초음파 비선형 파라미터 절대측정기술

Abstract

The nonlinear ultrasonic technique is a promising method that can evaluate microstructural defects such as thermal aging, fatigue and creep. In the nonlinear ultrasonic technique, the ultrasonic nonlinear parameter is measured as an evaluation indicator, which is determined by absolute displacement amplitudes of fundamental and harmonic components. However, it is difficult to measure the displacement amplitudes of the harmonic components because they are very small. Therefore, the piezoelectric detection method has been developed, which converts the detected electrical signal amplitude into the absolute displacement amplitude by through a calibration process to measure the ultrasonic nonlinear parameter. In this study, the proper window function and scaling factors were presented, and a guideline of the measurement system construction was proposed. In order to verify the proposed idea, two measurement processes were conducted: 1) increasing input power with fixed propagation distance and 2) increasing propagation distance with fixed input power. Two measurement results were similar each other and also were closely related with the reference. In conclusion, the proposed methods are useful for the absolute ultrasonic nonlinear parameter measurement.