Lamb wave tuning curve calibration for surface-bonded piezoelectric transducers

Abstract

Surface-bonded lead zirconate titanate (PZT) transducers have been widely used for guidedwave generation and measurement. For selective actuation and sensing of Lambwave modes, the sizes of the transducers and the driving frequency of the inputwaveform should be tuned. For this purpose, a theoretical Lamb wave tuningcurve (LWTC) of a specific transducer size is generally obtained. Here, the LWTCplots each Lamb wave mode’ amplitude as a function of the driving frequency.However, a discrepancy between experimental and existing theoretical LWTCs hasbeen observed due to little consideration of the bonding layer and the energydistribution between Lamb wave modes. In this study, calibration techniques fortheoretical LWTCs are proposed. First, a theoretical LWTC is developed when circularPZT transducers are used for both Lamb wave excitation and sensing. Then, theLWTC is calibrated by estimating the effective PZT size with PZT admittancemeasurement. Finally, the energy distributions among symmetric and antisymmetricmodes are taken into account for better prediction of the relative amplitudesbetween Lamb wave modes. The effectiveness of the proposed calibration techniquesis examined through numerical simulations and experimental estimation of theLWTC using the circular PZT transducers instrumented on an aluminum plate.