Bending transition in the penetration of a flexible intruder in a two-dimensional dense granular medium

Abstract

We study the quasi-static penetration of a flexible beam in a two-dimensional dense granular medium lying on an horizontal plate. Rather than a buckling-like behavior we observe a transition between a regime of crack-like penetration in which the fiber only shows small fluctuations around a stable straight geometry and a bending regime in which the fiber fully bends and advances through series of loading/unloading steps. We show that the shape reconfiguration of the fiber is controlled by a single non dimensional parameter: L/Lc, the ratio of the length of the flexible beam L to Lc, a bending elasto-granular length scale that depends on the rigidity of the fiber and on the departure from the jamming packing fraction of the granular medium. We show moreover that the dynamics of the bending transition in the course of the penetration experiment is gradual and is accompanied by a symmetry breaking of the granular packing fraction in the vicinity of the fiber. Together with the progressive bending of the fiber, a cavity grows downstream of the fiber and the accumulation of grains upstream of the fiber leads to the development of a jammed cluster of grains. We discuss our experimental results in the framework of a simple model of bending-induced compaction and we show that the rate of the bending transition only depends on the control parameter L/Lc.

Forces and flow induced by a moving intruder in a granular packing: coarse-graining and DEM simulations versus experiments

“…Following the works of Weinhart et al [42] and Algarra et al [43] we employed a coarse graining method to upscale the continuous velocity field from the positions of the particles and their velocities computed by DEM. Among other, this method has the advantage to satisfy the conservation equations of continuum mechanic.…”

Buckling of a rod penetrating into granular media

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Probing regolith-covered surfaces in low gravity

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