References of "Ponthot, Jean-Philippe"
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See detailAn advanced model of lubricated cold rolling with its comprehensive pilot mill validation
Boemer, Dominik; Carretta, Yves; Laugier, Maxime et al

in Journal of Materials Processing Technology (2021), 296

The increasing demand for thinner and harder steel strips requires the introduction of flexible lubrication systems that continuously adapt the lubrication conditions in existing rolling mills to not ... [more ▼]

The increasing demand for thinner and harder steel strips requires the introduction of flexible lubrication systems that continuously adapt the lubrication conditions in existing rolling mills to not saturate the stand capacity by excessive friction. To design these systems, this article introduces one of the most advanced models of lubricated cold rolling since it combines the following features in a single model: elasto-thermo-viscoplasticity of the strip, mixed lubrication by a thermo-piezoviscous lubricant, full-flooded lubrication or starvation, and a complete formulation of non-circular roll flattening. This model is then validated by a new semi-industrial data set, which is one of the most comprehensive ones since it includes: roughness measurements of the rolls and the strips, hardening laws of the strips by plane-strain compression tests, thermo-piezoviscous material laws of the lubricants and a large design space to isolate the influence of individual operating parameters. The results indicate that the changes of the rolling force and the forward slip with the rolling speed and the reduction can be quantitatively predicted except for the decreasing forward slip with the reduction. These predictions require to calibrate the coefficients of boundary friction, thermoplasticity and viscoplasticity for each rolled product as well as the inlet film thickness at each rolling speed, if starvation occurs. Once calibrated, the model therefore allows to predict the influences of various operating conditions, e.g. by how much the rolling force can be reduced if more lubricant becomes available at the entry of the roll bite. [less ▲]

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See detailSimulacion Numerica Del Ensayo De Traccion Simple Para Probetas Delgadas. Analisis Del Caso Limite 3D
Garcia-Garino, Carlos; Careglio, Claudio; Pacini, Elina et al

in XXIII Workshop de Investigadores en Ciencias de la Computación (2021)

El proyecto estudia el procesamiento en entornos de Cloud Computing de la simulación numérica de problemas con grandes deformaciones elastoplásticas. En muchos casos de interés se debe estudiar la ... [more ▼]

El proyecto estudia el procesamiento en entornos de Cloud Computing de la simulación numérica de problemas con grandes deformaciones elastoplásticas. En muchos casos de interés se debe estudiar la sensibilidad de los resultados del problema frente a cambios en los datos de entrada y/o en la discretización del problema de interés. Por ejemplo, la simulación numérica del ensayo de tracción simple en el rango de grandes deformaciones presenta estas características. Desde el punto de vista de Cloud Computing se estudiará la eficiencia de algoritmos de planificación de trabajos como es el caso de Ant Colony Optimization (ACO) y Particle Swarm Optimization (PSO) para llevar a cabo la asignación de trabajos propios del procesamiento paramétrico de este tipo de problemas. [less ▲]

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See detailPhase change driven adaptive mesh refinement in PFEM
Bobach, Billy-Joe ULiege; Falla, Romain ULiege; Boman, Romain ULiege et al

in https://popups.uliege.be/esaform21/index.php?id=3861 (2021)

The particle finite element method (PFEM) is used to simulate a simple phase change problem. This is a first step towards the simulation of additive manufacturing (AM) processes at the meso-scale, where ... [more ▼]

The particle finite element method (PFEM) is used to simulate a simple phase change problem. This is a first step towards the simulation of additive manufacturing (AM) processes at the meso-scale, where the liquid melt pool interacts with the surrounding solid material and undergoes phase change. The focus of this paper lies on strategies to deal with the release or absorption of latent heat in the PFEM, especially with regard to mesh refinement. We briefly describe how mesh refinement in PFEM works and how it can be chosen specifically to achieve convergence despite the highly non-linear latent heat term. It is found that good agreement with the literature can be achieved on a simple 1D phase change test case, while using an automatic local mesh refinement. [less ▲]

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See detailElement activation method and non-conformal dynamic remeshing strategy to model additive manufacturing
Laruelle, Cédric ULiege; Boman, Romain ULiege; Papeleux, Luc ULiege et al

in https://popups.uliege.be/esaform21/index.php?id=2320 (2021)

Modeling of Additive Manufacturing (AM) at the part scale involves non-linear thermo-mechanical simulations. Such a process also imposes a very fine discretization and requires altering the geometry of ... [more ▼]

Modeling of Additive Manufacturing (AM) at the part scale involves non-linear thermo-mechanical simulations. Such a process also imposes a very fine discretization and requires altering the geometry of the models during the simulations to model the addition of matter, which is a computational challenge by itself. The first focus of this work is the addition of an additive manufacturing module in the fully implicit in-house Finite Element code Metafor [1] which is developed at the University of Liège. The implemented method to activate elements and to activate and deactivate boundary conditions during a simulation is adapted from the element deletion algorithm implemented in Metafor in the scope of crack propagation [2]. This algorithm is modified to allow the activation of elements based on a user-specified criterion (e.g. geometrical criterion, thermal criterion, etc.). The second objective of this work is to improve the efficiency of the AM simulations, in particular by using a dynamic remeshing strategy to reduce the computational cost of the simulations. This remeshing is done using non-conformal meshes, where hanging nodes are handled via the use of Lagrange multiplier constraints. The mesh data transfer used after remeshing is based on projection methods involving finite volumes [3]. The presented model is then compared against a 2D numerical simulation of Direct Energy Deposition of a High-Speed Steel thick deposit from the literature [4]. [less ▲]

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See detailHigh velocity impact response of composite laminates using modified meso-scale damage
Rajaneesh, Anantharaju; Ponthot, Jean-Philippe ULiege; Bruyneel, Michaël ULiege

in International Journal of Impact Engineering (2021), 147

High velocity impact response of carbon fiber reinforced polymer unidirectional composite laminates with a quasi-isotropic stacking sequence impacted by a rigid spherical projectile is studied using ... [more ▼]

High velocity impact response of carbon fiber reinforced polymer unidirectional composite laminates with a quasi-isotropic stacking sequence impacted by a rigid spherical projectile is studied using finite element models. The intra-laminar meso-model originally proposed by Ladevèze (LMT-Cachan) for the ply behavior based on continuum damage mechanics, is extended in this paper to take into account ply fracture energies and in-situ strengths. Constitutive modeling relies on mesh size regularization (via a Bazant-type crack-band/smeared-crack formulation), on orthotropic material aligned mesh and on element erosion. Three different types of post-peak degradation strategies are considered and compared in the paper: (a) a damage rate bound model, and smeared-crack formulations based on (b) linear and (c) exponential softening laws. Models (b) and (c) are original contributions. Intra-laminar and inter-laminar damage models are implemented via user routines in LS-Dyna, for explicit dynamic analyses. The efficiency of the novel material models to predict high velocity impact response and to mitigate the mesh size effects is studied. Predictions from the developed models are validated by comparing with test data and numerical results from the literature, and demonstrate that the two new models based on smeared-crack formulations provide accurate results. [less ▲]

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See detailIMPLEMENTATION OF A RIG TEST FOR ROTOR/STATOR INTERACTION OF LOWPRESSURE COMPRESSOR BLADES AND COMPARISON OF EXPERIMENTAL RESULTS WITH NUMERICAL MODEL
Pacyna, Laura; Bertret, Alexandre; Derclaye, Alain et al

in Proceedings of ASME Turbo Expo 2020 (2020)

To investigate the contact phenomenon between the blade tip and the abradable coated casing, a rig test was designed and built. This rig test fills the following constraints: simplification of the low ... [more ▼]

To investigate the contact phenomenon between the blade tip and the abradable coated casing, a rig test was designed and built. This rig test fills the following constraints: simplification of the low-pressure compressor environment but realistic mechanical conditions, ability to test several designs in short time, at low cost and repeatability. The rig test gives the opportunity to investigate the behavior of different blade designs regarding the sought phenomenon, to refine and mature the phenomenon comprehension and to get data for the numerical tool validation. The numerical tool considers a 3D finite elements model of low-pressure compressor blades with a surrounding rigid casing combined with a specialized model to take into account the effects of the wear of the abradable coating on the blade dynamics. Numerical results are in good agreement with tests in terms of: critical angular speed, blade dynamics and wear pattern on the abradable coated casing [less ▲]

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See detailMechanical Characterization of the Elastoplastic Response of a C11000-H2 Copper Sheet
Pacheco, Matias; Garcia-Herrera, Claudio; Celentano, Diego ULiege et al

in Materials (2020), 13

This work presents an elastoplastic characterization of a rolled C11000-H2 99.90% pure copper sheet considering the orthotropic non-associated Hill-48 criterion together with a modified Voce hardening law ... [more ▼]

This work presents an elastoplastic characterization of a rolled C11000-H2 99.90% pure copper sheet considering the orthotropic non-associated Hill-48 criterion together with a modified Voce hardening law. One of the main features of this material is the necking formation at small strains levels causing the early development of non-homogeneous stress and strain patterns in the tested samples. Due to this fact, a robust inverse calibration approach, based on an experimental–analytical–numerical iterative predictor–corrector methodology, is proposed to obtain the constitutive material parameters. This fitting procedure, which uses tensile test measurements where the strains are obtained via digital image correlation (DIC), consists of three steps aimed at, respectively, determining (a) the parameters of the hardening model, (b) a first prediction of the Hill-48 parameters based on the Lankford coefficients and, (c) corrected parameters of the yield and flow potential functions that minimize the experimental–numerical error of the material response. Finally, this study shows that the mechanical characterization carried out in this context is capable of adequately predicting the behavior of the material in the bulge test. [less ▲]

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See detailModeling the mechanical response of a Dual-Phase steel based on individual-phase tensile properties.
Alvarez, Paulina; Muniz, Francisco; Celentano, Diego ULiege et al

in Metals (2020), 10(1031),

In this work, the engineering stress–strain tensile curve and the force-deflection bending curve of two Dual-Phase (DP) steels are modeled, combining the mechanical data of fully ferritic and fully ... [more ▼]

In this work, the engineering stress–strain tensile curve and the force-deflection bending curve of two Dual-Phase (DP) steels are modeled, combining the mechanical data of fully ferritic and fully martensitic steels. The data is coupled by a modified law of mixture, which includes a partition parameter q that takes into account the strength and strain distributions in both martensite and ferrite phases. The resulting constitutive model is solved in the context of the finite element method assuming a modified mixture rule in which a new parameter q0 is defined in order to extend the capabilities of the model to deal with triaxial stresses and strains and thus achieve a good agreement between experimental results and numerical predictions. The model results show that the martensite only deforms elastically, while the ferrite deforms both elastically and plastically. Furthermore, the partition factor q0 is found to strongly depend on the ferritic strain level. Finally, it is possible to conclude that the maximum strength of the studied DP steels is moderately influenced by the maximum strength of martensite. [less ▲]

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See detailAdvanced material models for damage and failure analysis of fiber reinforced composite structures
Rajaneesh, A; Bruyneel, Michaël ULiege; Ponthot, Jean-Philippe ULiege

in NAFEMS France Conference (2020)

Thin walled composite structures made of laminates with stacks of plies including continuous fibres (like UD or fabrics) are used in aircrafts, wind turbines, naval and automotive applications. In order ... [more ▼]

Thin walled composite structures made of laminates with stacks of plies including continuous fibres (like UD or fabrics) are used in aircrafts, wind turbines, naval and automotive applications. In order to propose predictive finite element simulation tools that are necessary to speed-up the time to market of new products, it is important to use material models that can accurately represent different failure modes at the ply level of a laminated composite structure. Additionally, damage at the ply interfaces, that is delamination, must also be taken into account in the model. Modelling progressive damage up to failure in laminated composite material is clearly a very difficult task. [less ▲]

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See detailAddition of a finite element activation method in an existing thermomechanical finite element code to model additive manufacturing
Laruelle, Cédric ULiege; Boman, Romain ULiege; Papeleux, Luc ULiege et al

Conference (2019, September)

With the rise of Additive Manufacturing (AM) technologies in the industry, it becomes more and more important to have a good understanding of such processes. However, there is still a crucial lack of ... [more ▼]

With the rise of Additive Manufacturing (AM) technologies in the industry, it becomes more and more important to have a good understanding of such processes. However, there is still a crucial lack of fundamental knowledge regarding AM. Hence, there is a high demand for the implementation of a model to accurately simulate an AM process. The complexity of such a simulation comes from multiple sources. Firstly, from the nature of the process. Indeed, it requires geometrically non-linear thermo-mechanical simulations. Secondly, the modeling of the material law is complex. Lastly, the geometry of the process imposes a very fine discretization (layers can be as small as a few μm). This creates models that are computationally costly. Moreover, the process requires altering the geometry of the model during the simulation to model the addition of matter, which is a computational challenge by itself. This work presents the addition of additive manufacturing in the fully implicit in-house Finite Element code “Metafor”, which considers large strains and includes thermo-mechanical simulations and crack propagation simulations. The focus of the work is to add an “additive manufacturing module” to the existing thermomechanical code Metafor. The implemented method to activate elements and to activate and deactivate boundary conditions during a simulation is adapted from the element deletion algorithm implemented in Metafor in the scope of crack propagation. Indeed, in crack propagation the deactivation of an element in a simulation was already possible, i.e. an element could be deactivated based on a certain crack propagation criterion. This algorithm is modified to allow the activation of elements based on a criterion (which can, in the case of AM, be the presence or not of the element in a certain “activation volume” modeling the moving laser). After implementing other AM specificities (heat source model, annealing temperature for alloys, etc), an effective thermomechanical simulation of Additive Manufacturing is obtained. The model is then compared against the literature, including numerical and experimental results from a thermal experimental calibration and a thermo-mechanical analysis of blown powder laser solid forming of Ti-6Al-4V. Temperature, deformation and stress fields are analyzed as well as the influence of different process parameters. [less ▲]

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See detailCoupling procedure of a cold rolling lubrication model with finite element asperity flattening
Boemer, Dominik ULiege; Carretta, Yves; Boman, Romain ULiege et al

Conference (2019, June 03)

Reducing the thickness of increasingly resistant, wider and thinner metal strips by cold rolling requires a strict friction control to maximize the throughput while preventing chattering. In the mixed ... [more ▼]

Reducing the thickness of increasingly resistant, wider and thinner metal strips by cold rolling requires a strict friction control to maximize the throughput while preventing chattering. In the mixed lubrication regime, friction is the result of interacting solid asperity tops of rough surfaces, i.e. those of the roll and the strip, in the presence of a lubricant, which partially supports the load. In the past, the METALUB model was developed to predict the rolling load and forward slip, which are representative of the friction state in cold rolling. This model is based on the slab method, the average Reynolds equation with flow factors, an adiabatic thermal model, various thermoviscoplastic strip and thermopiezoviscous lubricant material laws, elastic roll deformation methods and the analytical asperity flattening law by Wilson & Sheu [1]. This law describes the growth of solid/solid contact between the roll and the strip, and thus friction, with rising bulk strain due to the elongation of the material in the bite, increasing pressure on the asperity tops or decreasing lubricant pressure in the valleys. Since the law was derived by the upper-bound method for a simplified geometry, elastic deformations are neglected, the result is not the exact theoretical solution but an overestimation of the solid/solid contact area, and the law does not take a realistic representation of the asperity geometry into account. To alleviate these shortcomings, a coupling procedure between METALUB and our in-house finite element (FE) solver for large deformations, METAFOR, was created. This procedure starts by METALUB computing the strip elongation, the lubricant pressure and the interface pressure, which is the resulting average pressure of the asperities and the lubricant on the strip, along the roll bite with the classical law by Wilson & Sheu. Based on these values, a FE METAFOR simulation of the asperity flattening then computes the resulting solid/solid contact area and the lubricant film thickness, which can be used in a subsequent METALUB computation instead of the prediction by Wilson & Sheu. The elastoplastic FE model is particularly original since the flattening process is described in the extended plane strain state, i.e. that a strip portion with an arbitrary roughness profile, like the rigid roll portion, is modeled in the plane which is perpendicular to the rolling direction. In this plane, the expansion of the strip portion in the lateral directions is prevented due to the classical plane strain hypothesis in cold rolling, while its out-of-plane elongation is imposed by the METALUB result. The lubricant pressure is then imposed on its top, where it is not in contact with the roll, and the interface pressure pushes the portion against to roll by the application of this pressure on the lower edge. Hence, the previous shortcomings of the asperity flattening law by Wilson & Sheu were essentially removed from the cold rolling model by this coupling procedure. Furthermore, the numerical results were validated by experimental measurements of a semi-industrial pilot mill. [1] W. R. D. Wilson and S. Sheu (1988), Real area of contact and boundary friction in metal forming, Int. J. Mech. Sci., Vol. 30(7), pp. 475 - 489. [less ▲]

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See detailAdvances in material modeling for high velocity impacts on composites
Bruyneel, Michaël ULiege; Rajaneesh, A; Ponthot, Jean-Philippe ULiege et al

Conference (2019, June)

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See detailElement activation strategy for Additive Manufacturing, based on the element deletion algorithm
Laruelle, Cédric ULiege; Boman, Romain ULiege; Papeleux, Luc ULiege et al

Poster (2019, May 27)

With the rise of Additive Manufacturing (AM) technologies in the industry, it is becoming more and more crucial to have a good understanding of those processes. This leads to a high need for the ... [more ▼]

With the rise of Additive Manufacturing (AM) technologies in the industry, it is becoming more and more crucial to have a good understanding of those processes. This leads to a high need for the implementation of a model that can accurately simulate such a process. The difficulties of simulating AM can come from multiple sources. Firstly, from the nature of the process. Indeed, it requires a large deformation thermo-mechanical simulation. Secondly, the modeling of the material law is complex. Lastly, the geometry of the process imposes a very fine discretization (layers can be as small as a few μm). This creates models that are very computationally costly. Moreover, the process requires altering the geometry of the model during simulations to model the addition of matter, which is a computational challenge by itself. This poster presents the implementation of a three-dimensional thermal Finite Element Analysis (FEA) of AM in the fully implicit in-house Finite Element code “Metafor”. The main focus of the work is on mesh management techniques. The method to activate elements during a simulation is adapted from the element deletion algorithm (erosion method) implemented in Metafor in the scope of crack propagation. The final model is compared against literature results with a good agreement. [less ▲]

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See detailAdvances in cold rolling modeling at ULiège
Boemer, Dominik ULiege; Carretta, Yves; Boman, Romain ULiege et al

Scientific conference (2019, February 13)

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See detailEffective development of a finite-element solver at the University
Boman, Romain ULiege; Papeleux, Luc ULiege; Ponthot, Jean-Philippe ULiege

Conference (2018, August 29)

Software development is usually neglected by academic researchers in the field of computational solid mechanics. This lack of long-term strategy often leads to the loss of valuable numerical models and ... [more ▼]

Software development is usually neglected by academic researchers in the field of computational solid mechanics. This lack of long-term strategy often leads to the loss of valuable numerical models and algorithms. In the first part of this talk, the key ideas behind the management of the source code of METAFOR, a nonlinear finite-element solver developed at the University of Liège, are presented in detail. The primary goal is to continuously integrate all the developments into a single application so that future projects can safely rely on the results from the past. The second part of the talk exhibits several applications of metal forming processes computed with METAFOR and based on the Arbitrary Lagrangian Eulerian formalism. [less ▲]

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See detailComputational modeling of material forming processes
Ponthot, Jean-Philippe ULiege; Drapier, Sylvain; Feulvarch, Eric

in Comptes Rendus de l'Académie des Sciences. Série 2b, Mécanique (2018), 346(8), 615

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See detailComparison of stochastic and interval methods for uncertainty quantification of metal forming processes
Arnst, Maarten ULiege; Ponthot, Jean-Philippe ULiege; Boman, Romain ULiege

in Comptes Rendus Mécanique (2018), 346(8), 634-646

Various sources of uncertainty can arise in metal forming processes, or their numerical simulation, or both, such as uncertainty in material behavior, process conditions, and geometry. Methods from the ... [more ▼]

Various sources of uncertainty can arise in metal forming processes, or their numerical simulation, or both, such as uncertainty in material behavior, process conditions, and geometry. Methods from the domain of uncertainty quantification can help assess the impact of such uncertainty on metal forming processes and their numerical simulation, and they can thus help improve robustness and predictive accuracy. In this paper, we compare stochastic methods and interval methods, two classes of methods receiving broad attention in the domain of uncertainty quantification, through their application to a numerical simulation of a sheet metal forming process. [less ▲]

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See detailFinite element implementation of a strain rate sensitive model for impact simulation on composites
Flores, Paulo; Rajaneesh, A; Bruyneel, Michaël ULiege et al

Conference (2018, June)

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