Enhancement of the mode purity of shear horizontal mode of a thickness-shear transducer through design changes


In ultrasonic guided waves, arrays of thickness-shear piezoelectric transducers are often used to generate Lamb waves in plates and longitudinal/torsional waves in pipes. Although the ultrasonic output of the transducer is well known both numerically and experimentally, few results are available in the literature regarding the influence of geometry, electrode layout and materials on the ultrasonic output of the transducer: in particular, the influence of those parameters on the mode purity of the generated shear horizontal mode in plates require further investigation. Numerical simulations with finite element modelling (Comsol Multiphysics) have been conducted on a thickness-shear transducer on a plate to understand the influence of these parameters on the mode purity of the transducer. Experimental validation with a new prototype has been conducted to confirm the numerical results and compare them with different configurations. Moreover, the physical behaviour of the transducer is analysed by understanding the interaction between its surface and the waveguide. The desired physical behaviour of the transducer is also represented through an objective function and the various numerical and experimental results are compared to the objective function.