Phased Gratings Used in the Automated System of Ultrasonic Inspection of Disks

The Canadian firm R/D Tech offers the Tomoscan Focus immersion system for the ultrasonic inspection of disks. The description of the system and performance characteristics of a scanner and a phased grating (PG) used as a probe are considered. The experiment has definitely proved that longitudinal waves from a circular PG can detect reflectors 0.4 mm in diameter at 1.5- and 50-mm depths if the signal-to-noise ratio is 14 and 24 dB, respectively. For a focusing piezoelectric transducer (PET), the signal-to-noise ratio was ∼10 dB. When sounding a linear PG with shear waves, a flaw of 0.8 mm in diameter was detected, the signal-to-noise ratio being ∼23.5 dB. The Tomoscan Focus system allows testing at a higher sensitivity.