Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session M16: Collective Behavior in Driven Granular MediaFocus Live
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Sponsoring Units: GSNP Chair: Abe Clark, The Naval Postgraduate School |
Wednesday, March 17, 2021 11:30AM - 12:06PM Live |
M16.00001: Homogeneous Crystallization in Cyclically Sheared Frictionless Grains Invited Speaker: Weiwei Jin Many experiments over the past half century have shown that, for a range of protocols, granular materials compact under pressure and repeated small disturbances. A recent experiment on cyclically sheared spherical grains showed significant compaction via homogeneous crystallization (Rietz et al., 2018). Here we present numerical simulations of frictionless, purely repulsive spheres undergoing cyclic simple shear via Newtonian dynamics with linear viscous drag at fixed vertical load. We show that for sufficiently small strain amplitudes, cyclic shear gives rise to homogeneous crystallization at a volume fraction Φ = 0.646±0.001. This result indicates that neither friction nor gravity is essential for homogeneous crystallization in driven granular media. |
Wednesday, March 17, 2021 12:06PM - 12:18PM Live |
M16.00002: Sheared Amorphous Packings Display Two Separate Particle Transport Mechanisms Hu Zheng, Dong Wang, Joshua Dijksman, Jonathan Barés Shearing granular materials induces non-affine displacements. Such non-affine displacements have been studied extensively, and are known to correlate with plasticity and other mechanical features of amorphous packings. A well-known example is shear transformation zones as captured by the local deviation from affine deformation, D2min. We analyze sheared frictional athermal disc packings and show that there exists at least one additional mesoscopic transport mechanism that superimposes itself on top of local diffusive motion. We evidence this second transport mechanism in a homogeneous system via a diffusion tensor analysis and show that when this second mesoscopic transport is corrected for, the trace of the diffusion tensor equals the classic D2min. The new transport mechanism is consistently observed over a wide range of volume fractions and even for particles with different friction coefficients and is consistently observed also upon shear reversal, hinting at its relevance for memory effects. |
Wednesday, March 17, 2021 12:18PM - 12:30PM Live |
M16.00003: Energy dissipation for two particles in a vertically vibrating channel Kai Yang, Jeffrey Stuart Olafsen The “chattering ball” problem examined in the 1980’s consisted of a particle bouncing on a vertically vibrating plate under gravity as a simple nonlinear system that demonstrates rich dynamical behaviors. Here, we study the energy dissipation of two identical particles free to collide in a vertical channel in a shaken experiment. Both spherical particles are Delrin with a diameter of d=5.0 mm. Multiple cases are considered with driving frequencies, f, ranging from 23 to 32 Hz and acceleration magnitudes, Γ, from 1.78 to 3.53 g. The positions and velocities of each particle from the experiment are extracted by high speed imaging. The energy dissipation is evaluated in both the lab frame and the center of mass frame. The experimental results show that most data in the mechanical energy before and after collision cluster around a straight line with a slope slightly smaller than unity. The experimental results suggest that the mechanical energy after collision depends linearly on the mechanical energy before collision in most cases. However, some data indicates an occasional transfer of kinetic energy from the translational to the rotational degree of freedom and vice versa. |
Wednesday, March 17, 2021 12:30PM - 12:42PM Live |
M16.00004: Elastic-plastic transition induced by small-amplitude cyclic shearing of shear-jammed granular solids Yiqiu Zhao, Yuchen Zhao, Dong Wang, Hu Zheng, Bulbul Chakraborty, Ryan Kozlowski, Joshua Socolar We show experimentally that small amplitude cyclic shear has a dramatic effect on shear jammed granular packings. A shear-jammed state generated by forward shear can relax to an unjammed state or an elastically stable state, depending on the initial shear strain γi and the amplitude of the cyclic shear δγ. For γi less than a threshold value γc, cyclic shear on the order of 5% of γc causes the stress to relax to zero, and strobed particle dynamics is diffusive. The number of cycles needed to reach the unjammed state grows exponentially with increasing γi. For γi larger than γc, we see reversible elastic states lasting for thousands of cycles. The value of γc depends on both packing fraction and δγ. The long-lived elastic states have much smaller pressures than the initial shear-jammed packings but exhibit much stiffer responses to incremental shear strain. |
Wednesday, March 17, 2021 12:42PM - 12:54PM Live |
M16.00005: System size dependence in hydrogel sphere packing relaxation behaviour during cyclic loading Chandan Shakya, Jasper Van der Gucht, Joshua Dijksman Cyclic loading of amorphous particle packings induces many nontrivial mechanical effects including memory and hysteresis. Here we aim to study the emergence of such effects by experimentally probing the role of system size on the collective mechanics of soft particle packings. Hydrogel sphere packings are packings of soft, slippery spheres and therefore a model system that is one of the closest experimental realizations of an idealized granular packing. Despite their ideal behavior, hydrogel sphere packings already reveal system size dependence in their relaxation behavior. We find that individual hydrogel particles display very different relaxation behavior than packings of even four hydrogel spheres. We discuss how such collective effects get amplified with packing size and are influenced by other experimental settings such as the particle properties. |
Wednesday, March 17, 2021 12:54PM - 1:06PM Live |
M16.00006: Automated Measurement of the Profile of an Avalanching Conical Bead Pile Bennett W. Anderson, Susan Y Lehman A conical bead pile subject to slow driving is used as a model critical system to experimentally investigate the distributions of avalanche sizes and time between events. The pile is composed of roughly 20 000 steel beads, 3 mm in diameter; we drive the pile by adding one bead at a time to the apex of the pile. We record the changes in pile mass over the course of tens of thousands of bead drops to characterize the distribution of avalanche sizes. To better understand the dynamic effect of individual avalanches, we now capture a profile image of the pile at every bead drop. By automating analysis of the images in Matlab, we can track changes in the overall height of the pile as well as variations in the angle of repose as the pile responds to each bead drop when cohesion or height of the bead dropper varies. In our previous work, we have characterized the changes in avalanche size distribution as we tune the cohesion in the system. Specifically, as cohesion is added, the size and number of the largest avalanches in the system increase. We observe larger variations in the angle of repose as the cohesion is increased, and we correlate these variations in angle with the mass of individual avalanches. |
Wednesday, March 17, 2021 1:06PM - 1:18PM Live |
M16.00007: The Wave-Driven Oscillator: Granular Matter Levitated by Beating Sound Waves Mohammed Abdelaziz, David G Grier The acoustical force landscape created by beating between interfering sound waves |
Wednesday, March 17, 2021 1:18PM - 1:30PM Live |
M16.00008: Rheology of wet granular materials under quasi-static shear Kiwamu Yoshii, Michio Otsuki Small amounts of liquid drastically change the rheological property of granular materials due to the cohesive interaction given by capillary bridges between grains. |
Wednesday, March 17, 2021 1:30PM - 1:42PM Live |
M16.00009: Phase Transitions Affected by Interconversion and Applications to Three Atomistic Models Thomas Longo, Mikhail A Anisimov We present a general description of phase separation driven by spinodal decomposition in a binary fluid with molecular interconversion of the components. We show that without a "source'' of interconversion the system always reaches macroscopic phase separation with the domain growth enhanced by interconversion (slow phase amplification). Addition of a source of interconversion drives the system away from equilibrium and creates the possibility for arrested phase separation - the existence of non-growing (steady-state) mesoscopic phase domains. We apply the theory to three different atomistic models: the model of Glotzer et al., where interconversion is provided only by a reaction source independent from phase separation; the model of Buldyrev et al., where the presence of an external source can cause arrested phase separation or phase amplification; and the model of Uralcan et al., where an internal source originates from unbalanced intermolecular forces. The theory is in agreement with the results of simulations performed for these models. |
Wednesday, March 17, 2021 1:42PM - 1:54PM Live |
M16.00010: New parameters to characterize the nematic transition for rods deposition on 2D lattices Eugenio Vogel, Gonzalo Saravia, Antonio Ramirez-Pastor, Marcelo Pasinetti We tackle the problem of excluded volume deposition of rigid rods of length k unit cells over square lattices. Two new features are introduced: a) two new short-distance complementary order parameters (called Π and Σ) are defined, used and discussed to deal with the phases present as coverage increases; b) the interpretation is now done beginning at the high-coverage locally ordered phase (present regardless of the k value) which allows to interpret the low coverage nematic phase as an ergodicity breakdown present for k ≥ 7. In addition data analysis is now done by a combination of mutability (dynamical information theory method) and Shannon entropy (static distribution analysis). Moreover, a comparison between mutability and Shannon entropy is done reporting their advantages and disadvantages for dealing with this problem. Parameter Π turns out to better characterize this system through the entire parameter space. |
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