Void characterization using ultrasonic backscatter from void clusters

A technique to extract the deconvolved response of a single cavity from the backscattered ultrasonic signal received from a cluster of cavities is presented. First, a standard deconvolution removes noise and distortions of the signal caused either by the measuring system or the specimen. This is followed by homorphic deconvolution using the complex cepstrum to extract the response of a single cavity when signals from adjacent cavities in the cluster are superimposed on each other. The technique is applied to backscatter from a cluster of spherical cavities located in an epoxy specimen. The recovered signal compares favorably with the analytically calculated, backscattered time-domain response of a spherical cavity due to the incidence of a plane longitudinal wave on the single cavity. The radius of the cavity can be obtained from the extracted response using a simple formula derived from elastodynamic ray theory.