Effect of granular media on the vibrational response of a resonant structure: theory and experiment.
The acoustic response of a structure that contains a cavity filled with a loose granular material is analyzed. The inputs to the theory are the effective masses of each subsystem: that of the empty-cavity resonating structure and that of the granular medium within the cavity. This theory accurately predicts the frequencies, widths, and relative amplitudes of the various flexural mode resonances observed with rectangular bars, each having a cavity filled with loose tungsten granules. Inasmuch as the dominant mechanism for damping is due to adsorbed water at the grain-grain contacts, the significant effects of humidity on both the effective mass of the granular medium as well as on the response of the grain-loaded bars are monitored. Here, depending upon the humidity and the preparation protocol, it is possible to observe one, two, or three distinct resonances in a wide frequency range (1-5 kHz) over which the empty bar has but one resonance. These effects are understood in terms of the theoretical framework, which may simplify in terms of perturbation theories.
Schlumberger-Doll Research, One Hampshire Street, Cambridge, Massachusetts 02139, USA. jvalenza@slb.com
John J
JJ
Valenza
Chaur-Jian
CJ
Hsu
David Linton
DL
Johnson
D000162:Acoustics; D000401:Aircraft; D000535:Aluminum; D004581:Electronics / Q000379:methods*; D005579:Fossil Fuels; D006813:Humidity; D008962:Models, Theoretical; D013816:Thermodynamics; D014414:Tungsten; D014732:Vibration; D014867:Water
D005579:Fossil Fuels; D014867:Water; D000535:Aluminum; D014414:Tungsten