References of "Ponthot, Jean-Philippe"
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See detailA 3D Arbitrary Lagrangian Eulerian Formulation for the Numerical Simulation of Forming Processes. Application to cold roll forming and metal cutting
Boman, Romain ULg; Papeleux, Luc ULg; BUI, Q. V. et al

in Mota Soares, C. A. (Ed.) Proceedings of ECCM 2006, III European Conference on Computational Mechanics, Solids, Structures and Coupled Problems in Engineering (2006, June)

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See detailA variational formulation of constitutive models and updates in non-linear finite viscoelasticity
Fancello, Eduardo; Ponthot, Jean-Philippe ULg; Stainier, Laurent ULg

in International Journal for Numerical Methods in Engineering (2006), 65(11), 1831-1864

The purpose of this article is to present a general framework for constitutive viscoelastic models in finite strain regime. The approach is qualified as variational since the constitutive updates obey a ... [more ▼]

The purpose of this article is to present a general framework for constitutive viscoelastic models in finite strain regime. The approach is qualified as variational since the constitutive updates obey a minimum principle within each load increment. The set of internal variables is strain-based and employs, according to the specific model chosen, a multiplicative decomposition of strain into elastic and viscous components. The present approach shares the same technical procedures used for analogous models of plasticity or viscoplasticity, such as the Solution of a minimization problem to identify inelastic updates and the use of exponential mapping for time integration. However. instead of using the classical decomposition of inelastic strains into amplitude and direction, we take advantage of a spectral decomposition that provides additional facilities to accommodate, into simple analytical expressions, a wide set of specific models. Moreover, appropriate choices of the constitutive potentials allow the reproduction of other formulations in the literature. The final part of the paper presents a set of numerical examples in order to explore the characteristics of the formulation as well as its applicability to usual large-scale FEM analyses. Copyright (c) 2005 John Wiley [less ▲]

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See detailNumerical modelling and experimental validation of steel deep drawing processes - Part I. Material characterization
Garcia, Claudio; Celentano, Diego; Flores, F. et al

in Journal of Materials Processing Technology (2006), 172(3), 451-460

This work presents an experimental characterization of the mechanical behaviour of the EK4 deep drawing steel. The experimental procedure encompasses spectrometry, rnetalography, tension testing and ... [more ▼]

This work presents an experimental characterization of the mechanical behaviour of the EK4 deep drawing steel. The experimental procedure encompasses spectrometry, rnetalography, tension testing and hardness measurements. Special attention is devoted to the derivation of the elastic and plastic parameters involved in the assumed constitutive model based on the anisotropic Hill-48 yield criterion. The simulation of the deformation process during the whole tensile test is subsequently performed with the aim of assessing the adequateness of the proposed methodology. It should be mentioned that the material parameters obtained with this procedure are the basic data for the modelling and experimental validation of different deep drawing applications presented in Part II of this work. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailNumerical modelling and experimental validation of steel deep drawing processes - Part II. Applications
Garcia, Claudio; Celentano, Diego; Flores, Fernando et al

in Journal of Materials Processing Technology (2006), 172(3), 461-471

This paper presents the modelling and experimental validation of three different deep drawing applications: the Erichsen test, a cylindrical cup test and an industrial sheet metal forming process. The ... [more ▼]

This paper presents the modelling and experimental validation of three different deep drawing applications: the Erichsen test, a cylindrical cup test and an industrial sheet metal forming process. The sheet forrning material considered in the study is the EK4 steel characterized in Part I of this work. A finite element analysis of the deformation process is performed with a large strain hyperelastic shell formulation including the Hill-48 associate plasticity model. The experimental validation of the results provided by the simulation encompasses the punch force evolution together with the in-plane principal deformations and thickness distributions of the final deformed part. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailA viscoelastic formulation for finite strains: application to brain soft tissues
Fancello, Eduardo; Ponthot, Jean-Philippe ULg; Vigneron, Laura et al

in Proceedings of XXVII CILAMCE – Iberian Latin American Congress on Computational Methods in Engineering (2006)

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See detailSimulation of crashworthiness problems with improved contact algorithms for implicit time integration
Noels, Ludovic ULg; Stainier, Laurent ULg; Ponthot, Jean-Philippe ULg

in International Journal of Impact Engineering (2006), 32(5), 799-825

When studying crashworthiness problems, contact simulation can be the source of a number of problems. A first one is the discontinuities in the normal evolution for a boundary discretized by finite ... [more ▼]

When studying crashworthiness problems, contact simulation can be the source of a number of problems. A first one is the discontinuities in the normal evolution for a boundary discretized by finite elements. Another problem is the treatment of the contact forces that can introduce numerical energy in the system. In this paper, we propose to combine a method of discontinuity smoothing with the energy-momentum consistent scheme that recently appeared in the literature. (c) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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See detailAn energy momentum conserving algorithm using the variational formulation of visco-plastic updates
Noels, Ludovic ULg; Stainier, Laurent ULg; Ponthot, Jean-Philippe ULg

in International Journal for Numerical Methods in Engineering (2006), 65(6), 904942

In this paper we use the variational formulation of elasto-plastic updates proposed by Ortiz and Stainier (Comput. Methods Appl. Mech. Eng. 1999; 171:419-444) in the context of consistent time integration ... [more ▼]

In this paper we use the variational formulation of elasto-plastic updates proposed by Ortiz and Stainier (Comput. Methods Appl. Mech. Eng. 1999; 171:419-444) in the context of consistent time integration schemes. We show that such a formulation is well suited to obtain a general expression Of energy momentum conserving algorithms. Moreover, we present numerical examples that illustrate the efficiency of our developments. Copyright (c) 2005 John Wiley [less ▲]

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See detailEnergy conserving balance of explicit time steps to combine implicit and explicit algorithms in structural dynamics
Noels, Ludovic ULg; Stainier, Laurent ULg; Ponthot, Jean-Philippe ULg

in Computer Methods in Applied Mechanics & Engineering (2006), 195(19-22), 21692192

Recent developments have proved the advantage of combining both time implicit and time explicit integration algorithms in structural dynamics. A major problem is to define the initial conditions for the ... [more ▼]

Recent developments have proved the advantage of combining both time implicit and time explicit integration algorithms in structural dynamics. A major problem is to define the initial conditions for the implicit simulation on the basis of a solution obtained from an unbalanced explicit resolution. The unbalanced nature of the explicit algorithm leads to oscillations in the fields of interest. Therefore, the values obtained after an explicit computation cannot be used directly as initial conditions for an implicit simulation. In this paper, we develop such initial values that lead to a stable (no numerical creation of energy) and energy-conserving transition. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailProblem and challenges of image-guided neurosurgical navigation and intervention
Verly, Jacques ULg; Kavec, Martin; Vigneron, Lara M. et al

Conference (2006)

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See detailA cascade optimization methodology for automatic parameter identification and shape/process optimization in metal forming simulation
Ponthot, Jean-Philippe ULg; Kleinermann, Jean-Pascal

in Computer Methods in Applied Mechanics & Engineering (2006), 195(41-43), 5472-5508

Computer simulations of metal forming processes using the finite element method (FEM) are, today, well established. This form of simulation uses an increasing number of sophisticated geometrical and ... [more ▼]

Computer simulations of metal forming processes using the finite element method (FEM) are, today, well established. This form of simulation uses an increasing number of sophisticated geometrical and material models, relying on a certain number of input data, which are not always readily available. The aim of inverse problems, which will be considered here, is to determine one or more of the input data relating to these forming process simulations, thereby leading to a desired result. In this paper, we will focus on two categories of such inverse problems. The first category consists of parameter identification inverse problems. These involve evaluating the material parameters for material constitutive models that would lead to the most accurate results with respect to physical experiments, i.e. minimizing the difference between experimental results and FEM simulations. The second category consists of shape/process optimization inverse problems. These involve determining the initial geometry of the specimen and/or the shape of the forming tools, as well as some parameters of the process itself, in order to provide the desired final geometry after the forming process. These two categories of inverse problems can be formulated as optimization problems in a similar way, i.e. by using identical optimization algorithms. In this paper, we intend firstly to solve these two types of optimization problems by using different non-linear gradient based optimization methods and secondly to compare their efficiency and robustness in a variety of numerical applications. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailNumerical simulation in cold rolling using adiabatic strip model : application to large roll deformation
STEPHANY, A.; Ponthot, Jean-Philippe ULg; LEGRAND, N.

in AUSTRIB 06 (2006)

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See detailSimulation of complex impact problems with implicit time algorithms: Application to a turbo-engine blade loss problem
Noels, Ludovic ULg; Stainier, Laurent ULg; Ponthot, Jean-Philippe ULg

in International Journal of Impact Engineering (2005), 32(1-4), 358386

Recent developments, in non-linear structural dynamics, have led to a new kind of implicit algorithms: the energy-momentum conserving algorithm (EMCA) and the energy-dissipative, momentum-conserving ... [more ▼]

Recent developments, in non-linear structural dynamics, have led to a new kind of implicit algorithms: the energy-momentum conserving algorithm (EMCA) and the energy-dissipative, momentum-conserving algorithm. Contrarily to commonly used algorithms, such as the explicit central difference or the alpha-generalized method, the stability of those algorithms is always ensured in the non-linear range. Thanks to this unconditional stability the only requirement on the time step size is that it must be small enough to capture the physics. This requirement is less restrictive than a conditional stability. In previous works, we have developed a new formulation of the internal forces for a hypoelastic model, that leads to an EMCA. In this paper, we will extend this formulation to an energy-dissipative, momentum-conserving algorithm. We will prove with an academic example, that our algorithm is more accurate than the alpha-generalized method in the non-linear range. Then we will simulate a blade loss problem to demonstrate the efficiency of our developments on complex dynamics simulations. (c) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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See detailThermomechanical modeling of metals at finite strains: First and mixed order finite elements
Adam, Laurent; Ponthot, Jean-Philippe ULg

in International Journal of Solids and Structures (2005), 42(21-22), 5615-5655

The aim of this paper is to describe an updated EAS (Enhanced Assumed Strain) finite element formalism developed to model the thermomechanical behavior of metals submitted to large strains. We will also ... [more ▼]

The aim of this paper is to describe an updated EAS (Enhanced Assumed Strain) finite element formalism developed to model the thermomechanical behavior of metals submitted to large strains. We will also expose the use of mixed order elements (first order mechanical elements strongly coupled with quadratic thermal elements) which, as we will show, is of particular interest for modeling fast processes inducing important temperature gradients. The features of this formalism, used jointly with an Updated Lagrangian approach and an hypoelastic anisothermal constitutive formulation, will be described. Three applications involving finite strains and important thermomechanical couplings will be studied. The results obtained will be compared with the results given by the now classical SRI (Selective Reduced Integration) formalism. (c) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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See detailAn ALE Model for Numerical Simulation of Cold Roll Forming Process
Boman, Romain ULg; Papeleux, Luc ULg; Viet, B. Q. et al

in AIP Conference Proceedings (2005, August 05), 778

In this paper, the Arbitrary Lagrangian Eulerian formalism is used to compute the steady state of a 3D U-shaped cold roll forming process. Compared to the Lagrangian case, this method allows the use of a ... [more ▼]

In this paper, the Arbitrary Lagrangian Eulerian formalism is used to compute the steady state of a 3D U-shaped cold roll forming process. Compared to the Lagrangian case, this method allows the use of a refined mesh near the tools, leading to an accurate representation of the bending of the sheet with a limited computational time. The main problem of this kind of simulation is the rezoning of the nodes on the free surfaces of the sheet. A modified iterative isoparametric smoother is used to manage this geometrically complex and CPU expensive task. [less ▲]

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See detailNumerical Simulation of Cold Roll Forming Process
Bui, Quoc Viet; Papeleux, Luc ULg; Boman, Romain ULg et al

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

Cold roll-forming process of a U profile is modelled and simulated. The simulation is based on a 3D finite element analysis with the help of the home made Metafor code. The prediction on dimensions and ... [more ▼]

Cold roll-forming process of a U profile is modelled and simulated. The simulation is based on a 3D finite element analysis with the help of the home made Metafor code. The prediction on dimensions and deformed shape of the cold roll-formed sheet is in good agreement with the experimental results. Parametric study on roll forming parameters, such as the yield limit and the hardening property of materials, and the distance between stations is performed. [less ▲]

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