Ultrasonic wave propagation in water-saturated aluminum foams

In this paper, we present an experimental study of ultrasonic wave propagation in water-saturated cellular aluminum foams using the pulse transmission method. The aluminum foam samples have an essentially open cell structure with fixed cell size and structure, but different porosities (from 88% to 95%). Fast and slow longitudinal waves can be identified from measured transmission signals. The measured propagation velocities of two longitudinal waves agree with the predictions of Blot's theory. A corresponding spectral study suggests that the dispersions of both fast and slow waves are very small and only the low-frequency portion of the input pulse can travel through the samples in the fast and slow wave modes, while the high-frequency portion of the input pulse has been strongly attenuated in the medium. (C) 1998 Elsevier Science B.V. All rights reserved.