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4. Fluid-particle energy transfer in spiral jet milling

Author

Radjai, F., Dogbe, Selasi, Ghadiri, Mojtaba, Hassanpour, Ali, Hare, Colin, Wilson, David, Storey, Richard, Crosley, Iain, Nezamabadi, S., Luding, S., and Delenne, J.Y.

Subjects
Physics, Work (thermodynamics), Jet (fluid), QC1-999, Jet mill, Mechanical engineering, 02 engineering and technology, Mechanics, 021001 nanoscience & nanotechnology, Discrete element method, Grinding, Fluid power, 020401 chemical engineering, Particle, Particle size, 0204 chemical engineering, 0210 nano-technology
Abstract

Spiral jet milling is a size reduction process driven by the fluid energy of high velocity gas jets. Inter-particle and particle-wall interactions are responsible for size reduction. The process is energy intensive, but inefficient. The underlying mechanisms for size reduction in the mill are also not very well understood. The optimum grinding conditions are still currently found by trial and error experimentation. In this work, the Discrete Element Method coupled with Computational Fluid Dynamics is used to investigate the effects of different parameters on the particle collisional behaviour in a spiral jet mill. These include the particle concentration in the grinding chamber, the particle size, and the fluid power input. We report on our work analysing the efficiency of energy transfer and how it can be improved by changing the milling conditions and particle properties.

Published
2017

5. Automated discrete element method calibration using genetic and optimization algorithms

Author

Do, H.Q., Aragon, A.M., Schott, D.L., Radjai, F., Nezamabadi, S., Luding, S., and Delenne, J.Y.

Subjects
Optimization algorithm, Computer science, Physics, QC1-999, Rolling resistance, Model parameters, 02 engineering and technology, 021001 nanoscience & nanotechnology, Granular material, Discrete element method, Computational science, Test case, 020401 chemical engineering, Robustness (computer science), 0204 chemical engineering, 0210 nano-technology, Algorithm
Abstract

This research aims at developing a universal methodology for automated calibration of microscopic properties of modelled granular materials. The proposed calibrator can be applied for different experimental set-ups. Two optimization approaches: (1) a genetic algorithm and (2) DIRECT optimization, are used to identify discrete element method input model parameters, e.g., coefficients of sliding and rolling friction. The algorithms are used to minimize the objective function characterized by the discrepancy between the experimental macroscopic properties and the associated numerical results. Two test cases highlight the robustness, stability, and reliability of the two algorithms used for automated discrete element method calibration with different set-ups.

Published
2017

6. Flowability assessment of weakly consolidated powders

Author

Radjai, F., Stavrou, Alexandros Georgios, Hare, Colin, Hassanpour, Ali, Wu, Chuan-Yu, Nezamabadi, S., Luding, S., and Delenne, J.Y.

Subjects
Materials science, Consolidation (soil), Physics, QC1-999, 02 engineering and technology, Penetration (firestop), 021001 nanoscience & nanotechnology, Indentation hardness, Constraint factor, 020401 chemical engineering, Indentation, Forensic engineering, 0204 chemical engineering, Composite material, 0210 nano-technology, Shear testing
Abstract

The inability of cohesive powders to flow consistently and reliably is a major cause of process downtime and reduced efficiency across a wide range of powder processing industries. Most methods to assess powder flowability fail at low consolidation pressures (

Published
2017

7. Pomelo, a tool for computing Generic Set Voronoi Diagrams of Aspherical Particles of Arbitrary Shape

Author

Radjai, F., Weis, S., Schönhöfer, P.W.A., Schaller, F.M., Schröter, M., Schröder-Turk, G.E., Nezamabadi, S., Luding, S., Delenne, J.Y., Radjai, F., Weis, S., Schönhöfer, P.W.A., Schaller, F.M., Schröter, M., Schröder-Turk, G.E., Nezamabadi, S., Luding, S., and Delenne, J.Y.

Abstract

We describe the development of a new software tool, called “Pomelo”, for the calculation of Set Voronoi diagrams. Voronoi diagrams are a spatial partition of the space around the particles into separate Voronoi cells, e.g. applicable to granular materials. A generalization of the conventional Voronoi diagram for points or monodisperse spheres is the Set Voronoi diagram, also known as navigational map or tessellation by zone of influence. In this construction, a Set Voronoi cell contains the volume that is closer to the surface of one particle than to the surface of any other particle. This is required for aspherical or polydisperse systems. Pomelo is designed to be easy to use and as generic as possible. It directly supports common particle shapes and offers a generic mode, which allows to deal with any type of particles that can be described mathematically. Pomelo can create output in different standard formats, which allows direct visualization and further processing. Finally, we describe three applications of the Set Voronoi code in granular and soft matter physics, namely the problem of packings of ellipsoidal particles with varying degrees of particle-particle friction, mechanical stable packings of tetrahedra and a model for liquid crystal systems of particles with shapes reminiscent of pears.

Published
2017

8. Towards minimal models for realistic granular materials: Tomographic analysis of bidispersed assemblies of ellipsoid

Author

Radjai, F., Schaller, F.M., Punzmann, H., Schröder-Turk, G.E., Saadatfar, M., Nezamabadi, S., Luding, S., Delenne, J.Y., Radjai, F., Schaller, F.M., Punzmann, H., Schröder-Turk, G.E., Saadatfar, M., Nezamabadi, S., Luding, S., and Delenne, J.Y.

Abstract

In this paper, we report experimental results on granular compaction in a model system made of mono- and bidisperse ellipsoidal packings as well as sand packings with grain size polydispersity. The packings are subject to vertical tapping of varying duration (number of taps) and their internal three-dimensional structure is obtained using x-ray computed tomography. Particles positions and orientations are reconstructed and the global packing densities are computed. The analysis of the vertical and horizontal local packing fraction profiles reveal a homogeneous densification in the ellipsoidal packings, however, sand packings exhibit radial density gradient, possibly linked to the onset of convection.

Published
2017

9. A Numerical Strategy for the Compaction of Soft Particle Systems beyond Jamming Transition

Author

Nezamabadi, S., Radjai, Farhang, Averseng, Julien, Delenne, Jean-Yves, Conception en structures (CS), 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), Physique et Mécanique des Milieux Granulaires (PMMG), Physique et Mécanique des Milieux Granulaires, Ingénierie des Agro-polymères et Technologies Émergentes (UMR IATE), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA), and Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)

Subjects
[PHYS.MECA.MEMA]Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], [SPI.MECA.MEMA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph]
Published
2013

10. Computational homogenization of materials with local and global instabilities

Author

Nezamabadi, S., Zahrouni, H., Yvonnet, Julien, Potier-Ferry, M., Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux (LEM3), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM), Laboratoire de Modélisation et Simulation Multi Echelle (MSME), Université Paris-Est Marne-la-Vallée (UPEM)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM)-HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM), École Nationale Supérieure d'Arts et Métiers (ENSAM), Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM)-Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Paris-Est Marne-la-Vallée (UPEM), and YVONNET, Julien

Published
2012

11. Matériaux hyperélastique et Méthodes Asymptotique Numérique

Author

Nezamabadi, S., Zahrouni, H., Yvonnet, Julien, Laboratoire de Mécanique des Structures et des Systèmes Couplés (LMSSC), Conservatoire National des Arts et Métiers [CNAM] (CNAM), Laboratoire de physique et mécanique des matériaux (LPMM), Université Paul Verlaine - Metz (UPVM)-Institut National Polytechnique de Lorraine (INPL)-Ecole Nationale d'Ingénieurs de Metz (ENIM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Modélisation et Simulation Multi Echelle (MSME), Université Paris-Est Marne-la-Vallée (UPEM)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), YVONNET, Julien, HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM)-HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM), Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux (LEM3), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Arts et Métiers Sciences et Technologies, and HESAM Université (HESAM)-HESAM Université (HESAM)

Subjects
[SPI.MECA]Engineering Sciences [physics]/Mechanics [physics.med-ph], [SPI.MECA] Engineering Sciences [physics]/Mechanics [physics.med-ph]
Abstract

National audience; Dans cet article, on présente un algorithme numérique basé sur une technique de perturbationappelée Méthode Asymptotique Numérique (MAN) pour résoudre des problèmes non linéaires dans lecadre des matériaux hyperélastiques compressibles et incompressibles. L’efficacité et la précision de laméthode sont examinées en comparant cet algorithme avec la méthode classique de Newton-Raphsonpour des problèmes de structures en présence de grandes déformations hyperélastiques et instabilités.

Published
2011

12. A multiscale finite element approach for buckling analysis of elastoplastic long fibre composites

Author

Nezamabadi, S., Zahrouni, H., Yvonnet, Julien, Potier-Ferry, M., Laboratoire de Mécanique et Génie Civil (LMGC), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux (LEM3), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM), Laboratoire de Modélisation et Simulation Multi Echelle (MSME), Université Paris-Est Marne-la-Vallée (UPEM)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM)-HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM), Laboratoire de Mécanique des Structures et des Systèmes Couplés (LMSSC), Conservatoire National des Arts et Métiers [CNAM] (CNAM), Arts et Métiers Sciences et Technologies, Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Paris-Est Marne-la-Vallée (UPEM), École Nationale Supérieure d'Arts et Métiers (ENSAM), HESAM Université (HESAM)-HESAM Université (HESAM)-Arts et Métiers Sciences et Technologies, and HESAM Université (HESAM)-HESAM Université (HESAM)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SPI.GCIV]Engineering Sciences [physics]/Civil Engineering, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2010
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13. Multiscale microbuckling analysis of elastoplastic long fiber composites

Author

Nezamabadi, S., Zahrouni, H., Yvonnet, Julien, Potier-Ferry, M., YVONNET, Julien, Laboratoire de physique et mécanique des matériaux (LPMM), Université Paul Verlaine - Metz (UPVM)-Institut National Polytechnique de Lorraine (INPL)-Ecole Nationale d'Ingénieurs de Metz (ENIM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux (LEM3), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM), Laboratoire de Modélisation et Simulation Multi Echelle (MSME), Université Paris-Est Marne-la-Vallée (UPEM)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Mécanique des Structures et des Systèmes Couplés (LMSSC), Conservatoire National des Arts et Métiers [CNAM] (CNAM), École Nationale Supérieure d'Arts et Métiers (ENSAM), Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM)-Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM)-HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM), and Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Paris-Est Marne-la-Vallée (UPEM)

Subjects
[SPI]Engineering Sciences [physics], [SPI] Engineering Sciences [physics], [SPI.MECA.MSMECA] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Materials and structures in mechanics [physics.class-ph], [SPI.MECA.MSMECA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Materials and structures in mechanics [physics.class-ph]
Published
2009

15. Technique multi-échelle pour l'analyse du microflambage des composites

Author

Nezamabadi, S., Zahrouni, H., Yvonnet, Julien, Potier-Ferry, M., Laboratoire de Mécanique des Structures et des Systèmes Couplés (LMSSC), Conservatoire National des Arts et Métiers [CNAM] (CNAM), Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux (LEM3), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM), Laboratoire de Modélisation et Simulation Multi Echelle (MSME), Université Paris-Est Marne-la-Vallée (UPEM)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), YVONNET, Julien, École Nationale Supérieure d'Arts et Métiers (ENSAM), Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM)-Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Paris-Est Marne-la-Vallée (UPEM), and HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM)-HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM)

Subjects
ComputingMilieux_MISCELLANEOUS
Abstract

National audience

Published
2009

16. Multiscale Buckling Analysis of Heterogeneous Materials

Author

Yvonnet, Julien, Zahrouni, H., Nezamabadi, S., Potier-Ferry, M., YVONNET, Julien, Laboratoire de Modélisation et Simulation Multi Echelle (MSME), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Paris-Est Marne-la-Vallée (UPEM), Laboratoire de physique et mécanique des matériaux (LPMM), Université Paul Verlaine - Metz (UPVM)-Institut National Polytechnique de Lorraine (INPL)-Ecole Nationale d'Ingénieurs de Metz (ENIM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Mécanique des Structures et des Systèmes Couplés (LMSSC), Conservatoire National des Arts et Métiers [CNAM] (CNAM), and Université Paris-Est Marne-la-Vallée (UPEM)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SPI.MECA.MSMECA] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Materials and structures in mechanics [physics.class-ph], [SPI.MECA.MSMECA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Materials and structures in mechanics [physics.class-ph]
Published
2008

17. Detection of toxigenic bacillus cereus strains in powdered infant formula (PIF) milk by PCR assay

Author

Soltan Dallal, M. M., Nezamabadi, S., Mardaneh, J., zahra rajabi, and Sirdani, A.

Subjects
virulence, lcsh:R5-920, infants, polymerase chain reaction, fungi, bacillus cereus, molecular method, cross-sectional studies, infant formula, lcsh:Medicine (General)
Abstract

Background: In recent years, use of powdered infant formula (PIF) milk for neonates feed is increasing; therefore, the quality control (QC) of PIF products is very important. The aim of present study was detection of toxigenic Bacillus cereus species in PIF milk using PCR assay. Methods: The cross-sectional study was carried out on 125 samples of powdered infant formula milk (PIF) purchased between March 2015 and April 2016 in Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. Briefly, 0.1 dilutions were prepared and inoculated on Bacillus cereus selective media (MYP) and incubated at 30 °C for 24 hours. The suspicious colonies were verified using biochemical tests based on standard methods. Final confirmation of studied isolates was carried out by ITS gene detection using polymerase chain reaction (PCR) assay. Presence of nonhemolytic enterotoxin (NHE) (linked to diarrhoea syndrome) and emetic toxin (EM) (linked to emetic syndrome) virulence genes were investigated using polymerase chain reaction assay. Results: In this study, of 125 PIF samples, 84 (67.2%) were contaminated. Of various recovered bacteria from these samples, 110 bacterial isolates were suspected to be Bacillus spp. using phenotypic methods. The ITS PCR results showed that 91.8% of the isolates were B. cereus. Respectively, 53.63 and 79% of B. cereus isolates possessed NHE and EM virulence genes. Conclusion: Our data revealed that near 80% of Bacillus cereus isolates have emetic toxin (EM) gene, as result virulence potency of this isolates is very high. However, the low number of this organisms in foods is very important and food safety protocols for these opportunistic toxigenic bacteria should be revised. Since the pasteurization process is ineffective on B. cereus spores; therefore, spores can remain in PIF milk and the vegetative bacterial cells can cause food poisoning in neonates. Therefore, modification of foods quality control protocols is essential in order to identify virulence genes in this bacterium.

18. Modelling soft-particle materials

Author

Nezamabadi, S., Radjai, F., Averseng, J., Jean-Yves Delenne, Laboratoire de Mécanique et Génie Civil (LMGC), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Physique et Mécanique des Milieux Divisés (PMMD), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Structures Innovantes, Géomatériaux, ECOconstruction (SIGECO), Ingénierie des Agro-polymères et Technologies Émergentes (UMR IATE), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA), and Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université Montpellier 2 - Sciences et Techniques (UM2)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université de Montpellier (UM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)

Subjects
tassement mécanique, conditionnement, particule solide, simulation models, processing, [SPI.GPROC]Engineering Sciences [physics]/Chemical and Process Engineering, particule - surface interactions, modèle de simulation, interaction particule surface
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.

19. From continuum analytical description to discrete numerical modelling of localized fluidization in granular media

Author

Eduard Puig Montellà, Marcella Toraldo, Luc Sibille, Bruno Chareyre, Laboratoire sols, solides, structures - risques [Grenoble] (3SR ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), GéoMécanique, Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), F. Radjai, S. Nezamabadi, S. Luding and J.Y. Delenne, Sibille, Luc, and F. Radjai, S. Nezamabadi, S. Luding and J.Y. Delenne

Subjects
Physics, Continuum (measurement), Effective stress, QC1-999, [SPI.GCIV.GEOTECH]Engineering Sciences [physics]/Civil Engineering/Géotechnique, Granular media, Granular layer, Mechanics, [SPI.GCIV.CH]Engineering Sciences [physics]/Civil Engineering/Construction hydraulique, 01 natural sciences, 010305 fluids & plasmas, Free surface, 0103 physical sciences, [SPI.GCIV.GEOTECH] Engineering Sciences [physics]/Civil Engineering/Géotechnique, [SPI.GCIV.RISQ]Engineering Sciences [physics]/Civil Engineering/Risques, Chimney, Fluidization, Statistical physics, 010306 general physics, Porosity, [SPI.GCIV.CH] Engineering Sciences [physics]/Civil Engineering/Construction hydraulique, [SPI.GCIV.RISQ] Engineering Sciences [physics]/Civil Engineering/Risques
Abstract

We present analytical and numerical results on localized fluidization within a granular layer subjected to a local injection of fluid. As the injection rate increases the three different regimes previously reported in the literature are recovered: homogeneous expansion of the bed, fluidized cavity in which fluidization starts developing above the injection area, and finally the chimney of fluidized grains when the fluidization zone reaches the free surface. The analytical approach is at the continuum scale, based on Darcy’s law and Therzaghi’s effective stress principle. It provides a good description of the phenomenon as long as the porosity of the granular assembly remains relatively homogeneous. The numerical approach is at the particle scale based on the coupled DEM-PFV method. It tackles the more heterogeneous situations which occur at larger injection rates. A direct link is evidenced between the occurrence of the different regimes of fluidization and the injection aperture. Finally, the merging of chimneys in case of two injection points is investigated.

Published
2017

20. Sand - Rubber mixtures submitted to isotropic loading:A minimal model

Author

Platzer, Auriane, Rouhanifar, Salman, Richard, Patrick, Cazacliu, Bogdan, Ibraim, Erdin, and Radjai, S. Nezamabadi, S. Luding and J.Y. Delenne, F

Abstract

The volume of scrap tyres, an undesired urban waste, is increasing rapidly in every country. Mixing sand and rubber particles as a lightweight backfill is one of the possible alternatives to avoid stockpiling them in the environment. This paper presents a minimal model aiming to capture the evolution of the void ratio of sand-rubber mixtures undergoing an isotropic compression loading. It is based on the idea that, submitted to a pressure, the rubber chips deform and partially fill the porous space of the system, leading to a decrease of the void ratio with increasing pressure. Our simple approach is capable of reproducing experimental data for two types of sand (a rounded one and a sub-angular one) and up to mixtures composed of 50% of rubber.

Published
2017
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21. Linear and nonlinear elastic properties of dense granular packings: a DEM exploration

Author

Xiaoping Jia, Robert A. Guyer, Paul A. Johnson, Laure Lemrich, Jan Carmeliet, Radjai, F., Nezamabadi, S., Luding, Stefan, and Delenne, J. Y.

Subjects
Physics, Dependency (UML), Field (physics), QC1-999, Mode (statistics), Mechanics, 01 natural sciences, Discrete element method, 010305 fluids & plasmas, Stress (mechanics), Nonlinear system, Amplitude, 0103 physical sciences, 010306 general physics, Magnetosphere particle motion
Abstract

Discrete Element Method modeling is used to study the frequency spectrum of particle motion in dense 3D packings of glass beads with Hertz-Mindlin contacts. Frequency sweeps show a dependency of the resonant frequencies on the drive amplitude and confining stress on the system, showing material changes in the system. The amplitude dependency of the second thickness mode 3λ/4 as identified by the internal strain field scales as f ∝ σ1/6 while the confining stress dependency scales as f ∝ σ 2/3, as predicted by Hertzian theory., EPJ Web of Conferences, 140, ISSN:2100-014X, ISSN:2101-6275

Published
2017
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22. Contact networks and force transmission in aggregates of hexapod-shaped particles.

Author

Tran TD, Nezamabadi S, Bayle JP, Amarsid L, and Radjai F

Abstract

Hexapods, consisting of three mutually orthogonal arms, have been utilized as a representative nonconvex shape to demonstrate the impact of interlocking on the strength properties of granular materials. Nevertheless, the microstructural characteristics of hexapod packings, which underlie their strength, have remained insufficiently characterized. We use particle dynamics simulations to build isotropically-packed aggregates of hexapods and we analyze the effects of aspect ratio and interparticle friction on the microstructure and force transmission. We find that the packing fraction is an unmonotonic function of aspect ratio due to competition between steric exclusions and interlocking. Interestingly, the contact coordination number declines considerably with friction coefficient, showing the stronger effect of friction on the stability of hexapod packings as compared with sphere packings. The pair distribution functions show that local ordering due to steric exclusions disappears beyond the aspect ratio 3 and the hexapods touch their second neighbors. Remarkably, hexapods of aspect ratio 3 tend to align with their neighbors and form locally ordered structures, implying a contact coordination number which is highly sensitive to the confining pressure. We also show that the probability density function of forces between hexapods is similar to that of sphere packings but with broadening exponential fall-off of strong forces as aspect ratio increases. Finally, the elastic bulk modulus of the aggregates is found to increase considerably with aspect ratio as a consequence of the rapid increase of contact density and the number of contacts with second neighbors.

Published
2024
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23. Adverse events associated with immune checkpoint inhibitors in patients with breast cancer: A systematic review and meta-analysis.

Author

Balibegloo M, Nejadghaderi SA, Sadeghalvad M, Soleymanitabar A, Salehi Nezamabadi S, Saghazadeh A, and Rezaei N

Subjects
Female, Humans, Randomized Controlled Trials as Topic, Breast Neoplasms drug therapy, Immune Checkpoint Inhibitors adverse effects
Abstract

Background: Breast cancer is one of the most prevalent cancers with a high rate of mortality. Immune checkpoint inhibitors (ICIs) have shown promising results in breast cancer treatment. However, the incidences of adverse events (AEs) and immune-related AEs (irAEs) due to ICIs have not been investigated comprehensively. We aimed to determine any-grade and grade 3-5 AEs and irAEs of ICIs compared to the control group which were other conventional therapies in adults with breast cancer., Methods: We included controlled clinical trials that involved ICIs in adults with breast cancer to assess AEs and irAEs of ICIs. We systematically searched PubMed, EMBASE, Scopus, Web of Science, the Cochrane Central Register of Controlled Trials, Clinical-Trials.gov, and metaRegister of Controlled Trials up to March 12, 2021. Version 2 of the Cochrane risk-of-bias tool for randomized trials (RoB 2) was used for quality assessment., Results: Nine studies, including 4687 participants met our inclusion criteria. Rash and infusion reaction were the two most frequent irAEs of any-grade and grade 3-5. Among irAEs, hyperthyroidism had the most prominent difference between the two groups in favor of ICIs followed by hypothyroidism and adrenal insufficiency. Among grade 3-5 and any-grade non-immune AEs, increased aspartate aminotransferase (RR = 1.91; 95% CI, 1.11-3.28) and cough (RR = 1.32; 95%CI, 1.11-1.57) had the highest RRs in favor of ICIs, respectively. The frequencies of overall any-grade and grade 3-5 irAEs were higher in the ICI group., Conclusion: The results showed that all the AEs and irAEs of all the categories were more prevalent with ICIs., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Published
2021
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24. Tensile strength of granular aggregates: Stress chains across particle phase versus stress concentration by pores.

Author

Frank X, Radjaï F, Nezamabadi S, and Delenne JY

Abstract

We use the bond-based peridynamics approach to analyze the strength and fracture of dense granular aggregates with variable amount of a solid binding matrix, distributed according to a simple protocol in the interstitial space between particles. We show the versatility of the peridynamics approach in application to crack propagation and its scaling behavior in a homogeneous medium (in the absence of particles and pores). Then we apply this method to simulate the deformation and failure of aggregates as a function of the amount of the binding matrix under tensile loading. We find that the tensile strength is a strongly nonlinear function of the matrix volume fraction. It first increases slowly and levels off as the gap space in-between touching particles is gradually filled by the binding matrix, up to nearly 90% of the total pore volume, and then a rapid increase occurs to the maximum strength as the remaining interstitial space, composed of isolated pores between four or more particles, is filled. By analyzing the probability density functions of stresses in the particle and matrix phases, we show that the adhesion of the matrix to the particles and the thickening of stress chains (i.e., stresses distributed over larger cross sections) control the strength in the first case whereas the homogenizing effect of the matrix by filling the pores (hence reducing stress concentration) is at the origin of further increase of the strength in the second case. Interestingly, these two mechanisms contribute almost equally to the total strength.

Published
2020
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25. Additive rheology of complex granular flows.

Author

Vo TT, Nezamabadi S, Mutabaruka P, Delenne JY, and Radjai F

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.

Published
2020
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26. Evolution of wet agglomerates inside inertial shear flow of dry granular materials.

Author

Vo TT, Mutabaruka P, Nezamabadi S, Delenne JY, and Radjai F

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.

Published
2020
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27. Compaction of elastic granular materials: inter-particles friction effects and plastic events.

Author

Vu TL, Nezamabadi S, and Mora S

Abstract

The uni-axial compaction of granular materials made of elastic neo-Hookean particles is investigated in the quasi-static regime. Two-dimensional disk assemblies are simulated using the Finite Element model coupled with Contact Dynamics method for dealing both with finite deformations of the particles and contact interactions. Due to large deformations of the particles, the packing fraction of the system increases continuously during the compaction process, reaching values close to 1. The influence of the coefficient of friction between the particles on the macroscopic and micro-structural behaviors of the system is thoroughly discussed.

Published
2020
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28. Agglomeration of wet particles in dense granular flows.

Author

Trung Vo T, Nezamabadi S, Mutabaruka P, Delenne JY, Izard E, Pellenq R, and Radjai F

Abstract

In order to get insight into the wet agglomeration process, we numerically investigate the growth of a single granule inside a dense flow of an initially homogeneous distribution of wet and dry particles. The simulations are performed by means of the discrete element method and the binding liquid is assumed to be transported by the wet particles, which interact via capillary and viscous force laws. The granule size is found to be an exponential function of time, reflecting the conservation of the amount of liquid and the decrease of the number of available wet particles inside the flow during agglomeration. We analyze this behavior in terms of the accretion and erosion rates of wet particles for a range of different values of material parameters such as mean particle size, size polydispersity, friction coefficient and liquid viscosity. In particular, we propose a phase diagram of the granule growth as a function of the mean primary particle diameter and particle size span, which separates the parametric domain in which the granule grows from the domain in which the granule does not survive.

Published
2019
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29. Numerical simulations of the compaction of assemblies of rubberlike particles: A quantitative comparison with experiments.

Author

Vu TL, Barés J, Mora S, and Nezamabadi S

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.

Published
2019
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