Efficiency of Ultrasonic Comb Transducers

Abstract

Comb transducers are applied in ultrasonic testing for generation of Rayleigh or Lamb waves by scattering of the incident bulk waves onto surface waves at the periodic comb-substrate interface. Hence the transduction efficiency, although rarely discussed in literature, is an important factor for applications determining the quality of the measured ultrasonic signals. This paper presents the full-wave theory of comb transducers concluded by evaluation of their efficiency for a couple of examples of standard and certain novel configurations.

Rayleigh wave reflection from single surface imperfections on isotropic substrates

“…Nevertheless the closed-form solutions have been obtained only in the linear approximation with respect to height to wavelength ratio h / even for isotropic substrates. [4][5][6][7][8][9][10][11][12][13][14][15][16][17] One of the fundamental characteristics allowing to estimate the influence of the surface state on the SAW propagation is the reflection coefficient from single obstacles, such as steps or grooves. Various theoretical methods have been put forward to derive this coefficient: perturbation techniques, 4-7 variational method, 8 impedance method, 9,10 and integral equation method.…”

“…The Brewster-like angle exists both for a single surface defect and for a periodic array of defects. [13][14][15][16][17] During the past 2 decades a large number of papers have been published devoted to the extraction of the so-called coupling-of-mode ͑COM͒ parameters from numerical calculations for infinite periodic arrays of electrodes on piezoelectric substrates ͑see Refs. 1 and 2 and references therein͒.…”

Research on guided wave excitation mode control method of comb transducer

“…Multiple axial scan testing has, so the efficiency to detect surface crack defect is unsatisfied [2] . Artificial guided wave inspection uses inclined wedge transducer.…”