Mode counts in an aluminum foam.
Measurements of the ultrasonic modal density of a disordered elastic frame, a 20 pore-per-inch open-celled aluminum foam, are reported. While the material is dissipative, with a Q only around 700, sufficiently careful signal processing has allowed reliable counts of the modes up through a few hundred, corresponding to wavelengths comparable to the strut lengths. The modal density is found to be essentially constant over this range, and to bear no resemblance to theoretical estimates based on long-wavelength effective moduli.
Lobkis
O I
OI
Theoretical and Applied Mechanics, University of Illinois, Urbana 61801, USA.
Weaver
R L
RL