References of "Ponthot, Jean-Philippe"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailEnhanced ALE Data Transfer Strategy for Explicit and Implicit Thermomechanical Simulations of High-Speed Processes
Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in International Journal of Impact Engineering (2013), 53

The Arbitrary Lagrangian Eulerian (ALE) formalism, which allows the computational grid to move regardless of thematerial deformation, is a convenient way to avoid distortedmeshes in finite element ... [more ▼]

The Arbitrary Lagrangian Eulerian (ALE) formalism, which allows the computational grid to move regardless of thematerial deformation, is a convenient way to avoid distortedmeshes in finite element simulations. One crucial step of the ALE algorithm is the data transfer between the Lagrangian and the Eulerian meshes. In this paper, an enhanced transfer method is presented. It can handle complex finite elements which are integrated with more than one Gauss point. This method can thus be used either with an explicit or with an implicit time integration scheme. Choosing the adequate order of accuracy and the most appropriate number of physical fields to be transferred is always a compromise between the speed and the precision of the model. For example, some variables may be sometimes ignored during the transfer in order to decrease the CPU time. Therefore, the most effective way to use such an algorithm is demonstrated in this work by revisiting a classical ALE benchmark, the Taylor impact. An implicit thermomechanical ALE simulation of a high-speed tensile test is also presented and is compared to experimental results from the literature. [less ▲]

Detailed reference viewed: 49 (19 ULg)
Full Text
Peer Reviewed
See detailThe Impact of Surface Higher Order Differentiability in Two-dimensional Contact Elements
Nguyen, Duc Tue ULg; RAUCHS, Gast; Ponthot, Jean-Philippe ULg

in Journal of Computational & Applied Mathematics (2013), 246

The aim of this work is to propose new contact elements of higher order of differentiability for analysing two-dimensional frictionless contact problems. Several methods were proposed in the literature to ... [more ▼]

The aim of this work is to propose new contact elements of higher order of differentiability for analysing two-dimensional frictionless contact problems. Several methods were proposed in the literature to solve the problem caused by the lack of continuity resulting from the discretization. Among them are Bézier interpolation, Hermitian interpolation and splines. One of the difficulties in using Hermitian interpolation is to verify the partition of unity. Therefore, new elements that satisfy the C1 and C2 continuity at the interface are presented in this paper. These new contact elements are based on Hermitian polynomials for ensuring a higher order of continuity. The advantage is that this approach can be easily developed not only for linear elements but also for quadratic elements with higher order of differentiability. The performance of different surface representations is assessed through a comparison with a C0 surface discretization. Some numerical examples are used for assessing the accuracy and the convergence behaviour [less ▲]

Detailed reference viewed: 41 (6 ULg)
Full Text
Peer Reviewed
See detailNumerical simulation of finite strain viscoplastic problems
Garcia-Garino, Carlos; Andia fages, Susana; Mirasso, Anibal et al

in Journal of Computational & Applied Mathematics (2013), 246

A large strain elastoplastic constitutive model based on hyperelasticity and multiplicative decomposition of deformation gradient tensor is extended to viscous case, in a framework similar to the one that ... [more ▼]

A large strain elastoplastic constitutive model based on hyperelasticity and multiplicative decomposition of deformation gradient tensor is extended to viscous case, in a framework similar to the one that has been proposed by Ponthot in an hypoelastic context. In this way a very useful framework can be obtained, able to deal with both rate dependent and rate independent problems. In this work a review of theoretical details and numerical implementation of the model are discussed. Similarly to what is done in rate independent plasticity, a Newton–Raphson scheme has been used to solve the non linear consistency condition in order to compute the viscoplastic multiplier. A plane strain plate with a central circular hole under tension is simulated in order to test the proposed model. Large deformation effects are considered in all the simulations carried out. Different parameters of the constitutive model are varied in order to study the sensitivity of the proposed algorithm. [less ▲]

Detailed reference viewed: 22 (4 ULg)
Full Text
Peer Reviewed
See detailSubject-specific finite element modelling of canine long bones up to fracture
Laurent, Cédric; Bohme, Béatrice; d'Otreppe de Bouvette, Vinciane et al

in Computer Methods in Biomechanics and Biomedical Engineering. Imaging & Visualization (2013), 16

Long bone fracture constitutes a common reason for medical consultation within veterinary orthopaedic services. Owing to the specificities of the veterinary field, post-operative complications after a ... [more ▼]

Long bone fracture constitutes a common reason for medical consultation within veterinary orthopaedic services. Owing to the specificities of the veterinary field, post-operative complications after a fracture osteosynthesis are usually more numerous than those in human medicine, and therefore, there is a need to better understand which orthopaedic device(s) should be preferred for a given fracture. The interest of subjectspecific finite element (FE) simulations in the understanding of long bone mechanics has been largely emphasised (Helgason et al. 2008; Schileo et al. 2008). However, available studies are often limited by the many assumptions made throughout the procedure of creating a validated subject-specific FE model of a long bone, including geometry acquisition and modelling, assignment of realistic material properties and accurate validation of FE results based on ex vivo experiments. Particularly, fracture prediction has often been limited to the fracture onset prediction based on arbitrary criteria. Based on these previous studies, the objective of the present contribution is to propose and compare different subject-specific FE models of long bones that could accurately predict long bone response and failure. [less ▲]

Detailed reference viewed: 67 (6 ULg)
Full Text
Peer Reviewed
See detailAn efficient 3D implicit approach for the thermomechanical simulation of elastic–viscoplastic materials submitted to high strain rate and damage
Jeunechamps, Pierre-Paul; Ponthot, Jean-Philippe ULg

in International Journal for Numerical Methods in Engineering (2013), 94

This paper aims at presenting a general consistent numerical formulation able to take into account, in a coupled way, strain rate, thermal and damage effects on the behavior of materials submitted to ... [more ▼]

This paper aims at presenting a general consistent numerical formulation able to take into account, in a coupled way, strain rate, thermal and damage effects on the behavior of materials submitted to quasistatic or dynamic loading conditions in a large deformation context. The main features of this algorithmic treatment are as follows: -A unified treatment for the analysis and implicit time integration of thermo-elasto-viscoplastic constitutive equations including damage that depends on the strain rate for dynamic loading conditions. This formalism enables us to use dynamic thermomechanically coupled damage laws in an implicit framework. -An implicit framework developed for time integration of the equations of motion. An efficient staggered solution procedure has been elaborated and implemented so that the inertia and heat conduction effects can be properly treated. - An operator split-based implementation, accompanied by a unified method to analytically evaluate the consistent tangent operator for the (implicit) coupled damage–thermo-elasto-viscoplastic problem. -The possibility to couple any hardening law, including rate-dependent models, with any damage model that fits into the present framework. All the developments have been considered in the framework of an implicit finite element code adapted to large strain problems. The numerical model will be illustrated by several applications issued from the impact andmetal-forming domains. All these physical phenomena have been included into an oriented object finite element code (implemented at LTAS-MN2L, University of Liège, Belgium) named Metafor. [less ▲]

Detailed reference viewed: 44 (3 ULg)
Full Text
Peer Reviewed
See detailModeling thixoforming process using the eXtended Finite Element Method and the Arbitrary Lagrangian Eulerian formulation
Biotteau, Ewen; Bussetta, Philippe ULg; Ponthot, Jean-Philippe ULg

in Key Engineering Materials [=KEM] (2013), 554-557

In this contribution, one proposes a new strategy to model forming processes involving non-linear phenomena. The contact between the tool and the structure is enforced using a penalty approach. To free ... [more ▼]

In this contribution, one proposes a new strategy to model forming processes involving non-linear phenomena. The contact between the tool and the structure is enforced using a penalty approach. To free the user from the strict conforming between the structure and the mesh boundaries, one uses the level set and the extended finite element method for material/void interfaces. However, even if the finite element mesh does not need to conform with the boundaries, it still deforms with the structure. Then, an Arbitrary Lagrangian Eulerian formulation is introduced to relocate the mesh in its initial configuration and avoid distortions. From a user point of view, the whole calculation is then performed on a fixed Eulerian mesh. [less ▲]

Detailed reference viewed: 18 (1 ULg)
Full Text
See detailA continuous fluid/solid transition model for semi-solid material modeling. Application to thixoforging.
Ponthot, Jean-Philippe ULg; Koeune, Roxane; Boman, Romain ULg

in 33° SENAFOR (CD) (2013)

This paper deals with the simulation of two extrusion tests by thixoforming: a non stationary extrusion test and a double-cup extrusion test. The simulations are based on a thermo-mechanical one-phase ... [more ▼]

This paper deals with the simulation of two extrusion tests by thixoforming: a non stationary extrusion test and a double-cup extrusion test. The simulations are based on a thermo-mechanical one-phase constitutive law that has been presented in details in several previous papers. A campaign of experimental extrusion testing has been conducted on a steel alloy and the comparison between the numerical and experimental results will validate the model under study. A new feature that has been added to the model is also discussed: the introduction of the phase change thermal effects such as the fusion latent heat and the contraction of the material [less ▲]

Detailed reference viewed: 41 (8 ULg)
Full Text
Peer Reviewed
See detailA Thermomechanical Model Dedicated to Thixoforming. Application to Semi-Solid Forming
Koeune, Roxane; Ponthot, Jean-Philippe ULg

in Solid State Phenomena (2013), 192-193

This paper deals with the simulation of two extrusion tests by thixoforming: a non stationary extrusion test and a double-cup extrusion test. The simulations are based on a thermo-mechanical one-phase ... [more ▼]

This paper deals with the simulation of two extrusion tests by thixoforming: a non stationary extrusion test and a double-cup extrusion test. The simulations are based on a thermo-mechanical one-phase constitutive law that has been presented in details in previous papers. A campaign of experimental extrusion testing has been conducted on a steel alloy and the comparison between the numerical and experimental results will validate the model under study. A new feature that has been added to the model is also discussed: the introduction of the phase change thermal effects such as the fusion latent heat and the contraction of the material [less ▲]

Detailed reference viewed: 34 (7 ULg)
Full Text
Peer Reviewed
See detailImplicit 2D Numerical Simulation of Materials Submitetd to High Strain Rates including Fracture
Jeunechamps, Pierre-Paul; Ponthot, Jean-Philippe ULg

in Key Engineering Materials [=KEM] (2013), 535-536

In this paper, we present a general consistent numerical formulation able to take into account strain rate and thermal effects of the material behavior. A thermomechanical implicit approach for element ... [more ▼]

In this paper, we present a general consistent numerical formulation able to take into account strain rate and thermal effects of the material behavior. A thermomechanical implicit approach for element erosion to model material failure is also presented. The numerical model will be illustrated by applications both from the metal forming and the impact domain. All these physical phenomena have been included in an implicit dynamic oriented object finite element code (implemented at LTAS-MN²L, University of Liège, Belgium) named Metafor [less ▲]

Detailed reference viewed: 42 (7 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 80 (16 ULg)
Full Text
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 ▲]

Detailed reference viewed: 36 (14 ULg)
Full Text
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 ▲]

Detailed reference viewed: 65 (8 ULg)
Full Text
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 ▲]

Detailed reference viewed: 101 (14 ULg)
Full Text
Peer Reviewed
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

Detailed reference viewed: 67 (8 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 163 (28 ULg)
Full Text
Peer Reviewed
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)

Detailed reference viewed: 66 (4 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 202 (79 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 75 (34 ULg)
Full Text
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 ▲]

Detailed reference viewed: 97 (22 ULg)