@article {667, title = {Parallel implicit contact algorithm for soft particle systems}, journal = {Computer Physics Communications}, volume = {237}, year = {2019}, month = {Apr-01-2019}, pages = {17 - 25}, abstract = {

This paper presents a numerical technique to model soft particle materials in which the particles can undergo large deformations. It combines an implicit finite strain formalism of the Material Point Method and the Contact Dynamics method. In this framework, the large deformations of individual particles as well as their collective interactions are treated consistently. In order to reduce the computational cost, this method is parallelised using the Message Passing Interface (MPI) strategy. Using this approach, we investigate the uniaxial compaction of 2D packings composed of particles governed by a Neo-Hookean material behaviour. We consider compressibility rates ranging from fully compressible to incompressible particles. The packing deformation mechanism is a combination of both particle rearrangements and large deformations, and leads to high packing fractions beyond the jamming state. We show that the packing strength declines when the particle compressibility decreases, and the packing can deform considerably. We also discuss the evolution of the connectivity of the particles and particle deformation distributions in the packing. (C) 2018 Elsevier B.V. All rights reserved.

}, issn = {00104655}, doi = {10.1016/j.cpc.2018.10.030}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0010465518303904}, author = {Saeid Nezamabadi and Frank, Xavier and Jean-Yves Delenne and Julien Averseng and Farhang Radja{\"\i}} } @article {533, title = {Mechanical strength of wet particle agglomerates}, journal = {Mechanics Research Communications}, volume = {92}, year = {2018}, month = {Sep-2018}, pages = {1 - 7}, abstract = {

Using particle dynamics simulations, we investigate the strength and microstructure of agglomerates of wet frictional particles subjected to axial compression. The numerical model accounts for the cohesive and viscous effects of the binding liquid up to a debonding distance with the liquid assumed to be distributed homogeneously inside the agglomerate. We show that wet agglomerates undergo plastic deformation due to the rearrangements of primary particles during compression. The compressive strength is thus characterized by the plastic threshold before the onset of failure by the irreversible loss of wet contacts between primary particles. We find that the agglomerate plastic threshold is proportional to the characteristic cohesive stress defined from the liquid-vapor surface tension and the mean diameter of primary particles, with a prefactor that is a nearly linear function of the debonding distance and increases with size span. We analyze the agglomerate microstructure and, considering only the cohesive capillary forces at all bonds between primary particles, we propose an expression of the plastic strength as a function of the texture parameters such as the wet coordination number and packing fraction. This expression is shown to be consistent with our simulations up to a multiplicative factor reflecting the distribution of the capillary bridges. (C) 2018 Published by Elsevier Ltd.

Fig. 1. Schematic drawing of the forces acting on particle i by a contacting particle j{\textellipsis}

Fig. 2. Schematic representation of diametrical compression test (a), and snapshots of{\textellipsis}

Fig. 3. Snapshot of a granule under diametrical compression for α=1

Fig. 4. Vertical strength σzz normalized by the reference stress σc for different{\textellipsis}

Fig. 5. Normalized plastic strength of the granule for several values of the debonding{\textellipsis}

Fig. 6. Normalized plastic strength σp/σc of the granules for different values of the{\textellipsis}

Fig. 7. The initial wet coordination number Z0 of the granules for different values of{\textellipsis}

Fig. 8. The prefactor η in Eq

Fig. 9. The ZΦs in Eq

}, issn = {00936413}, doi = {10.1016/j.mechrescom.2018.07.003}, url = {https://www-sciencedirect-com.libproxy.mit.edu/science/article/pii/S0093641318301216}, author = {Vo, Thanh-Trung and Patrick Mutabaruka and Saeid Nezamabadi and Jean-Yves Delenne and Izard, Edouard and Roland Jean-Marc Pellenq and Farhang Radja{\"\i}} } @article {627, title = {Multiscale modeling for bioresources and bioproducts}, journal = {Innovative Food Science \& Emerging Technologies}, volume = {46}, year = {2018}, month = {Avr-2018}, pages = {41 - 53}, abstract = {

Designing and processing complex matter and materials are key objectives of bioresource and bioproduct research. Modeling approaches targeting such systems have to account for their two main sources of complexity: their intrinsic multi-scale nature; and the variability and heterogeneity inherent to all living systems. Here we provide insight into methods developed at the Food \& Bioproduct Engineering division (CEPIA) of the French National Institute of Agricultural Research (INRA). This brief survey focuses on innovative research lines that tackle complexity by mobilizing different approaches with complementary objectives. On one hand cognitive approaches aim to uncover the basic mechanisms and laws underlying the emerging collective properties and macroscopic behavior of soft-matter and granular systems, using numerical and experimental methods borrowed from physics and mechanics. The corresponding case studies are dedicated to the structuring and phase behavior of biopolymers, powders and granular materials, and to the evolution of these structures caused by external constraints. On the other hand machine learning approaches can deal with process optimizations and outcome predictions by extracting useful information and correlations from huge datasets built from experiments at different length scales and in heterogeneous conditions. These predictive methods are illustrated in the context of cheese ripening, grape maturity prediction and bacterial production.

}, issn = {14668564}, doi = {10.1016/j.ifset.2017.09.015}, url = {https://linkinghub.elsevier.com/retrieve/pii/S1466856417302230}, author = {Barnabe, M. and Blanc, Nicolas and Chabin, T. and Jean-Yves Delenne and Duri, A. and Frank, Xavier and Hugouvieux, V. and Lutton, E. and Mabille, F. and Saeid Nezamabadi and Perrot, N. and Farhang Radja{\"\i} and Ruiz, T. and Tonda, A.} } @article {626, title = {Rheology of granular materials composed of crushable particles}, journal = {The European Physical Journal E}, volume = {41}, year = {2018}, month = {Apr-11-2018}, pages = { Article Number 50 }, abstract = {

We investigate sheared granular materials composed of crushable particles by means of contact dynamics simulations and the bonded-cell model for particle breakage. Each particle is paved by irregular cells interacting via cohesive forces. In each simulation, the ratio of the internal cohesion of particles to the confining pressure, the relative cohesion, is kept constant and the packing is subjected to biaxial shearing. The particles can break into two or more fragments when the internal cohesive forces are overcome by the action of compressive force chains between particles. The particle size distribution evolves during shear as the particles continue to break. We find that the breakage process is highly inhomogeneous both in the fragment sizes and their locations inside the packing. In particular, a number of large particles never break whereas a large number of particles are fully shattered. As a result, the packing keeps the memory of its initial particle size distribution, whereas a power-law distribution is observed for particles of intermediate size due to consecutive fragmentation events whereby the memory of the initial state is lost. Due to growing polydispersity, dense shear bands are formed inside the packings and the usual dilatant behavior is reduced or cancelled. Hence, the stress-strain curve no longer passes through a peak stress, and a progressive monotonic evolution towards a pseudo-steady state is observed instead. We find that the crushing rate is controlled by the confining pressure. We also show that the shear strength of the packing is well expressed in terms of contact anisotropies and force anisotropies. The force anisotropy increases while the contact orientation anisotropy declines for increasing internal cohesion of the particles. These two effects compensate each other so that the shear strength is nearly independent of the internal cohesion of particles.

}, keywords = {CONTACT DYNAMICS METHOD; DISCRETE ELEMENT METHOD; SHEAR BANDS; NUMERICAL-SIMULATION; BED COMMINUTION; FRAGMENTATION; BREAKAGE; ROCK; DEM; MODEL}, issn = {1292-8941}, doi = {10.1140/epje/i2018-11656-1}, url = {http://link.springer.com/10.1140/epje/i2018-11656-1}, author = {Duc-Hanh Nguyen and Emilien Az{\'e}ma and Philippe Sornay and Farhang Radja{\"\i}} } @article {633, title = {Two-dimensional numerical simulation of chimney fluidization in a granular medium using a combination of discrete element and lattice Boltzmann methods}, journal = {Physical Review E}, volume = {97}, year = {2018}, month = {May-10-2018}, pages = { Article Number 052902 }, abstract = {

We present here a numerical study dedicated to the fluidization of a submerged granular medium induced by a localized fluid injection. To this end, a two-dimensional (2D) model is used, coupling the lattice Boltzmann method (LBM) with the discrete element method (DEM) for a relevant description of fluid-grains interaction. An extensive investigation has been carried out to analyze the respective influences of the different parameters of our configuration, both geometrical (bed height, grain diameter, injection width) and physical (fluid viscosity, buoyancy). Compared to previous experimental works, the same qualitative features are recovered as regards the general phenomenology including transitory phase, stationary states, and hysteretic behavior. We also present quantitative findings about transient fluidization, for which several dimensionless quantities and scaling laws are proposed, and about the influence of the injection width, from localized to homogeneous fluidization. Finally, the impact of the present 2D geometry is discussed, by comparison to the real three-dimensional (3D) experiments, as well as the crucial role of the prevailing hydrodynamic regime within the expanding cavity, quantified through a cavity Reynolds number, that can presumably explain some substantial differences observed regarding upward expansion process of the fluidized zone when the fluid viscosity is changed.

}, issn = {2470-0045}, doi = {10.1103/PhysRevE.97.052902}, url = {https://link.aps.org/doi/10.1103/PhysRevE.97.052902}, author = {Jeff Ngoma and Pierre Philippe and St{\'e}phane Bonelli and Farhang Radja{\"\i} and Jean-Yves Delenne} } @article {600, title = {Cohesive strength of iron ore granules}, journal = {EPJ Web of Conferences}, volume = {140}, year = {2017}, month = {Jun-30-2017}, pages = {Article Number 08020}, abstract = {

We present an experimental and numerical investigation of the mechanical strength of crude iron ore (Hematite) granules in which capillary bonds between primary particles are the source of internal cohesion. The strength is measured by subjecting the granules to vertical compression between two plates. We show that the behavior of the granules is ductile with a well-defined plastic threshold which increases with the amount of water. It is found that the compressive strength scales with capillary cohesion with a pre-factor that is nearly independent of size polydispersity for the investigated range of parameters but increases with friction coefficient between primary particles. This weak dependence may be attributed to the class of fine particles which, due to their large number, behaves as a cohesive matrix that controls the strength of the granule.

}, doi = {10.1051/epjconf/201714008020}, url = {http://www.epj-conferences.org/10.1051/epjconf/201714008020}, author = {Contreras, Rafael Jaimes and Berger, Nicolas and Izard, Edouard and Douce, Jean-Fran{\c c}ois and Koltsov, Alexey and Jean-Yves Delenne and Emilien Az{\'e}ma and Saeid Nezamabadi and van Loo, Fr{\'e}d{\'e}ric and Roland Jean-Marc Pellenq and Farhang Radja{\"\i}}, editor = {Luding, S.} } @article {602, title = {Compaction of granular materials composed of deformable particles}, journal = {EPJ Web of Conferences}, volume = {140}, year = {2017}, month = {Jun-30-2017}, pages = {Article Number 05013}, abstract = {

In soft particle materials such as metallic powders the particles can undergo large deformations without rupture. The large elastic or plastic deformations of the particles are expected to strongly affect the mechanical properties of these materials compared to hard particle materials more often considered in research on granular materials. Herein, two numerical approaches are proposed for the simulation of soft granular systems: (i) an implicit formulation of the Material Point Method (MPM) combined with the Contact Dynamics (CD) method to deal with contact interactions, and (i) Bonded Particle Model (BPM), in which each deformable particle is modeled as an aggregate of rigid primary particles using the CD method. These two approaches allow us to simulate the compaction of an assembly of elastic or plastic particles. By analyzing the uniaxial compaction of 2D soft particle packings, we investigate the effects of particle shape change on the stress-strain relationship and volume change behavior as well as the evolution of the microstructure.

}, doi = {10.1051/epjconf/201714005013}, url = {http://www.epj-conferences.org/10.1051/epjconf/201714005013}, author = {Thanh Hai Nguyen and Saeid Nezamabadi and Jean-Yves Delenne and Farhang Radja{\"\i}}, editor = {Luding, S.} } @article {601, title = {Effect of particle size distribution on 3D packings of spherical particles}, journal = {EPJ Web of Conferences}, volume = {140}, year = {2017}, month = {Jun-30-2017}, pages = {Article Number 02030}, abstract = {

We use molecular dynamics simulations of frictionless spherical particles to investigate a class of polydisperse granular materials in which the particle size distribution is uniform in particle volumes. The particles are assembled in a box by uniaxial compaction under the action of a constant stress. Due to the absence of friction and the nature of size distribution, the generated packings have the highest packing fraction at a given size span, defined as the ratio of the largest size to the smallest size. We find that, up to = 5, the packing fraction is a nearly linear function of . While the coordination number is nearly constant due to the isostatic nature of the packings, we show that the connectivity of the particles evolves with . In particular, the proportion of particles with 4 contacts represents the largest proportion of particles mostly of small size. We argue that this particular class of particles occurs as a result of the high stability of local configurations in which a small particle is stuck by four larger particles.

}, doi = {10.1051/epjconf/201714002030}, url = {http://www.epj-conferences.org/10.1051/epjconf/201714002030}, author = {Taiebat, Mahdi and Patrick Mutabaruka and Roland Jean-Marc Pellenq and Farhang Radja{\"\i}}, editor = {Saeid Nezamabadi and Luding, S. and Jean-Yves Delenne} } @article {606, title = {Modeling root growth in granular soils: effects of root stiffness and packing fraction}, journal = {EPJ Web of Conferences}, volume = {140}, year = {2017}, month = {Jun-30-2017}, pages = {Article Number 14013}, abstract = {

We use molecular dynamics simulations to investigate the effects of root bending stiffness and packing fraction on the path followed by a growing root in 2D packings of grains representing a soil. The root is modeled as a chain of elements that can grow in length and change their direction depending on the forces exerted by soil grains. We show that the root shape is mainly controlled by the bending stiffness of its apex. At low stiffness, the root randomly explores the pore space whereas at sufficiently high stiffness, of the order of soil hardness multiplied by mean grain size, the root follows a straight path across the soil. Between these two limits, the root shape can be characterized by the standard deviation of its re-directions at the scale of soil grains. We find that this shape parameter varies as a power-law function of the normalized bending stiffness.

}, doi = {10.1051/epjconf/201714014013}, url = {http://www.epj-conferences.org/10.1051/epjconf/201714014013}, author = {Fakih, Mahmoud and Jean-Yves Delenne and Farhang Radja{\"\i} and Fourcaud, Thierry}, editor = {Saeid Nezamabadi and Luding, S.} } @article {265, title = {Modeling soft granular materials}, journal = {Granular Matter}, volume = {19}, year = {2017}, month = {Jun-17-2017}, pages = {Article Number: 8}, abstract = {

Soft-grain materials such as clays and other colloidal pastes share the common feature of being composed of grains that can undergo large deformations without rupture. For the simulation of such materials, we present two alternative methods: (1) an implicit formulation of the material point method (MPM), in which each grain is discretized as a collection of material points, and (2) the bonded particle model (BPM), in which each soft grain is modeled as an aggregate of rigid particles using the contact dynamics method. In the MPM, a linear elastic behavior is used for the grains. In order to allow the aggregates in the BPM to deform without breaking, we use long-range center-to-center attraction forces between the primary particles belonging to each grain together with steric repulsion at their contact points. We show that these interactions lead to a plastic behavior of the grains. Using both methods, we analyze the uniaxial compaction of 2D soft granular packings. This process is nonlinear and involves both grain rearrangements and large deformations. High packing fractions beyond the jamming state are reached as a result of grain shape change for both methods. We discuss the stress-strain and volume change behavior as well as the evolution of the connectivity of the grains. Similar textures are observed at large deformations although the BPM requires higher stress than the MPM to reach the same level of packing fraction.

}, issn = {1434-5021}, doi = {10.1007/s10035-016-0689-y}, author = {Saeid Nezamabadi and Thanh Hai Nguyen and Jean-Yves Delenne and Farhang Radja{\"\i}} } @proceedings {337, title = {MPM with Frictional Contact for Application to Soft Particulate Materials}, journal = {PROCEEDINGS OF THE 1ST INTERNATIONAL CONFERENCE ON THE MATERIAL POINT METHOD (MPM 2017) Book Series: Procedia Engineering }, volume = {175}, year = {2017}, month = {Mar-23-2017}, pages = {141 - 147}, publisher = {Elsevier Ltd.}, address = {JAN 10-13, 2017, Delft, NETHERLANDS}, abstract = {

Soft particle materials are composed of discrete particles that can undergo large deformations without rupture. Most food products, many powders, colloidal pastes, vesicles and biological cells are soft particle systems. In order to model such materials, we present an efficient numerical approach combining an implicit formulation of the Material Point Method (MPM) and Contact Dynamics (CD) method. The MPM deals with bulk variables of an individual particle by discretizing it as a collection of material points, whereas the CD allows for the treatment of frictional contacts between particles. This model is applied for the simulation of the uniaxial compression of 2D soft-particle packings. The compaction is a nonlinear process in which new contacts are formed between particles and the contact areas increase. The change of particle shapes allows these materials to reach high packing fraction. We find that the contact specific surface, the orientation anisotropy and the aspect ratio of particles increase as a function of the packing fraction but at different rates. We also evidence the effect of friction, which favors strong stress chains and thus the elongation of particles, leading to larger values of the orientation anisotropy and the aspect ratio at a given level of packing fraction as compared to a frictionless particle packing.

}, issn = {18777058}, doi = {10.1016/j.proeng.2017.01.044}, author = {Saeid Nezamabadi and Thanh Hai Nguyen and Jean-Yves Delenne and Julien Averseng and Frank, Xavier and Farhang Radja{\"\i}}, editor = {Rohe, A and Kenichi Soga and Teunissen, H} } @article {623, title = {Nano-granular texture of cement hydrates}, journal = {EPJ Web of Conferences}, volume = {140}, year = {2017}, month = {Jun-30-2017}, pages = {Article Number 15027}, abstract = {

Mechanical behavior of concrete crucially depends on cement hydrates, the \“glue\” of cement. The design of high performance and more environmentally friendly cements demands a deeper understanding of the formation of the multiscale structure of cement hydrates, when they precipitate and densify. We investigate the precipitation and setting of nano-grains of cement hydrates using a combination of Monte Carlo and Molecular Dynamics numerical simulations and study their texture from nano up to the micron scale. We characterize the texture of cement hydrates using the local volume fraction distribution, the pore size distribution, the scattering intensity and the chord length distribution and we compare them with experiments. Our nano-granular model provides cement structure with realistic texture and mechanics and can be further used to investigate degradation mechanisms.

}, doi = {10.1051/epjconf/201714015027}, url = {http://www.epj-conferences.org/10.1051/epjconf/201714015027}, author = {Katerina Ioannidou and Franz-Josef Ulm and Pierre E. Levitz and Emanuela Del Gado and Roland Jean-Marc Pellenq}, editor = {Farhang Radja{\"\i} and Saeid Nezamabadi and Luding, S. and Jean-Yves Delenne} } @article {604, title = {Numerical insight into the micromechanics of jet erosion of a cohesive granular material}, journal = {EPJ Web of Conferences}, volume = {140}, year = {2017}, month = {Jun-30-2017}, pages = {Article Number 15017}, abstract = {

Here we investigate the physical mechanisms behind the surface erosion of a cohesive granular soil induced by an impinging jet by means of numerical simulations coupling fluid and grains at the microscale. The 2D numerical model combines the Discrete Element and Lattice Boltzmann methods (DEM-LBM) and accounts for the granular cohesion with a contact model featuring a paraboloidal yield surface. Here we review first the hydrodynamical conditions imposed by the fluid jet on a solid granular packing, turning then the attention to the impact of cohesion on the erosion kinetics. Finally, the use of an additional subcritical debonding damage model based on the work of Silvani and co-workers provides a novel insight into the internal solicitation of the cohesive granular sample by the impinging jet.

}, doi = {10.1051/epjconf/201714015017}, url = {http://www.epj-conferences.org/10.1051/epjconf/201714015017}, author = {Cuellar, Pablo and Benseghier, Zeyd and Luu, Li-Hua and St{\'e}phane Bonelli and Jean-Yves Delenne and Farhang Radja{\"\i} and Pierre Philippe}, editor = {Saeid Nezamabadi and Luding, S.} } @article {608, title = {Numerical modeling of the tensile strength of a biological granular aggregate: Effect of the particle size distribution}, journal = {EPJ Web of Conferences}, volume = {140}, year = {2017}, month = {Jun-30-2017}, pages = {Article Number 08013}, abstract = {

Wheat grains can be considered as a natural cemented granular material. They are milled under high forces to produce food products such as flour. The major part of the grain is the so-called starchy endosperm. It contains stiff starch granules, which show a multi-modal size distribution, and a softer protein matrix that surrounds the granules. Experimental milling studies and numerical simulations are going hand in hand to better understand the fragmentation behavior of this biological material and to improve milling performance. We present a numerical study of the effect of granule size distribution on the strength of such a cemented granular material. Samples of bi-modal starch granule size distribution were created and submitted to uniaxial tension, using a peridynamics method. We show that, when compared to the effects of starch-protein interface adhesion and voids, the granule size distribution has a limited effect on the samples\’ yield stress.

}, doi = {10.1051/epjconf/201714008013}, url = {http://www.epj-conferences.org/10.1051/epjconf/201714008013}, author = {Heinze, Karsta and Frank, Xavier and Val{\'e}rie Lullien-Pellerina and George, Matthieu and Farhang Radja{\"\i} and Jean-Yves Delenne}, editor = {Saeid Nezamabadi and Luding, S.} } @article {603, title = {Numerical study of the failure of materials embedding soft to hard particles}, journal = {EPJ Web of Conferences}, volume = {140}, year = {2017}, month = {Jun-30-2017}, pages = {Article Number 02029}, abstract = {

In this study, we use a bond-based peridynamic approach to investigate the mechanical strength and cracking of composite materials with spherical inclusions. The total volume fraction of particles and the particle-matrix toughness ratio were varied to cover a range of soft to hard inclusions. The mean particle damage was characterized together with crack patterns at a sub-particle scale. Three types of crack patterns are identified depending on the toughness ratio.

}, doi = {10.1051/epjconf/201714002029}, url = {http://www.epj-conferences.org/10.1051/epjconf/201714002029}, author = {Frank, Xavier and Jean-Yves Delenne and Farhang Radja{\"\i}}, editor = {Saeid Nezamabadi and Luding, S.} } @article {597, title = {Peridynamics simulation of the comminution of particles containing microcraks}, journal = {EPJ Web of Conferences}, volume = {140}, year = {2017}, month = {Jun-30-2017}, pages = {Article Number 07018}, abstract = {

In this study, we rely on a \’bond-based\’ peridynamic approach to investigate the strength and failure of 2D particles containing a collection of 1D microcracks. The mechanical tests were performed on disks under diametral compression. In an extensive parametric study, the distribution of microcracks was varied for different particle sizes. The evolution of yield stress with diameter and the probability of failure in terms of Weibull distributions are investigated in detail. Finally, by means of a floodfill algorithm, we analyze the variation of the mean fragment size as a function of the density of defects.

}, doi = {10.1051/epjconf/201714007018}, url = {http://www.epj-conferences.org/10.1051/epjconf/201714007018}, author = {Blanc, Nicolas and Frank, Xavier and Mayer-Laigle, Claire and Farhang Radja{\"\i} and Jean-Yves Delenne}, editor = {Saeid Nezamabadi and Luding, S. and Jean-Yves Delenne} } @article {622, title = {The Potential of Mean Force concept for bridging (length and time) scales in the modeling of complex porous materials}, journal = {EPJ Web of Conferences}, volume = {140}, year = {2017}, month = {Jun-30-2017}, pages = {Article Number 01009}, abstract = {

We introduce the concept of Potential of Mean Force, PMF, as a way to implement upscaling modeling from the nano-scale to micron-scale. A PMF is a free energy function representing in an effective way the interactions between objects (cement hydrates, clay platelets, etc.) at thermodynamics conditions. The PMF is therefore the key piece of information allowing to coarse-grained Physical-Chemistry information in a meso-scale model formulation. The use of PMF offers a huge computational advantage as it allows a straight up-scaling to the meso-scale while keeping essential interactions information that are the hallmark of Physical-Chemistry processes. Such a coarse-grained modeling integrates atomistic response into inter-particle potentials that fully propagate molecular scale information all the way to the meso-scale.

}, doi = {10.1051/epjconf/201714001009}, url = {http://www.epj-conferences.org/10.1051/epjconf/201714001009}, author = {Katerina Ioannidou and Benoit Carrier and Matthieu Vandamme and Roland Jean-Marc Pellenq}, editor = {Farhang Radja{\"\i} and Saeid Nezamabadi and Luding, S. and Jean-Yves Delenne} } @article {607, title = {Scaling behavior of immersed granular flows}, journal = {EPJ Web of Conferences}, volume = {140}, year = {2017}, month = {Jun-30-2017}, pages = {Article Number 09044}, abstract = {

The shear behavior of granular materials immersed in a viscous fluid depends on fluid properties (viscosity, density), particle properties (size, density) and boundary conditions (shear rate, confining pressure). Using computational fluid dynamics simulations coupled with molecular dynamics for granular flow, and exploring a broad range of the values of parameters, we show that the parameter space can be reduced to a single parameter that controls the packing fraction and effective friction coefficient. This control parameter is a modified inertial number that incorporates viscous effects.

}, doi = {10.1051/epjconf/201714009044}, url = {http://www.epj-conferences.org/10.1051/epjconf/201714009044}, author = {L. Amarsid and Jean-Yves Delenne and Patrick Mutabaruka and Yann Monerie and Perales, F. and Farhang Radja{\"\i}}, editor = {Saeid Nezamabadi and Luding, S.} } @article {605, title = {Small solar system bodies as granular systems}, journal = {EPJ Web of Conferences}, volume = {140}, year = {2017}, month = {Jun-30-2017}, pages = {Article Number 14011}, abstract = {

Asteroids and other Small Solar System Bodies (SSSBs) are currently of great scientific and even industrial interest. Asteroids exist as the permanent record of the formation of the Solar System and therefore hold many clues to its understanding as a whole, as well as insights into the formation of planetary bodies. Additionally, SSSBs are being investigated in the context of impact risks for the Earth, space situational awareness and their possible industrial exploitation (asteroid mining). In all these aspects, the knowledge of the geophysical characteristics of SSSB surface and internal structure are of great importance. Given their size, constitution, and the evidence that many SSSBs are not simple monoliths, these bodies should be studied and modelled as self-gravitating granular systems in general, or as granular systems in micro-gravity environments in particular contexts. As such, the study of the geophysical characteristics of SSSBs is a multi-disciplinary effort that lies at the crossroads between Granular Mechanics, Celestial Mechanics, Soil Mechanics, Aerospace Engineering and Computer Sciences.

}, doi = {10.1051/epjconf/201714014011}, url = {http://www.epj-conferences.org/10.1051/epjconf/201714014011}, author = {Hestroffer, Daniel and Adriano Campo Bagat{\'\i}n and Losert, Wolfgang and Opsomer, Eric and S{\'a}nchez, Paul and Scheeres, Daniel J. and Staron, Lydie and Taberlet, Nicolas and Yano, Hajime and Eggl, Siegfried and Lecomte, Charles-Edouard and Murdoch, Naomi and Farhang Radja{\"\i} and Richardson, Derek C. and Salazar, Marcos and Schwartz, Stephen R. and Tanga, Paolo}, editor = {Saeid Nezamabadi and Luding, S. and Jean-Yves Delenne} } @article {599, title = {Strength of wet agglomerates of spherical particles: effects of friction and size distribution}, journal = {EPJ Web of Conferences}, volume = {140}, year = {2017}, month = {Jun-30-2017}, pages = {Article Number 08021}, abstract = {

We investigate the mechanical behavior of wet granular agglomerates composed of spherical particles by means of molecular dynamics simulations. The capillary cohesion force is modeled as an attraction force at the contact between two particles and expressed as an explicit function of the gap and volume of the liquid bridge. We are interested in the effect of the friction coefficient between primary particles. The agglomerates are subjected to diametrical compression tests. We find that the deformation is ductile involving particle rearrangements. However, a well-defined stress peak is observed and the peak stress is used as a measure of the compressive strength of the agglomerate. The strength increases with friction coefficient but levels off at friction coefficients above 0.4. Furthermore, the compressive strength is an increasing function of particle size span.

}, doi = {10.1051/epjconf/201714008021}, url = {http://www.epj-conferences.org/10.1051/epjconf/201714008021}, author = {Vo, Thanh-Trung and Patrick Mutabaruka and Jean-Yves Delenne and Saeid Nezamabadi and Farhang Radja{\"\i}}, editor = {Luding, S.} } @article {598, title = {Wall roughness and nonlinear velocity profiles in granular shear flows}, journal = {EPJ Web of Conferences}, volume = {140}, year = {2017}, month = {Jun-30-2017}, pages = {Article Number 03090}, abstract = {

Inhomogeneous velocity profiles in granular flows are well known from both experiments and simulations, and considered as a hallmark of nonlocal behavior. By means of extensive contact dynamics simulations, we show that the sigmoidal velocity profiles in 2D flows of rigid disks are controlled by the roughness of driving boundary walls. We find that the velocity profile becomes linear for a critical value of wall roughness up to an exponential decay close to the walls with a characteristic length that does not depend on the flow thickness and rate. We describe the velocity profiles by introducing a state parameter that carries wall perturbation. By assuming that the local shear rate is a linear function of the state parameter, we obtain an analytical expression that fits velocity profiles. In this model, the nonlinear velocity profiles are explained in terms of the effects of wall roughness as boundary condition for the state parameter.

}, doi = {10.1051/epjconf/201714003090}, url = {http://www.epj-conferences.org/10.1051/epjconf/201714003090}, author = {Schuhmacher, Paul and Farhang Radja{\"\i} and St{\'e}phane Roux}, editor = {Saeid Nezamabadi and Luding, S. and Jean-Yves Delenne} } @article {252, title = {Data analytics for simplifying thermal efficiency planning in cities}, journal = {Journal of The Royal Society Interface}, volume = {13}, year = {2016}, month = {Apr-2016}, pages = {Article Number: 20150971}, abstract = {

More than 44\% of building energy consumption in the USA is used for space heating and cooling, and this accounts for 20\% of national CO2emissions. This prompts the need to identify among the 130 million households in the USA those with the greatest energy-saving potential and the associated costs of the path to reach that goal. Whereas current solutions address this problem by analysing each building in detail, we herein reduce the dimensionality of the problem by simplifying the calculations of energy losses in buildings. We present a novel inference method that can be used via a ranking algorithm that allows us to estimate the potential energy saving for heating purposes. To that end, we only need consumption from records of gas bills integrated with a building\&$\#$39;s footprint. The method entails a statistical screening of the intricate interplay between weather, infrastructural and residents\&$\#$39; choice variables to determine building gas consumption and potential savings at a city scale. We derive a general statistical pattern of consumption in an urban settlement, reducing it to a set of the most influential buildings\&$\#$39; parameters that operate locally. By way of example, the implications are explored using records of a set of (N= 6200) buildings in Cambridge, MA, USA, which indicate that retrofitting only 16\% of buildings entails a 40\% reduction in gas consumption of the whole building stock. We find that the inferred heat loss rate of buildings exhibits a power-law data distribution akin to Zipf\&$\#$39;s law, which provides a means to map an optimum path for gas savings per retrofit at a city scale. These findings have implications for improving the thermal efficiency of cities\&$\#$39; building stock, as outlined by current policy efforts seeking to reduce home heating and cooling energy consumption and lower associated greenhouse gas emissions.

}, issn = {1742-5689}, doi = {10.1098/rsif.2015.0971}, author = {Mohammad Javad Abdolhosseini Qomi and Noshadravan, Arash and Sobstyl, Jake M. and Toole, Jameson and Ferreira, Joseph and Roland Jean-Marc Pellenq and Franz-Josef Ulm and Gonzalez, Marta C.} } @article {153, title = {Bonded-cell model for particle fracture}, journal = {Physical Review E}, volume = {91}, year = {2015}, month = {Feb-09-2015}, pages = {Article Number: 022203}, abstract = {

Particle degradation and fracture play an important role in natural granular flows and in many applications of granular materials. We analyze the fracture properties of two-dimensional disklike particles modeled as aggregates of rigid cells bonded along their sides by a cohesive Mohr-Coulomb law and simulated by the contact dynamics method. We show that the compressive strength scales with tensile strength between cells but depends also on the friction coefficient and a parameter describing cell shape distribution. The statistical scatter of compressive strength is well described by the Weibull distribution function with a shape parameter varying from 6 to 10 depending on cell shape distribution. We show that this distribution may be understood in terms of percolating critical intercellular contacts. We propose a random-walk model of critical contacts that leads to particle size dependence of the compressive strength in good agreement with our simulation data.

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}, issn = {1539-3755}, doi = {10.1103/PhysRevE.91.022203}, author = {Duc-Hanh Nguyen and Emilien Az{\'e}ma and Philippe Sornay and Farhang Radja{\"\i}} } @article {161, title = {Effect of curvature and confinement on the Casimir-Polder interaction}, journal = {Physical Review A}, volume = {91}, year = {2015}, month = {Jan-30-2015}, abstract = {

Modifications of Casimir-Polder interactions due to confinement inside a cylindrical cavity and due to curvature in- and outside the cavity are studied. We consider a perfectly conducting cylindrical shell with a single particle (atom or macroscopic sphere) located next to its interior or exterior surface, or two atoms placed inside the shell. By employing the scattering approach, we obtain the particle-cavity interaction and the modification of the two-particle interaction due to the cavity. We consider both retardation and thermal effects. While for the atoms a dipole description is sufficient, for the macroscopic sphere we sum (numerically) over many multipole fluctuations to compute the interaction at short separations. In the latter limit we compare to the proximity approximation and a gradient expansion and find agreement. Our results indicate an confinement induced suppression of the force between atoms. General criteria for suppression and enhancement of Casimir interactions due to confinement are discussed.

}, issn = {1050-2947}, doi = {10.1103/PhysRevA.91.012516}, author = {Rodriguez-Lopez, Pablo and Emig, Thorsten and Noruzifar, Ehsan and Zandi, Roya} } @article {129, title = {Effects of shape and size polydispersity on strength properties of granular materials.}, journal = {Phys Rev E Stat Nonlin Soft Matter Phys}, volume = {91}, year = {2015}, month = {Mar-18-2015}, pages = {Article Number: 032203}, abstract = {

By means of extensive contact dynamics simulations, we analyze the combined effects of polydispersity both in particle size and in particle shape, defined as the degree of shape irregularity, on the shear strength and microstructure of sheared granular materials composed of pentagonal particles. We find that the shear strength is independent of the size span, but unexpectedly, it declines with increasing shape polydispersity. At the same time, the solid fraction is an increasing function of both the size span and the shape polydispersity. Hence, the densest and loosest packings have the same shear strength. At the scale of the particles and their contacts, we analyze the connectivity of particles, force transmission, and friction mobilization as well as their anisotropies. We show that stronger forces are carried by larger particles and propped by an increasing number of small particles. The independence of shear strength with regard to size span is shown to be a consequence of contact network self-organization, with the falloff of contact anisotropy compensated by increasing force anisotropy.

}, issn = {1550-2376}, doi = {10.1103/PhysRevE.91.032203}, author = {Duc-Hanh Nguyen and Emilien Az{\'e}ma and Philippe Sornay and Farhang Radja{\"\i}} } @proceedings {343, title = {Evolution of particle size distributions in crushable granular materials}, journal = {3rd International Symposium on Geomechanics from Micro to Macro}, volume = {Geomechanics from Micro to Macro}, year = {2015}, month = {Feb-02-2015}, pages = {275 - 280}, publisher = {CRC Press}, address = {SEP 01-03-2014 Univ Cambridge, Cambridge, ENGLAND}, abstract = {

By means of the contact dynamics method together with a particle fracture model, in which the particles are cohesive aggregates of irreducible polygonal fragments, we investigate the evolution of particle size distribution in the process of uniaxial compaction of granular materials. The case of single particle breakup under compressive stress is used to test the method and the influence of discretization (number of irreducible fragments). We show that the breaking threshold of the granular assembly scales with the internal cohesion of the particles but it depends also on the initial size distribution and irregularity of polygonal particle shapes. The evolution of size distribution proceeds by consecutive periods of intense particle crushing, characterized by local shattering instability, and periods of little breaking activity. Starting with either monodisperse or power-law distribution of particle sizes, the latter evolves towards a broad distribution of the fragmented particles with a nearly power-law distribution in the range of intermediate particle sizes. Interestingly, a finite number of large particles survive despite ongoing crushing process due to the more homogeneous distribution of forces in the presence of small fragmented particles filling the pores between larger particles.

}, isbn = {978-1-138-02707-7}, doi = {10.1201/b1739510.1201/b17395-48}, author = {Duc-Hanh Nguyen and Emilien Az{\'e}ma and Farhang Radja{\"\i} and Philippe Sornay}, editor = {Kenichi Soga and Krishna Kumar and Giovanna Biscontin and Kuo, Matthew} } @article {271, title = {Implicit frictional-contact model for soft particle systems}, journal = {Journal of the Mechanics and Physics of Solids}, volume = {83}, year = {2015}, month = {Oct-2015}, pages = {72 - 87}, abstract = {

We introduce a novel numerical approach for the simulation of soft particles interacting via frictional contacts. This approach is based on an implicit formulation of the Material Point Method, allowing for large particle deformations, combined with the Contact Dynamics method for the treatment of unilateral frictional contacts between particles. This approach is both precise due to the treatment of contacts with no regularization and artificial damping parameters, and robust due to implicit time integration of both bulk degrees of freedom and relative contact velocities at the nodes representing the contact points. By construction, our algorithm is capable of handling arbitrary particle shapes and deformations. We illustrate this approach by two simple 2D examples: a Hertz contact and a rolling particle on an inclined plane. We also investigate the compaction of a packing of circular particles up to a solid fraction well above the jamming limit of hard particles. We find that, for the same level of deformation, the solid fraction in a packing of frictional particles is above that of a packing of frictionless particles as a result of larger particle shape change.

}, issn = {00225096}, doi = {10.1016/j.jmps.2015.06.007}, author = {Saeid Nezamabadi and Farhang Radja{\"\i} and Julien Averseng and Jean-Yves Delenne} } @proceedings {358, title = {Micromechanical analysis of the surface erosion of a cohesive soil by means of a coupled LBM-DEM model}, journal = {IV International Conference on Particle-based Methods (PARTICLES 2015)}, volume = {PARTICLE-BASED METHODS IV-FUNDAMENTALS AND APPLICATIONS}, year = {2015}, month = {sept-30-2015}, pages = {519-528}, publisher = {International Center for Numerical Methods in Engineering (CIMNE)}, address = {SEP 28-30 2015 Barcelona, SPAIN}, abstract = {

The elementary mechanisms driving the ubiquitous surface erosion of cohesive geomaterials can be analysed from a micromechanical perspective combining well-known numerical techniques. Here, a coupled model combining the Discrete Element and Lattice Boltzmann methods (DEM-LBM) provides an insight into the solid-fluid interaction during the transient erosion caused by a vertical fluid jet impinging on the surface of a granular assembly. The brittle cementation providing cohesion between the solid grains is described here by means of a simple bond model with a single-parameter yield surface. The initial topology of the surface erosion tends to mimic the profile of fluid velocity directly above the soil surface. We find that both the rate of erosion and the magnitude of eroded mass depend directly on the micromechanical strength of the single solid bonds.

}, keywords = {Cohesion, DEM, LBM, Surface erosion}, url = {https://hal.archives-ouvertes.fr/hal-01269324}, author = {Cuellar, Pablo and Pierre Philippe and St{\'e}phane Bonelli and Benahmed, Nadia and Brunier-Coulin, Florian and Jeff Ngoma and Jean-Yves Delenne and Farhang Radja{\"\i}}, editor = {Onate, E and Bischoff, M and Owen, DRJ} } @proceedings {359, title = {Transient regime to fluidized chimney within a granular bed by means of a 2D DEM/LBM modeling}, journal = {IV International Conference on Particle-based Methods (PARTICLES 2015)}, volume = {PARTICLE-BASED METHODS IV-FUNDAMENTALS AND APPLICATIONS}, year = {2015}, month = {sept-30-2015}, pages = {558-566}, publisher = {International Center for Numerical Methods in Engineering (CIMNE)}, address = {SEP 28-30 2015 Barcelona, SPAIN}, abstract = {

Beyond a given threshold, an upward fluid flow at constant flowrate, injected through a small size section, is able to generate a fluidization along a vertical chimney over the entire height of a granular assembly. Fluidization is first initiated in the immediate vicinity of the injection hole and then the fluidized zone grows gradually until reaching the upper surface of the granular packing. In this work, we present numerical results on the kinetics of chimney fluidization in an immersed granular bed produced with two-dimensional simulations coupling the Discrete Element and Lattice Boltzmann Methods (DEM-LBM). A parametric study is carried out with 11 different sets of physical parameters and analyzed based on spatio-temporal diagrams. Then a dimensional analysis allows finding general scaling laws for both threshold and growth rate of the fluidized zone by use of two dimensionless numbers, namely Reynolds and Archimedes numbers, while quite simple empirical relationships can also be proposed.

}, keywords = {DEM, Fluidization, Granular Materials, LBM}, url = {https://hal.archives-ouvertes.fr/hal-01269325}, author = {Jeff Ngoma and Pierre Philippe and St{\'e}phane Bonelli and Cuellar, Pablo and Jean-Yves Delenne and Farhang Radja{\"\i}}, editor = {Onate, E and Bischoff, M and Owen, DRJ} } @article {273, title = {Effect of size polydispersity versus particle shape in dense granular media}, journal = {Physical Review E}, volume = {90}, year = {2014}, month = {Jul-21-2014}, pages = {Article Number: 012202}, abstract = {

We present a detailed analysis of the morphology of granular systems composed of frictionless pentagonal particles by varying systematically both the size span and particle shape irregularity, which represent two polydispersity parameters of the system. The microstructure is characterized in terms of various statistical descriptors such as global and local packing fractions, radial distribution functions, coordination number, and fraction of floating particles. We find that the packing fraction increases with the two parameters of polydispersity, but the effect of shape polydispersity for all the investigated structural properties is significant only at low size polydispersity where the positional and/or orientational ordering of the particles prevail. We focus in more detail on the class of side/side contacts, which is the interesting feature of our system as compared to a packing of disks. We show that the proportion of such contacts has weak dependence on the polydispersity parameters. The side- side contacts do not percolate but they define clusters of increasing size as a function of size polydispersity and decreasing size as a function of shape polydispersity. The clusters have anisotropic shapes but with a decreasing aspect ratio as polydispersity increases. This feature is argued to be a consequence of strong force chains (forces above the mean), which are mainly captured by side-side contacts. Finally, the force transmission is intrinsically multiscale, with a mean force increasing linearly with particle size.

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}, issn = {1539-3755}, doi = {10.1103/PhysRevE.90.012202}, author = {Duc-Hanh Nguyen and {\'e}ma, Emilien and Farhang Radja{\"\i} and Philippe Sornay} } @proceedings {346, title = {Geomechanics from Micro to MacroInteraction between two localized fluidization cavities in granular media : Experiments and numerical simulation}, journal = {3rd International Symposium on Geomechanics from Micro to Macro}, volume = {Geomechanics from Micro to Macro}, year = {2014}, month = {Sep-2014}, pages = {1571 - 1576}, publisher = {CRC Press}, address = {SEP 01-03-2014 Univ Cambridge, Cambridge, ENGLAND}, abstract = {

In this work, we present experimental and numerical results on the interaction between two localized fluidization cavities in an immersed granular packing. According to the gap between the two locally injected upward fluid flows, each fluidized cavity will evolve independently of the another, or conversely, the two cavities can interact with each other: they merge and eventually behave like a single cavity. Combined optical techniques are used for visualization of particle motion inside the granular media (Refractive Index-Matching between liquid and beads and Planar Laser-Induced Fluorescence), the experimental results are compared to a two-dimensional simulation based on coupled Discrete Element and Lattice Boltzmann Methods (DEM-LBM).

}, isbn = {978-1-138-02707-7}, doi = {10.1201/b17395-286}, author = {Jeff Ngoma and Pierre Philippe and St{\'e}phane Bonelli and Jean-Yves Delenne and Farhang Radja{\"\i}}, editor = {Kenichi Soga and Krishna Kumar and Giovanna Biscontin and Kuo, Matthew} } @proceedings {342, title = {Modelling soft-particle materials}, journal = {3rd International Symposium on Geomechanics from Micro to Macro}, volume = {Geomechanics from Micro to Macro}, year = {2014}, month = {Aug-26-2014}, pages = {43-48}, publisher = {CRC Press}, address = {SEP 01-03-2014 Univ Cambridge, Cambridge, ENGLAND}, abstract = {

Soft-particle materials include colloidal pastes, vesicles, many powders, microgels and suspensions. They share the common feature of being composed of particles that can undergo large deformations without rupture. For the simulation of such materials, we present a modelling approach based on an implicit formulation of the Material Point Method (MPM) interfaced with the Contact Dynamics (CD) method for the treatment of frictional contacts between particles. Each particle is discretized as a collection of material points. The information carried by the material points is projected onto a background mesh, where equations of motion are solved. The mesh solution is then used to update the material points. The implicit formulation of MPM allows for unconditional numerical stability and efficient coupling with implicit treatment of unilateral contacts and friction between the particles by the CD method. We use this model to analyse the compaction process of 2D soft-particle packings. The packing can reach high solid fractions by particle shape change and still flow plastically. The compaction is a nonlinear process in which new contacts are formed between particles and the contact areas increase. We find that the evolution of the packing fraction is a slow logarithmic function of the driving stress as a consequence of increasing contact area. We also evidence the effect of friction, which favours strong stress chains and thus the elongation of particles, leading to a larger packing fraction at a given level of compressive stress as compared to a frictionless particle packing.

}, url = {http://prodinra.inra.fr/record/370208}, author = {Saeid Nezamabadi and Farhang Radja{\"\i} and Julien Averseng}, editor = {Kenichi Soga and Krishna Kumar and Giovanna Biscontin} } @article {276, title = {Some micromechanical aspects of failure in granular materials based on second-order work}, journal = {Comptes Rendus M{\'e}canique}, volume = {342}, year = {2014}, month = {Mar-2014}, pages = {174 - 188}, abstract = {

This paper discusses the notion of failure in a granular assembly by examining the key microstructural mechanisms which are most likely to trigger the nucleation and propagation of instabilities within a granular material. For this purpose, the key variable to predict the occurrence of failure, known as second-order work, is expressed from variables on the grain scale. The local behaviour incidents (where contacts may open or slide), compared to the global response of the assembly, are analysed by two approaches. First, numerical computations made by a discrete element model confirm the microscopic definition of the second-order work. Secondly, a micromechanical model, based on a homogenization procedure, relating the macroscopic behaviour to microscopic ingredients, namely contact planes, points to a close link between the occurrence of failure on the macroscopic scale as well as on the contact planes.

}, issn = {16310721}, doi = {10.1016/j.crme.2014.01.006}, author = {Fran{\c c}ois Nicot and Hadda, Nejib and Sibille, Luc and Farhang Radja{\"\i} and Hicher, Pierre-Yves and Darve, F{\'e}lix} } @article {74, title = {Ultrahigh interlayer friction in multiwalled boron nitride nanotubes}, journal = {Nat Mater}, volume = {13}, year = {2014}, month = {Jul-2014}, pages = {688 - 693}, abstract = {

Friction at the nanoscale has revealed a wealth of behaviours that depart strongly from the long-standing macroscopic laws of Amontons\–Coulomb1, 2. Here, by using a \‘Christmas cracker\’-type of system in which a multiwalled nanotube is torn apart between a quartz-tuning-fork-based atomic force microscope (TF\–AFM) and a nanomanipulator, we compare the mechanical response of multiwalled carbon nanotubes (CNTs) and multiwalled boron nitride nanotubes (BNNTs) during the fracture and telescopic sliding of the layers. We found that the interlayer friction for insulating BNNTs results in ultrahigh viscous-like dissipation that is proportional to the contact area, whereas for the semimetallic CNTs the sliding friction vanishes within experimental uncertainty. We ascribe this difference to the ionic character of the BN, which allows charge localization. The interlayer viscous friction of BNNTs suggests that BNNT membranes could serve as extremely efficient shock-absorbing\ surfaces.

Multiwalled nanotube Christmas-cracker experimental set-up.

Frequency shift measured by the tuning fork versus the displacement of the piezoscanner during complete tensile load experiments.

}, isbn = {1476-1122}, doi = {10.1038/nmat3985}, author = {Nigues, A. and A. Siria and Vincent, P. and Poncharal, P. and Lyd{\'e}ric Bocquet} } @article {24, title = {Adsorption of Volatile Organic Compounds in pure silica CHA, *BEA, MFI and STT-type zeolites}, journal = {Microp. Mesop. Mater.}, volume = {173}, year = {2013}, month = {Jun-2013}, pages = {147{\textendash}154}, abstract = {

Four pure silica zeolites, chabazite (CHA-structure type) and SSZ-23 (STT-structure type) with cage-like structure and silicalite-1 (MFI-structure type) and beta (\∗BEA-structure type) with channel structure, were synthesized and fully characterized. Their sorption properties were examined using gravimetric method combined with Grand Canonical Monte Carlo simulations (GCMC). Of particular interest is the large difference in the adsorption rates of n-hexane, p-xylene and acetone observed for these zeosils at 25, 75 and 150\ \°C. As expected, in most cases, a decrease in the adsorption capacity is observed with increasing the molar volume of the used probe molecule and the temperature. An exception is observed for the pure silica CHA-type zeolite due to its small pore size which prevents molecules from entering its porosity. However, at higher temperature, the window size widens slightly and allows n-hexane and acetone, which have kinetic diameter close to the pore opening, to enter easily in chabazite. As a result, for this zeosil, an increase in the adsorption capacity compared to that obtained at 25\ \°C is observed. All these zeosils are promising for technological uses in car exhaust gas decontamination.

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}, doi = {10.1016/j.micromeso.2013.02.009}, author = {A. F. Cosseron and T. J. Daou and L. Tzanis and H. Nouali and I. Deroche and Benoit A. Coasne and V. Tchaber and J. Patarin} } @proceedings {365, title = {AIP Conference Proceedings A multiscale description of failure in granular materials}, journal = {7th International Conference on Micromechanics of Granular Media (Powders and Grains)}, volume = {Book Series: AIP Conference Proceedings POWDERS AND GRAINS 2013}, year = {2013}, month = {Jun-18-2013}, pages = {585-588}, publisher = {AIP}, address = {JUL 08-12 2013 Sydney, AUSTRALIA}, abstract = {

This paper presents conditions of initiation and development of failure in granular materials through a twodimensional discrete element model. General condition for the effective development of failure and its physical characteristics are recalled. Then relation between failure and the second order work expressed in terms of microscopic variables is discussed. Eventually, correspondence between a localized mode of failure marked with shear band patterns and space distribution of negative values of microscopic second-order work is investigated.

}, doi = {10.1063/1.4811999}, author = {Hadda, Nejib and Fran{\c c}ois Nicot and Sibille, Luc and Farhang Radja{\"\i} and Tordesillas, Antoinette and Darve, F{\'e}lix}, editor = {Yu, A and Dong, K and Yang, R} } @proceedings {367, title = {A benchmark for particle shape dependence}, journal = {7th International Conference on Micromechanics of Granular Media (Powders and Grains)}, volume = {Book Series: AIP Conference Proceedings POWDERS AND GRAINS 2013}, year = {2013}, month = {Jun-18-2013}, pages = {883-886}, publisher = {AIP}, address = {JUL 08-12 2013 Sydney, AUSTRALIA}, abstract = {

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 \η describing the degree of distortion from a perfectly circular shape. In particular, the shear strength is an increasing function of \η with nearly the same trend for all shapes, the differences being of second order compared to \η. We also observe a nontrivial behavior of packing fraction which, for all our simulated shapes, increases with \η from the random close packing fraction for disks, reaches a peak considerably higher than that for disks, and subsequently declines as \η is further increased. Finally, the analysis of contact forces for the same value of \η leads to very similar statistics regardless of our specific particle shapes.

}, doi = {10.1063/1.4812073}, author = {Gael Combe and C{\'e}cile Nouguier-Lehon and Emilien Az{\'e}ma and Krzysztof Szarf and Baptiste Saint-Cyr and Marie Chaze and Farhang Radja{\"\i} and Pascal Villard and Jean-Yves Delenne and Vincent Richefeu and Philippe Sornay and Charles Voivret and CEGEO Group}, editor = {Yu, A and Dong, K and Yang, R} } @article {283, title = {Micromechanical analysis of second order work in granular media}, journal = {Granular Matter}, volume = {15}, year = {2013}, month = {Apr-2013}, pages = {221 - 235}, abstract = {

This paper examines instabilities in granular materials from a microscopic point of view through numerical simulations conducted using a discrete element method on two three-dimensional specimens. The detection and the tracking of grain scale deformation mechanisms constitute the key point for a better understanding the failure process and puzzling out what lies behind the vanishing of the macroscopic second order work. For this purpose, the second order work from microscopic variables, involving contact force and branch vector, was introduced and tracked numerically. Then, all contacts depicting negative values of the second order work were deeply investigated, especially their spatial distribution (homogeneity, agglomeration, dispersion\…) within the specimen according to the density of the granular assembly and to the loading direction. A set of comparisons has been considered in this context in order to highlight how a specimen is populated with such contacts whether it is loaded along a direction included within the plastic tensorial zone or along a direction for which the specimen is likely to behave elastically (elastic tensorial zone). Moreover, these comparisons concerned also loading directions within the cone of instability so that links between the vanishing of both microscopic and macroscopic second order works can be established and the local mechanisms responsible for failure occurrence may be figured out.

}, issn = {1434-5021}, doi = {10.1007/s10035-013-0402-3}, author = {Hadda, Nejib and Fran{\c c}ois Nicot and Bourrier, Franck and Sibille, Luc and Farhang Radja{\"\i} and Darve, F{\'e}lix} } @article {299, title = {Mechanistic Approach to Pavement-Vehicle Interaction and Its Impact on Life-Cycle Assessment}, journal = {Transportation Research Record: Journal of the Transportation Research Board}, year = {2012}, month = {Dec-2012}, pages = {171 - 179}, abstract = {

The accuracy and the comprehensiveness of any pavement life-cycle assessment are limited by the ability of the supporting science to quantify the environmental impact. Pavement-vehicle interaction represents a significant knowledge gap that has important implications for many pavement life-cycle assessment studies. In the current study, the authors assumed that a mechanistic model that linked pavement structure and properties to fuel consumption could contribute to closing the uncertainty gap of pavement-vehicle interaction in life-cycle assessment of pavements. The simplest mechanistic pavement model, a Bernoulli-Euler beam on a viscoelastic foundation subjected to a moving load, was considered. Wave propagation properties derived from falling weight deflectometer time history data of FHWA\&$\#$39;s Long-Term Pavement Performance program were used to calibrate top-layer and substrate moduli for various asphalt and concrete systems. The model was validated against recorded deflection data. The mechanistic response was used to determine gradient force and rolling resistance to link deflection to vehicle fuel consumption. A comparison with independent field data provided realistic order-of-magnitude estimates of fuel consumption related to pavement-vehicle interaction as predicted by the model.

}, issn = {0361-1981}, doi = {10.3141/2306-20}, author = {Mehdi Akbarian and Moeini-Ardakani, Seyed and Franz-Josef Ulm and Nazzal, Munir} } @proceedings {354, title = {Microscopic Origins of Shear Strength in Packings Composed of Elongated Particles}, journal = {9th International Workshop on Bifurcation and Degradation in Geomaterials (IWBDG 2011)}, volume = {Springer Series in Geomechanics and Geoengineering - ADVANCES IN BIFURCATION AND DEGRADATION IN GEOMATERIALS}, year = {2012}, month = {Apr-11-2012}, pages = {21-27}, address = {MAY 23-26 2011 Porquerolles, FRANCE}, abstract = {

We investigate the rheology, force transmission and texture of granular materials composed of elongated particles by means of contact dynamics simulations. The particles have a rounded-cap rectangular (RCR) shape described by a single elongation parameter varying from 0 for a circular particle to 1 for an infinitely thin or long particle. We study the quasi-static behavior, structural and force anisotropies as a function of the elongation parameter for packings submitted to biaxial compression. The shear strength is found to increase linearly with this parameter whereas the solid fraction both at the initial isotropic state and in the critical state is nonmonotonous. We show that for these elongated particles a harmonic decomposition of the stress tensor provides a fairly good approximation of the internal state. Our data suggest that the increase of shear strength with reflects both enhanced friction mobilization and anisotropic particle orientation as the elongation of the particles increases.

}, keywords = {Elongated particles, Fabric properties, force transmission, Harmonic decomposition}, url = {https://hal.archives-ouvertes.fr/hal-00686728}, author = {Emilien Az{\'e}ma and Farhang Radja{\"\i}}, editor = {St{\'e}phane Bonelli and Dascalu, Cristian and Fran{\c c}ois Nicot} } @article {307, title = {Particle shape dependence in 2D granular media}, journal = {EPL (Europhysics Letters)}, volume = {98}, year = {2012}, month = {Apr-20-2012}, pages = {Article Number: 44008}, abstract = {

Particle shape is a key to the space-filling and strength properties of granular matter. We consider a shape parameter

describing the degree of distortion from a perfectly spherical shape. Encompassing most specific shape characteristics such as elongation, angularity and non-convexity, 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 with nearly the same trend for all shapes, the differences appearing thus to be of second order compared to . We also observe a non-trivial behavior of packing fraction which, for all our simulated shapes, increases with from the random close packing fraction for disks, reaches a peak considerably higher than that for disks, and subsequently declines as 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 .

}, issn = {0295-5075}, doi = {10.1209/0295-5075/98/44008}, author = {Baptiste Saint-Cyr and Krzysztof Szarf and Charles Voivret and Emilien Az{\'e}ma and Vincent Richefeu and Jean-Yves Delenne and Gael Combe and C{\'e}cile Nouguier-Lehon and Pascal Villard and Philippe Sornay and Marie Chaze and Farhang Radja{\"\i}} } @proceedings {352, title = {Modeling Porous Granular Aggregates}, journal = {9th International Workshop on Buifurcation and Degradation in Geomaterials (IWBDG 2011)}, volume = {Springer Series in Geomechanics and Geoengineering - ADVANCES IN BIFURCATION AND DEGRADATION IN GEOMATERIALS}, year = {2011}, month = {May-28-2011}, pages = {249 - 254}, publisher = {Springer Netherlands}, address = {MAY 23-26 2011 Porquerolles, FRANCE}, abstract = {

We rely on 3D simulations based on the Lattice Element Method (LEM) to analyze the failure of porous granular aggregates under tensile loading. We investigate crack growth by considering the number of broken bonds in the particle phase as a function of the matrix volume fraction and particle-matrix adhesion. Three regimes are evidenced, corresponding to no particle damage, particle abrasion and particle fragmentation, respectively. We also show that the probability density of strong stresses falls off exponentially at high particle volume fractions where a percolating network of jammed particles occurs. Decreasing the matrix volume fraction leads to increasingly broader stress distribution and hence a higher stress concentration. Our findings are in agreement with 2D results previously reported in the literature.

}, isbn = {978-94-007-1420-5}, issn = {1866-8755}, doi = {10.1007/978-94-007-1421-2_32}, author = {Rafik Aff{\`e}s and Vincent Topin and Jean-Yves Delenne and Yann Monerie}, editor = {St{\'e}phane Bonelli and Dascalu, Cristian and Fran{\c c}ois Nicot} } @proceedings {353, title = {Onset of Immersed Granular Avalanches by DEM-LBM Approach}, journal = {9th International Workshop on Buifurcation and Degradation in Geomaterials (IWBDG 2011)}, volume = {Springer Series in Geomechanics and Geoengineering - ADVANCES IN BIFURCATION AND DEGRADATION IN GEOMATERIALS}, year = {2011}, month = {May-28-2011}, pages = {109 - 115}, publisher = {Springer Netherlands}, address = {MAY 23-26 2011 Porquerolles, FRANCE}, abstract = {

We present 3D grain-fluid simulations based on the discrete element method interfaced with the lattice Boltzmann method and applied to investigate the initiation of underwater granular flows. We prepare granular beds of 800 spherical grains with different values of the initial solid fraction in a biperiodic rectangular box. In order to trigger an avalanche, the bed is instantaneously tilted to a finite slope angle above the maximum angle of stability. We simulate the dynamics of the transient flow for different solid fractions. In agreement with the experimental work of Iverson (Water Resour Res 36(7):1897\–1910, 2000) and Pailha et\ al. (Phys Fluids 20(11):111701, 2008), we find that the flow onset is controlled by the initial solid fraction.

}, isbn = {978-94-007-1420-5}, issn = {1866-8755}, doi = {10.1007/978-94-007-1421-210.1007/978-94-007-1421-2_14}, author = {Jean-Yves Delenne and Mansouri, M. and Farhang Radja{\"\i} and Moulay Sa{\"\i}d El Youssoufi and Seridi, A.}, editor = {St{\'e}phane Bonelli and Dascalu, Cristian and Fran{\c c}ois Nicot} }