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1. A Method to Compute Shadow Geometry in Open Building Information Modeling Authoring Tools: Automation of Solar Regulation Checking

Author

Charles Voivret, Dimitri Bigot, and Garry Rivière

Subjects
shading factor, building information modeling, solar protection, shadow geometry, regulation checking, automation, Building construction, TH1-9745
Abstract

Building solar protection regulations is essential to save energy in hot climates. The protection performance is assessed using a shading factor computation that models the sky irradiance and the geometry of shadow obstructing the surface of interest. While Building Information Modeling is nowadays a standard approach for practitioners, computing shadow geometry in BIM authoring tools is natively impossible. Methods to compute shadow geometry exist but are out of reach for the usual BIM authoring tool user because of algorithm complexity and non-friendly BIM implementation platform. This study presents a novel approach, dubbed solid clipping, to calculate shadow geometry accurately in a BIM authoring tool. The aim is to enhance project delivery by enabling solar control verification. This method is based on typical Computer Aided Design (CAD) in BIM authoring tools. The method is generic enough to be implemented using any BIM authoring tool’s visual and textual API. This work demonstrates that a thermal regulation, here the French overseas one, can be checked concerning solar protection, thanks to a BIM model. Beyond automation, this paper shows that, by directly leveraging the BIM model, designs presently not feasible by the usual process can be studied and checked.

Published
2023
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2. X-ray CT analysis of the evolution of ballast grain morphology along a Micro-Deval test: key role of the asperity scale

Author

Gaël Combe, Ivan Deiros Quintanilla, Fabrice Emeriault, Charles Voivret, Jean-Francois Ferellec, Laboratoire sols, solides, structures - risques [Grenoble] (3SR ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), GéoMécanique, Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Département recherche et développements (R&D - SNCF), and SNCF

Subjects
Ballast, Materials science, [SPI.GCIV.GEOTECH]Engineering Sciences [physics]/Civil Engineering/Géotechnique, 0211 other engineering and technologies, Scalar (physics), General Physics and Astronomy, Geometry, 02 engineering and technology, Surface finish, Edge (geometry), Tracking (particle physics), Track (rail transport), 01 natural sciences, Mechanics of Materials, 0103 physical sciences, General Materials Science, 010306 general physics, Asperity (geotechnical engineering), ComputingMilieux_MISCELLANEOUS, Smoothing, 021101 geological & geomatics engineering
Abstract

Ballast grains in railway tracks progressively wear due to the efforts exerted by the continuous passage of trains and the periodic maintenance operations. The initial sharp edges and vertices of the grains tend to become smoother and the surface texture is removed. This change in morphology plays a key role on the proper behaviour of the ballast layer and, consequently, on the frequency maintenance required on the track. The object of this paper is to improve the understanding of the wear process by tracking the morphology of a sample of grains submitted to an accelerated ageing using the Micro-Deval standard test. To this goal, X-ray Computed Tomography is used to scan a sample of grains at different states of wear and the resulting images are compared using 3D image analysis. A description of morphology evolution at different scales is provided using scalar parameters and spherical harmonic analysis, proving that the general form is not significantly changed during a standard Micro-Deval test. Thus a detailed analysis at the asperity level is performed, showing the key role of the edge broadening and vertex smoothing phenomena on ballast wear.

Published
2019

3. Population balance in confined comminution using a physically based probabilistic approach for polydisperse granular materials

Author

Pierre-Yves Hicher, Carlos Ovalle, Christophe Dano, and Charles Voivret

Subjects
Balance (metaphysics), education.field_of_study, Materials science, Population, 0211 other engineering and technologies, Computational Mechanics, Probabilistic logic, 02 engineering and technology, Geotechnical Engineering and Engineering Geology, Granular material, 01 natural sciences, Mechanics of Materials, 0103 physical sciences, General Materials Science, Geotechnical engineering, Comminution, 010306 general physics, education, 021101 geological & geomatics engineering
Published
2016

4. Railway Ballast: Grain Shape Characterization to Study its Influence on the Mechanical Behaviour

Author

Guillaume Perrin, Jean-Noël Roux, Noura Ouhbi, and Charles Voivret

Subjects
Ballast, Engineering, 0211 other engineering and technologies, Point cloud, Mechanical engineering, 02 engineering and technology, 01 natural sciences, Software, polyhedrons, generation, 0103 physical sciences, particle shape, POD, LMGC90, characterization, 010306 general physics, Engineering(all), 021101 geological & geomatics engineering, business.industry, Dimensionality reduction, DEM, Statistical model, General Medicine, Structural engineering, Characterization (materials science), Particle, simulations, Focus (optics), business
Abstract

As several studies showed, mechanical performance of ballast depends greatly on its size, mineralogy and shape. Unlike the formers, particle shape remains a poorly specified property. The main objective of the study is then to first characterize the shape of ballast, then to understand its impact on the mechanical performance, by means of numerical simulations using the Discrete Elements Method (DEM), performed on LMGC90 software, with ballast grains represented as irregular polyhedrons. Starting from a description obtained experimentally by 3D digitization of the particle surfaces as point clouds, we will present a method to characterize and generate a set of virtual grains that are morphologically representative of real ballast grains. The model relies on a statistical modelling of the ballast grain morphology based on a dimensionality reduction approach leading to an optimal and nearly exhaustive shape characterization. In this paper, we will focus on the efficiency of both characterizing and generating methods and describe their advantages, as well as an outlook for numerical simulations.

Published
2016
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5. Randomly-fluctuating heterogeneous continuum model of a ballasted railway track

Author

Lucio de Abreu Correa, Régis Cottereau, Charles Voivret, Juan Carlos Quezada, Sofia Costa D’Aguiar, Laboratoire de mécanique des sols, structures et matériaux (MSSMat), CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Laboratoire des sciences de l'ingénieur, de l'informatique et de l'imagerie (ICube), Institut National des Sciences Appliquées - Strasbourg (INSA Strasbourg), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-École Nationale du Génie de l'Eau et de l'Environnement de Strasbourg (ENGEES)-Réseau nanophotonique et optique, Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), SNCF : Innovation & Recherche, SNCF, École Nationale du Génie de l'Eau et de l'Environnement de Strasbourg (ENGEES)-Université de Strasbourg (UNISTRA)-Institut National des Sciences Appliquées - Strasbourg (INSA Strasbourg), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Institut National de Recherche en Informatique et en Automatique (Inria)-Les Hôpitaux Universitaires de Strasbourg (HUS)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, and Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Engineering, Discretization, Scale (ratio), Field (physics), Continuum (topology), business.industry, Applied Mathematics, Mechanical Engineering, Spectral element method, Computational Mechanics, [SPI.MECA.VIBR]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Vibrations [physics.class-ph], Ocean Engineering, [SPI.MECA.SOLID]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Solid mechanics [physics.class-ph], Free field, 01 natural sciences, Finite element method, 010305 fluids & plasmas, Stress field, Computational Mathematics, Computational Theory and Mathematics, 0103 physical sciences, Statistical physics, 010306 general physics, business, Simulation
Abstract

International audience; This paper proposes a description of a granular medium as a stochastic heterogeneous continuum medium. The heterogeneity of the material properties field recreates the heterogeneous stress field in a granular medium. The stochastic approach means that only statistical information, easily available, is required to construct the model. The heterogeneous continuum model is calibrated with respect to discrete simulations of a set of railway ballast samples. As they are continuum-based, the equilibrium equations can be solved on a large scale using a parallel implementation of an explicit time discretization scheme for the Finite Element Method. Simulations representative of the influence on the environment of the passage of a train on a ballasted railway track clearly show the influence of the heterogeneity. These simulations seem to correlate well with previously unexplained overly damped measurements in the free field.

Published
2017

6. 3D particle shape modelling and optimization through proper orthogonal decomposition

Author

Noura Ouhbi, Jean-Noël Roux, Guillaume Perrin, Charles Voivret, SNCF : Innovation & Recherche, SNCF, Thales (France), Rhéophysique, Laboratoire Navier (navier umr 8205), and Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Ballast, Aspect ratio, Generation · Stochastic, Characterization, Flatness (systems theory), Proper Orthogonal Decomposition, 0211 other engineering and technologies, General Physics and Astronomy, 02 engineering and technology, Granular material, 01 natural sciences, Modelling, 010305 fluids & plasmas, 0103 physical sciences, General Materials Science, Representation (mathematics), 021101 geological & geomatics engineering, Mathematics, Railway Ballast, Mathematical analysis, Shape, 16. Peace & justice, Multivariate kernel density estimation, Mechanics of Materials, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Probability distribution, Particle
Abstract

International audience; Based on Proper Orthogonal Decomposition (POD), a new method is presented in order to statistically characterize arbitrary particle shapes using an optimal choice of shape functions identified on a set of 1000 digitized railway ballast particles obtained through 3D Scan. The coefficients of the POD expansion enable a description of ballast grains with varying levels of accuracy. On exploiting the knowledge of their statistical distribution we are able, implementing an appropriate Multivariate Kernel Density Estimation (Multivariate KDE) method, to generate irregular particles with similar morphological features. The description and generation methods are validated by comparing statistical distributions of basic characteristics: surface area, volume, average radius, elongation, flatness, and aspect ratio. Using suitable geometric de-scriptors defining local curvatures, we identify which surface points might be regarded as forming faces. This shows that the proposed particle generation method is well suited for irregularly shaped granular materials, as a first geometric definition step, before numerical simulations of their collective mechanical properties are carried out by a Discrete Element code dealing with polyhedral shapes. We illustrate this process with the simple case of the assembling of a granular pack from a loose configuration, by one-dimensional compression, using different levels of accuracy in the representation of grain shape.

Published
2017

7. A risk assessment method for ballast flight; managing the rolling stock/infrastructure interaction

Author

Eliane Allain, Charles Voivret, Nicolas Paradot, and Gilles Saussine

Subjects
Ballast, Engineering, business.industry, Mechanical Engineering, Risk assessment, business, Analysis method, Simulation, Stock (geology), Marine engineering
Abstract

The evaluation of the level of risk resulting from the phenomenon of ballast flight is currently receiving considerable attention, due to its direct impact on the safety and reliability of commercial railway operations. Of particular interest are the effects of this phenomenon on both railway infrastructure and rolling stock. It is difficult to analyse the ballast flight phenomenon, due to its dependence on a large number of variable parameters. Investigations carried out at SNCF have led to the proposal of a global approach, called the stress–strength interference analysis method, which can be applied by considering a relevant indicator to evaluate the risk due to flying ballast. This paper presents the work on the application of the proposed analysis approach to the ballast flight phenomenon performed within the FP7 EU AeroTRAIN project. The approach considers the influence of the passage of dedicated rolling stock and the resistance of the track to the displacement of ballast. It leads to the proposal of a methodology to evaluate the risk of ballast flight in high-speed rail operations; this allows the evaluation of the degradation rate of railway infrastructure and rolling stock due to this phenomenon to be performed.

Published
2015

8. Wear of sharp aggregates in a rotating drum

Author

Charles Voivret, Fabrice Emeriault, Jean François Ferellec, Ivan Deiros Quintanilla, J.B. Toni, Gaël Combe, Laboratoire sols, solides, structures - risques [Grenoble] (3SR ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), SNCF Réseau [La Plaine st Denis], GéoMécanique, and Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])

Subjects
Ballast, Engineering, business.industry, Physics, QC1-999, [SPI.GCIV.GEOTECH]Engineering Sciences [physics]/Civil Engineering/Géotechnique, 0211 other engineering and technologies, Mechanical engineering, Wear coefficient, 02 engineering and technology, Mechanics, Surface finish, Tribology, Tracking (particle physics), Contact force, 021105 building & construction, Attrition test, Constant (mathematics), business, 021101 geological & geomatics engineering
Abstract

International audience; Aggregates constituting ballast layer wear due to the continuous passage of trains and during the necessary maintenance operations of the track. In order to develop efficient solutions for ballasted tracks design and maintenance, a proper knowledge of the degradation laws of ballast grains is needed. In tribology, the amount of wear due to friction when two surfaces are in contact is classically predicted by Archard’s equation. However, due to the continuous evolution of grain angularity and roughness, at the macro-scale wear coefficient cannot be assumed to remain constant, but will depend on the state of degradation of the grain surface. In order to adjust the model to this particular case, the Micro-Deval Attrition test is used. The rotating drum is stopped at intermediate stages and the amount of generated fine particles is measured. Thus the curve of mass loss along time is built. These results are then linked to Archard’s model using the values of contact forces and relative displacements extracted from discrete element simulations. Finally, a morphology analysis is performed tracking shape and roughness parameters at different stages of degradation using X-ray tomography and a laser profilometer.

Published
2017

9. Impact of the Heterogeneity of the Ballast on the Dynamical Behavior of the Ballast-Soil System

Author

Estelle Bongini, Baldrik Faure, Lucio De Abreu Correa, Sofia Costa D’Aguiar, Régis Cottereau, and Charles Voivret

Subjects
Ballast, Random field, 0211 other engineering and technologies, Parameterized complexity, Modulus, 02 engineering and technology, Mechanics, Solver, 01 natural sciences, 010101 applied mathematics, Homogeneous, SPHERES, 0101 mathematics, 021101 geological & geomatics engineering, Mathematics
Abstract

This paper discusses the dynamical behavior of a randomly-fluctuating heterogeneous continuum model of the ballast. The Young’s modulus is modeled as a random field parameterized by its average, its variance and a correlation model representing non-interpenetrating spheres. A numerical model of the ballast and the surrounding soil is then constructed based on an efficient implementation of an explicit spectral element solver on a large cluster of computers. This model allows to describe numerically the wave field generated in the ballast and soil by the passage of a train, as well as to construct dispersion equations for the ballast-soil model. The influence of heterogeneity is discussed by comparison with a similar model where the ballast is assumed homogeneous. Different values of the soil mechanical parameters are considered and compared. Finally, potential consequences for the design of the ballast are discussed.

Published
2017

10. Wave propagation in a stochastic media: dispersion curves for a ballasted railway track

Author

Lucio de Abreu Correa, Régis Cottereau, Charles Voivret, Aguiar, Sofia Costa D., Estelle Bongini, Baldrik Faure, Laboratoire de mécanique des sols, structures et matériaux (MSSMat), CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), SNCF : Innovation & Recherche, SNCF, and Université Paris-Saclay

Subjects
Wave propagation, Stochastic media, Dispersion Curves, [SPI.MECA.STRU]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Structural mechanics [physics.class-ph], Railway track
Abstract

International audience; This paper discusses the dynamical behavior of a randomly-fluctuating heterogeneous continuum model of the ballast. The Young’s modulus is modeled as a random field parameterized by its average, its variance and a correlation model. A numerical model of the ballast and the surrounding soil is then constructed based on an explicit spectral element solver. This model allows to describe numerically the wave field generated, as well as to construct dispersion relation for the ballast-soil model. The influence of heterogeneity is discussed by comparison with a similar homogeneous model.

Published
2017

11. Stochastic heterogeneous material modeling for wave propagation in a ballast layer

Author

Régis Cottereau, Sofia Costa D’Aguiar, Lucio de Abreu Correa, Charles Voivret, Baldrick Faure, and Estelle Bongini

Subjects
Ballast, Random field, Continuum (measurement), Computer science, Wave propagation, Physics, QC1-999, 0211 other engineering and technologies, Modulus, Parameterized complexity, 02 engineering and technology, Mechanics, Solver, 01 natural sciences, Homogeneous, 0103 physical sciences, Statistical physics, 010306 general physics, 021101 geological & geomatics engineering
Abstract

This paper discusses the dynamical behavior of a randomly-fluctuating heterogeneous continuum model of the ballast. The Young’s modulus is modeled as a random field parameterized by its average, its variance and a correlation model. A numerical model of the ballast and the surrounding soil is then constructed based on an explicit spectral element solver. This model allows to describe numerically the wave field generated, as well as to construct dispersion curves for the ballast-soil model. The influence of heterogeneity is discussed by comparison with a similar model where the ballast is assumed homogeneous.

Published
2017

12. Quantifying Degradation of Railway Ballast Using Numerical Simulations of Micro-deval Test and In-situ Conditions

Author

Ivan Deiros, Gaël Combe, Fabrice Emeriault, Charles Voivret, Laboratoire sols, solides, structures - risques [Grenoble] (3SR ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), SNCF Réseau [La Plaine st Denis], GéoMécanique, and Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])

Subjects
Ballast, Work (thermodynamics), Engineering, wear, business.industry, Micro-Deval, [SPI.GCIV.GEOTECH]Engineering Sciences [physics]/Civil Engineering/Géotechnique, 0211 other engineering and technologies, 02 engineering and technology, General Medicine, Structural engineering, Track (rail transport), Discrete element method, 021105 building & construction, Geotechnical engineering, Attrition test, Train, ballast grains, business, Engineering(all), 021101 geological & geomatics engineering, Degradation (telecommunications), Discrete Elements Method
Abstract

International audience; Throughout the life of the track, ballast grains wear as a result of both the trains passing over the track and the maintenance operations (tamping). The morphology of the grains is changed: they lose angularity and fine particles are produced, causing a gradual loss of track performance. Eventually ballast renewal becomes necessary. In order to predict the evolution of this degradation, a multi-scale study is proposed. A comparison between discrete element method (DEM) simulations of Micro-Deval attrition test and of the passage of trains over a sleeper is performed in order to both detect the different loading and wearing mechanisms involved and quantify the amount of friction work produced, which is directly related to friction wear. The same numerical approach is also used with the simulations of the track to detect families of contacts in order to determine characteristic loading paths at the micro-scale. Loads and displacements of both systems are then compared in order to discuss the relevance of the Micro-Deval test.

Published
2016

13. Effect of the crystallization of a solute on the cohesion in granular materials

Author

Jean-Yves Delenne, Charles Voivret, Fabien Soulié, Moulay Saïd El Youssoufi, C. Saix, Laboratoire de Mécanique et Génie Civil (LMGC), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Physique et Mécanique des Milieux Granulaires (PMMG), and Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Cement, Materials science, Capillary action, General Chemical Engineering, 0211 other engineering and technologies, Evaporation, Mineralogy, 04 agricultural and veterinary sciences, 02 engineering and technology, Cementation (geology), Granular material, law.invention, Physics::Fluid Dynamics, [PHYS.MECA.MEMA]Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], Condensed Matter::Soft Condensed Matter, Compressive strength, law, [SPI.MECA.MEMA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], 040103 agronomy & agriculture, Cohesion (geology), 0401 agriculture, forestry, and fisheries, Composite material, Crystallization, Physics::Atmospheric and Oceanic Physics, 021101 geological & geomatics engineering
Abstract

We study experimentally the macroscopic cohesion of wet granular materials during water evaporation and progressive crystallization of a solute between grains. The samples are wetted granular columns of cylindrical shape subjected to vertical compression tests. The compressive strength allows us to follow the evolution of the material from the capillary cohesion regime to the cemented cohesion regime. Surprisingly, we find that this transition is governed by a control parameter defined as the ratio of the crystallized solute mass to the total mass of the solute present in the sample rather than the absolute amount of the crystallized solute.

Published
2007

14. Stochastic heterogeneous material modeling for granular material. Application to wave propagation in ballasted railway track

Author

Régis Cottereau, Lucio Abreu Corrêa, Juan Carlos Quezada, Aguiar, Sofia Costa D., Charles Voivret, Laboratoire de mécanique des sols, structures et matériaux (MSSMat), CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Département recherche et développements (R&D - SNCF), SNCF, and CSMA

Subjects
Wave propagation, Heterogeneous medium, [PHYS.MECA]Physics [physics]/Mechanics [physics], Ballasted railway track
Abstract

International audience; In this work we consider the description of a granular material as an heterogeneous linear continuum medium and the wave propagation in this continuum medium. The purpose of this modeling is to represent the equivalent stress field obtained in a discrete granular model through a continuum stochastic field of mechanical proprieties. One model was build in a finite element method to identify this continuum stochastic proprieties. We applied this approach in a ballasted railway track. The dynamic equations are solved using a Spectral Element approach using one probabilistic model.

Published
2015

15. Finite Element-Discrete Element Coupling Strategies for the Modelling of Ballast-Soil Interaction

Author

Jean-Charles Voivret, Frédéric Dubois, Paul Taforel, Mathieu Renouf, Laboratoire de Mécanique et Génie Civil ( LMGC ), Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ), Réseaux, Moyens Informatiques, Calcul Scientifique ( Remics ), Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ), Physique et Mécanique des Milieux Divisés ( PMMD ), SNCF : Innovation & Recherche, SNCF, Laboratoire de Mécanique et Génie Civil (LMGC), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Réseaux, Moyens Informatiques, Calcul Scientifique (Remics), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), and Physique et Mécanique des Milieux Divisés (PMMD)

Subjects
Ballast, Engineering, Computer simulation, business.industry, Mechanical engineering, Context (language use), [SPI.MECA.SOLID]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Solid mechanics [physics.class-ph], Track (rail transport), Finite element method, Software, Finite Element Method (FEM), hybrid FEM/DEM model, Coupling (computer programming), Discrete Element Method (DEM), Non-Smooth Contact Dynamics (NSCD), [ SPI.MECA.SOLID ] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of the solides [physics.class-ph], 3D railway track modelling, LMGC90, Element (category theory), Soil/ballast interaction, business
Abstract

International audience; Numerous modelling strategies have been used over the last decade to improve the understanding of the physical behaviour of the railway track system thanks to numerical simulation. In this context, discrete element (DE) methods are traditionally used to describe the granular behaviour of the ballast layer of the railway track whereas finite element (FE) methods are used to model the whole track system (soil and ballast) in which ballast is modelled as a continuous medium. If both approaches offer relevant modelling frameworks to study railway track, this work aims at going further by coupling those two approaches in an hybrid FE-DE model, making possible the improvement of the understanding of the global behaviour of the railway track. This paper aims to describe different aspects of the methodologies which are currently in LMGC90 software.

Published
2015

17. Influence of 3D particle shape on the mechanical behaviour through a novel characterization method

Author

Jean-Noël Roux, Guillaume Perrin, Charles Voivret, and Noura Ouhbi

Subjects
Physics, Ballast, QC1-999, 0211 other engineering and technologies, 02 engineering and technology, Edge (geometry), 01 natural sciences, Discrete element method, Characterization (materials science), Distribution (mathematics), Face (geometry), 0103 physical sciences, Particle, Sensitivity (control systems), Statistical physics, 010306 general physics, Biological system, 021101 geological & geomatics engineering
Abstract

The sensitivity of the mechanical behaviour of railway ballast to particle shape variation is studied through Discrete Element Method (DEM) numerical simulations, focusing on some basic parameters such as solid fraction, coordination number, or force distribution. We present an innovative method to characterize 3D particle shape using Proper Orthogonal Decomposition (POD) of scanned ballast grains with a high accuracy. The method enables not only shape characterization but also the generation of 3D distinct and angular shapes. Algorithms are designed for face and edge recognition.

Published
2017

18. A probabilistic approach of confined comminution in polydisperse granular materials

Author

Pierre-Yves Hicher, Christophe Dano, Charles Voivret, and Carlos Ovalle

Subjects
Materials science, Breakage, Particle-size distribution, Probabilistic logic, Particle, Geotechnical engineering, Mechanics, Comminution, Granular material, Contact force
Abstract

We present a method to predict how grain size distribution (gsd) evolves during confined comminution. We describe particle breakage as a probabilistic phenomenon considering the single particle strength and the pdf of interparticle contact forces from DEM simulations. Our results show a good agreement with published experimental data.

Published
2013

19. Cushioning effect in highly polydisperse granular media

Author

Charles Voivret

Subjects
Materials science, Breakage, Isotropy, Cushioning, Micromechanics, Contact dynamics, Particle size, Composite material, Granular material, Power law
Abstract

Using the Contact Dynamics method in discrete simulations, this paper aims at studying the influence of the size polydispersity on the force transmission properties of 3D granular media. We focus on the micromechanical origin of the so-called “cushioning effect” that prevents the breakage of largest particles in confined comminution process. The samples are composed of nearly 104 spherical particles who’s size distribution follows a power law with different size span (ratio between the extreme sizes). To increase the representativity of our packings we use a fully periodic cell to overcome boundary influence on results. We study frictionless packing at isotropic equilibrium. We show that increasing the size span leads to an efficient space filling but also to an increased heterogeneous force network. To explain the cushioning we then investigate the role of each size class in force transmission.

Published
2013

20. A benchmark for particle shape dependence

Author

Gaël Combe, Cécile Nouguier-Lehon, Émilien Azéma, Krzysztof Szarf, Baptiste Saint-Cyr, Marie Chaze, Farhang Radjaï, Pascal Villard, Jean-Yves Delenne, Vincent Richefeu, Philippe Sornay, Charles Voivret, null CEGEO Group, Laboratoire sols, solides, structures - risques [Grenoble] (3SR), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), GéoMécanique, Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Laboratoire de Tribologie et Dynamique des Systèmes (LTDS), École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Ecole Nationale d'Ingénieurs de Saint Etienne-Centre National de la Recherche Scientifique (CNRS), Physique et Mécanique des Milieux Granulaires (PMMG), Laboratoire de Mécanique et Génie Civil (LMGC), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Ingénierie des Agro-polymères et Technologies Émergentes (UMR IATE), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA), Laboratoire des Combustibles Uranium (LCU), Service d'Analyses, d'Elaboration, d'Expérientations et d'Examens des combustibles (SA3E), Département d'Etudes des Combustibles (DEC), CEA-Direction de l'Energie Nucléaire (CEA-DEN), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-CEA-Direction de l'Energie Nucléaire (CEA-DEN), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Département d'Etudes des Combustibles (DEC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Département recherche et développements (R&D - SNCF), SNCF, Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Université Joseph Fourier - Grenoble 1 (UJF)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Université Joseph Fourier - Grenoble 1 (UJF)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Université Joseph Fourier - Grenoble 1 (UJF)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Laboratoire sols, solides, structures - risques [Grenoble] ( 3S-R ), Université Joseph Fourier - Grenoble 1 ( UJF ) -Institut National Polytechnique de Grenoble ( INPG ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes ( UGA ), Laboratoire de Tribologie et Dynamique des Systèmes ( LTDS ), École Centrale de Lyon ( ECL ), Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État ( ENTPE ) -Ecole Nationale d'Ingénieurs de Saint Etienne-Centre National de la Recherche Scientifique ( CNRS ), Physique et Mécanique des Milieux Granulaires ( PMMG ), Laboratoire de Mécanique et Génie Civil ( LMGC ), Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ), Ingénierie des Agro-polymères et Technologies Émergentes ( IATE ), Centre de Coopération Internationale en Recherche Agronomique pour le Développement ( CIRAD ) -Institut National de la Recherche Agronomique ( INRA ) -Université Montpellier 2 - Sciences et Techniques ( UM2 ) -Centre international d'études supérieures en sciences agronomiques ( Montpellier SupAgro ) -Université de Montpellier ( UM ) -Institut national d’études supérieures agronomiques de Montpellier ( Montpellier SupAgro ), Laboratoire des Combustibles Uranium ( LCU ), Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ), Département recherche et développements ( R&D - SNCF ), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS), Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Ecole Nationale d'Ingénieurs de Saint Etienne (ENISE)-Centre National de la Recherche Scientifique (CNRS), and Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université Montpellier 2 - Sciences et Techniques (UM2)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université de Montpellier (UM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)

Subjects
Materials science, 02 engineering and technology, [SPI.MECA.MSMECA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Materials and structures in mechanics [physics.class-ph], Atomic packing factor, Granular material, 01 natural sciences, Shape parameter, Contact force, [PHYS.MECA.MEMA]Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], Molecular dynamics, Shape Dependence, 0103 physical sciences, [SPI.MECA.MEMA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], [ PHYS.MECA.MSMECA ] Physics [physics]/Mechanics [physics]/Materials and structures in mechanics [physics.class-ph], 010308 nuclear & particles physics, Shear Test, Numerical analysis, Random close pack, Molecular Dynamic, Mechanics, [PHYS.MECA.MSMECA]Physics [physics]/Mechanics [physics]/Materials and structures in mechanics [physics.class-ph], 021001 nanoscience & nanotechnology, [ SPI.MECA.MSMECA ] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Materials and structures in mechanics [physics.class-ph], Polygones, Contact Dynamic, PACS: 45.70.-n, 81.05.Rm, 61.43.Hv, Classical mechanics, [ SPI.MECA.MEMA ] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], [ PHYS.MECA.MEMA ] Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], Clumps, Direct shear test, 0210 nano-technology, Granular Media
Abstract

International audience; Particle shape is a major parameter for the space-filling and strength properties of granular materials. For a systematic investigation of shape effect, a numerical benchmark test was set up within a collaborative group using different numerical methods and particles of various shape characteristics such as elongation, angularity and nonconvexity. Extensive 2D shear simulations were performed in this framework and the shear strength and packing fraction were compared for different shapes.We show that the results may be analyzed in terms of a low-order shape parameter h describing the degree of distortion from a perfectly circular shape. In particular, the shear strength is an increasing function of h with nearly the same trend for all shapes, the differences being of second order compared to h. We also observe a nontrivial behavior of packing fraction which, for all our simulated shapes, increases with h from the random close packing fraction for disks, reaches a peak considerably higher than that for disks, and subsequently declines as h is further increased. Finally, the analysis of contact forces for the same value of h leads to very similar statistics regardless of our specific particle shapes.

Published
2013

21. Particle shape dependence in 2D granular media

Author

Krzysztof Szarf, Emilien Azéma, C. Nouguier-Lehon, Vincent Richefeu, Jean-Yves Delenne, Pascal Villard, Charles Voivret, Gaël Combe, Philippe Sornay, B. Saint-Cyr, Cegeo, Farhang Radjai, Marie Chaze, Physique et Mécanique des Milieux Granulaires ( PMMG ), Laboratoire de Mécanique et Génie Civil ( LMGC ), Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire sols, solides, structures - risques [Grenoble] ( 3S-R ), Université Joseph Fourier - Grenoble 1 ( UJF ) -Institut National Polytechnique de Grenoble ( INPG ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes ( UGA ), Département recherche et développements ( R&D - SNCF ), SNCF, École Centrale de Lyon ( ECL ), Université de Lyon, Laboratoire Sols, Solides, Structures ( 3S ), Université Joseph Fourier - Grenoble 1 ( UJF ), Laboratoire des Combustibles Uranium ( LCU ), Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ), Laboratoire de Tribologie et Dynamique des Systèmes ( LTDS-ENSMSE ), École des Mines de Saint-Étienne ( Mines Saint-Étienne MSE ), Institut Mines-Télécom [Paris]-Institut Mines-Télécom [Paris]-École Centrale de Lyon ( ECL ), Université de Lyon-Université de Lyon-Ecole Nationale d'Ingénieurs de Saint Etienne-Centre National de la Recherche Scientifique ( CNRS ), Physique et Mécanique des Milieux Granulaires (PMMG), Laboratoire de Mécanique et Génie Civil (LMGC), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire sols, solides, structures - risques [Grenoble] (3SR), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Université Joseph Fourier - Grenoble 1 (UJF)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS), Département recherche et développements (R&D - SNCF), École Centrale de Lyon (ECL), Laboratoire Sols, Solides, Structures (3S), Université Joseph Fourier - Grenoble 1 (UJF), Laboratoire des Combustibles Uranium (LCU), Service d'Analyses, d'Elaboration, d'Expérientations et d'Examens des combustibles (SA3E), Département d'Etudes des Combustibles (DEC), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Département d'Etudes des Combustibles (DEC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire de Tribologie et Dynamique des Systèmes (LTDS), Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Ecole Nationale d'Ingénieurs de Saint Etienne-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Société Nationale des Chemins de Fer Français (SNCF), Ingénierie des Agro-polymères et Technologies Émergentes (UMR IATE), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université Montpellier 2 - Sciences et Techniques (UM2)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université de Montpellier (UM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Université de Lyon (COMUE), French government, Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS), and Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Ecole Nationale d'Ingénieurs de Saint Etienne (ENISE)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, ASSEMBLIES, FOS: Physical sciences, General Physics and Astronomy, ELLIPSOIDS, Condensed Matter - Soft Condensed Matter, Granular material, Atomic packing factor, 01 natural sciences, Convexity, Shape parameter, 010305 fluids & plasmas, [PHYS.MECA.MEMA]Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], [SPI]Engineering Sciences [physics], Distortion, [SDV.IDA]Life Sciences [q-bio]/Food engineering, [SPI.MECA.MEMA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], 0103 physical sciences, particle shape, granular matter, [SPI.GPROC]Engineering Sciences [physics]/Chemical and Process Engineering, shear strength, 010306 general physics, packing fraction, Random close pack, friction mobilization, Mechanics, PACKINGS, Condensed Matter::Soft Condensed Matter, [ PHYS.MECA.MEMA ] Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], [ SPI.MECA.MEMA ] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], Soft Condensed Matter (cond-mat.soft), Particle, Shear strength (discontinuity)
Abstract

Particle shape is a key to the space-filling and strength properties of granular matter. We consider a shape parameter $\eta$ describing the degree of distortion from a perfectly spherical shape. Encompassing most specific shape characteristics such as elongation, angularity and nonconvexity, $\eta$ is a low-order but generic parameter that we used in a numerical benchmark test for a systematic investigation of shape-dependence in sheared granular packings composed of particles of different shapes. We find that the shear strength is an increasing function of $\eta$ with nearly the same trend for all shapes, the differences appearing thus to be of second order compared to $\eta$. We also observe a nontrivial behavior of packing fraction which, for all our simulated shapes, increases with $\eta$ from the random close packing fraction for disks, reaches a peak considerably higher than that for disks, and subsequently declines as $\eta$ is further increased. These findings suggest that a low-order description of particle shape accounts for the principal trends of packing fraction and shear strength. Hence, the effect of second-order shape parameters may be investigated by considering different shapes at the same level of $\eta$., Comment: 5 pages, 8 figures

Published
2012

22. Rheology of granular materials composed of nonconvex particles

Author

Charles Voivret, Jean-Yves Delenne, Baptiste Saint-Cyr, Philippe Sornay, Farhang Radjai, Physique et Mécanique des Milieux Granulaires (PMMG), Laboratoire de Mécanique et Génie Civil (LMGC), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Combustibles Uranium (LCU), Service d'Analyses, d'Elaboration, d'Expérientations et d'Examens des combustibles (SA3E), Département d'Etudes des Combustibles (DEC), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Département d'Etudes des Combustibles (DEC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Ingénierie des Agro-polymères et Technologies Émergentes (UMR IATE), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA), Département recherche et développements (R&D - SNCF), SNCF, Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), CEA-Direction de l'Energie Nucléaire (CEA-DEN), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-CEA-Direction de l'Energie Nucléaire (CEA-DEN), Physique et Mécanique des Milieux Granulaires ( PMMG ), Laboratoire de Mécanique et Génie Civil ( LMGC ), Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ), Ingénierie des Agro-polymères et Technologies Émergentes ( IATE ), Centre de Coopération Internationale en Recherche Agronomique pour le Développement ( CIRAD ) -Institut National de la Recherche Agronomique ( INRA ) -Université Montpellier 2 - Sciences et Techniques ( UM2 ) -Centre international d'études supérieures en sciences agronomiques ( Montpellier SupAgro ) -Université de Montpellier ( UM ) -Institut national d’études supérieures agronomiques de Montpellier ( Montpellier SupAgro ), Département recherche et développements ( R&D - SNCF ), Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire des Combustibles Uranium ( LCU ), and Commissariat à l'énergie atomique et aux énergies alternatives ( CEA )

Subjects
Materials science, Isotropy, Mechanics, Granular material, Atomic packing factor, 01 natural sciences, 010305 fluids & plasmas, [PHYS.MECA.MEMA]Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], Rheology, [ PHYS.MECA.MEMA ] Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], [ SPI.MECA.MEMA ] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], 0103 physical sciences, [SPI.MECA.MEMA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], Shear strength, Particle, Contact dynamics, 010306 general physics, Anisotropy, ComputingMilieux_MISCELLANEOUS
Abstract

International audience; By means of contact dynamics simulations, we investigate the shear strength and internal structure of granular materials composed of two-dimensional nonconvex aggregates. We find that the packing fraction first grows as the nonconvexity is increased but declines at higher nonconvexity. This unmonotonic dependence reflects the competing effects of pore size reduction between convex borders of aggregates and gain in porosity at the nonconvex borders that are captured in a simple model fitting nicely the simulation data both in the isotropic and sheared packings. On the other hand, the internal angle of friction increases linearly with nonconvexity and saturates to a value independent of nonconvexity. We show that fabric anisotropy, force anisotropy, and friction mobilization, all enhanced by multiple contacts between aggregates, govern the observed increase of shear strength and its saturation with increasing nonconvexity. The main effect of interlocking is to dislocate frictional dissipation from the locked double and triple contacts between aggregates to the simple contacts between clusters of aggregates. This self-organization of particle motions allows the packing to keep a constant shear strength at high nonconvexity.

Published
2011

23. Force transmission in cohesive granular media

Author

Farhang Radjai, Vincent Topin, Vincent Richefeu, Charles Voivret, Jean-Yves Delenne, Emilien Azéma, Said El Youssoufi, Joe Goddard, Pasquale Giovine, and James T. Jenkins

Subjects
Condensed Matter::Soft Condensed Matter, Materials science, Classical mechanics, Capillary bridges, Discretization, Capillary action, Particle-size distribution, Particle size, Mechanics, Granular material, Discrete element method, Contact force
Abstract

We use numerical simulations to investigate force and stress transmission in cohesive granular media covering a wide class of materials encountered in nature and industrial processing. The cohesion results either from capillary bridges between particles or from the presence of a solid binding matrix filling fully or partially the interstitial space. The liquid bonding is treated by implementing a capillary force law within a debonding distance between particles and simulated by the discrete element method. The solid binding matrix is treated by means of the Lattice Element Method (LEM) based on a lattice-type discretization of the particles and matrix. Our data indicate that the exponential fall-off of strong compressive forces is a generic feature of both cohesive and noncohesive granular media both for liquid and solid bonding. The tensile forces exhibit a similar decreasing exponential distribution, suggesting that this form basically reflects granular disorder. This is consistent with the finding that not only the contact forces but also the stress components in the bulk of the particles and matrix, accessible from LEM simulations in the case of solid bonding, show an exponential fall-off. We also find that the distribution of weak compressive forces is sensitive to packing anisotropy, particle shape and particle size distribution. In the case of wet packings, we analyze the self-equilibrated forces induced by liquid bonds and show that the positive and negative particle pressures form a bi-percolating structure.

Published
2010

24. Multiscale Force Networks in Highly Polydisperse Granular Media

Author

Jean-Yves Delenne, Farhang Radjai, M. S. El Youssoufi, Charles Voivret, Département recherche et développements ( R&D - SNCF ), SNCF, Physique et Mécanique des Milieux Granulaires ( PMMG ), Laboratoire de Mécanique et Génie Civil ( LMGC ), Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ), Département recherche et développements (R&D - SNCF), Physique et Mécanique des Milieux Granulaires (PMMG), Laboratoire de Mécanique et Génie Civil (LMGC), and Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, fabric anisotropy, Strong interaction, 0211 other engineering and technologies, General Physics and Astronomy, 02 engineering and technology, Weak interaction, Granular material, 01 natural sciences, [PHYS.MECA.MEMA]Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], 0103 physical sciences, [SPI.MECA.MEMA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], Cohesion (geology), granular matter, force distribution, Contact dynamics, shear strength, 010306 general physics, Anisotropy, 021101 geological & geomatics engineering, polydspersity, Mechanics, Simple shear, Condensed Matter::Soft Condensed Matter, Classical mechanics, [ PHYS.MECA.MEMA ] Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], [ SPI.MECA.MEMA ] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], Particle size, contact anisotropy
Abstract

International audience; We investigate highly polydisperse packings subjected to simple shear by contact dynamics simula- tions. A major unsolved issue is how granular texture and force chains depend on the size polydispersity and how far they influence the shear strength. The numerical treatment was made possible by ensuring the statistical representativity of particle size classes. An unexpected finding is that the internal friction angle is independent of polydispersity. We show that this behavior is related to two mechanisms underlying the stability of force chains: (i) The class of largest particles captures strong force chains, and (ii) these chains are equilibrated by weak forces carried by increasingly smaller particles as the size span broadens. In the presence of adhesion between particles, the Coulomb cohesion increases with size polydispersity as a result of enhanced force anisotropy.

Published
2009

25. Morphology of Polydisperse Granular Media

Author

Moulay Saïd El Youssoufi, Farhang Radjai, Jean-Yves Delenne, and Charles Voivret

Subjects
Condensed Matter::Soft Condensed Matter, Nonlinear system, Uniform distribution (continuous), Materials science, Volume (thermodynamics), Dispersity, Deposition (phase transition), Particle, Mechanics, Anisotropy, Span (engineering)
Abstract

We investigate the morphology and space-filling properties of polydisperse densely-packed granular media in 2D. A numerical procedure is introduced to generate collections of circular particles with size distributions of variable size span. This particle generation procedure is used with a geometric deposition protocol in order to build large close-packed samples of prescribed polydispersity. The solid fraction is a strongly nonlinear function of the size span, and the highest levels of solid fraction occur for the uniform distribution by volume fractions. A transition occurs from a regime of topological disorder where the packing properties are governed by particle connectivity to a regime of metric disorder where pore-filling small particles prevail. The polydispersity manifests itself in the first regime through the variability of local coordination numbers. In the second regime, the material is homogeneous beyond only a few average particle diameters. We also show that the fabric anisotropy declines with size span.

Published
2009

26. Space-filling properties of polydisperse granular media

Author

Charles Voivret, Farhang Radjai, Jean-Yves Delenne, M. S. El Youssoufi, Département recherche et développements (R&D - SNCF), SNCF, Laboratoire de Mécanique et Génie Civil (LMGC), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Ingénierie des Agro-polymères et Technologies Émergentes (UMR IATE), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA), Physique et Mécanique des Milieux Granulaires (PMMG), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Département recherche et développements ( R&D - SNCF ), Laboratoire de Mécanique et Génie Civil ( LMGC ), Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ), Ingénierie des Agro-polymères et Technologies Émergentes ( IATE ), Centre de Coopération Internationale en Recherche Agronomique pour le Développement ( CIRAD ) -Institut National de la Recherche Agronomique ( INRA ) -Université Montpellier 2 - Sciences et Techniques ( UM2 ) -Centre international d'études supérieures en sciences agronomiques ( Montpellier SupAgro ) -Université de Montpellier ( UM ) -Institut national d’études supérieures agronomiques de Montpellier ( Montpellier SupAgro ), Physique et Mécanique des Milieux Granulaires ( PMMG ), Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), and Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)

Subjects
Uniform distribution (continuous), Materials science, Particle number, Dispersity, Geometry, Granular material, 01 natural sciences, 010305 fluids & plasmas, [PHYS.MECA.MEMA]Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], [ PHYS.MECA.MEMA ] Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], [ SPI.MECA.MEMA ] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], [SPI.MECA.MEMA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], 0103 physical sciences, Particle, Particle size, Statistical physics, 010306 general physics, Anisotropy, Porous medium, ComputingMilieux_MISCELLANEOUS
Abstract

We present a systematic investigation of the morphology and space-filling properties of polydisperse densely packed granular media in two dimensions. A numerical procedure is introduced to generate collections of circular particles with size distributions of variable shape and span constrained by explicit criteria of statistical representativity. We characterize the domain of statistically accessible distribution parameters for a bounded number of particles. This particle generation procedure is used with two different deposition protocols in order to build large close-packed samples of prescribed polydispersity. We find that the solid fraction is a strongly nonlinear function of the size span, and the highest levels of solid fraction occur for the uniform distribution by volume fractions. As the span is increased, a transition occurs from a regime of topological disorder where the packing properties are governed by particle connectivity to a regime of metric disorder where pore-filling small particles prevail. The polydispersity manifests itself in the first regime through the variability of local coordination numbers. We observe a continuous decrease of the number of particles with four contacts and the growth of two populations of particles with three and five contacts. In the second regime, radial distribution functions show that the material is homogeneous beyond only a few average particle diameters. We also show that the packing orientational order is linked with fabric anisotropy and it declines with size span.

Published
2007

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