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 S01: Non-Equilibrium and Transient Mechanics of Granular and Soft Materials IIFocus
|
Hide Abstracts |
Sponsoring Units: GSNP DSOFT DFD Chair: Abe Clark, The Naval Postgraduate School; Abhinendra Singh, Case Western Reserve University Room: Room 124 |
Thursday, March 9, 2023 8:00AM - 8:12AM |
S01.00001: When sandcastles collapse: the effect of interparticle cohesion on collapsing granular columns Ram Sudhir Sharma, Wladimir Sarlin, Langqi Xing, Cyprien Morize, Philippe Gondret, Alban Sauret Cohesive effects can drastically change the behavior of granular flows. For instance, powders are challenging to handle, and one can make a sandcastle with wet grains. We report experimental results for collapsing columns of cohesive grains, falling under their own weight in air. Two different geometries are considered: (i) a confined bi-dimensional rectangular column that flows and (ii) a 3D cylindrical column that spreads axisymmetrically on a horizontal surface. Two different physical sources of interparticle cohesion are considered, either through the addition of a small amount of water in initially dry grains such that they are in the pendular state or by the application of an artificial polymer coating. These are both rationalized together showing the general effects of cohesion on the morphology of the final deposit across these geometries. To this end, a characterization of the cohesive strength of the granular materials is obtained independently. Altogether, a dimensionless number relating the cohesive strength and the grain size is shown to capture the effects of cohesion. Despite different sources of cohesion at the grain scale, this allows for a unified macroscopic approach for its effects on collapses. With the explicit contribution of cohesion accounted, the cohesive granular collapse can be rationalized through the established final morphology for relaxed cohesionless piles. |
Thursday, March 9, 2023 8:12AM - 8:24AM |
S01.00002: Latent heat at the glass transition in a tapped granular pile Stefan Boettcher, Paula A Gago The compaction of a granular pile subjected to a series of discrete taps has been widely investigated due to its relevance in both, basic and applied science. The well-know Chicago experiment [1] showed that, given a granular pile subjected to taps of controlled intensity, it is possible to define the density of the system as a reversible function of the tap intensity. Using a continuum annealing protocol, where the intensity Γ of the tap was reduced at several distinct, constant variation rates dΓ after each tap, we have shown [2,3] that, although for high tap intensities the density φ of the system can indeed be defined solely by the tap intensity, for low tap intensities φ will become also a function of the protocol followed to reach the given intensity. This behaviour is characteristic of non-equilibrium (“glassy”) systems. The transition between these two regimes is accompanied by a region of high susceptibility, where a peak on the density fluctuations Δφ can be observed while the pile traverses the “glass” transition. In this presentation we will show that this region of high susceptibility is also accompanied by a hysteretic behaviour. We will discuss how the local effective energy of the perturbation [3], measured as the maximum kinetic energy of the grains during the tap as a function of its position on the pile, can be used to define a latent heat, responsible for this hysteretic behaviour. |
Thursday, March 9, 2023 8:24AM - 8:36AM |
S01.00003: Truss structure dynamics under oscillatory and transient conditions Sean C Fancher, Eleni Katifori, Prashant Purohit Truss structures form the skeleton of a wide variety of systems, from simple bridges to complex metamaterials. As these constructions are often exposed to a variety of forces, a proper understanding of how they respond to arbitrary perturbations is critical for ensuring optimal performance and stability. However, these dynamics are typically derived using lumped models that fail to properly account for the entire range of motion experienced by each bar. In this work, we derive an expansive model that maintains the microstructure fidelity by considering a network of linearly elastic bars connected by free joints and exploring its dynamics in Fourier space. We show that a linear, frequency dependent matrix relation exists between the forces applied to and displacement of the joints. The natural frequencies and modes can be obtained from null space of this matrix at the singular frequencies and are equivalent to those found by traditional lumped matrix methods under the limit of infinite splitting. We explore the solution set generated by this method for a small example truss and use this to transform back into temporal space so as to examine the transient dynamics of the system under finite time forces. |
Thursday, March 9, 2023 8:36AM - 9:12AM |
S01.00004: Creep and slow flow in athermal soft hydrogel suspensions Invited Speaker: Joshua A Dijksman The slow deformation observed when a material is exposed to a constant force is called "creep". Creep is commonly observed for many amorphous materials such as metals, colloidal systems and polymers. The slow motion of creep is usually thermally driven and challenging to understand, probe and control. We will describe how athermal, soft hydrogel suspensions displays interesting creep and slow flow behavior with easily quantifyable features. We will highlight two examples. We probed the creep properties of packings of athermal soft spheres with a sinking ball viscometer and the well-known split bottom geometry. We found that in the sinking ball viscometer tests, creep persists over large deformations and has a power law form, with diffusive dynamics. The creep amplitude is exponentially dependent on both applied stress and the concentration of hydrogel inside the solvent, suggesting that a competition between driving and confinement determines the dynamics. The split-bottom constant flow studies reveal a similar confinement effect, suppressing the unnaturally large shear bands that emerge in hydrogel suspensions. The observed scaling laws and flow dynamics provide a clear benchmark for new theory that explains slow flow and creep, and our work provides the tantalizing prospect that creep can be controlled by a boundary stress. |
Thursday, March 9, 2023 9:12AM - 9:24AM |
S01.00005: Creep in deformable particles under constant compressive strain Chandan Shakya, Jasper Van der Gucht, Joshua A Dijksman Packings of deformable particle are found in many contexts, ranging from powders to emulsions to foams to biological tissue. These packings show mechanical behavior that cannot be easily understood from the individual particle properties. One of these behaviors is creep: the slow deformation of the packing exposed to a constant stress. We present a study of creep in a model system composed of a packing of hydrogel spheres. Recent work has shown that in such soft particle packings, creep dynamics is set by the confining stress. We use custom rheological tools to drive a packing of submersed particles at a constant shear stress to observe their creep at a given compressive strain. In the phase space of applied shear stress and confining strain, we observe various types of creep behavior and will discuss these in the context of the viscoelastic nature of the particle mechanics. |
Thursday, March 9, 2023 9:24AM - 9:36AM |
S01.00006: Velocity and Shear Stress Profiles of a Sheared Athermal System with Pins AKM Sadman Mahmud, Michael J Bolish, Amin Danesh, Jean Luc Ishimwe, Xiang Li, Cacey S Bester, Brian Utter, Amy L Graves, Katharina Vollmayr-Lee We use molecular dynamics simulations to study a two-dimensional athermal, bidisperse system of particles with purely repulsive harmonic interactions. Via the motion of rough top and bottom walls composed of frozen particles, we shear the system at a constant rate. Energy is dissipated via a damping force |
Thursday, March 9, 2023 9:36AM - 9:48AM |
S01.00007: Stress Analysis of a Sheared Athermal System with Pins Michael J Bolish, AKM Sadman Mahmud, Amin Danesh, Jean Luc Ishimwe, Xiang Li, Cacey S Bester, Brian Utter, Amy L Graves, Katharina Vollmayr-Lee Numerous studies have investigated the jamming transition in granular media. Recent research has indicated that quenched disorder in the form of fixed pins provide additional stabilizing forces to the system, which causes the jamming threshold to decrease and therefore provides a fourth degree of freedom in the jamming transition. Using molecular dynamics simulations, we study a two-dimensional, granular system subjected to a wall-driven flow in the vicinity of jamming in order to understand how pins affect the dynamics of the system. We implement a shear by freezing the top and bottom of the binary mixture, and move the walls at a constant shear rate. The system is a 50:50 binary mixture with purely repulsive harmonic interactions of size ratio 0.004:1:1.4 of pins:small:large particles. Pins are located on a square lattice. We will present results concerning shear stress and pressure as a function of packing fraction and strain rate. We will also show preliminary results for the statistics of the shear stress as function of time. |
Thursday, March 9, 2023 9:48AM - 10:00AM |
S01.00008: Shear-driven ordering and disordering of frictional sphere suspensions in two 2D Abhishek K Sharma, Abhinendra Singh, Juan J De Pablo Dense granular suspensions are of great relevance in natural, biological, and industrial systems. Most studies of dense suspensions of frictional spheres are restricted to bidisperse/polydisperse systems to avoid ordering. However, in certain contexts ordering can be useful, e.g., for optical, photonic or plasmonic properties. Thus, it is important to study what microscopic constraints such as hydrodynamics and friction can affect the ordering of particles. In this study we analyze the ordering process in two dimensions, and how it is disrupted with local activation of friction. The lubricated-flow discrete element method (lf-DEM) simulation comprise of inertia-less spheres with short-range repulsion, short-range lubrication and stress-activated friction. We implement both sliding and rolling friction. Initially, we focus on the effect of sliding friction by itself, revealing two qualitatively different regimes depending on the value of shear stress. |
Thursday, March 9, 2023 10:00AM - 10:12AM |
S01.00009: Shear jamming in dense bidisperse frictional suspensions Abhinendra Singh The mechanism of shear thickening in dense suspensions has been linked to a stress-controlled transition from an unconstrained lubricated "frictionless'' to a constrained "frictional'' rheology. Recent particle simulations that constrain the relative motion between particles have been successful to reproduce both the discontinuous shear thickening (DST) and shear jamming (SJ) observed experimentally for rough and smooth particles. However, so far only monodisperse or weakly bidisperse cases are considered. We perform numerical simulations at a fixed volume fraction varying size ratio of particle radii (up to 1:8) and volume fraction of small particles. We find that at a constant volume fraction and size ratio, the viscosity of suspension varies non-monotonically with the fraction of small particles. In this presentation, we will investigate the relative contributions of stress carried by various types of contacts (small-small, small-big, big-big) and their respective microstructure. |
Thursday, March 9, 2023 10:12AM - 10:24AM |
S01.00010: Dynamic bonds as sticky friction in shear thickening dense suspensions Hojin Kim, Stuart J Rowan, Heinrich M Jaeger The discussion of frictional network formation has presented a new paradigm for understanding non-Newtonian shear-thickening behavior of dense suspensions. Recent studies have exclusively focused on volatile friction that instantaneously vanishes when the shear is ceased. We studied dense suspensions of thiol-functionalized particles suspended in ditopic polymers endcapped with benzalcyanoacetamide Michael-acceptors. The subsequent room temperature, catalyst free dynamic thia-Michael reactions can result in chemical friction between the particles when sheared, and the friction releases at the rest state. The frictional force can be tuned by the electronic nature of benzalcyanoacetamide moiety, and its relaxation strongly depends on the molecular weight of the ditopic polymers. These variables allow access to dense suspensions with a wide range of frictional force and stickiness. We found that such dynamic bond sticky friction drastically influences time-dependent rheology. |
Thursday, March 9, 2023 10:24AM - 10:36AM |
S01.00011: Propagating irreversibility fronts in cyclically sheared suspensions Joseph D Paulsen, J. M Schwarz, Jikai Wang The interface separating a liquid from its vapor phase is diffuse; the composition varies continuously from one phase to the other over a finite length. Recent experiments on dynamic jamming fronts in two dimensions [Waitukaitis et al., Europhys. Lett. 102, 44001 (2013)] identified a diffuse interface between jammed and unjammed disks. In both cases, the thickness of the interface diverges as a critical transition is approached. We investigate the generality of this behavior using a third system: A model of cyclically sheared non-Brownian suspensions. As we sediment the particles toward a boundary, we observe a diffuse traveling front that marks the interface between irreversible and reversible phases. We argue that the front width is linked to a diverging correlation length scale in the bulk, which we probe by studying avalanches near criticality. Our results show how diffuse interfaces may arise generally when an incompressible phase is brought to a critical point. |
Thursday, March 9, 2023 10:36AM - 10:48AM |
S01.00012: Non-equilibrium capillary self-assembly Stuart J Thomson, Jack-William Barotta, Daniel M Harris Existing, well-established principles of interfacial capillary self-assembly focus on the behavior of such systems at equilibrium. Inspired by recent experiments involving microscopic colloids, we herein study experimentally and theoretically the structural rearrangements between metastable states of clusters of millimetric spheres in non-equilibrium environments. The structural rearrangements are driven by a field of chaotic Faraday waves, which in turn play the role of an active bath. In contrast to colloids, inertial effects are non-negligible in our macroscopic system, prompting the development of a Langevin model of the noise-driven particle dynamics, informed by the fundamental aspects of the fluid system. We rationalize the occupation statistics and transition probabilities of the clusters, thereby informing new directions for non-invasive, directed self-assembly at the macroscale. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700