Ceramic-element transducers have been used successfully to calibrate aluminum flat-bottom-hole (FBH) reference blocks according to the American Society for Testing and Materials [ASTM] E127 protocol. Six different transducers with nominal resonance frequencies of 5 MHz were excited using an adjusted digital reproduction of the tuned waveform used at the National Institute of Standards and Technology (NIST) for calibrating reference blocks. A variable-width square wave excitation was also investigated. For each transducer the excitations were adjusted to match the frequency spectrum of the radiated pressure waveforms, monitored using a polymer membrane hydrophone, with the frequency spectrum of the corresponding pressure waveform generated by the quartz transducer long used at NIST for reference block calibrations. Results indicate that the routine calibration of E127-type reference blocks, using arbitrary ceramic piezoelectric transducers of the appropriate aperture and frequency, may be possible. This may ultimately allow for the calibration of long metal-path, small FBH reference blocks which are of critical interest to the metals and aerospace industries, but which cannot be calibrated using the current E127 protocol.
Proceedings Title: 1998 ASNT Spring Conference
Conference Dates: March 23-27, 1998
Conference Location: Anaheim, CA
Conference Title: The 9th Asia-Pacific Conference on Nondestructive Testing in Conjunction with ASNT's 1998 Spring Conference and 7th Annual Research Symposium
Pub Type: Conferences
Reference blocks, Ultrasonic transducer, Ultrasonics