NEWLY DESIGNED ACOUSTIC LENS FOR POINT-FOCUSING OF SURFACE WAVES: USE OF CONVENTIONAL ULTRASONIC TRANSDUCER
Byoung-Geuk Kim and Sekyung Lee, and Teruo Kishi* Failure Prevention Research Center, Korea Research Institute of Standards and Science P. O. Box 102, Yusong, Taejon, Republic of Korea *Research Center for Advanced Science and Technology The University of Tokyo, Komaba 4-6-1, Meguro-ku Tokyo 153, JAPAN
In the ultrasonic contact testing of materials, focusing transducers have been used to increase sound intensity and to improve resolution. Recently, we had presented a method [1], [2] for point-focusing of surface waves by which the acoustic contact lens of the transducer was in a shape obtained by rotating a right-angled triangle to have a critical angle for the generation of surface waves. Then, a piezoelectric elements should have a curved shape to fit the convex surface of the lens, and we used PVDF films. In the present work, we designed a new acoustic lens on which a curved piezoelectric element was not required and a conventional ultrasonic transducer could be used for the intensive focusing of surface waves. In this method, we employed a principle that after the ultrasonic waves had been firstly reflected from the curved surface in the lens, the waves could be converted into surface waves. Also, using a simple model, we estimated the stress pattern on the symmetry axis of the focusing transducer. The sound intensity of the focusing transducer presented in the present work was higher about 20 dB than using PVDF films. The newly designed transducer was very effective and practical for the intensive focusing of surface waves. The stress pattern predicted using the model showed good agreement with the experimental result. REFERENCES
B. G. Kim, J. O. Lee and S. Lee, "New Design and Analysis for Point-Focusing -----Contact Testing", IEEE Trans. UFFC, 40(2), pp. 162-166
Byoung G. Kim, Se K. Lee and Jae O. Lee, "Ultrasonic Contact Transducer For Point-Focussing Surface Waves", US Patent, No. 5094108, 1992
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.Vol. 4, pages 2599 - 2604 Publisher:Ashgate Publishing Company
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