Defect Detection With Ultrasonic Spectroscopy

Ultrasonic spectroscopy is a nondestructive test method which supplements conventional ultrasonic inspection through the application of spectrum analysis technology. It consists of examining the frequency components or spectra of ultrasonic pulses reflected from a material being tested. This can be accomplished with a spectrum analyzer which is an electronic instrument that separates a received waveform into its individual frequency components and displays them on a cathode ray tube (CRT). The spectrum analyzer is in itself a relatively complex subject; however, in order to discuss ultrasonic spectroscopy in more basic terms, one can think of the operation of a spectrum analyzer as analogous to a prism separating sunlight into its color constituents. The following sections introduce ultrasonic spectroscopy principles and discuss advantages it offers for detection of defects located close to the front or back surface of a test sample (i. e. , near -and far surface defects).