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Academic Articles
Regular Paper (Invited) Vol.2 (2010/2011) p.181 - p.190
 

Efficient Transduction of Circumferential Lamb Waves by a Pair of Line Focus Type Noncontact Air-coupled Ultrasonic Transducers and its Application for Accurate Measurement of Pipe Wall Thickness

 
Hideo NISHINO1, Kenichi YOSHIDA1, Tadashi ASANO1, Yuta TANIGUCHI1, Hitoshi OGAWA2, Masakazu TAKAHASHI3, Yukio OGURA3
 
1 The University of Tokushima, 2-1 Minami-josanjima, Tokushima-city, Tokushima 770-8506, Japan
2 Tokushima Prefectural Industrial Technology Center, 11-2 Saikai, Saiga-town, Tokushima-city, Tokushima 770-8021, Japan
3 Japan Probe Co. Ltd., 1-1-14 Nakamura-town, Minami-ward, Yokohama-city, Kanagawa 232-0033, Japan
 
Abstract
Efficient transduction of a circumferential (C-) Lamb wave by a pair of noncontact air-coupled ultrasonic transducers (NAUTs) was presented. A line focus type (LFT-) of the NAUT was employed for the efficient transduction of the C-Lamb wave, which was designed so as to take an almost same angle of the incident longitudinal beam on the circular pipe surface. Outstanding characteristics of the LFT-NAUT for the C-Lamb wave transduction were theoretically and experimentally shown in comparison to those of the conventional plane type (CPT-) NAUT. The efficiency of the C-Lamb wave generated and detected by the LFT-NAUT took about 20 times higher than that by the CPT-NAUT. As for an application of the C-Lamb wave generated by the LFT-NAUT, a novel method of an accurate estimation of pipe wall thickness was introduced and evaluated with a theoretical model. It was confirmed that the maximum error between the experiments and the theoretical model was at around 10 πm.
 
Keywords
ultrasonic, nondestructive evaluation, pipe wall thinning, Lamb wave, circumferential Lamb wave, guided wave, health monitoring, noncontact air-coupled ultrasonic transducer
 
Full Paper: PDF EJAM Vol.2 pp.181-190 "Efficient Transduction of Circumferential Lamb Waves by a Pair of Line Focus Type Noncontact Air-coupled Ultrasonic Transducers and its Application for Accurate Measurement of Pipe Wall Thickness"
Article Information
Article history:
Received 22 November 2010
Accepted 3 February 2011