Open celled foamed aluminum typically consists of an irregular frame of solid struts with typical lengths of the order of millimeters and thicknesses of a fraction of a millimeter. Total aluminum volume fractions are of the order of 10%. Quoted values of static modulus and mass density allow one to infer long wavelength ( much greater than strut length ) ultrasonic wave speeds. These predictions are compared with the velocities observed in 100kHz transient signals. At higher frequencies, where wavelengths are comparable to strut lengths, ultrasound can be transported only diffusively. Wavespeeds are unmeasurable, and of little meaning anyway. We therefore also report on ultrasonic measurements appropriate for the high frequency regime. These include diffusivity, absorption and modal density. Recent literature has reported measurements of diffusivities and absorption in other materials, particularly in metallic polycrystals. Measurements of modal densities are new.
Publisher
Department of Theoretical and Applied Mechanics. College of Engineering. University of Illinois at Urbana-Champaign
Series/Report Name or Number
TAM R 858
1997-6019
ISSN
0073-5264
Type of Resource
text
Language
eng
Permalink
http://hdl.handle.net/2142/112562
Sponsor(s)/Grant Number(s)
National Science Foundation 97/07 CMS 97 01142 97/07
Copyright and License Information
Copyright 1997 Board of Trustees of the University of Illinois
TAM technical reports include manuscripts intended for publication, theses judged to have general interest, notes prepared for short courses, symposia compiled from outstanding undergraduate projects, and reports prepared for research-sponsoring agencies.
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