Abstract
We investigate the propagation of waves in dense static granular packings made of soft and stiff particles subjected to hydrostatic stress. Physical experiments in a triaxial cell equipped with broadband piezoelectric wave transducers have been performed at ultrasound frequencies. The time of flight is measured in order to study the combined effect of applied stress and rubber content on the elastic properties of the mixtures. The bulk stiffness deduced from the wave speed is nonlinear and non-monotonic with the increasing percentage of rubber with a more prominent effect at higher pressures. Moreover, in the frequency domain, a spectral analysis gives insights on the transition from a glass- to a rubber-dominated regime and the influence of rubber particles on the energy dissipation. Mixtures with rubber content below 30% show enhanced damping properties, associated with slightly higher stiffness and lighter weight.
Highlights
The behaviour of particulate mixtures is of interest for a large number of materials, and applications, including sintering, ceramics, gels, mineral processing, pharmaceutics, environmental and geotechnical engineering
This paper is organized as follows: In §2, we describe the details of the experimental set-up; we show the experimentally obtained elastic stiffness of the mixtures in §3; frequency analysis of different glass-rubber mixtures are shown in §4; in §5, we compute the quality factor of particular samples using the spectral ratio method
Differences in size, density, stiffness and shape of particles could lead to segregation in granular mixtures
Summary
The behaviour of particulate mixtures is of interest for a large number of materials, and applications, including sintering, ceramics, gels, mineral processing, pharmaceutics, environmental and geotechnical engineering. ‘Scattering’ is the reflection of the sound waves in directions other than propagation due to energy distribution on an expanding wavefront Another reason for amplitude decay is the energy absorption due to viscous momentum interaction, as related to material properties. A granular material showing maximum attenuation Q−1 in a certain frequency range, along with high stiffness and low density This allows for a novel design methodology for calm, smooth, and smart materials that can be better in various aspects than their separate components. This paper is organized as follows: In §2, we describe the details of the experimental set-up; we show the experimentally obtained elastic stiffness of the mixtures in §3; frequency analysis of different glass-rubber mixtures are shown in §4; in §5, we compute the quality factor of particular samples using the spectral ratio method.
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