Excitation and propagation of elastic waves by interdigital transducers for non-destructive evaluation of plates

Abstract

Excitation and propagation of elastic waves by inter-digital transducer (IDT) for non-destructive evaluation (NDE) of plate structures is studied by considering the electromechanical coupling effect and the interaction between IDT and host plate. An analytical model is formulated and solved to serve as a guide for the optimal design of IDT in NDE of cracks in plates. The effects of finger spacing, width and number of fingers are evaluated and an optimal combination proposed to achieve sufficient mode selectivity and excitation strength while keeping the time-span of the signal package small. Mobile double-sided IDT is proposed as an efficient device where excitation strength is designed to be strong and focused. It is then fabricated in-house and used to develop a procedure for accurate locating and determination of the extent of cracks in plates. The proposed device and recommended procedure are shown to be efficient and accurate in locating and determining the extent of a linear, piecewise linear and curve cracks in three aluminum plates.