Study on an EMAT Configuration for Higher-order Mode of Guided Wave

Abstract

In recent years, industrial plants and social infrastructures have been aging. As the countermeasure, non-destructive testings are highly expected. Because ultrasonic guided waves can propagate over long distance with low attenuation, they are suitable for non-destructive testing for long structures such as rods and cables. One type of ultrasonic transducers is an electromagnetic acoustic transducer (EMAT), which is composed of magnets and coils. It is capable of generating a variety of ultrasonic waves by selecting configurations of magnets and coils.
In this paper, for the purpose of generating higher-order modes of cylindrical guided waves, considering possible configurations of EMATs, we conducted experiments of guided waves transmitted and detected by EMATs for an aluminium rod. We calculated group velocities from measuring propagation time. Experimental results of group velocities, showing good agreement with theoretical ones, confirmed generation of higher-order modes. Further, numerical simulations also confirmed it by showing displacement distributions of corresponding modes.