Comparison of ultrasonic nonlinear parameters measured by PZT and LiNbO₃ transducers

Abstract

The ultrasonic nonlinear techniques have been known as effective methods to evaluate a microstructure change of material. The ultrasonic nonlinear characteristic can be evaluated by the second-order ultrasonic nonlinear parameter β determined from the amplitudes of fundamental and second harmonic frequency components. The ultrasonic nonlinear parameter is generally measured by using a contact transducer; PZT and LiNbO₃ transducers are commonly used. However, the measurement result may be dependent on the equipment. Here in, we are curious about whether the nonlinear parameters measured by different transducers are identical. Therefore, in this study, we compare the ultrasonic nonlinear parameters measured by different transducers, PZT and LiNbO₃. For the experiment, the Al6061 specimens heat treated at 220°C with different aging time 60, 600, and 6000 min were prepared, and then the ultrasonic nonlinear parameter was measured by using two different kinds of transducer, PZT and LiNbO₃. The results showed that the tendency of measured nonlinear parameter was similar regardless of the type of transducer.