The Digital Ultrasonic Instrument

In order to provide a capability for performing advanced signal processing on ultrasonic and acoustic emission signals at speeds that are sufficient for practical applications, a high speed Digital Ultrasonic Instrument (DUI) has been developed. The DUI performs its processing entirely digitally and therefore can do the phase- and frequency-sensitive processing which is necessary in many advanced NDE techniques. Its speed of computations is sufficient to handle pulse repetition frequencies (PRFs) of several hundred Hertz. Three applications of the DUI are described, one each in the areas of flaw detection, flaw characterization and acoustic emission source characterization. The first application is improved near surface flaw detection by the use of subtraction of front surface echoes. The second application is a real-time operator-interactive method for correcting a flaw signal to remove system response and interface signals and thereby prepare the flaw signal for flaw characterization techniques such as the Born Inversion. The third application is the automatic identification of sources of acoustic emission in a fastener-hole geometry.