Fast Fourier transform method for determining velocities of ultrasonic Rayleigh waves using a comb transducer

Shuzeng Zhang; Canhui Cheng; Xiongbing Li; Tribikram Kundu

doi:10.1016/j.ultras.2022.106754

Fast Fourier transform method for determining velocities of ultrasonic Rayleigh waves using a comb transducer

Ultrasonics. 2022 Aug:124:106754. doi: 10.1016/j.ultras.2022.106754. Epub 2022 Apr 30.

Authors

Shuzeng Zhang¹, Canhui Cheng², Xiongbing Li³, Tribikram Kundu⁴

Affiliations

¹ School of Traffic and Transportation Engineering, Central South University, Changsha, Hunan 410075, China. Electronic address: sz_zhang@csu.edu.cn.
² School of Traffic and Transportation Engineering, Central South University, Changsha, Hunan 410075, China.
³ School of Traffic and Transportation Engineering, Central South University, Changsha, Hunan 410075, China; Key Laboratory of Traffic Safety on Track, Central South University, Ministry of Education, 410075, China.
⁴ Department of Civil & Architectural Engineering & Mechanics, University of Arizona, Tucson, AZ, 85721, USA.

PMID: 35512578
DOI: 10.1016/j.ultras.2022.106754

Abstract

A convenient, accurate and precise method is proposed to determine velocities of ultrasonic Rayleigh waves in different materials by extracting central frequencies of signals, which are measured by a comb transducer and converted to the frequency domain using the fast Fourier transformation (FFT). The velocities can be calculated as c_r = fl, where f is the central frequency of the wave signal and l is the teeth spacing or period of the comb transducer. The experimental measurements are easy to do, as long as the Rayleigh wave reflected from the standard reflectors are measured using one comb transducer, without knowing the wave propagation distances and times. Results show that the proposed technique has a high level of precision, as the central frequencies are very stable. The same comb transducer is used to measure the Rayleigh wave velocities in different materials where the velocities vary from 2100 m/s to 3400 m/s. Comparison of the experimental results with those measured using the time-of-flight method showed a high level of accuracy - all relative errors were found to be less than 1%.

Keywords: Comb transducer; FFT method; Ultrasonic Rayleigh wave; Velocity measurement.