Relationship between dilatancy, stresses and plastic dissipation   in a granular material with rigid grains

Évesque, P.; Stefani, C.

doi:10.1051/jp2:1991143

Cited by 4 publications

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“…The standard way to gain access to the physics of the deformation process in non-cohesive solids is through so-called triaxial test experiments [2,3], in which a cylindrical (rock or granular medium) specimen is subjected to an axial compression defining the maximum principal stress component a, and to a lateral confining pressure p=cY 3 , while being kept at a fixed temperature T. Typical stress-strain curves (q=al-0 3 as a function of deformation el along the axial compression a 1 ) are shown on fig.1 [2,3]. In the regimes of relatively small deformations studied during a typical triaxial test, the deformation is essentially homogeneous over the sample, except at the point of instability where q is maximum [3], at which a localized shear band appears.…”

Section: Introductionmentioning

confidence: 99%

“…In the regimes of relatively small deformations studied during a typical triaxial test, the deformation is essentially homogeneous over the sample, except at the point of instability where q is maximum [3], at which a localized shear band appears. The interest of triaxial test is to allow to predict the behavior of larger inhomogeneous samples by using finite element calculation.…”

Section: Introductionmentioning

confidence: 99%

“…The choice of U 2 =dK/deI is based on stability considerations. Balancing the mechanical work done during a tri-axial test with the energy dissipated through plastic deformation (internal friction), one obtains [3] that the limit of stability is given by dK/de 1 = 0, so that the sample becomes unstable at a change of sign of dK/de 1 . From fig.l, dK/de 1 is positive when the system is stable and becomes negative at the unstability threshold.…”

Section: Introductionmentioning

confidence: 99%

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A Dynamical System Theory of Large Deformations and Patterns in Non-Cohesive Solids

Évesque

Sornette

1992

MRS Proc.

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We propose a dynamical system theory of triaxial-test deformationS and localization bifurcation in brittle media. We apply it to predict that localization may occur in a packing looser than "critical" and that the general localization shape is a spiral staircase in axisymmetric 3-D cells. These two facts have recently been confirmed experimentally. This theory provides a framework for understanding the development of complex deformation patterns from the mechanics of localization and rupture.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Dynamical System Theory of Large Deformations and Patterns in Non-Cohesive Solids

Évesque

Sornette

1992

MRS Proc.

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Simulation of flow and mixing of particles in a rotating and rocking cylinder

et al. 1998

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Granular material in a cylindrical vessel undergoing rotational and rocking motions is modeled using a discrete element method. Rotational motion supplemented by rocking is compared to purely rotational motion via linear density profiles, velocity fields, and axial concentration profiles. The rocking motion, which imparts a time-dependent flow perturbation to purely rotational motion, dramatically enhanced mixing in laborat o y studies. Simulation results appear to agree well with experimental results and observations. IntroductionMany technical fields deal with mixing of granular materials, including chemical, agricultural, ceramic, mechanical, civil and soil engineering, the life sciences, physics, and pharmacy. Although researchers in these fields consider a wide range of physical characteristics and flow regimes, they share a common interest: the need to understand and characterize bulkflow powder behavior. Powder processing has been recently characterized by chemical engineers as having a legacy of neglect (Ennis et al., 1994). Awareness of this neglect has motivated a recent resurgence of both experimental investigations (McCarthy et al., 1996;Hill and Kakalios, 1995;Brone et al., 1997) and theoretical approaches (Johnson et al., 1990;Edwards and Mounfield, 1996). It has become fashionable in a sense to study powders, not only because of their complexity but also because there is a growing need in industry to reliably manufacture high-quality products.Although practitioners have attempted to handle powder problems using empirical approaches, more detailed studies of the physics of powders are required. Some researchers have suggested that granular materials might be a different state of matter (Jaeger et al., 1996). Interest in the physics of powders has increased dramatically in the past decade, starting with the analysis of sand piles (Baxter et al., 1989(Baxter et al., , 1993Bak and Chen, 1991), prompted by analogies with self-organized critical systems (Bak et al., 1988). Fundamental questions concerning how and why granular materials behave alternaCorrespondence concerning this article should be addressed to F. J. Muzrio tively like a liquid when flowing down an inclined chute and like a solid when forming a sloping surface remain to be answered (Glanz, 1995). A growing research community is currently investigating microscopic theories (Jaeger et al., 1996;Jaeger and Nagel, 1992;Evesque and Stefani, 1991;Evesque et al., 1992; Mehta, 19941, as well as unit operations typically found in industry, such as blending, sampling, discharge, fluidization, and granulation. The kinetic theory developed for fast-flowing low-density solids has achieved some success in modeling Couette flows and flows down inclined planes, but industrial systems are often more complex. Civil and soil engineers are mainly interested in strain effects (failure) produced by external forces and the effect of time on the development of strain. The chemical engineering community, on the other hand, has focused primarily on mixing and tran...

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Plasticity and geophysical flows: A review

Ancey

2007

Journal of Non-Newtonian Fluid Mechanics

352

277

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The objective of this review is to examine how the concept of plasticity is used in geophysical fluid dynamics. Rapid mass movements such as snow avalanches or debris flows involve slurries of solid particles (ice, boulder, clay, etc.) within an interstitial fluid (air, water). The bulk behavior of these materials has often been modeled as plastic materials, i.e., a plastic material yields and starts to flow once its stress state has significantly departed from equilibrium. Two plastic theories are of common use in fluid dynamics: Coulomb plasticity and viscoplasticity. These theories have little in common, since ideal Coulomb materials are two-phase materials for which pore pressure and friction play the key role in the bulk dynamics, whereas viscoplastic materials (e.g., Bingham fluids) typically behave as single-phase fluids on the macroscopic scale and exhibit a viscous behavior after yielding. Determining the rheological behavior of geophysical materials remains difficult because they encompass coarse, irregular particles over a very wide range of size. Consequently, the true nature of plastic behavior for geophysical flows is still vigorously debated. In this review, we first set out the continuum-mechanics principles used for describing plastic behavior. The notion of yield surface rather than yield stress is emphasized in order to better understand how tensorial constitutive equations can be derived from experimental data. The notion of single-phase or two-phase behaviors on the macroscopic scale is then examined using a microstructural analysis on idealized suspensions of spheres within a Newtonian fluid; for these suspensions, the single-phase approximation is valid only at very high or low Stokes numbers. Within this framework, the bulk stress tensor can also be constructed, which makes it possible to give a physical interpretation to yield stress. Most of the time, depending on the bulk properties (especially, particle size) and flow features, bulk behavior is either Coulomb-like or viscoplastic in simple-shear experiments. The consequences of the rheological properties on the flow features are also examined. Some remarkable properties of the governing equations describing thin layers flowing down inclined surfaces are discussed. Finally, the question of parameter fitting is tackled: since rheological properties cannot be measured directly in most cases, they must be evaluated from field data. As an example, we show that the Coulomb model successfully captures the main traits of avalanche motion, but statistical analysis demonstrates that the probability distribution of the friction coefficient is not universal.

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Relationship between dilatancy, stresses and plastic dissipation in a granular material with rigid grains

Cited by 4 publications

References 0 publications

A Dynamical System Theory of Large Deformations and Patterns in Non-Cohesive Solids

A Dynamical System Theory of Large Deformations and Patterns in Non-Cohesive Solids

Simulation of flow and mixing of particles in a rotating and rocking cylinder

Plasticity and geophysical flows: A review

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