Surface Flaw Detection of Rotating Bodies Using Laser Ultrasound

Abstract

Laser ultrasound is an effective method for noncontact flaw detection, material property measurement, and temperature measurement. In this research, laser ultrasound was applied to surface flaw detection of rotating specimens, for which conventional techniques such as ultrasonic inspection using transducers cannot be applied. A SUS316 specimen with artificial slits of depth 1 mm machined in the radial and tangential directions was used. By synchronizing the rotation frequency of the specimen with the laser repetition rate, the presence of the slits could be detected from the waveform and frequency spectrum of the surface acoustic waves. The results obtained when the specimen was under rotation was in agreement with the results obtained when the specimen was at rest. Furthermore, the detection position was scanned in the tangential direction by slight desynchronization of the specimen rotation and laser irradiation. The presence of slits could be detected with high accuracy by using the ratio of different frequency components of the obtained waveform.