Compacting an assembly of soft balls far beyond the jammed state: Insights from three-dimensional imaging

A soft departure from jamming: the compaction of deformable granular matter under high pressures

“…4,76 This is found to be true regardless of frictional strength 2,4 and has been found to persist to relatively high pressures in experiments. 10 Here, we measure Z c by calculating the smallest value of Z force and adjusting it to maximize the power-law domain at low packing fractions finding Z c ∼ 5.05 for rough grains and Z c ∼ 5.2 for smoother grains. In comparison for DEM systems, we measure Z c ∈ [4.52,4.57] and Z c ∈ [4.91,4.98] for high- and low-friction calibrations, respectively.…”

“…Such a rapid increase in the pressure near ϕ = 1 has also been previously identified in other works on deformable grains. 10,14,28 Additionally, slip may become relatively easier at grain–grain contacts as asperities flatten due to high normal forces decreasing G P / K P . This combined effect on ν P has also been previously observed in various experimental studies of compacted powders.…”

“…At high pressures, the behavior of granular materials has been less explored in the literature. Experimentally, various techniques have been used to probe highly compressed granular media 6–9 finding notable changes in behavior including a transformation in the functional shape of distributions of contact forces 6 and a transition to continuum behavior 10 with increasing pressure. Computational studies have leveraged both finite element method (FEM) based models, 11–14 the material point method (MPM), 8,15,16 and bonded particle models (BPM) 15,17,18 to explicitly represent the elastic deformation of grains.…”