Structural health monitoring of plate by using ultrasonic Lamb wave and time reversal, multiple signal classification beam forming.

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The objective of this study is to detect structural defects such as delaminations and notches in a plate by exciting it at a frequency to selectively generate a specific Lamb wave and recording reflected wave signals with a piezoelectric wafer sensor/actuator array. Here, the lowest symmetric (S0) and anti‐symmetry (A0) modes are excited by adjusting excitation frequency to increase signal‐to‐noise‐ratio. Note that the measured wave signals consist of the wave signals reflected from the defects as well as the boundaries of the plate. For the purpose of reducing the effects of the reflective waves from the boundaries and pinpointing out the structural defect locations in a high spatial resolution, it is proposed to apply a time reversal (TR), multiple signal classification (MUSIC) algorithm to the measured signals. Through an experimental measurement made with an array installed on a plate, it is demonstrated that the TR MUSIC beam forming procedure can be used to effectively identify the structural defect...