Increasing the scanning range of Lamb wave based SHM systems by optimizing the sensor design and excitation frequency

The objective of the paper is to investigate and to optimize parameters which effect the excitation of Lamb waves generated by adhesively bonded piezoceramic actuators. Particularly, the influence of the adhesive layer and the resonances of the actuator are examined both numerically and experimentally. Understanding these properties helps to develop energy efficient structural health monitoring (SHM) systems, meaning that less energy is needed to excite waves with the same scanning range. Knowing the main influence parameters a numerical optimization is proposed, which is aimed at increasing the range of the excited waves by optimizing the sensor geometry and the excitation frequency. Various tests with different test specimens have been performed. An evolutionary based algorithm is used to find the optimal configuration. It has been found that small changes in the geometry and an optimized excitation frequency elevate the amplitudes of the signal measured with a piezoelectric transducer significantly.