Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session TT01: V: Non-Equilibrium and Transient Mechanics of Granular and Soft Materials |
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Sponsoring Units: GSNP DSOFT DFD Chair: Joshua Socolar, Duke University Room: Virtual Room 1 |
Tuesday, March 21, 2023 3:30PM - 3:42PM |
TT01.00001: Grain-scale origins of ultrastability in cyclically driven shear-jammed granular material Joshua E Socolar, Yiqiu Zhao, Yuchen Zhao, Dong Wang, Hu Zheng, Bulbul Chakraborty Ultrastable states in granular system can be produced by subjecting a shear-jammed sample to small-amplitude cyclic shear. In such states, all the particle positions and contact forces are reproduced after each shear cycle so that a strobed image of the stresses and particle positions appears static, and the behavior of the system is nearly perfectly elastic. In the present work, we use photoelastic imaging methods to examine the evolution of contact forces within a shear cycle after an ultrastable state is formed in a layer of plastic discs. We find that there are two types of contacts: non-persistent contacts that reversibly open and close; and persistent contacts that never open. We show that the non-persistent contacts make a non-negligible contribution to the emergent shear modulus. |
Tuesday, March 21, 2023 3:42PM - 3:54PM |
TT01.00002: Jamming-controlled shear stiffening in particle-filled soft solids Yiqiu Zhao, Haitao HU, Qin Xu Dispersing hard particles into a soft polymer gel forms a soft composite that is widely used in mechanical and biomedical applications. The global mechanics of such composites are strongly affected by the collective interactions among the embedded particles. Predicting the nonlinear mechanical features of such materials presents a great challenge. To address the problem, we performed a systematic experimental study on a model system consisting of micron-sized polystyrene spheres randomly dispersed in a crosslinked polydimethylsiloxane (PDMS) matrix. We found that the shear modulus of densely filled samples grows significantly, in some cases more than ten-fold, under small deformations. Inspired by the stress-controlled shear-thickening effects in dense suspensions, we proposed a phenomenological model that explains the stiffening effect through critical scaling laws near a stress-dependent jamming point. The model not only captured our observations but also predicted the emergence of mechanical instability for extremely dense samples. Our work provides the experimental evidence to support that jamming criticality controls the responses of soft composites, and revealed a similar role played by the particle contact networks in determining both the elasticity of dense particle-filled soft solids and the rheology of dense granular suspension. |
Tuesday, March 21, 2023 3:54PM - 4:06PM |
TT01.00003: Emergent elasticity in shear-jammed granular materials under cyclic shear Yuchen Zhao, Dong Wang, Hu Zheng, Bulbul Chakraborty, Joshua E Socolar While granular packings formed by a shear-jamming process may collapse completely under external perturbations, a recent experiment demonstrated that an "ultrastable" state can be produced by subjecting a shear-jammed sample to small-amplitude cyclic shear. In such states, all the particle positions and contact forces are reproduced after each shear cycle so that a strobed image of the stresses and particle positions appears static, and the behavior of the system is nearly perfectly elastic. To gain insight into the surprising emergence of elasticity in this disordered, frictional, shear-jammed system, we calculated the spatial correlations of the stress tensor in ultrastable states and compared them to the predictions of the Vector Charge Theory of Granular mechanics (VCTG). The local stresses are measured using photoelastic techniques. We show that our experimental results can be fit well by VCTG, assuming a uniaxial symmetry of the contact networks. The fits reveal that the response of the ultrastable states to additional applied stress is substantially more isotropic than that of the original shear-jammed states. Our work provides additional insight into the effect of oscillatory deformation in modifying the mechanical properties of a jammed granular packing. |
Tuesday, March 21, 2023 4:06PM - 4:18PM |
TT01.00004: Quaking in sand -- Dynamics of granular shear flow at the "quasi-static" limit W.-C. Lee, Cheng-En Tsai We propose a minimal model that produces repetitive quaking of soft particles under steady shearing in numerical experiments. As opposed to using fixed Columb friction, we include a characteristic velocity above which the tangential force weakens. Our study at the non-inertial limit, where granular flows would inevitably be rate-independent in conventional treatments, establishes a state diagram spanned by two axes: the mean contact per particle versus a dimensionless shear rate with the grain size and the velocity weakening taken into account. Quaking behaviors reported previously with our prior laboratory experiments are now justified with values of this dimensionless shear rate, indicative of a transition between fully frictional “solid” and free slipping “liquid”. The mean contact number links the packing density to the mechanical stability. The sign of jumps in mean contact number divides the quaking states into two types and reveals a switch of the underlying mechanism. Our amendment to the conventional model renders the non-inertia limits of granular flow rate-dependent and produces intriguing dynamics, that might shed light on understanding the buildup of earthquakes and their precursors. |
Tuesday, March 21, 2023 4:18PM - 4:30PM |
TT01.00005: Mechanical energy transfer for two particles in a vertically vibrating channel Kai Yang, Jeffrey S Olafsen We present an experiment and simulation study of two colliding particles in a vertically shaken channel driven sinusoidally. The two identical Delrin particles both have a diameter of d=5.0 mm. Multiple cases are considered for driving frequencies, f, ranging from 23 to 32 Hz and the acceleration magnitudes, Γ, from 1.78 to 3.53 g. The coefficient of restitution is observed to depend on the impact velocity strongly in both experiment and simulation. Super-elastic collisions, where the coefficient of restitution is measured to be exceeding unity, are also observed in this experiment. We examined the relative velocity and the total mechanical energy of the two particles before and after collisions in both the lab frame and the center of mass frame. Both experimental and simulation results in the lab and center of mass frame suggest the super-elastic collisions result from an occasional mechanical energy transfer between the rotational and translational degrees of freedom. |
Tuesday, March 21, 2023 4:30PM - 4:42PM |
TT01.00006: Fragility in a macroscopic model of a glass-forming liquid based on a nonvibrating granular system under a time-dependent magnetic field Cecilio Tapia-Ignacio, Ruben Fossion, Fernando Donado We study the glass transition in a nonvibrating granular system composed of magnetic steel pellets under a variable magnetic field at a fixed particle concentration. The applied magnetic field is a superposition of a constant component and a sinusoidal component and is given by B=Bc+Bosen(2πft), where Bc is a constant magnetic field during an experiment, and can vary between 0 and 33 Gauss, Bo is the amplitude of the sinusoidal magnetic field which remains constant at 66 Gauss, and f is the oscillation frequency that takes the value of 9.25 Hz. It is observed that the fragility index changes if the Bc field changes. As the constant field increases, the system goes from a fragile to a strong glass-forming liquid behavior. |
Tuesday, March 21, 2023 4:42PM - 4:54PM |
TT01.00007: Modeling and Simulation of Collective Behavior in Actin-Propelled Beads Narges Kelly, Thomas G Fai, Guillaume Duclos, Benjamin A Strain, Amélie Chardac, Izaiah Alvarado Many biological systems exhibit collective behavior and self-organization where actin plays an important role in their movement. Organisms such as the bacterium Listeria monocytogenes exploit actin polymerization to gain motility. Similarly, self-organized motility has been realized in vitro through colloidal systems that use actin polymerization to self-propel. We model the flocking behavior observed experimentally involving these active beads by numerically solving a set of reaction-diffusion-based differential equations. We aim to collect statistics on relevant properties of the flocks, such as their size and persistence, and compare with experimental data. The goal of the project is to use simulations to further test hypotheses on how system parameters such as actin concentration, particle number density, and particle-to-system size ratio control the collective behavior of these active beads. |
Tuesday, March 21, 2023 4:54PM - 5:06PM |
TT01.00008: Collective dynamics of swarmalators with time-delayed interactions Oleg Kogan, Kevin O'Keeffe, Nick S Blum In this work we studied the effects of time delay in interactions on collective dyanmics of a population of swarmalators - phase oscillators that synchronize in time while swarming through space. We found new collective behaviors induced by the delay - a pseudo-crystaline state in which swarmalators form a quasi-static cluster, and a boiling state in which swarmalators near the boundary of the cluster perform convective motions. In both cases, the route to these states takes place through a long oscillatory ``breathing'' transient. We developed a continuum theory that allowed reduction from 2N equations to just two. This theory captures the density profile at later stages of the breathing transient, as well as the frequency and decay rates of breathing oscillations. Swarmalators have recently been realized in robotics labs, and may also play a role as a useful model for embryonic development, and collective motion of organisms. |
Tuesday, March 21, 2023 5:06PM - 5:18PM |
TT01.00009: Fluttering induced flow in a closed chamber Oz Oshri, Yuri Feldman, Kirill Goncharuk We study the emergence of a fluid flow in a closed chamber that is driven by the dynamical deformations of an elastic sheet. The sheet is compressed between the sidewalls of the chamber and partitions it into two separate parts, each of which is initially filled with an inviscid fluid. When fluid exchange is allowed between the two compartments of the chamber, the sheet becomes unstable, and its motion displaces the fluid from rest. We derive an analytical model that accounts for the coupled, two-way, fluid-sheet interaction. We show that the system depends on four dimensionless parameters: the normalized lateral displacement of the sheet, Δ, the normalized vertical dimension of the chamber, the normalized initial volume difference between the two parts of the chamber, vdu(0), and the structure-to-fluid mass ratio, λ. We investigate the dynamics at the early times of the system's evolution and at moderate times. We obtain the growth rates and the frequency of vibrations around the second and the first buckling modes, respectively. Analytical solutions are derived for these linear stability characteristics within the limit of the small-amplitude approximation. At moderate times, we investigate how the sheet escapes from the second mode. Given the chamber's dimensions, we show that the initial energy of the sheet is mostly converted into hydrodynamic energy of the fluid if λ«1, and into kinetic energy of the sheet if λ»1. In both cases most, initial energy is released at time tp∝ln[Δ1/2/vdu(0)]/σ, where σ is the growth rate. |
Tuesday, March 21, 2023 5:18PM - 5:30PM |
TT01.00010: Anomalous heating dynamics in the stochastically driven system. Aritra Kundu Driven interacting classical and quantum systems exhibit exotic novel dynamical phases characterised by non-trivial crossover in diffusion properties of these phases. |
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