| Abstract: | A new amplitude correlation and differencing (ACD) method for the detection of flaw changes using digital pulse-echo ultrasonic data is proposed. The ACD method is based on signal processing techniques applied to digitized pulse amplitudes from scans of the same transducer recorded during two separate ultrasonic inspections. Changes in flaws with a wide variety of sizes and other characteristics can be detected, provided the change is in a direction perpendicular to the centre line of the ultrasonic beam.Practical experience of this method was gained by analysis of ultrasonic data from two inspections of a weld, separated by a year. The effectiveness of the ACD method for flaw monitoring is compared with that of the 6 dB drop sizing method, before and after resolution improvement by the synthetic aperture focusing technique (SAFT). |
