Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session F14: Jamming of Particulate Matter II |
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Sponsoring Units: GSNP GSOFT Chair: Mark Shattuck, CCNY Room: 273 |
Tuesday, March 14, 2017 11:15AM - 11:27AM |
F14.00001: Microscopic origins of shear jamming Robert Behringer, Dong Wang Granular materials exhibit novel jamming phenomena in response to applied shear. In this talk, we will explore the jamming of a system of frictional disks with inter-particle friction coefficient of 0.7. In the experiments, the system is subject to simple shear at constant density, starting from a force-free state. In response to shear, force chains/force networks emerge and are a key feature of the shear jamming process. We explore the nature and mechanics of the force chain evolution during this process. We use simple measures to characterize the appearance of the force network by tracking groups of three particles, or trimers. Force chains can be described in terms of collections of trimers, as well as other structures, such as branches, where force chains merge/split. Small changes in select trimers and branches are at the heart of the shear jamming process. We describe these processes and present statistical data to show how these small scale structures influence the shear jamming process. [Preview Abstract] |
Tuesday, March 14, 2017 11:27AM - 11:39AM |
F14.00002: Geometric strengthening of fluid-sheared granular beds Abe Clark, Mark Shattuck, Nicholas Ouellette, Corey O'Hern Fluid flowing over a granular bed exerts a shear stress on the grains. Predicting when grains move is crucial to, e.g., understanding geomorphology or mitigating soil erosion. Grain structure is assumed to play a crucial role in determining bed strength, either through packing density or contact angles of surface grains. Experiments have documented bed strengthening, even for beds of nearly monodisperse grains (i.e., excluding segregation effects), but the relevant state variables that determine bed strength are not understood. We perform molecular dynamics simulations of granular beds that search for stability under a model fluid shear force with overdamped dynamics. We find that the strength of these beds is determined primarily by the contact structure, not compactification. We observe critical scaling and a diverging length scale in the grain dynamics near a nonzero value of the applied shear force, which denotes the strongest configuration of an infinite granular bed. Notably, our numerical value agrees with experiments in the limit of low shear Reynolds number, where a heretofore unexplained plateau is observed in the critical stress versus shear Reynolds number. Our results suggest that this plateau is related to granular bed structure, not fluid mechanical effects. [Preview Abstract] |
Tuesday, March 14, 2017 11:39AM - 11:51AM |
F14.00003: Shear jamming of bumpy grains John Treado, Abram Clark, Thibault Bertrand, Corey O'Hern, Mark Shattuck Packings of frictional disks are known to jam under isotropic compression at a well defined volume fraction $\phi_J(\mu)$ in the large system limit, where $\mu$ is the static friction coefficient. Recent experiments have suggested that jammed disk packings can be generated below $\phi_J(\mu)$ using applied shear at constant volume. Using molecular dynamics simulations, we compress and shear bidisperse frictional disks. Friction is modeled using geometrical asperities (i.e. bumps) on the grain surface. We start with unjammed configurations at $\phi<\phi_J(\mu)$, apply athermal quasi-static shear, and measure the strain at which each system jams. We find that the average shear strain at jamming onset increases with system size and the difference in packing fraction from $\phi_J(\mu)$, in agreement with our recent studies of frictionless grains. Our results suggest that jamming of frictional and frictionless disk packings can be described using a single framework, and that shear jamming at $\phi<\phi_J$ disappears in the large system limit. [Preview Abstract] |
Tuesday, March 14, 2017 11:51AM - 12:03PM |
F14.00004: Tuning Shear Jamming by Basal Assisted Couette Shear Yiqiu Zhao, Jonathan Bar\'{e}s, Robert Behringer Granular matter with packing fraction $\phi_S<\phi<\phi_J$ can be jammed by applying shear strain. However, the stress-strain relation in shear jamming transition is not very well understood. Part of the difficulty is that the strain inside the granular system is very complicated and hard to control. In this work, by using a novel Couette shear apparatus capable of generating arbitrary shear profiles, we study the stress-strain relation during shear jamming transition for granular system under different kinds of controlled interior strain. The novel Couette shear apparatus consists of 21 independently movable rings and two circular boundaries. The apparatus can shear the granular sample not only from the boundaries but also from the bottom. The granular sample is made of about 2000 bi-disperse photo elastic disks, making it possible to extract force information. [Preview Abstract] |
Tuesday, March 14, 2017 12:03PM - 12:15PM |
F14.00005: Shearing Low-frictional 3D Granular Materials David Chen, Hu Zheng, Robert Behringer Shear jamming occurs in frictional particles over a range of packing fractions, from random loose to random dense. Simulations show shear jamming for frictionless spheres, but over a vanishing range as the system size grows. We use packings of submerged and diffractive index-matched hydrogel particles to determine the shear-induced microscopic response of 3D, low-frictional granular systems near jamming, bridging the gap between frictionless and low friction packings. We visualize the particles by a laser scanning technique, and we track particle motion along with their interparticle contact forces from its 3D-reconstructions. [Preview Abstract] |
Tuesday, March 14, 2017 12:15PM - 12:27PM |
F14.00006: Rate Equations for the Shear-Jamming Process Edwin Faican, Dong Wang, Robert Behringer, Bulbul Chakraborty Shear jamming is a process in which an assembly of grains transform from a fluid-like to a solid-like state without a change in density. This occurs through an evolution of the contact network and a steady buildup of contacts per grain. Analysis of experimental data shows that the trajectories in contact space, projected on to subspaces such as the space of 2 and 3 contact grains, resemble a spiral approaching a fixed point as the system approaches the shear-jammed state. We propose that the evolution of contacts can be modeled by reaction kinetics in which n-mers can be transformed to (n+1)-mers or (n-1)-mers, where the n-mers represent grains with n contacts. Using this model, we can map the shear-jamming process to a set of rate equations, where the rates specify the rate of change of n-contact grains per strain step. We can determine the rate constants by fitting the complete experimental trajectories to the prediction of the model. We will present results for for a range of packing fractions and a range of friction coefficients. Visualizing the shear jamming process as a set of reactions in contact-number space provides a new perspective into how stable, force bearing structures are created through shearing. [Preview Abstract] |
Tuesday, March 14, 2017 12:27PM - 12:39PM |
F14.00007: Impact and interaction of granular streams in waters Brian Utter, Alex Christensen, Emily Hobbs, Harry Mandeles, Jacob Parkhouse We experimentally investigate the flow and interaction of granular streams in water, composed of either hydrophobic grains impacting a water surface from above or the interaction of two counter-propagating streams of non-hydrophobic particles. We characterize the stability and character of the aggregates formed in impacting jets with variations of hydrophobic concentration, stream diameter, and drop height. We find that increased hydrophobic grain concentration leads to increased aggregation due to an effectively cohesive interaction mediated by entrained air and, at lower concentrations, the stream exhibits a lateral instability. Under bidirectional flow, we observe a clogging transition and show that the jamming probability increases as a function of the number of beads in the system and decreases with channel diameter, and that the clog undergoes an instability with increased channel width due to lateral variations in particle density. [Preview Abstract] |
Tuesday, March 14, 2017 12:39PM - 12:51PM |
F14.00008: Shear of ordinary, elongated and geometrically cohesive granular mixtures Daniel Gysbers, Scott Franklin We report on shear of granular particles in an annular planar Couette shear. Particles are cut from acrylic sheet, are essentially incompressible, and constrained in a vertical stack in a thin gap between two concentric cylinders. The annular radius of curvature is much larger than the particle length scale, and so the experiment is quasi-2D and allows for arbitrarily large pure-shear strains. The shear is imposed from the top, with the confining pressure controlled by varying the compressive weight from above. Particle shapes include binary mixtures of disks, ellipses and spherocylinders, U-shaped particles with elliptical or spherical sides, and chiral particles that can be aligned with or against the shear. We investigate the extent of the shear band as a function of confining pressure and pile thickness, and track isolated non-circular particles to identify their impact on the shear of the surrounding ordinary granular material. We also investigate interactions between non-circular particles, looking for aggregation or other collective behaviors. [Preview Abstract] |
Tuesday, March 14, 2017 12:51PM - 1:03PM |
F14.00009: Emergent SO(3) Symmetry of the Frictionless Shear Jamming Transition Marco Baity-Jesi, Carl P. Goodrich, Andrea J. Liu, Sidney R. Nagel, James P. Sethna We study the shear jamming of athermal frictionless soft spheres, and find that in the thermodynamic limit, a shear-jammed state exists with different elastic properties from the isotropically-jammed state. For example, shear-jammed states can have a non-zero residual shear stress in the thermodynamic limit that arises from long-range stress-stress correlations. As a result, the ratio of the shear and bulk moduli, which in isotropically-jammed systems vanishes as the jamming transition is approached from above, instead approaches a constant. Despite these striking differences, we argue that in a deeper sense, the shear jamming and isotropic jamming transitions actually have the same symmetry, and that the differences can be fully understood by rotating the six-dimensional basis of the elastic modulus tensor. [Preview Abstract] |
Tuesday, March 14, 2017 1:03PM - 1:15PM |
F14.00010: Absorbing states in periodically sheared particle packings near the jamming transition Maxim Lavrentovich, Andrea Liu, Sidney Nagel We apply quasistatic oscillatory shear to two-dimensional, constant-pressure packings of jammed particles interacting with Hertzian potentials at zero temperature. If the shear amplitude is sufficiently small, the motion becomes reversible after relatively few training cycles. In such an ``absorbing state'' the system returns to its exact starting configuration even though the system undergoes large rearrangements and visits multiple potential energy minima during a cycle. We study the character of these absorbing states as we decrease the pressure and approach the jamming transition. At high pressure, once in an absorbing state, the system returns to its initial configuration after each shear oscillation. As the jamming transition is approached, the periodicity of the motion increases and it takes an increasing number of cycles before all the particles return to their original positions. [Preview Abstract] |
Tuesday, March 14, 2017 1:15PM - 1:27PM |
F14.00011: On Connection Between Topology and Memory Loss in Sheared Granular Materials Lenka Kovalcinova, Miro Kramar, Konstantin Mischaikow, Lou Kondic We present combined results of discrete element simulations and topological data analysis that allows us to characterize the geometrical properties of force networks. Our numerical setup consists of the system of cylindrical particles placed inside rectangular box with periodic boundary conditions along the horizontal direction. System dynamics is driven by constant shearing speed of the top and bottom walls (in the opposite directions) and pressure applied on the top wall in a dense flow regime. Our study reveals the origin of memory loss in granular systems through local rapid changes in force networks. To understand these rapid events we analyze the evolution of the largest Lyapunov exponent in a simpler case of granular system without inter-particle friction and explore a correlation with topological measures. Surprisingly, our results suggest that the memory loss is driven mainly by {\it pressure} even in the case of fixed inertial number. We conclude that the interplay between physical properties of the granular system and force network geometry is a key to understand the dynamics of the sheared systems. [Preview Abstract] |
Tuesday, March 14, 2017 1:27PM - 1:39PM |
F14.00012: Mapping the Discontinuous Shear Thickening Transition to an Equilibrium Phase Transition Jetin E Thomas, Kabir Ramola, Abhinendra Singh, Jeff Morris, Bulbul Chakraborty Discontinuous Shear Thickening, the abrupt change in viscosity of a dense suspension as the rate of shear is increased, appears to arise, at least for certain systems, because the inter-particle contacts change from lubricated to frictional in nature. This change also manifests at the microscopic level as clustering of vertices in a dual space representation of forces (the force-tiling representation), opening the door for microscopic theories to describe DST. We model this collective reorganization of vertices as an equilibrium phase transition between an isotropic and a clustered phase of particles interacting via an ultra-soft potential of the form of step function [1]. We find signatures of a new phase transition at low densities: a regime that had not been investigated earlier but is relevant to DST. We use a cluster-based analysis scheme to compare the predictions of this model with numerical simulations of dense non-Brownian suspensions. We find that near DST, several properties of the point pattern of vertices bear a remarkable similarity to those arising in this simple model. We discuss generalizations to other potentials and examine the mapping for conditions of shear jamming. [1] W. Klein, et. al., Physica A 205, 738 (1994) [Preview Abstract] |
Tuesday, March 14, 2017 1:39PM - 1:51PM |
F14.00013: Dynamic shear fronts in dense suspensions Endao Han, Matthieu Wyart, Ivo Peters, Heinrich Jaeger Dense suspensions are fluid-like when perturbed gently, but they are able to turn into a solid under impact, shear, or extension. Previous work has shown that this dynamic solidification is related to a rapidly propagating shear front. To better understand these phenomena, we extended the phenomenological model developed by Wyart and Cates (PRL, 2014), which explains shear thickening and shear jamming of dense suspensions in the steady state, and applied the new model to a one-dimensional system that undergoes simple shear starting from rest, i.e., includes a transient state. We designed a quasi-one-dimensional experiment to test the numerical results given by the model. Both the calculations and the experiments show that the applied strain is the key parameter that needs to be considered when extending the steady-state behavior to include the transient response of the system. [Preview Abstract] |
Tuesday, March 14, 2017 1:51PM - 2:03PM |
F14.00014: Failures of Angoricity as a Granular State Variable Ephraim Bililign, Karen Daniels Stress-based ensembles incorporating temperature-like variables have been proposed as a route to an equation of state for granular materials. To test the efficacy of this approach, we perform experiments on a photoelastic granular system under three loading conditions: uniaxial compression, biaxial compression, and simple shear. This procedure gives us quantitative knowledge of the interparticle forces and contacts for an ensemble of configurations. Under all three histories, we find that the symmetric component of the force-moment tensor is exponentially-distributed, while the antisymmetric component is Boltzmann-distributed. Using this modified theory, we observe that the two components of the associated temperature-like variable, angoricity, are linearly related to confining pressure. However, the proportionality constant for this equation of state is both volume- and history-dependent. Therefore, we find the stress-based ensemble to be volume-dependent and angoricity to be a variable of process. [Preview Abstract] |
Tuesday, March 14, 2017 2:03PM - 2:15PM |
F14.00015: Interlocking in stochastically microcracked materials provides tensile stiffness deep into the granular regime. Catalin Picu, Anirban Pal We study the mechanical behavior of two- and three-dimensional, stochastically microcracked continua in the range of crack densities above the transport percolation threshold. We show that these materials retain stiffness under tensile loading up to crack densities much larger than the transport percolation threshold, due to topological interlocking of sample sub-domains. At these crack densities the material is granular with a broad distribution of fragment sizes. As the crack density increases, this distribution becomes narrower. We relate the variation of the stiffness with the evolution of the fragment size distribution and the effective density of microcracks. We associate this behavior to that of itacolumite, a sandstone of unusual flexibility. [Preview Abstract] |
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