Experimental micromechanical analysis of a 2D granular material: relation between structure evolution and loading path

Calvetti, Francesco; Combe, Gaël; Lanier, J.

doi:10.1002/(sici)1099-1484(199704)2:2<121::aid-cfm27>3.0.co;2-2

Cited by 253 publications

(79 citation statements)

References 19 publications

(12 reference statements)

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“…Calvetti et al [20] presented the evolution of material anisotropy under complex loading condition including principal axes rotations based on laboratory tests on wooden roller stacks. Numerically, discrete element method (DEM) [21] has been used in numerous studies on material responses to biaxial/triaxial shearing and direct/simple tests [22][23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Macro deformation and micro structure of 3D granular assemblies subjected to rotation of principal stress axes

Yang

2016

Granular Matter

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This paper presents a numerical investigation on the behavior of three dimensional granular materials during continuous rotation of principal stress axes using the discrete element method. A dense specimen has been prepared as a representative element using the deposition method and subjected to stress rotation at different deviatoric stress levels. Significant plastic deformation has been observed despite that the principal stresses are kept constant. This contradicts the classical plasticity theory, but is in agreement with previous laboratory observations on sand and glass beads. Typical deformation characteristics, including volume contraction, deformation non-coaxiality, have been successfully reproduced. After a larger number of rotational cycles, the sample approaches the ultimate state with constant void ratio and follows a periodic strain path. The internal structure anisotropy has been quantified in terms of the contact-based fabric tensor. Rotation of principal stress axes densifies the packing, and leads to the increase in coordination numbers. A cyclic rotation in material anisotropy has been observed. The larger the stress ratio, the structure becomes more anisotropic. A larger fabric trajectory suggests more significant structure re-organization when rotating and explains the occurrence of more significant strain rate. The trajectory of the contactnormal based fabric is not centered in the origin, due to the anisotropy in particle orientation generated during sample generation which is persistent throughout the shearing process. The sample sheared at a lower intermediate principal stress ratio (b = 0.0) has been observed to approach a smaller strain trajectory as compared to the case b = 0.5, consistent with a smaller fabric trajectory and less significant structural re-organisation. It also experiences less volume contraction with the out-of plane strain component being dilative.

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Section: Introductionmentioning

confidence: 99%

Macro deformation and micro structure of 3D granular assemblies subjected to rotation of principal stress axes

Yang

2016

Granular Matter

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“…Most of these efforts were limited to shearing relatively large cylindrical rods or circular/oval discs under simple shear or plane stress/strain loading configurations and used optical methods to track deformations [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Strain tensor determination of compressed individual silica sand particles using high-energy synchrotron diffraction

et al. 2013

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The three-dimensional x-ray diffraction (3DXRD) nondestructive technique was used to measure lattice strains within individual sand particles subjected to compressive loading. Three experiments were conducted on similar single columns of silica sand particles with particle sizes between 0.595 mm and 0.841 mm. In each experiment, three sand particles were placed inside an acrylic mold with an inner diameter of 1 mm. Multiple in situ 3DXRD scans were acquired for each sand column as compressive load was increased. The volume-averaged lattice strain tensor was calculated for each sand particle. In addition, particle orientation and volumetric strain were calculated for individual sand particles. The axial normal strain  zz exhibited a linear response in the range of 0 to 10 -3 when the applied compressive axial load (F) increased from 0 to ~30 N when one particle in the sand column fractured. Stress tensor of individual particles was calculated from the acquired lattice strain measurements and elastic constants of silica sand that were reported in the literature. To the best of our knowledge, there have been no reported experimental measurements of the lattice strain tensor measurements within individual silica sand particles. The quantitative measurements reported in this paper at the particle level are very valuable for developing, validating or calibrating micromechanics-based finite element and discrete element models to predict the constitutive behavior of granular materials. 3DXRDrepresents an exciting new non-destructive technique to directly measure constitutive behavior at the scale of individual particles.

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“…Thus, if several independent convolutions are applied, p q approaches a Gaussian distribution if q < 5/3, and it approaches a Lévy distribution for q > 5/3 [6]. We performed quasistatic simple shear tests with 1γ2ε apparatus which is fully described in [21,22]. The granular packing is made of pilings of cylindrical rods which mimics a 2D granular material enclosed by a rectangular frame, with initial dimensions of 0.56 m × 0.47 m. Then, the vertical sides of this rectangular parallelogram are shortened or elongated to apply a constant normal stress in the vertical direction, σ n = 50 kPa.…”

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confidence: 99%

Experimental Validation of a Nonextensive Scaling Law in Confined Granular Media

et al. 2015

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In this letter, we address the relationship between the statistical fluctuations of grain displacements for a full quasistatic plane shear experiment, and the corresponding anomalous diffusion exponent, α. We experimentally validate a particular case of the so-called Tsallis-Bukman scaling law, α = 2/(3 − q), where q is obtained by fitting the probability density function (PDF) of the measured fluctuations with a q-Gaussian distribution, and the diffusion exponent is measured independently during the experiment. Applying an original technique, we are able to evince a transition from an anomalous diffusion regime to a Brownian behavior as a function of the length of the strain-window used to calculate the displacements of grains in experiments. The outstanding conformity of fitting curves to a massive amount of experimental data shows a clear broadening of the fluctuation PDFs as the length of the strain-window decreases, and an increment in the value of the diffusion exponent -anomalous diffusion. Regardless of the size of the strain-window considered in the measurements, we show that the Tsallis-Bukman scaling law remains valid, which is the first experimental verification of this relationship for a classical system at different diffusion regimes. We also note that the spatial correlations show marked similarities to the turbulence in fluids, a promising indication that this type of analysis can be used to explore the origins of the macroscopic friction in confined granular materials. Turbulence is one of the most complex, but ubiquitous, phenomena observed in Nature and it is related with the underlying mechanisms responsible for the micro-macro upscale causing wide-ranging effects on classical systems, like macroscopic friction in granular solids or turbulent flow regime in fluids [1][2][3][4]. The presence of multiple scales in time and space is an additional defy to a comprehensive theoretical description, and a particular effort is made in the literature to perform experiments and simulations in order to validate the proposed theoretical descriptions, particularly Tsallis nonextensive (NE) statistical mechanics [5][6][7][8].A paradigmatic work relating anomalous diffusion and turbulent-like behavior in confined granular media was presented by Radjai and Roux [4], using numerical simulations, and confirmed qualitatively by experiments by Combe and collaborators [7,8]. Radjai and Roux coined a new expression to characterize the analogies between fluctuations of particle velocities in quasistatic granular flows and the velocity fields observed in turbulent fluid flow in high Reynolds number regime, the "granulence". Most of the evidences of the granulence are based in simulations using discrete element method (DEM) but, unfortunately, one can verify a lack of quantitative experimental verification in the last years, limiting the knowledge of the micromechanics of this system based almost exclusively on numerical evidences.In the present work, we aim exactly to fill this gap by contributing with the experiment...

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Experimental micromechanical analysis of a 2D granular material: relation between structure evolution and loading path

Cited by 253 publications

References 19 publications

Macro deformation and micro structure of 3D granular assemblies subjected to rotation of principal stress axes

Macro deformation and micro structure of 3D granular assemblies subjected to rotation of principal stress axes

Strain tensor determination of compressed individual silica sand particles using high-energy synchrotron diffraction

Experimental Validation of a Nonextensive Scaling Law in Confined Granular Media

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