Shear banding, discontinuous shear thickening, and rheological phase transitions in athermally sheared frictionless disks

Vågberg, Daniel; Olsson, Peter; Teitel, S.

doi:10.1103/physreve.95.052903

Cited by 13 publications

(8 citation statements)

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“…These results are important, since they extend to the family of polygonal grains previous results obtained for disks [43], pentagons [31], and spheres [30]. In a broader context, it is worth mentioning that it was recently conjectured that the absence of dilatancy in frictionless systems can be at the origin of discontinuous shear thickening in some dense suspensions [51][52][53][54]. Our analyses support such hypothesis for suspensions composed of nonspherical particles.…”

Section: Discussionsupporting

confidence: 85%

Combined effects of contact friction and particle shape on strength properties and microstructure of sheared granular media

et al. 2020

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We present a systematic numerical investigation concerning the combined effects of sliding friction and particle shape (i.e., angularity) parameters on the shear strength and microstructure of granular packings. Sliding friction at contacts varied from 0 (frictionless particles) to 0.7, and the particles were irregular polygons with an increasing number of sides, ranging from triangles to disks. We find that the effect of local friction on shear strength follows the same trend for all shapes. Strength first increases with local friction and then saturates at a shape-dependent value. In contrast, the effect of angularity varies, depending on the level of sliding friction. For low friction values (i.e., under 0.3), the strength first increases with angularity and then declines for the most angular shapes. For high friction values, strength systematically increases with angularity. At the microscale, we focus on the connectivity and texture of the contact and force networks. In general terms, increasing local friction causes these networks to be less connected and more anisotropic. In contrast, increasing particle angularity may change the network topology in different directions, directly affecting the macroscopic shear strength. These analyses and data constitute a first step toward understanding the joint effect of local variables such as friction and grain shape on the macroscopic rheology of granular systems.

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Section: Discussionsupporting

confidence: 85%

Combined effects of contact friction and particle shape on strength properties and microstructure of sheared granular media

et al. 2020

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“…Baumgarten et al [15] have argued that tangential viscous interactions, even if they are small, are necessary to obtain dynamic critical scaling for the linear visco-elasticity of jammed systems. Similarly, Vagberg et al [16] demonstrate the key role that this tangential dissipation plays for the small-strainrate rheology. In a different system, solid-solid friction between particles leads to shear-thickening where the associated frictionless system would only display shear-thinning [17].…”

Section: Introductionmentioning

confidence: 83%

Discontinuous shear-thinning in adhesive dispersions

2019

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We present simulations for the steady-shear rheology of a model adhesive dispersion in the dense regime. We vary the range of the attractive inter-particle forces u as well as the strength of the dissipation b. For large dissipative forces, the rheology is governed by the Weisenberg number Wi ∼ bγ/u and displays Herschel-Bulkley form σ = σy + cWi ν with exponent ν = 0.45. Decreasing the strength of dissipation, the scaling with Wi breaks down and inertial effects show up. The stress decreases via the Johnson-Samwer law ∆σ ∼ T 2/3 s arXiv:1809.06128v2 [cond-mat.soft]

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“…, witḣ r i the center of mass velocity, ω i the angular velocity about the center of mass, and s ij the moment arm from the center of i to the point of contact with j [27]. We use Newton's equation of motion,…”

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confidence: 99%

“…Collision elasticity is measured by Q = √ m s k e /(k d D s ) = 2, which would be the quality factor of a corresponding damped oscillator. We integrate the equations of motion using a modified velocity Verlet algorithm [27] with step size ∆t/t 0 = 0.05. We use N = 1024 particles.…”

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confidence: 99%

Orientational Ordering in Athermally Sheared, Aspherical, Frictionless Particles

et al. 2019

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We numerically simulate the uniform athermal shearing of bidisperse, frictionless, two dimensional spherocylinders and three dimensional prolate ellipsoids. We focus on the orientational ordering of particles as an asphericity parameter α → 0 and particles approach spherical. We find that the nematic order parameter S2 is non-monotonic in the packing fraction φ, and that as α → 0 S2 stays finite at jamming and above. The approach to spherical particles thus appears to be singular. We also find that sheared particles continue to rotate above jamming, and that particle contacts preferentially lie along the narrowest width of the particles, even as α → 0.Models of athermal (T = 0) granular materials have often focused on the simplest case of spherical particles. Recently, however, more attention has been paid to the case of elongated particles with lower rotational symmetry [1]. The question then arises whether such elongated particles will orientationally order as the particle density increases, so as to pack more efficiently. While elongated particles in thermal equilibrium are known to have a nematic orientational ordering transition [2, 3], recent works have found that such particles do not orientationally order upon athermal isotropic compression [4][5][6][7][8].Orientational ordering is, however, found when elongated particles are placed in an athermal uniform shear flow. In this case, drag forces between the particle and the flow will cause the particle to tumble [9]. If the particle is asymmetrical, with unequal eigenvalues of its moment of inertia tensor, tumbling will have a non-uniform rotational velocity; the torque from drag forces will vary with the particle's orientation, and the particle will on average align with the flow direction. For a finite density of colliding particles, nematic ordering remains but the nematic director becomes oriented at a finite angle with respect to the flow direction [10][11][12][13][14][15][16][17][18].Here we investigate the nematic ordering of frictionless, aspherically shaped particles, athermally sheared at constant strain rateγ, putting the system into a steady state of simple shear flow. We consider behavior as an asphericity parameter α → 0, and the particles approach spherical. We find the surprising result that a finite nematic ordering persists even as α → 0, suggesting that the shear driven jamming of aspherical particles has a singular limit as α → 0. Since most particles in nature are not truly spherical, our result may have broad implications for granular shear flows.Models: We consider two different numerical models: (i) spherocylinders in two dimensions (2D), and (ii) prolate ellipsoids in three dimensions (3D). In both cases we take a bidisperse distribution of particle sizes, with equal numbers of big and small particles. We use softcore particles with a one-sided harmonic elastic repulsion. The system length is L in all directions, with periodic boundary conditions along the flow directionx, and Lees-Edwards boundary conditions [19] with a uniform stra...

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Shear banding, discontinuous shear thickening, and rheological phase transitions in athermally sheared frictionless disks

Cited by 13 publications

References 70 publications

Combined effects of contact friction and particle shape on strength properties and microstructure of sheared granular media

Combined effects of contact friction and particle shape on strength properties and microstructure of sheared granular media

Discontinuous shear-thinning in adhesive dispersions

Orientational Ordering in Athermally Sheared, Aspherical, Frictionless Particles

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