15 results on '"Nezamabadi, Saeid"'
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2. Modelling the compaction of plastic particle packings
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Nezamabadi, Saeid, Ghadiri, Mojtaba, Delenne, Jean-Yves, and Radjai, Farhang
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- 2022
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3. Modeling soft granular materials
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Nezamabadi, Saeid, Nguyen, Thanh Hai, Delenne, Jean-Yves, and Radjai, Farhang
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- 2017
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4. Rheology of soft granular materials: uniaxial compression.
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Nezamabadi, Saeid, Radjai, Farhang, Mora, Serge, Delenne, Jean-Yves, and Ghadiri, Mojtaba
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GRANULAR materials , *RHEOLOGY , *DEFORMATION potential , *MATERIAL point method , *PACKING fractions - Abstract
Soft granular materials are assemblies of highly deformable grains interacting via surface forces. The large grain deformations of these materials differ them from hard granular systems, in which, their behaviors are essentially governed by grain rearrangements. In this paper, we study the uniaxial compression of soft granular materials using a numerical approach based on the Material Point Method allowing for large grain deformations, coupled with the Contact Dynamics method for the treatment of unilateral frictional contacts between grains. Considering the neo-Hookean and elasto-plastic grains, the compaction of 2D soft granular packings is analyzed. We focus essentially on the evolution of the packing vertical stress as a function of the packing fraction and the predictive models are proposed. [ABSTRACT FROM AUTHOR]
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- 2021
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5. Modelling and rheology of soft granular materials
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Nezamabadi, Saeid, Nguyen, Thanh Hai, Frank, Xavier, Delenne, Jean-Yves, Radjai, Farhang, Physique et Mécanique des Milieux Divisés (PMMD), 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 Réactions et Génie des Procédés (LRGP), Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL), Ingénierie des Agro-polymères et Technologies Émergentes (UMR IATE), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université de Montpellier (UM)-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)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)
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Granular materials ,Contact dynamics ,[SPI.FLUID]Engineering Sciences [physics]/Reactive fluid environment ,Material point method ,MPI ,[SPI.GPROC]Engineering Sciences [physics]/Chemical and Process Engineering ,[PHYS.MECA]Physics [physics]/Mechanics [physics] ,Soft matter ,[SPI.MAT]Engineering Sciences [physics]/Materials - Abstract
International audience; Many materials can be described as granular materials composed of soft or ultra-soft grains. Mostfood products, metal powders, microgels and many suspensions are soft-grain systems. Despite their different mechanisms of deformability, depending on their composition and structure, their common feature is that they can undergo large strains without rupture. As a result, these materials can reach high packing fractions beyond random close packing through both grain rearrangements and grain shape change. Until now, because of the lack of proper numerical and experimental tools, their compaction behavior under stress, volume change behaviour under shear and microstructure have mostly remained unexplored.In this work, we present a numerical technique to model soft granular materials in which the grains can undergo extensive shape change and large deformations. It combines an implicit formalism of the Material Point Method and the Contact Dynamics method [1-3]. In this framework, the large deformations of individual grains 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 elastic grains. We consider compressibility rates ranging from fully compressible to incompressible grains. The packing deformation mechanism is a combination of both grain rearrangements and large deformations, and leads to high packing fractions beyond the jamming state. We show that the packing strength declines when the grain compressibility decreases, and the packing can deform considerably. We also investigate the evolution of the connectivity of the grains and grain deformation distributions in the packing.REFERENCES[1] S. Nezamabadi, F. Radjai, J. Averseng, J.-Y. Delenne, “Implicit frictional-contact model for soft particle systems”, Journal of the Mechanics and Physics of Solids, 83: 72-87, 2015.[2] S. Nezamabadi, T.-H. Nguyen, J.-Y. Delenne, F. Radjai, “Modeling soft granular materials”, Granular Matter, 19: 8, 2017.[3] S. Nezamabadi, X. Frank, J.-Y. Delenne, J. Averseng, F. Radjai, “Parallel implicit contact algorithm for soft particle systems”, Computer Physics Communications, In press.
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- 2019
6. Additive rheology of complex granular flows.
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Vo, Thanh Trung, Nezamabadi, Saeid, Mutabaruka, Patrick, Delenne, Jean-Yves, and Radjai, Farhang
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GRANULAR flow ,FRICTION ,PARTICLE dynamics ,GRANULAR materials ,DIMENSIONLESS numbers ,RHEOLOGY - Abstract
Granular flows are omnipresent in nature and industrial processes, but their rheological properties such as apparent friction and packing fraction are still elusive when inertial, cohesive and viscous interactions occur between particles in addition to frictional and elastic forces. Here we report on extensive particle dynamics simulations of such complex flows for a model granular system composed of perfectly rigid particles. We show that, when the apparent friction and packing fraction are normalized by their cohesion-dependent quasistatic values, they are governed by a single dimensionless number that, by virtue of stress additivity, accounts for all interactions. We also find that this dimensionless parameter, as a generalized inertial number, describes the texture variables such as the bond network connectivity and anisotropy. Encompassing various stress sources, this unified framework considerably simplifies and extends the modeling scope for granular dynamics, with potential applications to powder technology and natural flows. Granular materials are abundant in nature, but we haven't fully understood their rheological properties as complex interactions between particles are involved. Here, Vo et al. show that granular flows can be described by a generalized dimensionless number based on stress additivity. [ABSTRACT FROM AUTHOR]
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- 2020
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7. Compaction of granular materials composed of deformable particles.
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Thanh Hai Nguyen, Nezamabadi, Saeid, Delenne, Jean-Yves, and Radjai, Farhang
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GRANULAR materials , *COMPACTING , *DEFORMATIONS (Mechanics) , *MECHANICAL behavior of materials , *MATERIAL point method - 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. [ABSTRACT FROM AUTHOR]
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- 2017
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8. Analysis of dense packing of highly deformed grains.
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Thi Lo Vu, Nezamabadi, Saeid, Barés, Jonathan, and Mora, Serge
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GRANULAR materials , *PACKING (Mechanical engineering) , *DEFORMATIONS (Mechanics) , *STRAINS & stresses (Mechanics) , *FRICTION , *COMPRESSION loads - Abstract
This paper concerns modeling of soft granular materials in which the grains are highly deformable. In order to simulate these materials, an approach based on an implicit formulation of the Material Point Method in the context of the finite strain theory, allowing for large deformations of grains, coupled with the Contact Dynamics method for the treatment of unilateral frictional contacts between grains, is proposed. In this context, the Mooney-Rivlin constitutive relationship is applied with two different set of elastic parameters. Considering these two material behaviors, a uniaxial compression of 2D soft granular packings is analyzed. The stress-strain relation and the evolution of the packing fraction as well as of the connectivity of the grains are discussed. [ABSTRACT FROM AUTHOR]
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- 2017
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9. Cohesive strength of iron ore granules.
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Jaimes Contreras, Rafael, Berger, Nicolas, Izard, Edouard, Douce, Jean-François, Koltsov, Alexey, Delenne, Jean-Yves, Azema, Emilien, Nezamabadi, Saeid, van Loo, Frédéric, Pellenq, Roland, and Radjai, Farhang
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COHESIVE strength (Mechanics) ,IRON ores ,GRANULAR materials ,MECHANICAL behavior of materials ,COMPRESSIVE strength - 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. [ABSTRACT FROM AUTHOR]
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- 2017
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10. Parallel implicit contact algorithm for soft particle systems.
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Nezamabadi, Saeid, Frank, Xavier, Delenne, Jean-Yves, Averseng, Julien, and Radjai, Farhang
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PARALLEL algorithms , *DEFORMATIONS (Mechanics) , *MESSAGE passing (Computer science) , *STRAINS & stresses (Mechanics) , *COMPRESSIBILITY , *GRANULAR materials - Abstract
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. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
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11. Implicit frictional-contact model for soft particle systems.
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Nezamabadi, Saeid, Radjai, Farhang, Averseng, Julien, and Delenne, Jean-Yves
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COMPUTER simulation , *MATERIAL point method , *DEFORMATIONS (Mechanics) , *FRICTION , *MATHEMATICAL regularization , *DAMPING (Mechanics) - 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. [ABSTRACT FROM AUTHOR]
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- 2015
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12. Effects of particle compressibility on structural and mechanical properties of compressed soft granular materials.
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Vu, Thi-Lo, Nezamabadi, Saeid, and Mora, Serge
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COMPRESSIBILITY , *MECHANICAL behavior of materials , *GRANULAR materials , *PARTICLES - Abstract
Changes in the mechanical properties of granular materials, induced by variations in the intrinsic compressibility of the particles, are investigated by means of numerical simulations based on the combination of the Finite Element and Contact Dynamics methods. Assemblies of athermal 2D particles are subjected to quasi-static uni-axial compactions up to packing fractions close to 1. We show that the effect of the compressibility of the particles both on the global and the local stresses, can be described by considering only the packing fraction of the system. This result, demonstrated in the whole range of accessible packing fractions in case of frictionless particles, remains relevant for moderate inter-particles coefficients of friction. The small discrepancies observed with frictional particles originate from irreversible local reorganizations in the system, the later being facilitated by the compressibility of the particles. [ABSTRACT FROM AUTHOR]
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- 2021
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13. Mechanical strength of wet particle agglomerates.
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Vo, Thanh-Trung, Mutabaruka, Patrick, Nezamabadi, Saeid, Delenne, Jean-Yves, Izard, Edouard, Pellenq, Roland, and Radjai, Farhang
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MATERIAL plasticity , *DISCRETE element method , *GRANULAR materials , *LAGRANGE equations , *COMPUTER simulation - Abstract
Highlights • Agglomerates of wet particles undergo plastic deformation before breaking. • The plastic strength is proportional to the characteristic capillary stress. • The effect of particle size span is mainly included in the characteristic stress. • The amount of liquid affects the strength through the wet coordination number. 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. [ABSTRACT FROM AUTHOR]
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- 2018
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14. Evolution of wet agglomerates inside inertial shear flow of dry granular materials.
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Thanh-Trung Vo, Mutabaruka, Patrick, Nezamabadi, Saeid, Delenne, Jean-Yves, and Radjai, Farhang
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GRANULAR flow , *GRANULAR materials , *VISCOSITY , *SURFACE tension , *PARTICLE dynamics , *INDEX numbers (Economics) , *PHASE space - Abstract
We use particle dynamics simulations to investigate the evolution of a wet agglomerate inside homogeneous shear flows of dry particles. The agglomerate is modeled by introducing approximate analytical expressions of capillary and viscous forces between particles in addition to frictional contacts. During shear flow, the agglomerate may elongate, break, or be eroded by loss of its capillary bonds and primary particles. By systematically varying the shear rate and surface tension of the binding liquid, we characterize the rates of these dispersion modes. All the rates increase with increasing inertial number of the flow and decreasing cohesion index of the agglomerate. We show that the data points for each mode collapse on a master curve for a dimensionless scaling parameter that combines the inertial number and the cohesion index. The erosion rate vanishes below a cutoff value of the scaling parameter. This leads to a power-law borderline between the vanishing erosion states and erosion states in the phase space defined by the inertial number and the cohesion index. [ABSTRACT FROM AUTHOR]
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- 2020
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15. Numerical simulations of the compaction of assemblies of rubberlike particles: A quantitative comparison with experiments.
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Vu, Thi-Lo, Barés, Jonathan, Mora, Serge, and Nezamabadi, Saeid
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GRANULAR materials , *FINITE element method , *COMPACTING , *COMPUTER simulation , *PARTICLES , *DEFORMATION of surfaces - Abstract
Using the contact dymanics method together with the finite element method, we simulate the uniaxial compression of assemblies of elastic cylinders. The numerical model accounts for finite deformations of the particles through the neo-Hookean constitutive equation and solid friction between the particles. A quantitative comparison with experiments carried out with centimetric rubberlike cylinders, with local deformations of the particles determined by image correlation, is proposed. We show that the simulations accurately capture the details of both the microstructure and the macroscopic behavior of the real granular system, demonstrating the relevancy of the numerical approach. [ABSTRACT FROM AUTHOR]
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- 2019
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