing for Incremental Forming Simulation
Rabahallah, François ULg; Bouffioux, Chantal ULg; Duchene, Laurent ULg et al

in Proceedings of the Advances in Materials and Processing Technologies Conference (2010)

This work presents an advanced numerical methodology which aims to improve the simulations of incremental forming processes [3]. A specific numerical treatment is required to optimize the remeshing ... [more ▼]

This work presents an advanced numerical methodology which aims to improve the simulations of incremental forming processes [3]. A specific numerical treatment is required to optimize the remeshing procedure, in order to decrease the simulation CPU time and deals with the strong process nonlinearities. The algorithm remeshing procedure is implemented in the Lagamine FE code [2] developed at the University of Liège. An elastoplastic law is combined with an isotropic kinematic hardening model. The identification procedure for the material parameters determination takes into account a set of mechanical tests (inverse approach). Numerical simulations of the forming of a pyramid part with two wall angles are performed in order to address the robustness of the implementation and the ability of this numerical methodology to predict the force values. Comparisons between measured and predicted force values are performed. [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 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 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 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 detailModel Identification and FE Simulations Effect of Different Yield Loci and Hardening Laws in Sheet Forming
Flores, Paulo; Duchene, Laurent ULg; Bouffioux, Chantal ULg et al

in International Journal of Plasticity (2007), 23(3), 420-449

The bi-axial experimental equipment [Flores, P., Rondia, E., Habraken, A.M., 2005a. Development of an experimental equipment for the identification of constitutive laws (Special Issue). International ... [more ▼]

The bi-axial experimental equipment [Flores, P., Rondia, E., Habraken, A.M., 2005a. Development of an experimental equipment for the identification of constitutive laws (Special Issue). International Journal of Forming Processes] developed by Flores enables to perform Bauschinger shear tests and successive or simultaneous simple shear tests and plane strain tests. Flores investigates the material behavior with the help of classical tensile tests and the ones performed in his bi-axial machine in order to identify the yield locus and the hardening model. With tests performed on one steel grade, the methods applied to identify classical yield surfaces such as [Hill, R., 1948. A theory of the yielding and plastic flow of anisotropic materials. Proceedings of the Royal Society of London A 193, 281–297; Hosford, W.F., 1979. On yield loci of anisotropic cubic metals. In: Proceedings of the 7th North American Metalworking Conf. (NMRC), SME, Dearborn, MI, pp. 191–197] ones as well as isotropic Swift type hardening, kinematic Armstrong–Frederick or Teodosiu and Hu hardening models are explained. Comparison with the Taylor–Bishop–Hill yield locus is also provided. The effect of both yield locus and hardening model choices is presented for two applications: plane strain tensile test and Single Point Incremental Forming (SPIF). [less ▲]

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See detailStudy of a 2024 aluminium rod produced by Rotary Forging
Habraken, Anne ULg; Bouffioux, Chantal ULg; Carton, Marc ULg et al

in Journal of Materials Processing Technology (2007), 184

An investigation of the rotary forging process of a 2024 aluminium rod is summarised. Some dispersion in mechanical properties and chemical composition of the base material is permitted. Samples of two ... [more ▼]

An investigation of the rotary forging process of a 2024 aluminium rod is summarised. Some dispersion in mechanical properties and chemical composition of the base material is permitted. Samples of two material batches were selected: one just stays near the upper limit of tolerance and the other has mean properties. Tensile and compression tests confirm the different mechanical behaviours and allow the identification of constitutive laws parameters. Optical metallography after T3 and T10 thermal treatments and differential thermal analysis provide the grain size and precipitation characteristics of each material batch, which explain their different mechanical behaviours. The industrial rod studied is usually forged in two operations: a first forging process, then a T10 thermal treatment followed by a second forging step. Industrial practise shows that manufacturing the rod with one forging step fails. FEM simulations of the process coupled with a fracture criterion confirm the advantage of a two-step process compared to a single forging step. [less ▲]

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See detailValidation of a new finite element for incremental forming simulation using a dynamic explicit approach
Henrard, Christophe ULg; Bouffioux, Chantal ULg; Duchene, Laurent ULg et al

in Key Engineering Materials [=KEM] (2007), 344

A new method for modeling the contact between the tool and the metal sheet for the incremental forming process was developed based on a dynamic explicit time integration scheme. The main advantage of this ... [more ▼]

A new method for modeling the contact between the tool and the metal sheet for the incremental forming process was developed based on a dynamic explicit time integration scheme. The main advantage of this method is that it uses the actual contact location instead of fixed positions, e.g. integration or nodal points. The purpose of this article is to compare the efficiency of the new method, as far as accuracy and computation time are concerned, with finite element simulations using a classic static implicit approach. In addition, a sensitivity analysis of the mesh density will show that bigger elements can be used with the new method compared to those used in classic simulations. [less ▲]

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See detailElasto-plastic material parameter identification by inverse methods: sensitivity matrix calculation
Cooreman, Steven; Bouffioux, Chantal ULg; Lecompte, David et al

in Proceedings of the SEM annual conference and exposition 2006 (2006)

Inverse methods offer a powerful tool for the determination of the elasto-plastic material properties. Contrary to standard tests, these methods can deal with heterogeneous stress and strain-fields which ... [more ▼]

Inverse methods offer a powerful tool for the determination of the elasto-plastic material properties. Contrary to standard tests, these methods can deal with heterogeneous stress and strain-fields which have a larger information contents and hence allow the simultaneous identification of several material parameters. Moreover, it is expected that the obtained material parameters are more accurate, since these heterogeneous deformation fields are much closer to those occurring in real (metal) forming operations. The principle of the inverse method for the identification of material parameters presented in this paper is to compare an experimentally measured strain field to that computed by a Finite Element (FE) model. The material parameters in the FE model are iteratively tuned in such a way that both strain fields match each other as close as possible. One of the building blocks in this identification procedure is the updating algorithm for the material parameters in the FE model. The key problem of this updating algorithm is the determination of the sensitivity matrix, which expresses the sensitivities of the strains with respect to the material parameters. This paper presents an analytical method for the calculation of this sensitivity matrix in case of simple tensile tests. [less ▲]

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See detailComputation of the sensitivity matrix used for Elasto-plastic material parameter identification by inverse methods
Cooreman, Steven; Bouffioux, Chantal ULg; Lecompte, David et al

in Congress on theoretical and applied Mechanics, Mons, Belgium, May 2006 (2006)

Inverse methods offer a powerful tool for the determination of the elasto-plastic material properties. Contrary to standard tests, these methods can deal with heterogeneous stress and strain-fields which ... [more ▼]

Inverse methods offer a powerful tool for the determination of the elasto-plastic material properties. Contrary to standard tests, these methods can deal with heterogeneous stress and strain-fields which have a larger information contents and hence allow the simultaneous identification of several material parameters. Moreover, it is expected that the obtained material parameters are more accurate, since these heterogeneous deformation fields are much closer to those occurring in real (metal) forming operations. The principle of the inverse method for the identification of material parameters presented in this paper is to compare an experimentally measured strain field to that computed by a Finite Element (FE) model. The material parameters in the FE model are iteratively tuned in such a way that both strain fields match each other as closely as possible. One of the building blocks in this identification procedure is the updating algorithm for the material parameters in the FE model. The key problem of this updating algorithm is the determination of the sensitivity matrix, which expresses the sensitivities of the strains with respect to the material parameters. This paper presents an analytical method for the calculation of this sensitivity matrix in case of simple tensile tests. [less ▲]

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See detailEffect of FEM choices in the modelling of incremental forming of aluminium sheets
He, S.; Van Bael, A.; Van Houtte, P. et al

in Banabic, D. (Ed.) Proceedings of the 8th ESAFORM Conference on Material Forming (2005)

This paper investigates the process of single point incremental forming of an aluminium cone with a 50-degree wall angle. Finite element (FE) models are established to simulate the process. Different FE ... [more ▼]

This paper investigates the process of single point incremental forming of an aluminium cone with a 50-degree wall angle. Finite element (FE) models are established to simulate the process. Different FE packages have been used. Various aspects associated with the numerical choices as well as the material and process parameters have been studied. The final geometry and the reaction forces are presented as the results of the simulations. Comparison between the simulation results and the experimental data is also made. [less ▲]

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See detailDevelopment of a contact model adapted to incremental forming
Henrard, Christophe ULg; Bouffioux, Chantal ULg; Godinas, A. et al

in Banabic, D. (Ed.) Proceedings of the 8th ESAFORM Conference on Material Forming (2005)

The objective of this article is to present the development of a new method for taking into account the contact between the tool and the blank during incremental forming. First, the need for such a model ... [more ▼]

The objective of this article is to present the development of a new method for taking into account the contact between the tool and the blank during incremental forming. First, the need for such a model is justified. Then, the basic features of the adapted dynamic explicit scheme are presented, followed by the new algorithms proposed and their programming. Finally, some conclusions and perspectives are drawn. [less ▲]

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