Acoustically induced stresses in elastic cylinders and their visualization

The interior field in elastic cylinders immersed in a fluid and subject to an incident acoustic plane wave has been studied here via an application of the resonance scattering theory (RST), first formulated by Flax et al. [J. Acoust. Soc. Am. 63, 723 (1978)]. The interior field has been shown to consist solely of resonant amplitudes, with a substantial amount of penetration of the incident field into the scatterer occurring only at and near-resonance frequencies. Experimental measurements of stress distributions in a finite glass cylinder isonified by a normally incident acoustic pulse and viewed by axially transmitted light are presented as a function of ka (range of 5–55). The results show that the largest variations in light intensity occur for specific values of ka that correspond to resonance modes of the elastic glass cylinder. A model of the dynamics of the interior motions inside such a cylinder, and corresponding strain equations, are developed and combined with birefringence expressions for the purpose of predicting the light distributions. The elastic body is shown to undergo resonances in the radial and angular directions, except for the merely radial motions of the breathing mode. Calculated light distributions are shown to correspond to measured distributions.