References of "Boman, Romain"
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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 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 detailFinite element modelling of composite structures under crushing load
Chiu, Louis N.S.; Falzon, Brian G.; Boman, Romain ULg et al

in Composite Structures (2015)

This paper details the theory and implementation of a composite damage model, addressing damage within a ply (intralaminar) and delamination (interlaminar), developed for the simulation of the crushing of ... [more ▼]

This paper details the theory and implementation of a composite damage model, addressing damage within a ply (intralaminar) and delamination (interlaminar), developed for the simulation of the crushing of laminated composite structures. It includes a more accurate determination of the characteristic length to achieve mesh objectivity in capturing intralaminar damage consisting of matrix cracking and fibre failure, a load-history dependent material response, an isotropic hardening nonlinear matrix response, as well as a more physically-based interactive matrix damage mechanism. The developed damage model requires a set of material parameters obtained from a combination of standard and non-standard material characterisation tests. The fidelity of the model mitigates the need to manipulate, or “calibrate”, the input data to achieve good agreement with experimental results. This intralaminar damage model was implemented as a VUMAT subroutine, and used in conjunction with an existing interlaminar damage model, in Abaqus/Explicit. This approach was validated through the simulation of the crushing of a cross-ply composite tube with a tulip-shaped trigger, loaded in uniaxial compression. Despite the complexity of the chosen geometry, excellent correlation was achieved with experimental results. [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 Low-Cost Digital Image Correlation Technique for Characterising the Shear Deformation of Fabrics for Draping Studies
Pierce, R. S.; Falzon, B. G.; Thompson, M. C. et al

in Strain (2015)

A novel digital image correlation (DIC) technique has been developed to track changes in textile yarn orientations during shear characterisation experiments, requiring only low-cost digital imaging ... [more ▼]

A novel digital image correlation (DIC) technique has been developed to track changes in textile yarn orientations during shear characterisation experiments, requiring only low-cost digital imaging equipment. Fabric shear angles and effective yarn strains are calculated and visualised using this new DIC technique for bias extension testing of an aerospace grade, carbon-fibre reinforcement material with a plain weave architecture. The DIC results are validated by direct measurement, and the use of a wide bias extension sample is evaluated against a more commonly used narrow sample. Wide samples exhibit a shear angle range 25% greater than narrow samples and peak loads which are 10 times higher. This is primarily due to excessive yarn slippage in the narrow samples; hence, the wide sample configuration is recommended for characterisation of shear properties which are required for accurate modelling of textile draping [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 nonlinear mechanical problems using Metafor
Boman, Romain ULg

Scientific conference (2014, May 16)

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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 detailImplementation of a non-orthogonal constitutive model for the finite element simulation of textile composite draping
Pierce, Robert S; Falzon, Brian G; Thompson, Mark C et al

in Applied Mechanics and Materials (2014), 553

In the pursuit of producing high quality composite aircraft structures at a low cost, out-of-autoclave manufacturing processes for textile reinforcements are being simulated with increasing accuracy. This ... [more ▼]

In the pursuit of producing high quality composite aircraft structures at a low cost, out-of-autoclave manufacturing processes for textile reinforcements are being simulated with increasing accuracy. This paper focuses on the continuum-based, finite element modelling of textile composites as they deform during the draping process. A non-orthogonal constitutive model tracks yarn orientations within a material subroutine developed for Abaqus/Explicit, resulting in the realistic determination of fabric shearing and material draw-in. Supplementary material characterisation was experimentally performed in order to define the tensile and non-linear shear behaviour accurately. The validity of the finite element model has been studied through comparison with similar research in the field and the experimental lay-up of carbon fibre textile reinforcement over a tool with double curvature geometry, showing good agreement. [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 detailArbitrary Lagrangian Eulerian simulations of stationary and non-stationary metal forming processes
Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in AIP Conference Proceedings (2013, December 16), 1567

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See detailAn implicit erosion algorithm for the numerical simulation of metallic and composite materials submitted to high strain rate.
Ponthot, Jean-Philippe ULg; Boman, Romain ULg; Jeunechamps, Pierre-Paul et al

in Proceedings Indian National Science Academy (2013), 79/4(Part A), 519-528

In this paper, we present a general consistent numerical formulation able to take into account strain rate, damage and thermal effects of the material behaviour. A thermomechanical implicit approach for ... [more ▼]

In this paper, we present a general consistent numerical formulation able to take into account strain rate, damage and thermal effects of the material behaviour. A thermomechanical implicit approach for element erosion to model material failure is also presented. This approach can be applied both to ductile fracture for metals, relying on a continuum damage mechanics approach, coupled to different fracture criteria, as well as composite material failure described with either a failure criterion or a progressive damage model. The numerical models will be illustrated by different quasi-static and high strain rate applications for both metallic alloys and composite materials. All these physical phenomena have been included in an implicit dynamic object-oriented finite element code (implemented at LTAS-MN²L, University of Liège, Belgium) named Metafor [1]. [less ▲]

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See detailNumerical simulation of the Roll forming of thin-walled sections and evaluation of corner strength enhancement
Rossi, Barbara ULg; Degée, Hervé ULg; Boman, Romain ULg

in Finite Elements in Analysis & Design (2013), 72

Cold roll forming modifies the mechanical properties of thin-walled profiles by strain hardening. The understanding of this phenomenon, which is rather good for profiles made of traditional construction ... [more ▼]

Cold roll forming modifies the mechanical properties of thin-walled profiles by strain hardening. The understanding of this phenomenon, which is rather good for profiles made of traditional construction steel, is mandatory for assessing the member resistance. Less information is however available for profiles made of materials exhibiting a pronounced degree of nonlinearity of the stress-strain curve such as high-strength and stainless steels. Current codes generally encounter difficulties for modelling this fabrication process because of the size of industrial mills. Indeed, accurate modelling of the continuous cold roll forming process using finite elements requires a huge number of elements leading to excessive CPU times. Therefore, modellers usually reduce the geometry of the formed sheet or increase the size of the finite elements, inducing a loss of accuracy in the results. In this work, the finite element software METAFOR is used to model cold roll forming of channel profiles made of high-strength and stainless steels. The numerical results, expressed in terms of corner strength enhancement versus radius–to–thickness ratio, are compared against an existing predictive model. [less ▲]

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See detailVerification of a novel material model to predict damage in composite structures
Chiu, Louis N.S.; Falzon, Brian G.; Boman, Romain ULg et al

in International Conference on Structural Integrity and Fracture (2013, July 11)

An intralaminar damage model (IDM), based on continuum damage mechanics, was developed for the simulation of composite structures subjected to damaging loads. This model can capture the complex ... [more ▼]

An intralaminar damage model (IDM), based on continuum damage mechanics, was developed for the simulation of composite structures subjected to damaging loads. This model can capture the complex intralaminar damage mechanisms, accounting for mode interactions, and delaminations. Its development is driven by a requirement for reliable crush simulations to design composite structures with a high specific energy absorption. This IDM was implemented as a user subroutine within the commercial finite element package, Abaqus/Explicit[1]. In this paper, the validation of the IDM is presented using two test cases. Firstly, the IDM is benchmarked against published data for a blunt notched specimen under uniaxial tensile loading, comparing the failure strength as well as showing the damage. Secondly, the crush response of a set of tulip-triggered composite cylinders was obtained experimentally. The crush loading and the associated energy of the specimen is compared with the FE model prediction. These test cases show that the developed IDM is able to capture the structural response with satisfactory accuracy. [less ▲]

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See detailContributions to the process modelling of resin infusion under flexible tooling (RIFT) manufacturing for composite aerostructures
Pierce, R.S.; Falzon, B.G.; Thompson, M.C. et al

in Proceedings of ICCM19 (2013, July)

The cost of manufacturing textile-reinforced composite aerostructures using Resin Infusion under Flexible Tooling (RIFT) can be reduced by computational modelling. This paper outlines the current progress ... [more ▼]

The cost of manufacturing textile-reinforced composite aerostructures using Resin Infusion under Flexible Tooling (RIFT) can be reduced by computational modelling. This paper outlines the current progress and contributions made towards this goal. A continuum-based material model was incorporated into a finite element package to simulate the draping of a dry carbon fibre fabric. It accurately tracks the changes in the warp and weft fibre orientations and has been experimentally validated. Material characterisation was performed to determine the tensile and shear properties of a plain weave fabric reinforcement material. In support of bias extension shear testing, an accessible Digital Image Correlation (DIC) approach was developed for accurate optical strain measurement. A relationship between permeability and shear angle was also experimentally determined using a novel permeability measurement technique. Future work is planned to combine all these aspects in an infusion model and demonstrate the complete process model. [less ▲]

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See detailNumerical simulations of asperity crushing using boundary conditions encountered in cold-rolling
Carretta, Yves ULg; Boman, Romain ULg; Legrand, Nicolas et al

in Key Engineering Materials [=KEM] (2013), 554-557

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, two finite elements models are presented. The first one represents the flattening of a serrated asperity field in plane-strain conditions. The results are compared to the experiments published by Sutcliffe [1]. The second one is a tri-dimensional asperity model flattened by a rigid plane. The boundary conditions applied to this model correspond to the ones encountered in a real cold-rolling case. The results are compared to the relative contact area computed by a strip rolling model using the analytical laws proposed by Wilson & Sheu [2] and Marsault [3]. [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 Proceedings of Coupled Problems 2013 (2013, June)

Detailed reference viewed: 53 (19 ULg)