Numerical Investigation of Air-Coupled Generation of Lamb Waves Using Rectangular Phased Arrays

In the case of non-destructive testing and evaluation (NDT & NDE) of plate structures ultrasonic Lamb waves are used. Very often air-coupled ultrasonic transducers are used for non-contact Lamb wave excitation and reception. This method has a very serious drawback: global insertion losses for an air-coupled system may be 120–160dB typically, so optimum vibration excitation in tested material is needed. A numerical investigation has been performed in order to evaluate air-coupled Lamb wave excitation in an isotropic single layer plastic film using square transducer. A new method of excitation using planar phased arrays with rectangular elements has been proposed.