References of "Ponthot, Jean-Philippe"
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See detailDEM modeling of ball mills with experimental validation: influence of contact parameters on charge motion and power draw
Boemer, Dominik ULg; Ponthot, Jean-Philippe ULg

in Computational Particle Mechanics (2016)

Discrete element method simulations of a 1:5-scale laboratory ball mill are presented in this paper to study the influence of the contact parameters on the charge motion and the power draw. The position ... [more ▼]

Discrete element method simulations of a 1:5-scale laboratory ball mill are presented in this paper to study the influence of the contact parameters on the charge motion and the power draw. The position density limit is introduced as an efficient mathematical tool to describe and to compare the macroscopic charge motion in different scenarios, i.a. with different values of the contact parameters. While the charge motion and the power draw are relatively insensitive to the stiffness and the damping coefficient of the linear spring-slider-damper contact law, the coefficient of friction has a strong influence since it controls the sliding propensity of the charge. Based on the experimental calibration and validation by charge motion photographs and power draw measurements, the descriptive and predictive capabilities of the position density limit and the discrete element method are demonstrated, i.e. the real position of the charge is precisely delimited by the respective position density limit and the power draw can be predicted with an accuracy of about 5 %. [less ▲]

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See detailTwo novel ways to impose free-slip boundary conditions in fluid-structure interaction problems using the Particle Finite Element Method
Cerquaglia, Marco Lucio ULg; Deliège, Geoffrey ULg; Boman, Romain ULg et al

Conference (2016, June 09)

As well known, the imposition of boundary conditions is, in many cases, the trickiest part in solving differential problems, both from a physical and numerical standpoint. This work focuses on the way ... [more ▼]

As well known, the imposition of boundary conditions is, in many cases, the trickiest part in solving differential problems, both from a physical and numerical standpoint. This work focuses on the way boundary conditions are accounted for in the solution of fluid-structure interaction problems using the Particle Finite Element Method (PFEM). In particular, the PFEM traditionally employs no-slip conditions on the fluid-solid interfaces. Our aim is twofold. On the one hand, we demonstrate that, in the framework of the PFEM, the no-slip hypothesis is too strong in some cases, leading to erroneous physical results, and that a free-slip condition is to be preferred instead; we therefore propose two novel ways to impose free-slip conditions, devoting special attention to generality, simplicity and robustness. On the other hand, we show how the use of free-slip boundary conditions can also be beneficial with regards to two major problems arising from the remeshing procedure employed by the PFEM: the violation of the mass conservation principle and the introduction of spurious pressure oscillations. [less ▲]

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See detailLagrangian and arbitrary Lagrangian Eulerian simulations of complex roll-forming processes
Crutzen, Yanick ULg; Boman, Romain ULg; Papeleux, Luc ULg et al

in Comptes Rendus Mécanique (2016), 344(4-5), 251-266

The Arbitrary Lagrangian Eulerian (ALE) formalism is a breakthrough technique in the numerical simulation of the continuous-type roll-forming process. In contrast to the classical Lagrangian approach, the ... [more ▼]

The Arbitrary Lagrangian Eulerian (ALE) formalism is a breakthrough technique in the numerical simulation of the continuous-type roll-forming process. In contrast to the classical Lagrangian approach, the ALE formalism can compute the hopefully stationary state for the entire mill length with definitely effortless set-up tasks thanks to a nearly-stationary mesh. In this paper, advantages of ALE and Lagrangian formalisms are extensively discussed for simulating such continuous-type processes. Through a highly complex industrial application, the ease of use of ALE modelling is illustrated with the in-house code METAFOR. ALE and Lagrangian results are in good agreement with each other. [less ▲]

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See detailMesh Management Methods in Finite Element Simulations of Orthodontic Tooth Movement
Mengoni, Marlène ULg; Ponthot, Jean-Philippe ULg; Boman, Romain ULg

in Medical Engineering & Physics (2016), 38(2), 140-147

In finite element simulations of orthodontic tooth movement, one of the challenges is to represent long term tooth movement. Large deformation of the periodontal ligament and large tooth displacment due ... [more ▼]

In finite element simulations of orthodontic tooth movement, one of the challenges is to represent long term tooth movement. Large deformation of the periodontal ligament and large tooth displacment due to bone remodelling lead to large distortions of the finite element mesh when a Lagrangian formalism is used. We propose in this work to use an Arbitrary Lagrangian Eulerian (ALE) formalism to delay remeshing operations. A large tooth displacement is obtained including effect of remodelling without the need of remeshing steps but keeping a good-quality mesh. Very large deformations in soft tissues such as the periodontal ligament is obtained using a combination of the ALE formalism used continuously and a remeshing algorithm used when needed. This work demonstrates that the ALE formalism is a very efficient way to delay remeshing operations. [less ▲]

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See detailA numerical study of hypoelastic and hyperelastic large strain viscoplastic Perzyna type models
Careglio, Claudio; Canales Cardenas, Cristian ULg; García Garino, Carlos et al

in Acta Mechanica (2016)

For the case ofmetalswith large viscoplastic strains, it is necessary to define appropriate constitutive models in order to obtain reliable results from the simulations. In this paper, two large strain ... [more ▼]

For the case ofmetalswith large viscoplastic strains, it is necessary to define appropriate constitutive models in order to obtain reliable results from the simulations. In this paper, two large strain viscoplastic Perzyna type models are considered. The first constitutive model has been proposed by Ponthot, and the elastic response is based on hypoelasticity. In this case, the kinematics of the constitutive model is based on the additive decomposition of the rate deformation tensor. The second constitutive model has been proposed by García Garino et al., and the elastic response is based on hyperelasticity. In this case, the kinematics of the constitutive model is based on the multiplicative decomposition of the deformation gradient tensor. In both cases, the resultant numerical models have been implemented in updated Lagrangian formulation. In this work, global and local numerical results of the mechanical response of both constitutive models are analyzed and discussed. To this end, numerical experiments are performed and different parameters of the constitutive models are tested in order to study the sensitivity of the resultant algorithms. In particular, the evolution of the reaction forces, the effective plastic strain, the deformed shapes and the sensitivity of the numerical results to the finite element mesh discretization have been compared and analyzed. The obtained results show that both models have a very good agreement and represent very well the characteristic of the viscoplastic constitutive model. [less ▲]

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See detailTwo 3D thermomechanical numerical models of friction stir welding processes with a trigonal pin
Bussetta, Philippe; Feulvarch, Eric; Tongne, Amèvi et al

in Numerical Heat Transfer : Part A. Applications (2016)

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See detailComparison of residual stresses on long rolled profiles measured by X-ray diffraction, ring core and the sectioning methods and simulated by FE method
Bouffioux, Chantal ULg; Pesci, Raphaël; Boman, Romain ULg et al

in Thin-Walled Structures (2016), 104

Sheet piles are produced by hot rolling, a cooling step and, if required, by a straightening operation. Numerical simulations indicate that the stress field is almost homogeneous through the thickness ... [more ▼]

Sheet piles are produced by hot rolling, a cooling step and, if required, by a straightening operation. Numerical simulations indicate that the stress field is almost homogeneous through the thickness, justifying the comparison of X-ray diffraction, ring core and the sectioning methods applied after the cooling step and after the straightening process. The equipment, the steps of the experimental procedures and the results are detailed, showing the limits, the specificities and the advantages of each method. Moreover, the amplitude and the distribution of the stresses along the width of the sections present good agreement with results of numerical simulations. [less ▲]

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See detailA quadratic contact element passing the patch test
Nguyen, Duc-Tué; Rauchs, Gast; Ponthot, Jean-Philippe ULg

in Key Engineering Materials [=KEM] (2016), 681

For the two dimensional contact modeling, the standard node-to-segment quadratic contact elements are known to exhibit oscillations of the contact pressure. This situation is particularly critical when ... [more ▼]

For the two dimensional contact modeling, the standard node-to-segment quadratic contact elements are known to exhibit oscillations of the contact pressure. This situation is particularly critical when using the penalty method with a high penalty parameter because the amplitude of the oscillations increase with increasing penalty parameter. The aim of this article is to present a method for removing the oscillations of contact pressure observed while using quadratic contact element. For this purpose, the nodal forces at the slave and at the master nodes need to be evaluated appropriately. One possibility is to develop a suitable procedure for computing the nodal forces. In that sake, we selected the approach first proposed in [35] in an appropriate manner. After presenting the improved quadratic contact element, some numerical examples are illustrated in this paper to compare the standard quadratic node-to-segment element with the proposed element. The examples show that the proposed element can strongly reduce the oscillating contact pressure for both plane and curved contact surfaces. [less ▲]

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See detailThe Influence of Equivalent Contact Area Computation in 3D Extended Node to Surface Contact Elements
Wautelet, Gaëtan ULg; Papeleux, Luc ULg; Ponthot, Jean-Philippe ULg

in Key Engineering Materials [=KEM] (2016), 681

This paper extends the frictionless penalty-based node to contact formulation with area regularization to a 3D framework. Based on our previous work [1] focused on axisymmetric modeling, two computational ... [more ▼]

This paper extends the frictionless penalty-based node to contact formulation with area regularization to a 3D framework. Based on our previous work [1] focused on axisymmetric modeling, two computational methods are also considered for the determination of the slave node area. The first method, named as the geometrical approach, is based on a force equivalence system, while the second one, named as the consistent approach, is derived from a more sophisticated scheme elaborated upon the virtual work principle. Then, the extended contact elements are derived for the contact formulations with geometrical and consistent area regularization and a consistent linearization is provided accordingly, which guarantees a quadratic rate of convergence of the global Newton Raphson iterative procedure. Finally, two numerical examples assess the performance of both contact formulations with area regularization and demonstrates the robustness and the efficiency of the node to surface contact formulation with consistent area regularization in reproducing a constant contact pressure distribution across the interface between a deformable body and a analytically-defined rigid body, irrespective of the mesh. Our findings will certainly encourage further developments towards the design of a penalty based node to surface contact algorithm passing the contact patch test, as was already done successfully in 2D contact problems [2]. [less ▲]

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See detail3D numerical models using a fluid or a solid formulation of FSW processes with non-cylindrical pin
Bussetta, Philippe; Dialmi, Narges; Chiumenti, Michele et al

in Advanced Modeling and Simulation in Engineering Sciences (2015), 2(27),

Friction Stir Welding (FSW) process is a relatively recent welding process (patented in 1991). FSW is a solid-state joining process during which materials to be joined are not melted. During the FSW ... [more ▼]

Friction Stir Welding (FSW) process is a relatively recent welding process (patented in 1991). FSW is a solid-state joining process during which materials to be joined are not melted. During the FSW process, the behavior of the material is at the interface between solid mechanics and fluid mechanics. In this paper, a 3D numerical model of the FSW process with a non-cylindrical tool based on a solid formulation is compared to another one based on a fluid formulation. Both models use advanced numerical techniques such as the Arbitrary Lagrangian Eulerian (ALE) formulation, remeshing or the Orthogonal Sub-Grid Scale method (OSS). It is shown that these two formulations essentially deliver the same results. [less ▲]

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See detailOn the numerical simulation of sheet metal blanking process
Canales Cardenas, Cristian ULg; Bussetta, Philippe; Ponthot, Jean-Philippe ULg

in International Journal of Material Forming (2015)

The use of the blanking process has been widely spread in mass production industries. In this technique, the quality of the final product is directly related to the setting parameters of the process and ... [more ▼]

The use of the blanking process has been widely spread in mass production industries. In this technique, the quality of the final product is directly related to the setting parameters of the process and the material response of the sheet. In the present work, a general framework based on the finite element method for the simulation of the sheet metal blanking process is presented. The proposed approach properly addresses all the numerical challenges related to blanking. First, an extension of elasto-viscoplastic constitutive equations for the large strain regime is used to take into account the material strain-rate sensitivity. Then, the inertial effects coming from high velocity operations are considered by means of an implicit time integration scheme. Moreover, the frictional contact interactions are simulated with the classical Coulomb law and an energetically consistent formulation of area regularization. Finally, ductile fracture is modeled thanks to the element deletion method coupled with a fracture criterion. The blanking process is then simulated for different setting parameters. The accuracy of this approach is evaluated by comparing the numerical predictions to experimental results for both quasi-static and dynamic conditions. Good agreement is found between experimental and numerical results for all cases. [less ▲]

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See detailAn enhanced version of a bone remodelling model based on the continuum damage mechanics theory.
Mengoni, Marlène ULg; Ponthot, Jean-Philippe ULg

in Computer Methods in Biomechanics & Biomedical Engineering (2015), 18(12), 1367-1376

The purpose of this work is to propose an enhancement of Doblaré and García's internal bone remodelling model based on the continuum damage mechanics theory. In their paper, they stated that the evolution ... [more ▼]

The purpose of this work is to propose an enhancement of Doblaré and García's internal bone remodelling model based on the continuum damage mechanics theory. In their paper, they stated that the evolution of the internal variables of the bone microstructure, and its incidence on the modification of the elastic constitutive parameters, may be formulated following the principles of Continuum Damage Mechanics, although no actual damage was considered. The resorption and apposition criteria (similar to the damage criterion) were expressed in terms of a mechanical stimulus. However, the resorption criterion is lacking a dimensional consistency with the remodelling rate. We here propose an enhancement to this resorption criterion, insuring the dimensional consistency while retaining the physical properties of the original remodelling model. We then analyse the change in the resorption criterion hypersurface in the stress space for a 2D analysis. We finally apply the new formulation to analyse the structural evolution of a 2D femur. This analysis gives results consistent with the original model but with a faster and more stable convergence rate. [less ▲]

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See detailLagrangian and Arbitrary Lagrangian Eulerian Simulations of Complex Roll Forming Processes
Crutzen, Yanick ULg; Boman, Romain ULg; Papeleux, Luc ULg et al

Conference (2015, July)

Finite element simulation of the roll forming process is regarded as an essential tool for the early design and optimization stages of a roll forming mill. However, such simulations are generally ... [more ▼]

Finite element simulation of the roll forming process is regarded as an essential tool for the early design and optimization stages of a roll forming mill. However, such simulations are generally incredibly time-consuming, limited to some simple cases and to the pre-cut forming method. In contrast to the classical Lagrangian approach, the Arbitrary Lagrangian Eulerian (ALE) formalism, which consists in decoupling the motion of the material and the mesh, can simulate the continuous process for the entire roll forming line at reasonable CPU cost by using a nearly-stationary mesh. In this work, the numerical results are compared to some experimental data on a U-channel in order to validate both Lagrangian and ALE models using our in-house code METAFOR. Furthermore, advantages of the ALE formalism are highlighted with the simulation of a tubular rocker panel on a 16-stand forming mill, which is a real industrial mill. [less ▲]

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See detailComparison of fracture prediction models on sheet metal blanking simulations
Canales Cardenas, Cristian ULg; Boman, Romain ULg; Bussetta et al

Conference (2015, July)

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See detailSimulations lagrangienne et arbitraire lagrangienne eulérienne du procédé de profilage
Crutzen, Yanick ULg; Boman, Romain ULg; Papeleux, Luc ULg et al

in Actes du 12e Colloque National en Calcul des Structures (2015, May)

L’application du formalisme Arbitraire Lagrangien Eulérien (ALE) à la simulation numérique du procédé de profilage permet de calculer l’état espéré stationnaire du procédé de type continu en modélisant de ... [more ▼]

L’application du formalisme Arbitraire Lagrangien Eulérien (ALE) à la simulation numérique du procédé de profilage permet de calculer l’état espéré stationnaire du procédé de type continu en modélisant de manière efficace l’intégralité de la ligne grâce à un maillage quasi-Eulérien. Ce type de simulation sera comparé à l’approche classique en formalisme Lagrangien dans le cadre d’une application industrielle de profilage. Les performances de la parallélisation de l’algorithme ALE seront analysées dans l’état actuel des développements du code de calcul METAFOR. [less ▲]

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