Array transducers can allow wavelength and frequency selectivity and can be used to generate different types of waves, such as ultrasonic bulk or guided waves. Dual-array transducers consist of two interlaced arrays, where the elements of each array are electrically connected. Therefore, by driving each array with a pair of phased pulses one can achieve a degree of wave generation control that allows unidirectional generation, unlike single array transducers that generate waves in both 0° and 180° directions with respect to the array's longitudinal axis. In this paper, we present a one-dimensional analytical model to determine the ultrasonic waves generated by dual-array transducers based on the excitability of the array in the frequency-wavenumber domain, the so-called operation region, determined by the joint spatial and temporal spectrum of the dual-array. We further exploited it to analyse the effectiveness of unidirectional generation with time-delayed excitation signals that provide ideal constructive or destructive interferences. The model also provides the time-domain received waveforms, which were compared to experimentally generated shear-horizontal ultrasonic guided waves, with a dual periodic permanent magnet array electromagnetic acoustic transducer, showing very good agreement. The adequate selection of the excitation signal allowed one to obtain up to about 40 dB unidirectionality experimentally.
Keywords: Analytical model; Dual-array transducers; Electromagnetic acoustic transducer; Frequency–wavenumber domain; Unidirectional generation.
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