References of "Ponthot, Jean-Philippe"
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See detailContinuous Roll Forming Simulation using Arbitrary Lagrangian Eulerian Formalism
Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in Key Engineering Materials [=KEM] (2011), 473

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See detailApplication of the Arbitrary Lagrangian Eulerian Formalism to Stationary Roll Forming Simulations
Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in Advanced Materials Research (2011), 189-193

Due to the length of the mill, accurate modelling of stationary solution of continuous cold roll forming by the finite element method using the classical Lagrangian formulation usually requires a very ... [more ▼]

Due to the length of the mill, accurate modelling of stationary solution of continuous cold roll forming by the finite element method using the classical Lagrangian formulation usually requires a very large mesh leading to huge CPU times. In order to model industrial forming lines including many tools in a reasonable time, the sheet has to be shortened or the element size has to be increased leading to inaccurate results. On top of this, applying loads and boundary conditions on this smaller sheet is usually more difficult than in the continuous case. Moreover, transient dynamic vibrations, which are unnecessarily computed, may appear when the sheet hits each tool, decreasing the convergence rate of the numerical simulation. Beside this classical Lagrangian approach, an alternative method is given by the Arbitrary Lagrangian Eulerian (ALE) formalism which consists in decoupling the motion of the material and the mesh. Starting from an initial guess of the sheet geometry between the rolls, the numerical simulation is performed until the stationary state is reached with a mesh, the nodes of which are fixed in the rolling direction but are free to move on perpendicular plane, following the geometrical boundary of the sheet. The whole forming line can then be modelled using a limited number of brick and contact elements because the mesh is only refined near the tools where bending and contact occur. In this paper, ALE results are compared to previous Lagrangian simulations and experimental measurement on a U-channel, including springback. [less ▲]

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See detailAdvances in Metal Forming Simulation of using Arbitrary Lagrangian Eulerian Formalism
Ponthot, Jean-Philippe ULg; Boman, Romain ULg

in Khan, Akhtar; Meredith, C.; Farrokh, B. (Eds.) Macro to Nano-scale Inelastic Deformation and Failure of Materials & Multi-scale Modeling : Proceedings of PLASTICITY'11, Seventeenth International Symposium on Plasticity and its Current Applications (2011, January)

Accurate modelling of stationary solution of continuous cold roll forming by the finite element method using the classical Lagrangian formulation usually requires a very large mesh leading to huge CPU ... [more ▼]

Accurate modelling of stationary solution of continuous cold roll forming by the finite element method using the classical Lagrangian formulation usually requires a very large mesh leading to huge CPU times. An alternative method is given by the Arbitrary Lagrangian Eulerian (ALE) formalism which consists in decoupling the motion of the material and the mesh. Starting from an initial guess of the sheet geometry between the rolls, the numerical simulation is performed until the stationary state is reached with a mesh. In this paper, ALE results are compared to previous Lagrangian simulations and experimental measurement on a U-channel, including springback [less ▲]

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See detailA non-linear homogeneous model for bone-like materials under compressive load.
Mengoni, Marlène ULg; Voide, Romain; Toye, Dominique ULg et al

in Nithiarasu, P.; Löhner, R.; van Loon, R. (Eds.) et al Conference Proceedings - 2nd International Conference on Computational & Mathematical Biomedical Engineering (2011)

Using morphological data provided by computed tomography, finite element (FE) models can be used to compute the mechanical response of bone and bone-like materials without describing the complex local ... [more ▼]

Using morphological data provided by computed tomography, finite element (FE) models can be used to compute the mechanical response of bone and bone-like materials without describing the complex local microarchitecture. A constitutive law is here developed and proposed for this purpose. It captures the non-linear structural behavior of bone-like materials through the use of fabric tensors. It also allows for irreversible strains using a plastic material model, allowing hardening of the yield parameters. These characteristics are expressed in a constitutive law based on the anisotropic continuum damage theory coupled with isotropic elastoplasticity in a finite strains framework. This law is implemented into Metafor, a non-linear FE software. Simulations of cylindrical samples undergoing stepwise compression are presented. [less ▲]

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See detailOn the periodontal ligament representation in orthodontic tooth movement modelisation
Mengoni, Marlène ULg; Ponthot, Jean-Philippe ULg

Conference (2011)

Orthodontic tooth movement (OTM) is the result of bone remodeling at the interface with the periodontal ligament (PDL) around a mechanically loaded tooth in response to a biomechanical stimulus. Modeling ... [more ▼]

Orthodontic tooth movement (OTM) is the result of bone remodeling at the interface with the periodontal ligament (PDL) around a mechanically loaded tooth in response to a biomechanical stimulus. Modeling of the PDL therefore plays an important role in the process of modeling OTM. However when producing a finite element model from clinical computer tomography data, the PDL cannot be segmented and its geometry is approximated by many authors from the root geometry. The aim of this study is to propose alternatives to a geometrical representation of the PDL using either simple spring elements between the teeth and alveolar bone or bilateral sticking contact conditions. Results consist in a comparison of the hydrostatic and Von-Mises stresses in the bone along the root as well as the strain energy used in a bone remodeling algorithm when a 1N force is applied to a single rooted tooth crown. While both models can well represent the pressure (hydrostatic stress) transfer from the tooth to the bone, the bilateral sticking contact conditions show better results to transfer the shear stress as well as the strain energy. [less ▲]

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See detailNumerical Simulations of Asperity Crushing - Application to Cold Rolling
Carretta, Yves ULg; Legrand, Nicolas; Laugier, Maxime et al

in Proceedings of ESAFORM : Belfast, 27-29th april 2011 (2011)

Asperity flattening has a huge influence on friction and wear in metal forming processes. Nevertheless, phenomena that occur at the microscopic scale are still not well understood. Since no experiments ... [more ▼]

Asperity flattening has a huge influence on friction and wear in metal forming processes. Nevertheless, phenomena that occur at the microscopic scale are still not well understood. Since no experiments can be easily performed in real forming conditions, numerical models are essential to achieve a better knowledge of what happens in these contact regions. In this paper, two finite elements models are presented. The first one represents the flattening of a serrated asperity field in plane strain conditions. The results are compared to the experiments conducted by Sutcliffe [1]. The second one is a tri-dimensional asperity model flattened by a rigid plane. The boundary conditions applied to this model correspond to the ones encountered in a real cold rolling case. The results are compared to the relative contact area computed by a strip rolling model using the analytical laws proposed by Wilson & Sheu [2] and Marsault [3]. [less ▲]

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See detailNUMERICAL SIMULATIONS OF THIXOFORMING PROCESSES: DEVELOPMENT AND COMPARISON OF SEVERAL SEMI-SOLID CONSTITUTIVE LAWS
Koeune, Roxane ULg; Ponthot, Jean-Philippe ULg

(2011)

ABSTRACT This paper deals with the development, and the comparison, of several constitutive laws in the frame of the simulation of thixoforming processes. The comparison is based on the simulation of a ... [more ▼]

ABSTRACT This paper deals with the development, and the comparison, of several constitutive laws in the frame of the simulation of thixoforming processes. The comparison is based on the simulation of a simple academic test that is well representative of the thixotropic behavior: a simple shear test, with shear-rate step-up and step-down. [less ▲]

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See detailMultiple material mesh generation for biomedical applications
D'Otreppe, Vinciane ULg; Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in Proceedings of the 9th belgian day on biomedical engineering (2010, November 26)

The finite element method is commonly used in biomedical applications for the simulation of the behaviour of biological structures. However, extracting finite element meshes from medical images is still ... [more ▼]

The finite element method is commonly used in biomedical applications for the simulation of the behaviour of biological structures. However, extracting finite element meshes from medical images is still very challenging. We propose an innovative system to create accurate multiple domain tetrahedral meshes from medical images. Our approach is based on an enhanced Marching Tetrahedra algorithm that extracts the boundary surfaces delimiting the different material domains in an integrated manner. Moreover, a surface reconstruction method is employed to ensure that the resulting mesh is a smooth and accurate surface representation of the original sampled structure. Mesh smoothing and decimation algorithms are also revised to conform to the multiple material nature of the system as well as to adhere to the underlying volume data. [less ▲]

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See detailMultiple Material Mesh Generation For Biomedical Applications
D'Otreppe, Vinciane ULg; Boman, Romain ULg; Ponthot, Jean-Philippe ULg

Poster (2010, November 26)

The finite element (FE) method is commonly used in biomedical applications for the simulation of the behaviour of biological structures. A key component in FE simulation is the creation of a finite ... [more ▼]

The finite element (FE) method is commonly used in biomedical applications for the simulation of the behaviour of biological structures. A key component in FE simulation is the creation of a finite element mesh. In medical applications, the meshes should be directly generated from the medical scans. Moreover, biological structures are usually composed of several inner regions that need to be separately segmented, labelled and meshed to be able to apply different material properties in the finite element model. A procedure to create surface meshes from a multi-valued volume data sets is proposed. Following properties are guaranteed: (1) The generated mesh consists of a set of non manifold triangle meshes that separate each connected component in the labelled data set. These interface meshes join each other consistently along their boundaries, i.e., no T junctions nor gaps may appear. (2) The surface mesh is a geometrically accurate representation of the data represented in the medical scans. However, it is not be tainted by the typical aliasing and staircase artifacts that are due to the discrete nature of the voxels. [less ▲]

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See detailEnhanced FEM-based Modeling of Brain Shift Deformation in Image-Guided Neurosurgery
Vigneron, Lara M.; Boman, Romain ULg; Ponthot, Jean-Philippe ULg et al

in Journal of Computational & Applied Mathematics (2010), 234

We consider the problem of improving outcomes for neurosurgery patients by enhancing intraoperative navigation and guidance. Current navigation systems do not accurately account for intraoperative brain ... [more ▼]

We consider the problem of improving outcomes for neurosurgery patients by enhancing intraoperative navigation and guidance. Current navigation systems do not accurately account for intraoperative brain deformation. We focus on the brain shift deformation that occurs just after the opening of the skull and dura. The heart of our system is a nonrigid registration technique using a biomechanical model. We specifically work on two axes: the representation of the structures in the biomechanical model and the evaluation of the surface landmark displacement fields between intraoperative MR images. Using the modified Hausdorff distance as an image similarity measure, we demonstrate that our approach significantly improves the alignment of the intraoperative images. ' 2009 Elsevier B.V. All rights reserved. [less ▲]

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See detailContinuous Roll Forming Simulation Using Arbitrary Lagrangian Eulerian Formalism
Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in Khalili, Nasser; Valliappan, Somasundaram; Li, Qing (Eds.) et al Proceedings of the joint 9th World Congress on Computational Mechanics and 4th Asian Pacific Congress on Computational Mechanics (2010, July)

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See detailAdvances in Numerical Simulation of Stationary Processes using Arbitrary Lagrangian Eulerian Formalism. Application to Roll Forming Process.
Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in ECCM 2010, 4th European Conference on Computational Mechanics (2010, May)

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See detailSmooth multiple-region mesh generation for biomedical applications
D'Otreppe, Vinciane ULg; Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in ECCM 2010, 4th European Conference on Computational Mechanics (2010, May)

The finite element method is commonly used in biomedical applications for the simulation of the behaviour of biological structures. However, extracting finite element meshes from medical data is still ... [more ▼]

The finite element method is commonly used in biomedical applications for the simulation of the behaviour of biological structures. However, extracting finite element meshes from medical data is still very challenging. In this article, an innovative system that efficiently reconstructs smooth, multi-material, 3D surface meshes from medical images is presented. Our approach is based on an enhanced Marching Tetrahedra algorithm, which extracts boundary surfaces between different materials within one sweep of the image stack in an integrated manner. Moreover,Multi-Level Partition of Unity implicit models are used to obtain a smooth and accurate surface representation of the original binary sampled surface. Mesh smoothing and decimation algorithms were also revised to adapt to the multi-material nature of the system as well as to adhere to the underlying volume data. [less ▲]

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See detailIsotropic continuum damage/repair model for alveolar bone remodelling
Mengoni, Marlène ULg; Ponthot, Jean-Philippe ULg

in Journal of Computational & Applied Mathematics (2010), 234

Several authors have proposed mechanical models to predict long term tooth movement, considering both the tooth and its surrounding bone tissue as isotropic linear elastic materials coupled to either an ... [more ▼]

Several authors have proposed mechanical models to predict long term tooth movement, considering both the tooth and its surrounding bone tissue as isotropic linear elastic materials coupled to either an adaptative elasticity behavior or an update of the elasticity constants with density evolution. However, tooth movements obtained through orthodontic appliances result from a complex biochemical process of bone structure and density adaptation to its mechanical environment, called bone remodeling. This process is far from linear reversible elasticity. It leads to permanent deformations due to biochemical actions. The proposed biomechanical constitutive law, inspired from Doblaré and García (2002) [30], is based on a elasto-viscoplastic material coupled with Continuum isotropic Damage Mechanics (Doblaré and García (2002) [30] considered only the case of a linear elastic material coupled with damage). The considered damage variable is not actual damage of the tissue but a measure of bone density. The damage evolution law therefore implies a density evolution. It is here formulated as to be used explicitly for alveolar bone, whose remodeling cells are considered to be triggered by the pressure state applied to the bone matrix. A 2D model of a tooth submitted to a tipping movement, is presented. Results show a reliable qualitative prediction of bone density variation around a tooth submitted to orthodontic forces. [less ▲]

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