References of "Boman, Romain"
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See detailRelating Local Permeability Changes to the Deformation of Preforms during the Manufacture of Complex-Shaped Composite Structures
Pierce, Robert S; Falzon, Brian G; Boman, Romain ULg

in Proceedings of the 15th Australian Aeronautical Conference (2013, February)

The transition to using carbon-fibre composites in the primary structure of passenger aircraft is now well established with focus shifting towards reducing manufacturing costs. This study reports on ... [more ▼]

The transition to using carbon-fibre composites in the primary structure of passenger aircraft is now well established with focus shifting towards reducing manufacturing costs. This study reports on initial results in the development of accurate numerical process modelling tools for resin-infused composite structures. A continuum-based, finite element material model has been developed to simulate the draping of a dry carbon fibre fabric, accurately tracking the changes in the warp and weft fibre orientations. A multiple ply draping example demonstrates the large variation of shear angles that are prevalent in forming processes. The relationship between shear angle and permeability was studied experimentally as it is integral to the accuracy of the resin infusion modelling process. The anisotropic permeability of the plain weave fabric was observed to increase by a factor of five as the shear locking angle was approached, with principal permeability values, K1 and K2, increasing and decreasing by a factor of approximately two, respectively. [less ▲]

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See detailA Continuum Damage Mechanics Model for the Analysis of the Crashworthiness of Composite Structures: A work in progress
Chiu, Louis N S; Falzon, Brian G; Boman, Romain ULg

in Proceedings of the 15th Australian Aeronautical Conference (2013, February)

The crashworthiness capability of an aircraft structure is dependent on its ability to attenuate crash loading via the controlled deformation of energy absorbing devices. An energy-based constitutive ... [more ▼]

The crashworthiness capability of an aircraft structure is dependent on its ability to attenuate crash loading via the controlled deformation of energy absorbing devices. An energy-based constitutive relation was employed to model the behaviour of carbon fibre reinforced epoxy resin composite material under crush loading. Each of the damage modes in the fibre and matrix was treated separately with its own damage initiation and progression relationships as well as a damage parameter that tracks damage progression. Each damage parameter dictates the reduction in stiffness in the respective principal loading directions. This model was implemented for a 3D solid brick element in contrast to shell-based formulations currently available. Crushing composite structures were modelled and the results validated against experimental data. The force-displacement response / specific energy absorption and the failure modes obtained from the simulation show that the underlying physics of the crushing have been captured by the proposed model but that further work is required for reliable quantitative correlation. [less ▲]

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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 ▲]

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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 ▲]

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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 ▲]

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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 ▲]

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See detailMixed Lubrication Regime in Cold Strip Rolling
Carretta, Yves ULg; Boman, Romain ULg; Legrand, Nicolas et al

in 2nd Annual ArcelorMittal CFD and Thermomechanics Days 2012 (2012, January)

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See detailALE Simulations of Metal Forming Processes
Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in Akhtar S. Khan; Farhoud Kabirian; Jian Liu (Eds.) Non-linear Response of Conventional & Advanced Materials, and Multi-scale Modeling (2012, January)

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See detailGenerating smooth surface meshes from multi-region medical images
D'Otreppe, Vinciane ULg; Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in International Journal for Numerical Methods in Biomedical Engineering (2012), 28(6-7), 642-660

Thanks to advances in medical imaging technologies and numerical methods, Patient-Specific Modelling is more and more used to improve diagnosis and to estimate the outcome of surgical interventions. It ... [more ▼]

Thanks to advances in medical imaging technologies and numerical methods, Patient-Specific Modelling is more and more used to improve diagnosis and to estimate the outcome of surgical interventions. It requires the extraction of the domain of interest from the medical scans of the patient, as well as the discretisation of this geometry. However, extracting smooth multi-material meshes that conform to the tissue boundaries described in the segmented image is still an active field of research. We propose to solve this issue by combining an implicit surface reconstruction method with a multi-region mesh extraction scheme. The surface reconstruction algorithm is based on multi-level partition of unity implicit surfaces which we extended to the multi-material case. The mesh generation algorithm consists in a novel multidomain version of the marching tetrahedra. It generates multi-region meshes as a set of triangular surface patches consistently joining each other at material junctions. This paper presents this original meshing strategy, starting from boundary points extraction from the segmented data, to heterogeneous implicit surface definition, multi-region surface triangulation and mesh adaptation. Results indicate that the proposed approach produces smooth and high-quality triangular meshes with a reasonable geometric accuracy. Hence, the proposed method is well suited for subsequent volume mesh generation and Finite Element simulations. [less ▲]

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See detailImage-based Finite Element Mesh Generation for Microstructures
D'Otreppe, Vinciane ULg; Mengoni, Marlène ULg; Boman, Romain ULg et al

Conference (2011, November 14)

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See detailComparison of Data Transfer Methods between Meshes in the Frame of the Arbitrary Lagrangian Eulerien Formalism
Bussetta, Philippe ULg; Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in Proceedings of "Fifth International Conference on Advanced COmputationalMethods in ENgineering" (2011, November)

In nonlinear solid Mechanics, the Arbitrary Lagrangian Eulerian (ALE) formalism is a common way to avoid mesh distortion when very large deformations occur in the modelled process. Usually, the ALE ... [more ▼]

In nonlinear solid Mechanics, the Arbitrary Lagrangian Eulerian (ALE) formalism is a common way to avoid mesh distortion when very large deformations occur in the modelled process. Usually, the ALE resolution procedure is based on an “operator split”, the second part of which is a Data Transfer between two meshes sharing the same topology (same number of nodes and same number of element neighbours for each of them). Thanks to this interesting property, classical ALE transfer algorithms can bemuchmore optimised in terms of CPU time than the ones that are used in the frame of a complete remeshing. However, the resulting CPU-efficient transfer schemes suffer from two main drawbacks. The first one is a spurious crosswind diffusion coming from the corner fluxes that have been neglected. The second issue is the number of explicit transfer steps which may become very large when the element size decreases. In this paper, these classical ALE Data Transfer methods are compared to more general algorithms which do not make any assumption on the topology of both meshes. [less ▲]

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See detailEffects of the roll forming process on the mechanical properties of thin-walled sections made of non linear metallic materials
Rossi, Barbara ULg; Boman, Romain ULg; Degée, Hervé ULg

in Proceedings of the 6th International Conference on Thin Walled Structures: ICTWS2011, Timisoara 5-7 September 2011 (2011, September 05)

It is well known that the cold-forming process is likely to significantly enhance the mechanical properties of the profile by strain hardening leading to increased resistance compared to a resistance ... [more ▼]

It is well known that the cold-forming process is likely to significantly enhance the mechanical properties of the profile by strain hardening leading to increased resistance compared to a resistance assessment based on nominal properties. It is thus necessary to accurately determine the mechanical properties after the cold process of fabrication. The knowledge on these enhanced properties is rather good for profiles made of traditional construction steel (carbon steel with yield strength between 200 and 400 MPa) characterized by an elasticplastic behaviour. However less information is available for profiles made of materials exhibiting a non linear stress-strain relationship. In this context, the paper presents a parametric study on roll-profiled channel sections. For that purpose, the finite element code METAFOR developed at the LTAS division of the University of Liège is used to simulate the forming process of profiles made of high strength steel and of stainless steel. In the simulations, different values of the radius to thickness ratio of the corners are considered. The results of the numerical simulations are expressed in terms of resulting proof strength in the corners versus the radius to thickness ratio for the different materials. They are finally compared to existing predictive formulations. Additional considerations are also given on the forming process itself (i.e. on the configuration of the rolls or on the springback). [less ▲]

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See detailNumerical Simulation of Stationary Roll Forming using ALE formalism
Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in Oñate, E.; Owen, D. R. J.; Peric, D. (Eds.) et al Computational Plasticity XI - Fundamentals and Applications (2011, September)

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See detailMETALUB – A Slab Method Software for the Numerical Simulation of Mixed Lubrication Regime in Cold Strip Rolling
Carretta, Yves ULg; Boman, Romain ULg; Stephany, Antoine et al

in Proceedings of the Institution of Mechanical Engineers - Part J - Journal of Engineering Tribology (2011), 225(9), 894-904

A cold rolling model taking into account mixed lubrication regime has been developed and included into a simulation software named MetaLub. The main objective is to enhance the performances of rolling ... [more ▼]

A cold rolling model taking into account mixed lubrication regime has been developed and included into a simulation software named MetaLub. The main objective is to enhance the performances of rolling mills from a lubrication point of view. It means that lubricant rheology but also roll diameters and roughness, etc., can be optimised to improve stability and efficiency of the rolling tool. The main features of MetaLub, are briefly presented in this paper. Then, two studies of the influence of rolling speed and negative forward slip are discussed. The obtained numerical results are presented and compared to some experimental data from literature and from ArcelorMittal facilities in order to validate the model and to show its capacity to understand and help to improve industrial rolling conditions. [less ▲]

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See detailInfluence of thermoelectric coupling on pacemaker activity generated by mechano-electric feedback in a one-dimensional ring-shaped model of cardiac fiber
Collet, Arnaud ULg; Desaive, Thomas ULg; Pierard, Luc ULg et al

in XXIIIrd congress of the International Society of Biomechanics, July 3-7, 2011 (2011, July 05)

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See detailInfluence of thermoelectric coupling on pacemaker activity generated by mechano-electric feedback in a one-dimensional ring-shaped model of cardiac fiber
Collet, Arnaud ULg; Desaive, Thomas ULg; Pierard, Luc ULg et al

Poster (2011, July 05)

Recently, the influence of thermal processes on electrophysiology has clearly been underlined, using a FitzHugh–Nagumo-type (FHN-type) model. When the temperature is raised, the action potential duration ... [more ▼]

Recently, the influence of thermal processes on electrophysiology has clearly been underlined, using a FitzHugh–Nagumo-type (FHN-type) model. When the temperature is raised, the action potential duration (APD) has been shown to shorten, while the action potential (AP) amplitude decreases, and the conduction velocity increases. In the present study, we investigate the effects of thermoelectric coupling on mechano-electric feedback (MEF), and more specifically, on pacemaker activity generated by MEF. To investigate these effects, thermoelectric coupling is introduced in a one-dimensional ring-shaped electromechanical model of cardiac fiber, which takes into account excitation-contraction coupling (ECC), as well as MEF. [less ▲]

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See detailDamage and Fracture of Materials Submitted to High Strain Rates. A Thermomechanically Implicit Coupled Approach with Element Erosion
Jeunechamps, Pierre-Paul; Boman, Romain ULg; Papeleux, Luc ULg et al

in Proceedings of the 3rd International Conference on Impact Loading of Lightweight Structures (2011, June 28)

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See detailInfluence of thermoelectric coupling on pacemaker activity generated by mechano-electric feedback in a one-dimensional ring-shaped model of cardiac fiber
Collet, Arnaud ULg; Desaive, Thomas ULg; Pierard, Luc ULg et al

Poster (2011, June 01)

The mechano-electric feedback (MEF) in the heart consists in the influence of the tissue deformations on the cardiac electrical activity. Under certain conditions, tissue deformations can generate ... [more ▼]

The mechano-electric feedback (MEF) in the heart consists in the influence of the tissue deformations on the cardiac electrical activity. Under certain conditions, tissue deformations can generate electrical perturbations via stretch-activated channels, such that the membrane potential can exceed the threshold value needed in order to trigger cardiac action potentials (APs). In the present study, we have developed a one-dimensional ring-shaped model of cardiac fiber taking into account three different couplings: the excitation-contraction coupling (ECC), the MEF and the thermoelectric coupling (TEC). The main goal of this work is to examine the effects of the TEC on the different properties of the pacemaker activity generated by the MEF. [less ▲]

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See detailThermomechanical simulation of roll forming process based on the coupling of two independent solvers
Carretta, Yves ULg; Boman, Romain ULg; Stephany, Antoine et al

in Proceedings of the IV International Conference on Computational Methods for Coupled Problems in Science and Engineering COUPLED PROBLEMS 2011 (2011, June)

This paper deals with an industrial application of a coupling procedure involving two different computer programs : MetaLub and ThermRoll. The first one models the mechanical phenomena occurring in the ... [more ▼]

This paper deals with an industrial application of a coupling procedure involving two different computer programs : MetaLub and ThermRoll. The first one models the mechanical phenomena occurring in the roll-bite during cold rolling such as elasto-plastic strip strains, elastic-roll deformations, asperity flattening and lubricant flow. The second one uses the previous results to compute the steady-state temperature field of the work-roll and the strip. These two codes are briefly described and a model of an industrial stand demonstrates the importance of the thermomechanical coupling in order to get a better understanding of the process. [less ▲]

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