Comment on 'Repulsive Contact Interactions Make Jammed Particulate Systems Inherently Nonharmonic'

Jamming on deformable surfaces

Jamming is a fundamental transition that governs the mechanical behavior of particulate media, including sand, foam and dense suspensions but also biological tissues: Upon compression, particulate media can change from freely flowing to a disordered solid. Jamming has previously been conceived as a bulk phenomenon involving particle motions in fixed geometries. In a diverse class of soft materials, however, solidification can take place in a deformable geometry, such as on the surface of a fluid droplet or in the formation of a bijel. In these systems the nature and dynamics of jamming remains…

Jamming, two-fluid behaviour and 'self-filtration' in concentrated particulate suspensions

We study the flow of model experimental hard sphere colloidal suspensions at high volume fraction $Φ$ driven through a constriction by a pressure gradient. Above a particle-size dependent limit $Φ_0$, direct microscopic observations demonstrate jamming and unjamming--conversion of fluid to solid and vice versa--during flow. We show that such a jamming flow produces a reduction in colloid concentration $Φ_{x}$ downstream of the constriction. We propose that this `self-filtration' effect is the consequence of a combination of jamming of the particulate part of the system and continuing flow of t…

Vibrations in jammed solids: Beyond linear response

We propose a `phase diagram' for particulate systems that interact via purely repulsive contact forces, such as granular media and colloidal suspensions. We identify and characterize two distinct classes of behavior as a function of the input kinetic energy per degree of freedom $T_0$ and packing fraction deviation above and below jamming onset $Δϕ=ϕ- ϕ_J$ using numerical simulations of purely repulsive frictionless disks. Iso-coordinated solids (ICS) only occur above jamming for $Δϕ> Δϕ_c(T_0)$; they possess average coordination number equal to the isostatic value ($< z> = z_{\rm iso}$) requi…

Signature of jamming under steady shear in dense particulate suspensions

Under an increasing applied shear stress ($σ$), viscosity of many dense particulate suspensions increases drastically beyond a stress onset ($σ_0$), a phenomenon known as discontinuous shear-thickening (DST). Recent studies point out that some suspensions can transform into a stress induced solid-like shear jammed (SJ) state at high particle volume fraction ($ϕ$). SJ state develops a finite yield stress and hence is distinct from a shear-thickened state. Here, we study the steady state shear-thickening behaviour of dense suspensions formed by dispersing colloidal polystyrene particles (PS) in …

Shock driven jamming and periodic fracture of particulate rafts

A tenuous monolayer of hydrophobic particles at the air-water interface often forms a scum or raft. When such a monolayer is disturbed by the localized introduction of a surfactant droplet, a radially divergent surfactant shock front emanates from the surfactant origin and packs the particles into a jammed, compact, annular band with a packing fraction that saturates at a peak packing fraction $ϕ^*$. As the resulting two-dimensional, disordered elastic band grows with time and is driven radially outwards by the surfactant, it fractures to form periodic triangular cracks with robust geometrical…

无序粒子系统的线性控制理论

Linear control theory for jammed particle systems

本文利用线性控制理论研究无序颗粒材料在应力下的动态行为，发现平均可控性与颗粒重新排列密切相关，且通过调节时间尺度可优化预测能力。

利用深度图神经网络对近堵塞悬浮液中摩擦接触网络的鲁棒预测

Robust Prediction of Frictional Contact Network in Near-Jamming Suspensions Employing Deep Graph Neural Networks

本研究提出基于深度图卷积网络（DeepGCN）的机器学习方法，用于预测近堵塞悬浮液中的摩擦接触网络（FCN），在广泛相空间和参数变化下展现出鲁棒泛化能力，为颗粒系统性质预测提供了可迁移技术。