A novel pulse-echo piezoelectric transducer for detecting quasi-static component induced by an ultrasonic longitudinal wave

For effectively detecting the quasi-static component (QSC) of an ultrasonic longitudinal wave, which is closely related to the elastic nonlinearity of material, we proposed a novel pulse-echo piezoelectric transducer consisting of a high-frequency piezoelectric wafer, a frequency selective isolation layer, a low-frequency piezoelectric wafer, and an acoustic backing. The high-frequency wafer generates the primary longitudinal wave (PLW) tone burst, while the high- and low-frequency wafers receive the pulse echo containing both the PLW component and QSC, respectively. We analyze the pulse-echo formation of the high-frequency PLW tone burst in a specimen, and conduct numerical simulations and experiments to validate the effectiveness of the proposed transducer. The results demonstrate that the low-frequency receiver is more efficient at detecting the QSC, even though the high-frequency wafer can also receive the echo of the QSC pulse. Specifically, the QSC pulse can still be detected by the low-frequency receiver when the high-frequency PLW tone burst is completely attenuated. The novel pulse-echo transducer proposed in this paper expands the design perspectives for transducers used in ultrasonic non-destructive testing.