Views on Microstructures in Granular Materials (original) (raw)
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Views on Microstructures in Granular Materials: the Preface
2020
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Some statistics about research on granular materials during the last decade
EPJ Web of Conferences
In this work we present several statistical analyses about research on the subject of granular materials during the last ten years. These statistics are based on the set of articles published in the Granular Materials section of Physical Review E during this period, comprising roughly 1000 documents (including rapid communications). We estimate the degree of contribution of countries, academic institutions, authors, and articles, in terms of the frequency of appearance on the articles' affiliations and the number of citations. On the first hand, these analyses serve as a recognition to researchers and research communities that have notably contributed to the development of knowledge on granular materials. On the second hand, the presented statistics allow for identifying countries and institutions where research in granular materials is the most developed, and also places where it can be developed in the future. Finally, these analyses allow for highlighting which cooperations amongst countries have been the most active during the last decade, which in turn allows for identifying potential links to be created and developed across this research network.
Micro structures of granular materials with various grain size distributions
Powder Technology, 2012
The effect of the grain size distribution on the micro structure of granular materials has not been fully understood. Especially, few works is currently available on the coordination number of the well-graded granular mixtures due to the difficulty and uncertainness of experimental measurement. This research aims at studying systematically the effects of grain size distribution on the coordination number and constructing a model to predict the frequency distribution of the coordination number of granular materials on the basis of their grain size distribution. Using a two-dimensional Discrete Element Method, nine types of disk assemblies were packed densely or loosely and their coordination numbers and void ratios were measured. Simulation results indicated that the coordination number and the void ratio generally decreased with increasing grain size dispersion. The authors found a general relationship between the number of contact points and the particle size which can be applied to granular materials having various grain size distributions. In the case of densely packed assemblies, this relationship is applicable to predict the frequency distribution of coordination number only from their grain size distribution.
Microstructural characteristics of planar granular solids
2013
The microstructure of granular materials is the main factor determining their macroscopic behaviour. We study systematically the statistical characteristics of volume elements (called quadrons) of microstructures of mono-and polydisperse planar disc packs granular and report a number of new results. The packs analysed were of different intergranular friction coef¿cients ,μ, contained about 20,000 discs each and were brought to mechanical equilibrium under identical isotropic compression stresses from three different initial states: loose, intermediate and dense. Our ¿ndings are the following. (i) The rattlers volume fraction φ r is not affected by the disc size distribution (DSD). (ii) Excluding the rattlers, we ¿nd that the relation between the packing fraction φ and the mean coordination numberz is independent of the initial state. Together with result (i), this allows us to separate the effects of the DSD and the initial state on the microstructure. (iii) We relate analyticallȳ z, φ and the (normalised) mean quadron volumev. (iv) Combining (iii) and a relation betweenz and the mean cell order,ē, derived from Euler's topological relation, we show that (ii) is a result of the geometrical relation betweenv andē. (v) The probability density function of the quadron volumes, normalised byv , is universal for all the studied systems and it can be ¿t reasonably well by a Γ distribution.
Acta Mechanica, 2008
The formation of strain localization influences the stability and stiffness of the soil mass or geosystem. The thickness of shear bands provides insight into overall strength and stiffness inside the granular body, and the shear band angle gives information about the failure surface in a given soil or soil mass. Thus, it is important to be able to predict when a shear band forms and how this zone of intense deformation is located and oriented within the granular medium. A rational finite element analysis for capturing the formation and development of shear bands has been formulated by using a micropolar continuum in finite element analysis. Hardening parameters including nonsymmetric stress and length scale are implemented for a realistic stressstrain analysis. Implementation and simulations of the model will be discussed in the Part II of this research. The micro-macro structure relation for finite element analysis based on this formulation paper will be simulated in the corresponding paper.
Contribution to the Study of Mechanical Behavior of Granular Media
Recent Advances in Environmental Science from the Euro-Mediterranean and Surrounding Regions (2nd Edition), 2021
This paper aimed at an experimental study carried out in a laboratory on calcite sand in order to characterize the behavior of the granular media using oedometric tests. Enormous quantities of this type of material exist in nature. In addition, it is the most used in various industrial sectors, especially in civil engineering in such fields as the manufacture of railway ballast. In these fields, the mechanical interactions between particles govern the macroscopic behavior of these materials. All grains constituting these materials have very diverse geometric and mechanical characteristics. Similarly, the solicitations interact between them are subjected, during the development phases, to the cycles of transport and storage. These materials often have complex behaviors due to the large number of their constituents, the complex role of local geometry (shape and grain arrangement) as well as the variety of interactions between grains (contact and friction). As a result, this study was devoted to studying the effects of the initial grain size curve, the initial density state, the consolidation stress, and the type of test on the mechanical properties. So, the overall mechanical behavior of these granular materials is strongly dependent on the spreading particle size, in contrast to the tight case. In addition, while the state of density can be influenced by the saturation mode, it is more marked for the dry mode.
On the effect of fines content on the micro-mechanical behavior of gap graded granular materials
Academic Journal of Civil Engineering, 2017
Dans cet article, nous présentons une étude micro-mécanique de l'effet du pourcentage de particules fines sur le comportement mécanique des matériaux granulaires à granulométrie lacunaire en utilisant la simulation numérique réalisée avec la Méthode des Éléments Discrets. Différents échantillons ayant un pourcentage de particules fines variant de 0% à 30% sont simulés. Cette étude montre que le pourcentage de particules fines influence significativement la résistance au cisaillement et la dilatance des échantillons granulaires. Lorsque le pourcentage de particules fines augmente, des particules fines viennent en contact avec des particules grossières and renforcent les dernières. De plus, la fraction de particules fines devient plus dense et participe plus à supporter la contrainte déviatoire appliquée.
Structural Characterization of Porous and Granular Materials
IOR 2011 - 16th European Symposium on Improved Oil Recovery, 2011
We review a recently-proposed method for quantifying internal structures of porous and granular materials in two and three dimensions. The method offers a systematic way to derive relations between the microstructure of such materials and their bulk properties. Preliminary results are presented for planar granular packs.
Morphological characterization and elastic response of a granular material
Computational Materials Science, 2021
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