Development of the lens-focused air-coupled ultrasonic transducer for non-destructive testing

To realize highly efficient excitation and reception, a focused air-coupled ultrasonic transducer was developed based on concave spherical aluminum alloy acoustic lens and double spherical matching layers. Firstly, the effect of different volume fractions of the piezoelectric ceramics on the 1-3 piezoelectric composite performance was analyzed using series-parallel theory. The 1-3 piezoelectric composite with a volume fraction of 60 % was proposed. Secondly, the lens-focused air-coupled ultrasonic transducer was developed, the simulation and experimental results showed that the focused area of the transducer was at 18 mm. The double spherical matching layers greatly increased the energy to air of the transducer. Finally, the signal amplitude and sensitivity of the developed transducer was twice and 45.0 % higher than that of flat-plate transducer in the CFRP composite detection experiments. Thus, the developed transducer showed a greater advantage in practical application.