[Étude micromécanique de la plasticité des matériaux granulaires]
La déformation plastique des matériaux granulaires est étudiée du point de vue micromécanique, dans lequel l'assemblage des particules et des contacts entre particules est considéré comme une structure mécanique. Ceci est fait de trois façons. Tout d'abord, en analysant le degré de redondance du système obtenu en comparant le nombre de degrés de liberté lié aux forces de contact avec le nombre d'équations d'équilibre ; Deuxièmement, en déterminant le spectre des valeurs propres de la matrice de rigidité de la structure qui est représentée par les particules et leurs contacts ; Troisièmement, en étudiant l'évolution pour une déformation imposée du tenseur de rigidité du milieu continu élastique équivalent au système analysé. Pour une déformation imposée, le degré de redondance évolue rapidement vers un état avec une petite redondance, c'est-à-dire que le système devient quasi isostatique. Le spectre des valeurs propres du système montre les modes singuliers et quasi singuliers au niveau de la résistance au cisaillement maximale et en grandes déformations. Le tenseur de rigidité élastique du milieu continu équivalent devient fortement anisotrope pour une déformation imposée, et fait apparaître la nature non affine de la déformation. L'hypothèse d'un tenseur de rigidité élastique, qui est constant dans des relations constitutives élasto-plastiques des matériaux granulaires, est généralement incorrecte. Globalement, le comportement macroscopique plastique est lié d'une part aux frottements aux contacts et d'autre part à l'évolution du réseau de contacts que l'on peut assimiler à un mécanisme d'endommagement.
Plastic deformation of granular materials is investigated from the micromechanical viewpoint, in which the assembly of particles and interparticle contacts is considered as a mechanical structure. This is done in three ways. Firstly, by investigating the degree of redundancy of the system by comparing the number of force degrees of freedom at contacts with the number of governing equilibrium equations; Secondly, by determining the spectrum of eigenvalues of the stiffness matrix for the structure that is represented by the particles and their contacts; Thirdly, by investigating the evolution with imposed strain of the continuum elastic stiffness tensor of the system. It is found that, with increasing imposed strain, the degree of redundancy rapidly evolves towards a state with small redundancy, i.e. the system becomes nearly statically determinate. The spectrum of the system shows many singular and near-singular modes at peak shear strength and at large strain. The continuum elastic stiffness tensor becomes strongly anisotropic with increasing imposed strain and shows strong non-affinity of deformation. The assumption of a constant and isotropic elastic stiffness tensor in elasto-plastic continuum constitutive relations for granular materials is generally incorrect. Overall, the plastic continuum behaviour of granular materials originates from the plastic frictional behaviour at contacts and from damage in the form of changes in the contact network.
Mot clés : Milieux granulaires, Plasticité, Micromécanique
Niels P. Kruyt 1
@article{CRMECA_2010__338_10-11_596_0, author = {Niels P. Kruyt}, title = {Micromechanical study of plasticity of granular materials}, journal = {Comptes Rendus. M\'ecanique}, pages = {596--603}, publisher = {Elsevier}, volume = {338}, number = {10-11}, year = {2010}, doi = {10.1016/j.crme.2010.09.005}, language = {en}, }
Niels P. Kruyt. Micromechanical study of plasticity of granular materials. Comptes Rendus. Mécanique, Volume 338 (2010) no. 10-11, pp. 596-603. doi : 10.1016/j.crme.2010.09.005. https://comptes-rendus.academie-sciences.fr/mecanique/articles/10.1016/j.crme.2010.09.005/
[1] A discrete numerical model for granular assemblies, Géotechnique, Volume 9 (1979), pp. 47-65
[2] The behaviour of an assembly of rotund, rigid, cohesionless particles I and II, Proceedings of the Royal Society of London A, Volume 286 (1965), pp. 62-97
[3] Initial fabric and their relation to mechanical properties of granular material, Soils and Foundations, Volume 12 (1972), pp. 19-36
[4] Constitution of mechanics of granular materials through graph theory (S.C. Cowin; M. Satake, eds.), US–Japan Seminar on Continuum-Mechanical and Statistical Approaches to Granular Materials, Elsevier, Amsterdam, the Netherlands, 1978, pp. 47-62
[5] Distribution of directional data and fabric tensors, International Journal of Engineering Science, Volume 22 (1984), pp. 149-164
[6] Observations on stress–force–fabric relationships in idealized granular materials, Mechanics of Materials, Volume 9 (1990), pp. 65-80
[7] Photoelastic verification of a mechanical model for the flow of a granular materials, Journal of the Mechanics and Physics of Solids, Volume 20 (1972), pp. 337-351
[8] Micromechanical study of elastic moduli of loose granular materials, Journal of the Mechanics and Physics of Solids, Volume 58 (2010), pp. 1286-1301
[9] Structured deformation in granular materials, Mechanics of Materials, Volume 31 (1999), pp. 407-429
[10] Quasi-static shear deformation of a soft particle system, Powder Technology, Volume 109 (2000), pp. 179-191
[11] Frictional collapse of granular assemblies, Journal of Applied Mechanics (Transactions of the ASME), Volume 71 (2004), pp. 350-358
[12] Modelling of microscopic mechanisms in granular material (J.T. Jenkins; M. Satake, eds.), Mechanics of Granular Materials: New Models and Constitutive Relations, Elsevier, Amsterdam, the Netherlands, 1983, pp. 137-149
[13] Geometric origin of mechanical properties of granular materials, Physical Review E, Volume 61 (2000), pp. 6802-6836
[14] Quasistatic rheology and the origins of strain, Comptes Rendus Physique, Volume 3 (2002), pp. 131-140
[15] Jamming at zero temperature and zero applied stress: the epitome of disorder, Physical Review E, Volume 68 (2003), p. 011306
[16] Shear strength, dilatancy, energy and dissipation in quasi-static deformation of granular materials, Journal of Statistical Mechanics: Theory and Experiment (2006), p. P07021
[17] Space-filling bearings, Physical Review Letters, Volume 65 (1990), pp. 3223-3226
[18] Critical state and evolution of coordination number in simulated granular materials, International Journal of Solids and Structures, Volume 41 (2004), pp. 5763-5774
[19] A micromechanically-based constitutive model for frictional deformation of granular materials, Journal of the Mechanics and Physics of Solids, Volume 48 (2000), pp. 1541-1563
[20] Fluctuations and the effective moduli of an isotropic, random aggregate of identical, frictionless spheres, Journal of the Mechanics and Physics of Solids, Volume 53 (2005), pp. 197-225
[21] Micromechanical definition of an entropy for quasi-static deformation of granular materials, Journal of the Mechanics and Physics of Solids, Volume 57 (2009), pp. 634-655
[22] Micromechanical aspects of isotropic granular assemblies with linear contact interactions, Journal of Applied Mechanics (Transactions of the ASME), Volume 55 (1988), pp. 17-23
[23] Statistics of the elastic behaviour of granular materials, International Journal of Solids and Structures, Volume 38 (2001), pp. 4879-4899
[24] Micro–macro transition for anisotropic, frictional granular packings, International Journal of Solids and Structures, Volume 41 (2004), pp. 5821-5836
[25] Why effective medium theory fails in granular materials, Physical Review Letters, Volume 83 (1999), pp. 5070-5073
[26] On the elastic moduli of two-dimensional assemblies of disks: relevance and modeling of fluctuations in particle displacements and rotations, Computers and Mathematics with Applications, Volume 55 (2008), pp. 245-256
[27] Statics and kinematics of discrete Cosserat-type granular materials, International Journal of Solids and Structures, Volume 40 (2003), pp. 511-534
Cité par Sources :
☆ This study is an extended version of that reported by N.P. Kruyt, L. Rothenburg, Plasticity of granular materials: a structural-mechanics view, in: M. Nakagawa, S. Luding (Eds.), Powders and Grains 2009, in: AIP Conference Proceedings, vol. 1145, 2009, pp. 1073–1076.
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