Wave propagation in piezoelectric coupled plates by use of interdigital transducer. Part 2: Wave excitation by interdigital transducer

In the second part of the research on wave propagation in the piezoelectric coupled plate by interdigital transducer (IDT), the analytical model of the wave excitation by IDT with both infinite and finite length is derived the first time. This work is an extension of the research on the application of IDT in the piezoelectric media, which is mainly used in time delay device. The extension of the research can provide an analytical solution for the wave excitation by IDT in a metal substrate surface bonded by a piezoelectric layer. Such solution may have practical values in many fields, i.e. the health monitoring of structures. In addition, such an extension enables the piezoelectric coupling effects fully modelled in the mathematical model. The analysis is based on the type of surface wave solution discussed in Part 1 of the research paper. The derivation of the solution for the case of infinitely long IDT is under a hypothesis of certain configuration of the IDT wavelength. The validity of the hypothesis is verified for most of IDT wavelength designs. The analysis of the wave propagation by use of a finitely long IDT is further obtained by Fourier transform. The mathematical analysis shows that the wave propagation excited by the IDT is exactly the surface wave which was studied in Part 1 [Int. J. Solids Struct., 39, 1119–1130] of the research. Hence, the analytical solution of the wave propagation in the piezoelectric coupled plate is derived, which reveals the surface wave propagating in the structure. This theoretical research is useful for the application of health monitoring of structures by IDT, and may be used as the framework for the design of IDT in wave excitation of smart structures