Mechanical impulse propagation in a three-dimensional packing of spheres confined at constant pressure

Santibáñez, Francisco; Zuñiga, René; Melo, Francisco

doi:10.1103/physreve.93.012908

Cited by 13 publications

(16 citation statements)

References 39 publications

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“…As the ratio of wave amplitude to static pressure was varied by several orders of magnitude, a smooth transition from constant to amplitude-dependent wavefront speed was found, in accordance with the Hertzian contact force law. Similar experiments confirmed these observations 19 . These findings are all examples of strongly nonlinear behavior of the granular packing itself.…”

Section: Introductionsupporting

confidence: 87%

Acoustic waves in granular packings at low confinement pressure

Tell

Dreißigacker

Tchapnda

et al. 2020

Review of Scientific Instruments

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Elastic properties of a granular packing show nonlinear behavior determined by its discrete structure and nonlinear inter-grain force laws. Acoustic waves show a transition from constant, pressuredependent sound speed to a shock-wave like behavior with amplitude-determined propagation speed. This becomes increasingly visible at low static confinement pressure as the transient regime shifts to lower wave amplitudes for lower static pressure. In microgravity, confinement pressure can be orders of magnitude lower than in a ground based experiment. Also, the absence of hydrostatic gradients allows for much more homogeneous and isotropic pressure distribution. We present a novel apparatus for acoustic wave transmission measurements at such low packing pressures. A pressure control loop is implemented by a microcontroller that monitors static force sensor readings and adjusts the position of a movable wall with a linear motor until the desired pressure is reached. Measurements of acoustic waves are possible using accelerometers embedded in the granular packing as well as piezos. For excitation we use a voice coil-driven wall, with a large variety of signal shapes, frequencies and amplitudes. This enables experiments both in the linear and strongly nonlinear regime.

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Section: Introductionsupporting

confidence: 87%

Acoustic waves in granular packings at low confinement pressure

Tell

Dreißigacker

Tchapnda

et al. 2020

Review of Scientific Instruments

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“…The short initial impact is about 0.2 ms wide: its spectrum (not shown; see Ref. [17]) extends from dc to 8 kHz approximately. The three rightmost columns present the acceleration of the transmitted waves, first in a dry medium and then with two different interstitial viscosities.…”

Section: Experimental Setup and Observationsmentioning

confidence: 95%

“…1 and Ref. [17]) consists in a packing of approximately 3000 spherical glass particles (density ρ g = 2400 kg/m 3 , radius R g = 2.5 mm, Young modulus E g = 69 GPa, Poisson's ratio ν g = 0.2, and surface roughness Ra 10 nm [26,47]) confined inside a thin deformable latex sheet. The sheet is hermetically sealed and clamped between two square plates made of a rigid plastic.…”

Section: Experimental Setup and Observationsmentioning

confidence: 99%

“…The impacting head of the pendulum consists in a piece of brass in front of which a spherical glass particles has been glued. The contact duration depends on the mass (57 g) of the head [7], which has been chosen so that the initial excitation is about a fraction of a millisecond [17]. A collision thus generates a broadband excitation from dc to few kilohertz.…”

Section: Experimental Setup and Observationsmentioning

confidence: 99%

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Effect of an interstitial fluid on the dynamics of three-dimensional granular media

2019

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The propagation of mechanical energy in granular materials has been intensively studied in recent years given the wide range of fields that have processes related to this phenomena, from geology to impact mitigation and protection of buildings and structures. In this paper, we experimentally explore the effect of an interstitial fluid on the dynamics of the propagation of a mechanical pulse in a granular packing under controlled confinement pressure. The experimental results reveal the occurrence of an elastohydrodynamic mechanism at the scale of the contacts between wet particles. We describe our results in terms of an effective medium theory, including the presence of the viscous fluid. Finally, we study the nonlinear weakening of the granular packing as a function of the amplitude of the pulses. Our observations demonstrate that the softening of the material can be impeded by adjusting the viscosity of the interstitial fluid above a threshold at which the elastohydrodynamic interaction overcomes the elastic repulsion due to the confinement. arXiv:1808.03150v2 [physics.flu-dyn]

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“…[50]), discussing different choices for the fluidity parameter, or the sound waves propagation (see e.g. [51]).…”

Section: A a Case Study: The Single Blockmentioning

confidence: 99%

Induced and endogenous acoustic oscillations in granular faults

Arcangelis

Lippiello

Ciamarra

et al. 2018

Phil. Trans. R. Soc. A.

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The frictional properties of disordered systems are affected by external perturbations. These perturbations usually weaken the system by reducing the macroscopic friction coefficient. This friction reduction is of particular interest in the case of disordered systems composed of granular particles confined between two plates, as this is a simple model of seismic fault. Indeed, in the geophysical context frictional weakening could explain the unexpected weakness of some faults, as well as earthquake remote triggering. In this manuscript we review recent results concerning the response of confined granular systems to external perturbations, considering the different mechanisms by which the perturbation could weaken a system, the relevance of the frictional reduction to earthquakes, as well as discussing the intriguing scenario whereby the weakening is not monotonic in the perturbation frequency, so that a re-entrant transition is observed, as the system first enters a fluidized state and then returns to a frictional state.

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Mechanical impulse propagation in a three-dimensional packing of spheres confined at constant pressure

Cited by 13 publications

References 39 publications

Acoustic waves in granular packings at low confinement pressure

Acoustic waves in granular packings at low confinement pressure

Effect of an interstitial fluid on the dynamics of three-dimensional granular media

Induced and endogenous acoustic oscillations in granular faults

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