Quantitative broadband ultrasonic backscatter: An approach to nondestructive evaluation in acoustically inhomogeneous materials

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Abstract
In the present paper we investigate the use of a broadband backscatter technique to obtain the frequency dependence of the longitudinal‐wave ultrasonic backscatter coefficient from a collection of scatterers in a solid. Measurements of the backscatter coefficient were obtained over the range 0.1<ka<3.0 from model systems consisting of dilute suspensions of randomly distributed crown glass spheres in hardened polyester resin. The results of these measurements were in good agreement with theoretical prediction. Consequently, broadband measurements of the ultrasonic backscatter coefficient may represent a useful approach toward characterizing the physical properties of scatterers in intrinsically inhomogeneous materials such as composites, metals, and ceramics, and may represent an approach toward nondestructive evaluation of these materials.