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Thomas Brunet, Xiaoping Jia, Pascale Massaad, Pierre Mills

{. Ultrasound Propagation in Cohesive Granular Materials. Thomas Brunet, Xiaoping Jia, Pascale Massaad, Pierre Mills. propagation of elastic wave in dense granular media under stress. P. P. Polydisperse glass beads d ~ 600-800 µm. L. l >> d Coherent Ballistic Wave (E).

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Thomas Brunet, Xiaoping Jia, Pascale Massaad, Pierre Mills

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  1. { Ultrasound Propagation in Cohesive Granular Materials Thomas Brunet, Xiaoping Jia, Pascale Massaad, Pierre Mills propagation of elastic wave in dense granular media under stress P P Polydisperse glass beadsd ~ 600-800 µm L l >> dCoherent Ballistic Wave (E) l ~ dMultiple Scattering Wave (S), i.e. acoustic speckles Dry bead packing Wet bead packing by oil: F ~ 0,015% (Jia et al, PRL 1999; P&G 2001) (Jia, PRL 2004) Diffusive transport of multiple scattering waves : Measurements of compressional (L) and shear (T) wave velocities providing elastic modulii (K, G) Effective Medium Theory (hertzian scaling law) : { where • Short correlation length of force chains probing cohesive granular material with elastic waves Energy dissipation in a wet granular medium Capillary effects on the structure and elastic properties (all liquids) Decreasing the geometric coordination number due to the adhesion by liquid bridges Lubrication effects on the elastic properties(only trioléïne) Mechanism of contact recruitment due to the presence of the adsordedliquidfilms wetting liquid increase dramatically dissipation in the medium, especially when the liquid is lubricant • Ultrasonic absorption measurements with controlled grain surfaces and wetting liquids • Understanding the dissipation mechanism Current Study: where the « active » coordination number Zwet(P) is significantly increased due to lubrication.

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