A Nondestructive Diagnostic Method Based on Swept-Frequency Ultrasound Transmission-Reflection Measurements

A particular nondestructive diagnostic technique is proposed to measure depth and thickness of unwanted inclusions inside laminate-type materials (gaps, delaminations, cracks, for example). The method is based on the frequency-domain analysis of transmission and reflection coefficient measured on the material under test when it is irradiated by a CW ultrasound beam whose frequency varies over a suitable frequency range. By measuring the frequency distance between two adjacent minima in the attenuation and reflection coefficients the thickness and depth of the inclusion can be obtained. A practical implementation of the technique is suggested and the first experimental results obtained by a laboratory setup are reported. © 1992 IEEE