References of "Ponthot, Jean-Philippe"
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See detailEfficient ALE mesh management for 3D quasi-Eulerian problems
Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in International Journal for Numerical Methods in Engineering (2012), 92(10), 857-890

In computational solid mechanics, the ALE formalism can be very useful to reduce the size of finite element models of continuous forming operations such as roll forming. The mesh of these ALE models is ... [more ▼]

In computational solid mechanics, the ALE formalism can be very useful to reduce the size of finite element models of continuous forming operations such as roll forming. The mesh of these ALE models is said to be quasi-Eulerian because the nodes remain almost fixed—or almost Eulerian—in the main process direction, although they are required to move in the orthogonal plane in order to follow the lateral displacements of the solid. This paper extensively presents a complete node relocation procedure dedicated to such ALE models. The discussion focusses on quadrangular and hexahedral meshes with local refinements. The main concern of this work is the preservation of the geometrical features and the shape of the free boundaries of the mesh. With this aim in view, each type of nodes (corner, edge, surface and volume) is treated sequentially with dedicated algorithms. A special care is given to highly curved 3D surfaces for which a CPU-efficient smoothing technique is proposed. This new method relies on a spline surface reconstruction, on a very fast weighted Laplacian smoother with original weights and on a robust reprojection algorithm. The overall consistency of this mesh management procedure is finally demonstrated in two numerical applications. The first one is a 2D ALE simulation of a drawbead, which provides similar results to an equivalent Lagrangian model yet is much faster. The second application is a 3D industrial ALE model of a 16-stand roll forming line. In this case, all attempts to perform the same simulation by using the Lagrangian formalism have been unsuccessful. [less ▲]

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See detailThree-dimensional Modelling of Asperity Crushing
Carretta, Yves ULg; Boman, Romain ULg; Legrand, Nicolas et al

Conference (2012, October)

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 experiment can ... [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 experiment 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, a threedimensional model of a rough strip flattened by a rigid rough tool is presented. The boundary conditions applied to this model correspond to the ones encountered in a real cold-rolling case. The results are compared to experimental measurements from the pilot mill of ArcelorMittal Maizières R&D. [less ▲]

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See detailArbitrary Lagrangian Eulerian Modelling of Tension Levelling
Boman, Romain ULg; Parrico, Anthony; Legrand, Nicolas et al

in Matériaux et Techniques (2012, October), 100(Hors série 2012), 40-42

This paper presents a two-dimensional model of tension levelling using the Arbitrary Lagrangian Eulerian (ALE) approach. During the simulation, the ALE mesh remains globally fixed along the rolling ... [more ▼]

This paper presents a two-dimensional model of tension levelling using the Arbitrary Lagrangian Eulerian (ALE) approach. During the simulation, the ALE mesh remains globally fixed along the rolling direction. Therefore, the required number of finite elements is much smaller than in the Lagrangian case and smaller CPU times are obtained for the same accuracy on the results. The ALE model is first validated against a classical equivalent Lagrangian model. Then, both sets of numerical results are compared to experimental measurements from the pilot mill of ArcelorMittal Maizières R&D. [less ▲]

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See detailModeling frictional contact conditions with the penalty method in the extended finite element framework
Biotteau, Ewen ULg; Ponthot, Jean-Philippe ULg

Scientific conference (2012, September 12)

This paper introduces an application of the eXtended Finite Element Method (XFEM) to model metal forming processes. The X-FEM is used to account for material interfaces and reduce the meshing constraints ... [more ▼]

This paper introduces an application of the eXtended Finite Element Method (XFEM) to model metal forming processes. The X-FEM is used to account for material interfaces and reduce the meshing constraints due to the shape of the tools and the evolving configuration of the structures. Large deformations and non-linear behaviors are also accounted for, but this contribution focuses in the modeling of frictional conditions on the interface. In X-FEM simulations, the constraint of impenetrability is usually imposed using Lagrange multiplier methods. For such strategies, stabilisation algorithms are needed to prevent the apparition of instabilities due to the introduction of dual unknowns. The strategy presented here proposes to manage the contact using the penalty approach. As it requires no additional variables, it is not submitted to the same kind of instabilities. The contact problem is modeled using integration sub-elements, defined on the boundary of the structure, on which the contact constraints have to be enforced. [less ▲]

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See detailA bone remodelling model for long term orthodontic tooth movement.
Mengoni, Marlène ULg; D'Otreppe, Vinciane ULg; Ponthot, Jean-Philippe ULg

in Journal of Biomechanics (2012, July), 45(Supplement 1), 180

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See detailDevelopment of a biomechanical model of deer antler cancellous bone based on X-ray microtomographic images
de Bien, Charlotte ULg; Mengoni, Marlène ULg; D'Otreppe, Vinciane ULg et al

in Micro-CT User Meeting 2012 - Abstract Book (2012, April)

Finite element models accurately compute the mechanical response of bone and bone-like materials when the models include their detailed microstructure. The aim of this paper is to develop and validate a ... [more ▼]

Finite element models accurately compute the mechanical response of bone and bone-like materials when the models include their detailed microstructure. The aim of this paper is to develop and validate a biomechanical model for deer antler cancellous bone tissue based on X-ray microtomographic images. In order to simulate the mechanical behavior under compressive load using a finite element model, images obtained by X-ray microtomography were exported into Metafor, which is an non-linear finite element software initially developed at University of Liège for metal forming processes. This software has recently found biomedical applications. The ultimate goal is to compare model predictions with the mechanical behavior observed experimentally using the Skyscan material testing stage under compression mode. The creation of the biomechanical model mesh from segmented μCT images, its integration into the software Metafor and the simulation of a compression test are described in this paper. [less ▲]

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See detailA fully nonlinear finite element model for orthodontic tooth movement prediction
Mengoni, Marlène ULg; D'Otreppe, Vinciane ULg; Ponthot, Jean-Philippe ULg

in Proceedings of the 10th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering. (2012, April)

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

in International Journal for Numerical Methods in Biomedical Engineering (2012), 28(2), 334-348

Finite element (FE) models accurately compute the mechanical response of bone and bone-like materials when the models include their detailed microstructure. In order to simulate non-linear behavior, which ... [more ▼]

Finite element (FE) models accurately compute the mechanical response of bone and bone-like materials when the models include their detailed microstructure. In order to simulate non-linear behavior, which currently is only feasible at the expense of extremely high computational costs, coarser models can be used if the local morphology has been linked to the apparent mechanical behavior. The aim of this paper is to implement and validate such a constitutive law. This law is able to capture the non-linear structural behavior of bone-like materials through the use of fabric tensors. It also allows for irreversible strains using an elastoplastic material model incorporating hardening. These features are expressed in a constitutive law based on the anisotropic continuum damage theory coupled with isotropic elastoplasticity in a finite strains framework. This material model was implemented into Metafor, a non-linear FE software. The implementation was validated against experimental data of cylindrical samples subjected to compression. Three materials with bone-like microstructure were tested : aluminum foams of variable density (ERG, Oakland, CA), PLA (polylactic acid) foam (CERM, University of Liège) and cancellous bone tissue of a deer antler (Faculty of Veterinary Medicine, University of Liège). [less ▲]

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See detailThe adapted augmented Lagrangian method: a new method for the resolution of the mechanical frictional contact problem
Bussetta, Philippe ULg; Daniel, Marceau; Ponthot, Jean-Philippe ULg

in Computational Mechanics (2012), 49(2), 259-275

The aim of this work is to propose a new numerical method for solving the mechanical frictional contact problem in the general case of multi-bodies in a three dimensional space. This method is called ... [more ▼]

The aim of this work is to propose a new numerical method for solving the mechanical frictional contact problem in the general case of multi-bodies in a three dimensional space. This method is called adapted augmented Lagrangian method (AALM) and can be used in a multi-physical context (like thermo-electro-mechanical fields problems). This paper presents this new method and its advantages over other classical methods such as penalty method (PM), adapted penalty method (APM) and, augmented Lagrangian method (ALM). In addition, the efficiency and the reliability of the AALM are proved with some academic problems and an industrial thermo-electromechanical problem. [less ▲]

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See detailA finite volume based data transfer method for remeshing. Application to metal forming problems
Bussetta, Philippe ULg; Ponthot, Jean-Philippe ULg

in Proceedings of the 18th International Symposium on Plasticity & Its Current Applications (2012, January)

The resolution of many nonlinear solid mechanical problems with the Finite Elements Method requires remeshing when very large deformations occur. The remeshing operation is divided into two parts: the ... [more ▼]

The resolution of many nonlinear solid mechanical problems with the Finite Elements Method requires remeshing when very large deformations occur. The remeshing operation is divided into two parts: the generation of the new mesh and the data transfer from the old to the new mesh. In dynamic plasticity problems, two kinds of fields have to be transferred: the first is defined thanks to the nodal values and the second one is defined at the integration points. These two kinds of fields are transferred thanks to an original computation of the Data Transfer Method based on the Finite Volume Elements. This method is compared to another one using Mortar Elements to solve metal forming problems. [less ▲]

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See detailMixed Lubrication Regime in Cold Strip Rolling
Carretta, Yves ULg; Boman, Romain ULg; Legrand, Nicolas et al

in 2nd Annual ArcelorMittal CFD and Thermomechanics Days 2012 (2012, January)

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See detailALE Simulations of Metal Forming Processes
Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in Akhtar S. Khan; Farhoud Kabirian; Jian Liu (Eds.) Non-linear Response of Conventional & Advanced Materials, and Multi-scale Modeling (2012, January)

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See detailMechanical Buckling of Composite Panels with/without Cutouts
Pascan, Oana; Zhang, Weihong; Ponthot, Jean-Philippe ULg

in International Journal of Plant Engineering and Management (2012), 17(2), 65-76

A simpli ed analytical solution suitable for simple stacking sequences was developed using the Euler buckling theory, the structure's equations of equilibrium and laminate panel mathematical formulation ... [more ▼]

A simpli ed analytical solution suitable for simple stacking sequences was developed using the Euler buckling theory, the structure's equations of equilibrium and laminate panel mathematical formulation. Comparing these results with numerical results reveals the ac- curacy of the method and even more, allows us to validate the numerical analysis. Therefore, two important results are obtained : a simpli ed analytical solution for the buckling problem and vali- dation of the numerical results. Another important and novel nding is related to the in uence of the angle ply orientation and of the cutouts, on the buckling load. Under symmetrical boundary conditions and loading case, rectangular panels with elliptical cutouts, give better results for 90 oriented plies than for 0 oriented ones. With a compression load applied in the X direction, and with material properties 10 times better in X direction than in Y direction, the best results are obtained when the load is aligned with the Y direction associated to the material reference frame. Moreover, panels with cutouts seem to behave better than panels without cutouts under certain ply orientation angles. [less ▲]

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See detailGenerating smooth surface meshes from multi-region medical images
D'Otreppe, Vinciane ULg; Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in International Journal for Numerical Methods in Biomedical Engineering (2012), 28(6-7), 642-660

Thanks to advances in medical imaging technologies and numerical methods, Patient-Specific Modelling is more and more used to improve diagnosis and to estimate the outcome of surgical interventions. It ... [more ▼]

Thanks to advances in medical imaging technologies and numerical methods, Patient-Specific Modelling is more and more used to improve diagnosis and to estimate the outcome of surgical interventions. It requires the extraction of the domain of interest from the medical scans of the patient, as well as the discretisation of this geometry. However, extracting smooth multi-material meshes that conform to the tissue boundaries described in the segmented image is still an active field of research. We propose to solve this issue by combining an implicit surface reconstruction method with a multi-region mesh extraction scheme. The surface reconstruction algorithm is based on multi-level partition of unity implicit surfaces which we extended to the multi-material case. The mesh generation algorithm consists in a novel multidomain version of the marching tetrahedra. It generates multi-region meshes as a set of triangular surface patches consistently joining each other at material junctions. This paper presents this original meshing strategy, starting from boundary points extraction from the segmented data, to heterogeneous implicit surface definition, multi-region surface triangulation and mesh adaptation. Results indicate that the proposed approach produces smooth and high-quality triangular meshes with a reasonable geometric accuracy. Hence, the proposed method is well suited for subsequent volume mesh generation and Finite Element simulations. [less ▲]

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See detailEvaluation of the mechanical properties of plasma-sprayed coating by nanoindentation technology
Guo, Weichao; Rauchs, Gast; Papeleux, Luc ULg et al

in Mechanics & Industry (2012), 13(3), 151-162

In this paper, the mechanical properties of plasma-sprayed coatings are evaluated using the technology of nanoindentation. According to the indentation curve (load versus indenter’s displacement), which ... [more ▼]

In this paper, the mechanical properties of plasma-sprayed coatings are evaluated using the technology of nanoindentation. According to the indentation curve (load versus indenter’s displacement), which is recorded in an indentation experiment, the mechanical behaviour of the plasma-sprayed coating is investigated via inverse analysis using numerical optimization algorithms. The tip rounding of imperfect indenters is investigated in parameter identification. Subsequently, the hardness on the top surface and on the vertical cross section of the plasma-sprayed coating are investigated. The results show that the hardness on the top surface of the coating depends on the indentation depth. Moreover, the results show that the hardness on the cross section of the coating is significantly affected by the substrate if the indentation impression is too close to the coating-substrate interface. [less ▲]

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See detailThree-Dimensional Large Starin Elasto-Viscoplastic Constitutive Model.
Ribero, Melisa; Careglio, Claudio; Garcia Garino, Carlos et al

in Cardona, A (Ed.) Proceedings of MECOM 2012, Mecanica Computational Vol XXXI (2012)

In a previous work, J. Ponthot et al., Mec Comput, XXIV:441-454 (2005), have extended a large strain elastoplastic constitutive model based on hyperelasticity and multiplicative decomposition of ... [more ▼]

In a previous work, J. Ponthot et al., Mec Comput, XXIV:441-454 (2005), have extended a large strain elastoplastic constitutive model based on hyperelasticity and multiplicative decomposition of deformation gradient tensor, to viscous case based on a contribution of the same main author . In this way a very useful tool has been obtained, able to deal with both rate dependent and rate independent problems. In this work a brief review of theoretical details is presented and numerical implementation of the model in a three-dimensional finite element code (SOGDE3D) is performed. The finite element code was developed for solving elastoplasticity in solids under large strains in three-dimensional space. A Newton Raphson scheme has been used to solve the non-linear consistency condition in order to compute the viscoplastic multiplier. An analysis of large viscoplastic deformation problems under plane strain condition are provided in order to test the proposed model. A comparison between two and three-dimensional versions of SOGDE code is achieved to validate the implementation and some results available in the literature helped to confirm the correct recovery of elastoplastic response by the viscoplastic model. [less ▲]

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See detailDevelopment of a thorax CT-scan based finite element model for thoracic injury assessment
Nsiampa, Nestor; D'Otreppe, Vinciane ULg; Robbe, Cyril ULg et al

Conference (2011, November 14)

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See detailImage-based Finite Element Mesh Generation for Microstructures
D'Otreppe, Vinciane ULg; Mengoni, Marlène ULg; Boman, Romain ULg et al

Conference (2011, November 14)

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See detailComparison of Data Transfer Methods between Meshes in the Frame of the Arbitrary Lagrangian Eulerien Formalism
Bussetta, Philippe ULg; Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in Proceedings of "Fifth International Conference on Advanced COmputationalMethods in ENgineering" (2011, November)

In nonlinear solid Mechanics, the Arbitrary Lagrangian Eulerian (ALE) formalism is a common way to avoid mesh distortion when very large deformations occur in the modelled process. Usually, the ALE ... [more ▼]

In nonlinear solid Mechanics, the Arbitrary Lagrangian Eulerian (ALE) formalism is a common way to avoid mesh distortion when very large deformations occur in the modelled process. Usually, the ALE resolution procedure is based on an “operator split”, the second part of which is a Data Transfer between two meshes sharing the same topology (same number of nodes and same number of element neighbours for each of them). Thanks to this interesting property, classical ALE transfer algorithms can bemuchmore optimised in terms of CPU time than the ones that are used in the frame of a complete remeshing. However, the resulting CPU-efficient transfer schemes suffer from two main drawbacks. The first one is a spurious crosswind diffusion coming from the corner fluxes that have been neglected. The second issue is the number of explicit transfer steps which may become very large when the element size decreases. In this paper, these classical ALE Data Transfer methods are compared to more general algorithms which do not make any assumption on the topology of both meshes. [less ▲]

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