• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.3
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• pp.240-245
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• 2004

Torsional characteristics of nonuniform circular waveguides were studied experimentally by using an in-plane laser vibrometer. The circumferential displacement along the axis of a rod was measured as a response of the torsional oscillation excited at one end of the rod. The experimental results obtained for a stepped circular rod and a conically-tapered rod were compared with theoretical predictions. The results of this paper show the possibility of using the in-plane laser vibrometer for the measurement of torsional vibrations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.609-616
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• 2001

The vibrational characteristics of nonuniform circular rods have been studied theoretically and experimentally in this paper. The differential equation of torsional motion expressed in terms of the angular displacement has been solved exactly and approximately for a stepped circular rod and for a conically-tapered rod. Solutions of the boundary-value problem have yielded the natural frequencies, mode shapes and forced responses of the rods. The theoretical solutions of forced response have been verified by comparing them with experimental ones.

• The Journal of the Acoustical Society of Korea
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• v.22 no.7
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• pp.545-553
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• 2003

This paper is concerned with protecting piezoelectric transducers used in an ultrasonic flowmeter from the high temperature of hot fluid in a pipe by using a waveguide and with improving the propagation of ultrasonic longitudinal vibration in the waveguide. Waveguide material has been chosen for efficient insulation of heat transferred in the waveguide, and the minimum length of the waveguide for protecting piezoelectric transducer has been estimated. Forced response of the longitudinal vibration in a uniform circular rod has been obtained and the length of the waveguide has been selected for maximum amplitude. Longitudinal vibration response of a conically-tapered rod excited at a natural frequency has been obtained to confirm that wave motion is amplified as the cross-sectional size of the waveguide decreases along the axial direction. The fact that dispersion of a pulse wave in a waveguide is reduced as the cross-sectional radius is decreased has been examined theoretically and confirmed experimentally by using a single-rod waveguide. A bundle-type waveguide has proven to be a practical one through the evaluation of the wave propagation performance.