Built-in diagnostics for identifying an anomaly in plates using wave scattering

A diagnostic technique based on a built-in network of piezoelectric actuators and sensors was proposed for detecting the location and size of an anomaly in isotropic plates. The technique consists of three major components: Diagnostic wave generation, Signal processing, and Damage identification. For diagnostic wave generation, the technique uses a piezoelectric disc as an actuator to generate specific diagnostic waves propagating in the plates. The neighboring piezoelectric discs used as sensors to record the propagating waves. The difference in the sensor measurements before and after the introduction of an anomaly based on identical actuator inputs was used to characterize the anomaly.; A signal processing scheme based on the joint time-frequency analysis was developed to convert sensor measurements into sensor and scatter spectrograms in time-frequency domain. An identification technique was developed to estimate the location and the size of an anomaly based on the spectrograms. For location estimation, the technique uses the time-of-flight data of the scatter spectrogram of each actuator-sensor pair in the network. For size prediction, a minimization scheme was developed to compare a measured scatter spectrogram with a calculated one based on an analytical model.; Based on the proposed technique, a computer code IDWAVE was developed for automatic wave generation, signal processing, and anomaly interpretation in aluminum plates. To verify the technique and the computer code, experiment was conducted on aluminum plates with added thicknesses and circular cutouts as anomalies. PZT discs were mounted on the surfaces of the plates. A PC-based hardware system was developed to implement the computer code. Experiments showed satisfactory s showed satisfactory diagnostic results.