References of "Ponthot, Jean-Philippe"
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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 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 detailNumerical prediction of resulting rollover shapes and sheared edges after blanking process
Canales Cardenas, Cristian ULg; Boman, Romain ULg; Bussetta, Philippe et al

Conference (2015, April)

Over the years, the simulation of manufacturing processes has introduced several numerical challenges for researchers in computational mechanics. In particular, the numerical modeling of sheet metal ... [more ▼]

Over the years, the simulation of manufacturing processes has introduced several numerical challenges for researchers in computational mechanics. In particular, the numerical modeling of sheet metal blanking process involves different numerical issues that must be carefully treated: a large and highly localized deformation in the shearing zone prior to fracture, complex contact interactions between the tools and the metallic sheet and finally, the ductile failure phenomenon. Despite that this process is one of the most widely used cutting techniques for mass production, the process parameters are normally set by empirical evidence due to the physical complexity resulting from the extreme amount of shearing involved. In addition, the strain-rate dependent behavior of the material must be taken into account due to high punch velocities encountered in practice. Thus, an accurate numerical tool is extremely desirable to optimize the setting parameters of this technique and will lead to a better understanding of the process. [less ▲]

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See detailA comparative study of finite strain formulations in the buckling of cruciform columns
Careglio, Claudio; Canales Cardenas, Cristian ULg; Garcia Garino, Carlos et al

Conference (2015, April)

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See detailOn some drawbacks and possible improvements of a lagrangian finite element approach for simulating incompressible flows
Cerquaglia, Marco Lucio ULg; Deliège, Geoffrey ULg; Boman, Romain ULg et al

Conference (2015)

In this paper a Lagrangian finite element approach for the simulation of incompressible flows is presented, based on the so-called Particle Finite Element Method (PFEM). The spatial discretization and the ... [more ▼]

In this paper a Lagrangian finite element approach for the simulation of incompressible flows is presented, based on the so-called Particle Finite Element Method (PFEM). The spatial discretization and the definition of the boundary terms are discussed in detail with a specific focus on free-surface flows. Additionally, some problems that can arise from the use of such a method are pointed out. Some numerical examples are given and discussed in the last section of the paper. [less ▲]

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See detailMaterial Flow Visualization Friction Stir Welding via Particle Tracing
Dialami, Narges; Chiumenti, Michele; Cervera, Miguel et al

in International Journal of Material Forming (2015), 8

This work deals with the modeling of the material flow in Friction Stir Welding (FSW) processes using particle tracing method. For the computation of particle trajectories, three accurate and ... [more ▼]

This work deals with the modeling of the material flow in Friction Stir Welding (FSW) processes using particle tracing method. For the computation of particle trajectories, three accurate and computationally efficient integration methods are implemented within a FE model for FSW process: the Backward Euler with Sub-stepping (BES), the 4-th order Runge-Kutta (RK4) and the Back and Forth Error Compensation and Correction (BFECC) methods. Firstly, their performance is compared by solving the Zalesak’s disk benchmark. Later, the developed methodology is applied to some FSW problems providing a quantitative 2D and 3D view of the material transport in the process area. The material flow pattern is compared to the experimental evidence. [less ▲]

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See detailComplementary approaches for the numerical simulation of the Micro- Plasto-Hydrodynamic Lubrication regime
Hubert, Cédric; Dubois, André; Dubar, Laurent et al

in Key Engineering Materials [=KEM] (2015), 651-653

This paper presents recent investigations in the field of lubricant escapes from asperities. This phenomenon, named Micro Plasto Hydrodynamic Lubrication (MPHL), induces friction variation during metal ... [more ▼]

This paper presents recent investigations in the field of lubricant escapes from asperities. This phenomenon, named Micro Plasto Hydrodynamic Lubrication (MPHL), induces friction variation during metal forming processes. A better understanding of MPH lubrication would lead to a better management of friction, which is a central element in most sheet metal forming processes. To fulfil that goal, experiments were conducted in plane strip drawing using a transparent upper tool in order to observe lubricant flow around macroscopic pyramidal cavities. These experiments were then numerically reproduced with two complementary Finite Element models. The numerical results are discussed in this paper and show good agreement with experimental measurements. [less ▲]

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See detailEfficient 3D transfer operators based on numerical integration
Bussetta, Philippe ULg; Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in International Journal for Numerical Methods in Engineering (2015), 102(3-4), 892-929

This paper deals with data transfer between two meshes as it happens in a finite element context when a remeshing has to be performed. We propose a finite-volume-based data transfer method for an ... [more ▼]

This paper deals with data transfer between two meshes as it happens in a finite element context when a remeshing has to be performed. We propose a finite-volume-based data transfer method for an efficient remeshing of three-dimensional solid mechanics problems. The originality of this transfer method stems from a linear reconstruction of the fields to be transferred on an auxiliary finite volume mesh, a fast computation of the transfer operator and the application to the complete remeshing of 3D problems. This procedure is applicable to both nodal values and discrete fields defined at quadrature points. In addition, a data transfer method using mortar elements is presented. The main improvement made to this second method comes from a fast computation of mortar elements. These two data transfer methods are compared with the simplest transfer method, which consists of a classical interpolation. After some academic examples, we present 2D forging and 3D friction stir welding applications. [less ▲]

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See detailA generic anisotropic continuum damage model integration scheme adaptable to both ductile damage and biological damage-like situations
Mengoni, Marlène ULg; Ponthot, Jean-Philippe ULg

in International Journal of Plasticity (2015), 66

This paper aims at presenting a general versatile time integration scheme applicable to anisotropic damage coupled to elastoplasticity, considering any damage rate and isotropic hardening formulations ... [more ▼]

This paper aims at presenting a general versatile time integration scheme applicable to anisotropic damage coupled to elastoplasticity, considering any damage rate and isotropic hardening formulations. For this purpose a staggered time integration scheme in a finite strain framework is presented, together with an analytical consistent tangent operator. The only restrictive hypothesis is to work with an undamaged isotropic material, assumed here to follow a J2 plasticity model. The only anisotropy considered is thus a damage-induced anisotropy. The possibility to couple any damage rate law with the present algorithm is illustrated with a classical ductile damage model for aluminium, and a biological damage-like application. The later proposes an original bone remodelling law coupled to trabecular bone plasticity for the simulation of orthodontic tooth movements. All the developments have been considered in the framework of the implicit non-linear finite element code Metafor (developed at the LTAS/MN2L, University of Liège, Belgium - www.metafor.ltas.ulg.ac.be). [less ▲]

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See detailMicro-plasto-hydrodynamic lubrication: a fundamental mechanism in cold rolling
Laugier, Maxime; Boman, Romain ULg; Legrand, Nicolas et al

in Advanced Materials Research (2014), 966-967

Micro Plasto-Hydrodynamic (MPH) lubrication is a general mechanism in metal forming that consists in a re-lubrication of tool-piece solid contacts by an outflow of lubricant from pressurized “pockets” ... [more ▼]

Micro Plasto-Hydrodynamic (MPH) lubrication is a general mechanism in metal forming that consists in a re-lubrication of tool-piece solid contacts by an outflow of lubricant from pressurized “pockets” promoted by the plastic deformation. MPH lubrication is one of the main sources of friction variation (e.g. uncontrolled friction) in metal forming processes like strip drawing or cold rolling. This paper presents experimental results giving evidence of the MPH lubrication mechanism in cold rolling and a new lubrication model that predicts for strip drawing conditions MPH lubrication initiation and lubricant extension along the solid contacts initially in boundary condition. This MPH model could be implemented in a cold rolling model soon to help in high strength steels developments on cold rolling mills. [less ▲]

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See detailNumerical Simulation of Double Cup Extrusion Test Using the Arbitrary Lagrangian Eulerian Formalism
Boman, Romain ULg; Koeune, Roxane; Ponthot, Jean-Philippe ULg

in Idelsohn, Sergio R. (Ed.) Numerical Simulations of Coupled Problems in Engineering (2014)

In this chapter Double Cup Extrusion Test (DCET) is modelled using the finite element method with the help of the Arbitrary Lagrangian Eulerian (ALE) formalism. DCET is a tribological test involving very ... [more ▼]

In this chapter Double Cup Extrusion Test (DCET) is modelled using the finite element method with the help of the Arbitrary Lagrangian Eulerian (ALE) formalism. DCET is a tribological test involving very large deformations which are traditionally dealt with complicated and costly remeshing algorithms. Since the topology of ALE meshes should remain constant throughout the simulation, twovery thin layers of auxiliary elements are added to the initial mesh of the billet where the material is expected to flow. This numerical trick is combined with an original and efficient node relocation procedure which allows the model to take into account complex geometries of punches. The presented model is firstly validated for limited punch strokes thanks to a purely Lagrangian simulation. It is then compared with results from the literature. Eventually the general nature and the effectiveness of this numerical strategy is demonstrated by a fully-coupled thermomechanical simulation of thixoforming where the final shape of the billet is compared to experimental measurements. [less ▲]

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See detailOn the numerical simulation of sheet metal blanking process
Canales Cardenas, Cristian ULg; Bussetta, Philippe ULg; Habraken, Anne ULg et al

Conference (2014)

One of the most widely used cutting techniques in sheet metal forming processes for mass production is the blanking process. In this process, a metallic sheet is placed between a die and a blankholder ... [more ▼]

One of the most widely used cutting techniques in sheet metal forming processes for mass production is the blanking process. In this process, a metallic sheet is placed between a die and a blankholder, and is then cut by the action of a punch which moves downward. The quality of the final product is directly linked to the resulting shape of the cut edge. Due to the complexity of the separation step, the set-up of the blanking process in practice is often driven by empirical knowledge. Thus, an accurate numerical tool is extremely desirable to optimize the setting parameters of this technique and will lead to a better understanding of the entire process. The numerical approach must be able to deal with three main issues involved in blanking: large and localized deformation, friction and contact, and ductile fracture. Furthermore, due to requirements of mass production the punch velocity is normally high and the effects of the strain rate must also be considered. Several approaches have been developed in order to model this cutting process but its accuracy still presents some numerical challenges. [less ▲]

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See detailEffect of viscosity on the robustness of the element deletion method for crack propagation modelling
Canales Cardenas, Cristian ULg; Ponthot, Jean-Philippe ULg

Conference (2014)

The numerical simulation of crack propagation in solids is of main importance in fracture mechanics and has been extensively studied over the years. Several approaches have been developed in order to ... [more ▼]

The numerical simulation of crack propagation in solids is of main importance in fracture mechanics and has been extensively studied over the years. Several approaches have been developed in order to describe the evolving geometry of a crack [1{6], but despite the research e orts some challenges are still present. A commonly used technique in Finite Element codes is the element deletion method due to the simplicity of its numerical implementation and possible extension to 3D. Furthermore, it is possible to couple this method with any failure criterion or damage model without additional considerations. This advantages are extremely desirable for numerical approaches involving high computational costs, e.g. the multi-scale computational homogenization [7, 8], where the element deletion method can be used at the micro-scale to simulate the nucleation, growth and coalescence of micro-voids [9]. [less ▲]

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See detailAn implementation of the generalized Maxwell viscoelastic constitutive model
Careglio, Claudio; Canales Cardenas, Cristian ULg; Papeleux, Luc ULg et al

in Bertolino, Graciela; Cantero, Mariano; Storti, Mario (Eds.) et al Mecánica Computacional Vol XXXIII (2014)

Viscoelastic problems deserve great interest in Computational Mechanics literature. In the last years different approaches have been proposed in order to model viscoelastic problems, as in the case of the ... [more ▼]

Viscoelastic problems deserve great interest in Computational Mechanics literature. In the last years different approaches have been proposed in order to model viscoelastic problems, as in the case of the generalized Maxwell model and its numerical implementation. In particular Kaliske and Rothert (M. Kaliske and H. Rothert, Comput. Mech., 19(3): 228-239 (1997)) discussed basic reological models and the formulation of a generalized Maxwell model and the corresponding implementation of three dimensional viscoelastic model both for small and large strain cases. The numerical implementation addressed by Kaliske and Rothert is quite simple for small strain case and can be extended to a large strain format amenable to be included in finite element codes SOGDE and Metafor. The implementation of the discussed model in a 1D constitutive model, written in Matlab, is addressed. The well known relaxation and creep tests are simulated and compared with analytical results. Furthermore, the influence of constitutive parameters on the viscoelastic response is discussed. In addition, the model is implemented in Finite Element codes and the obtained results are compared with the 1D ones. [less ▲]

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See detailAn overview of nonintrusive characterization, propagation, and sensitivity analysis of uncertainties in computational mechanics
Arnst, Maarten ULg; Ponthot, Jean-Philippe ULg

in International Journal for Uncertainty Quantification (2014), 4

In this paper, we offer a short overview of a number of methods that have been reported in the computational-mechanics literature for quantifying uncertainties in engineering applications. Within a ... [more ▼]

In this paper, we offer a short overview of a number of methods that have been reported in the computational-mechanics literature for quantifying uncertainties in engineering applications. Within a probabilistic framework, we describe the characterization of uncertainties using mathematical statistics methods, the propagation of uncertainties through computational models using either Monte Carlo sampling or stochastic expansion methods, and the sensitivity analysis of uncertainties using variance- and differentiation-based methods. We restrict our attention to nonintrusive methods that can be implemented as wrappers around existing computer programs, thus requiring no modification of the source code. We include some recent advances in the propagation and sensitivity analysis of uncertainties that are characterized by arbitrary probability distributions that may exhibit statistical dependence. Finally, we demonstrate the methods integrated in the proposed overview through a nonlinear engineering application relevant to metal forming. [less ▲]

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See detailThe influence of equivalent contact area computation in extended node to surface contact elements
Wautelet, Gaëtan ULg; Ponthot, Jean-Philippe ULg

in Key Engineering Materials [=KEM] (2014), 618

This article aims at extending the node to surface formulation for contact problems with an area regularization as proposed by [1]. For that purpose, two methods are proposed to compute the equivalent ... [more ▼]

This article aims at extending the node to surface formulation for contact problems with an area regularization as proposed by [1]. For that purpose, two methods are proposed to compute the equivalent contact area attributed to each slave node. The first method, which is based on a geometrical approach through force equivalence, is an original extension of the one proposed in [1] for two-dimensional contact problems, i.e. plane stress and plane strain state, to the axisymmetric modelling context. The second method relies on an energy consistent way obtained through the virtual work principle and the same expression for the equivalent contact area as the one originally cited in [2] is then recovered. First, the node to surface strategy with area regularization is introduced and the aforementioned methods for the equivalent contact area are presented in detail and compared. Afterwards a consistent linearization technique is applied to achieve a quadratic convergence rate in the Newton Raphson iterative procedure used to solve the non-linear equilibrium equations of the underlying finite element model. Finally, two axisymmetric numerical examples are provided in order to compare the aforementioned equivalent contact area evaluations and to demonstrate the performance and the robustness of the consistent approach especially in the neighbourhood the revolution axis. [less ▲]

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See detailComparison of a Fluid and a Solid Approach for the Numerical Simulation of Friction Stir Welding with a Non‐Cylindrical Pin
Bussetta, Philippe ULg; Dialami, Narges; Boman, Romain ULg et al

in Steel Research International (2014), 85(6), 968-979

Friction stir welding (FSW) process is a solid‐state joining process during which materials to be joined are not melted. As a consequence, the heat‐affected zone is smaller and the quality of the weld is ... [more ▼]

Friction stir welding (FSW) process is a solid‐state joining process during which materials to be joined are not melted. As a consequence, the heat‐affected zone is smaller and the quality of the weld is better with respect to more classical welding processes. Because of extremely high strains in the neighborhood of the tool, classical numerical simulation techniques have to be extended in order to track the correct material deformations. The Arbitrary Lagrangian–Eulerian (ALE) formulation is used to preserve a good mesh quality throughout the computation. With this formulation, the mesh displacement is independent from the material displacement. Moreover, some advanced numerical techniques such as remeshing or a special computation of transition interface is needed to take into account non‐cylindrical tools. During the FSW process, the behavior of the material in the neighborhood of the tool is at the interface between solid mechanics and fluid mechanics. Consequently, a numerical model of the FSW process based on a solid formulation is compared to another one based on a fluid formulation. It is shown that these two formulations essentially deliver the same results in terms of pressures and temperatures. [less ▲]

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See detailEffect of the kinematic hardening in the simulations of the straightening of long rolled profiles
Bouffioux, Chantal ULg; Boman, Romain ULg; Caillet, Nicolas et al

in Key Engineering Materials [=KEM] (2014), 611-612

Residual stresses and lack of straightness appear during the cooling of sheet piles where the initial temperature field is not homogeneous. To meet the standards, the long hot rolled pieces are ... [more ▼]

Residual stresses and lack of straightness appear during the cooling of sheet piles where the initial temperature field is not homogeneous. To meet the standards, the long hot rolled pieces are straightened using a series of rollers placed alternately above and below the pieces with shifts which create a succession of bendings. The process is modeled to study the impact of the industrial parameters ( the duration of the cooling and the rollers positions), to improve the final geometry and to reduce the residual stresses.Tests are carried out on this structural steel to observe the material behavior, then material laws are chosen and parameters of these laws are defined using and inverse method. Two sets of material data are obtained: for the first one, the hardening is supposed to be isotropic, and for the second one, additional tests are performed to describe isotropic and kinematic hardenings.The cooling followed by the straightening is then simulated by the finite element with these two sets of date. The comparison of the rollers forces, the deformation and the residual stresses show the impact of the kinematic hardening on such a process where the material undergoes a sucession of the tensions and compressions. The real forces applied by the rollers,the real curvature of the interlocks at the end of the straightening process and the distribution of the residual longitudinal stresses measured on the web using the ring core method are used to validate the numerical model. [less ▲]

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See detailA one phase thermomechanical model for the numerical simulation of semi-solid material behavior. Application to thixoforming
Koeune, Roxane; Ponthot, Jean-Philippe ULg

in International Journal of Plasticity (2014), 58

This work deals with the development of an appropriate constitutive model for semi-solid thixoforming processes of metallic alloys. These processes rely on a very specific material behavior called ... [more ▼]

This work deals with the development of an appropriate constitutive model for semi-solid thixoforming processes of metallic alloys. These processes rely on a very specific material behavior called thixotropy that can be displayed by some metallic alloys heated up to their semi-solid state. It is a particular evolutionary behavior which is characterized by a solidlike behavior at rest and a liquid flow during shearing, thus by a decrease of the viscosity and of the resistance to deformation while sheared. An original one-phase thermo-elasto-viscoplastic constitutive model has been developed. The basic idea is to extend the classical isotropic hardening and viscosity models beyond the solid state by considering two more non-dimensional internal scalar parameters. The semi-solid state is treated as a particular case, and one of the main features of the proposed constitutive model is that it remains valid over a wide range of temperatures, starting from room temperature to above the liquidus in a continuous manner, thus allowing a continuous transition between classical solid and fluid behavior. Another feature is that, after the forming step, it is possible to simulate the cooling down of the component back to room temperature using the elastic–viscoplastic model. So it is possible to estimate residual stresses, something that is definitely impossible while using a fluid-like model or a rigid viscoplastic approach. The presented model is illustrated and validated by means of representative numerical applications, as two different extrusion tests are carried out and the computed predictions are compared to experimental results. [less ▲]

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See detailA LARGE STRAIN ELASTO-VISCOPLASTIC NUMERICAL MODEL
Careglio, Claudio; Canales Cardenas, Cristian ULg; Ribero, Melisa et al

in Bustamante, Roger (Ed.) Proceedings of PACAM XIV (2014)

A large strain elasto-viscoplastic Perzyna model was proposed by Ponthot. The resultant numerical model computes the elastic response using an hypoelastic model. A viscoplastic multiplier was proposed ... [more ▼]

A large strain elasto-viscoplastic Perzyna model was proposed by Ponthot. The resultant numerical model computes the elastic response using an hypoelastic model. A viscoplastic multiplier was proposed, then both inviscid (elastoplastic) and elastic limiting cases can be easily recovered. More recently the authors have included this viscoplastic model in a large strain constitutive model based on hyperelasticity and multiplicative decomposition of deformation gradient tensor. In this work a brief summary of both, hypoelastic and hyperelastic based large strain models of viscoplasticity is provided. Large strain examples are simulated in order to test the discussed models. Different parameters of the constitutive model are tested in order to study the sensitivity of the resultant algorithm. From the obtained results can be said that both models show a very good agree and represent very well the characteristic of the viscoplastic constitutive model. [less ▲]

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