Lamb Waves Tunning on Aluminium Plates for Structure Health Monitoring.

The method for defects detection inside the mechanical structures, namely aerospace structures, using the Lamb waves is widespread because of its benefits: it is nondestructive, may reveal the presence and size of defects with high accuracy and does not require any expensive equipment for application. One of the ways to implement this method consists in mechanically exciting a point of the plate using a piezoelectric actuator followed by the signal collection by means of a piezoelectric transducer located in another point of the same plate surface. By interpreting the shape, the phase and amplitude of the collected signal the presence of a defect, its type and size can be highlighted. As a specimen of mechanical structure, a rectangular aluminum plate has been used. The generation of the Lamb waves in the plate was performed with a signal of certain optimal frequency values that need to be determined in advance. The procedure for determining the optimal frequency values is called tuning and consists in measuring and processing the signals amplitude values for multiple frequencies of the excitation signal, ranging between 10-800 kHz. The article deals both with the procedure description and the relevant results obtained for aluminum plates of different sizes. [ABSTRACT FROM AUTHOR]