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Structural Health Monitoring (SHM) techniques have an important role in the performance of mechanical structures. In particular, piezoelectric transducers (PZT) have been employed for establishing damage detection processes in SHM systems. However, despite their wide use, there is limited information in the literature regarding important characteristics for SHM applications, such as the shape, dimensions and frequencies to use, which can affect the performance of the system used to detect the damage. This article investigates longitudinal and flexural waves for applications using circular piezoelectric transducers bonded to thin plates. The methodology allows one to obtain optimal frequencies to create and capture both types of waves and understand the influence of the geometric characteristics of these transducers on the damage detection. Numerical simulations are carried out to show that a change in the parameters of the piezoelectric transducers can maximize the waves amplitudes incoming at the sensor. Results from experimental tests are presented to demonstrate the proposed methodology. New equations are introduced and they compute output voltage and determine optimal frequencies to monitor the structure. The findings contribute to establishing a more efficient design of a damage detection process involving plate-like structures in SHM systems based on wave propagation.

The design of structural health monitoring (SHM) systems usually involves the selection of actuators and sensors, defining their positions on the structure, and post-processing output signals. The definition of the characteristics of the excitation signals before investigating the structural condition is also an important task to be considered to establish a damage detection process. In this context, the present article introduces an approach to determine the optimal parameters to detect symmetric damage in plates when considering perpendicular incidence of flexural waves in the damage. Circular piezoelectric transducers are applied to create and measure the waves. Optimal frequencies to detect the damage, create and measure the flexural waves are observed, which are described in terms of the properties of damage and the piezoelectric transducers, and these frequencies must be close to guarantee good damage detectability. Experimental tests are carried out by considering a rectangular aluminum plate with circular piezoelectric transducers coupled to its surface. Experimental results demonstrate the proposed approach, and the results show that it contributes to establishing more efficient SHM systems.