Abstract
Cylindrical internal defects in carbon steel specimens were detected noncontactly and nondestructively from the measurements of ultrasonic diffraction signals using the laser ultrasonic technique. Laser beams used for both ultrasonic generation and detection have a 0.7-mm diameter. Spatial profiles of the diffracted ultrasonic amplitude were measured for the internal defects of 0.5 to 5.0 mm in diameter, which were in good agreement with the profiles calculated by using Cornu's spiral. This method can be useful for the noncontact detection of internal defects in metal, and is considered to be applicable to the noncontact sizing of the internal defects such as those in power plant components.
