Measurement Method of Transmission System Transfer Function to Obtain Ultrasonic Displacement Amplitude Incident on Materials

The ultrasonic nonlinearity parameter β is determined from the ratio of the second-order harmonic displacement amplitude to the fundamental frequency displacement amplitudes. The piezo-electric detection method, which converts the electrical output of the receiving transducer into displacement amplitude via a transfer function that is obtained from the calibration measurement, is used to measure the ultrasonic nonlinearity parameter β. However, the measured ultrasonic nonlinearity parameter β contains the material nonlinearity and system nonlinearity generated from the measurement condition. This study proposes an algorithm that can measure the fundamental and second-order-frequency displacement amplitude components incident on materials. Based on the proposed algorithm, it is possible to measure the displacement amplitude of fundamental and second-order-harmonic-frequency ultrasonic waves incident on the material. Moreover, the proposed method can improve the reliability of ultrasonic nonlinearity parameter measurement