Ultrasonic Nondestructive Evaluation of Cylindrical Samples with Surface Acoustic Waves

Abstract The paper reports experimental methodology and results of nondestructive evaluation and flaw imaging in cylindrical samples using surface acoustic waves (SAW) generated with conventional longitudinal wave transducers attached to the sample surface. A very thin layer of couplant (or even dry coupling) was used to provide efficient SAW generation in the direction normal to a cylinder element in the frequency range 5–15 MHz. A single B-scan mode was sufficient to inspect a total surface of cylindrical shafts of ceramic and metal engine valves. A delay of the processing time gate allowed us to analyze any of the successive SAW revolutions implementing a specific “transmission B-scan” with a single probe. Amplitude and phase contrast of the B-scans obtained demonstrate the system capability to detect valve radius deviations of ∼ 1 μm and cracked flaws with sizes down to ∼ 30 μm.