The principle of ultrasonic work is mainly based on the propagation characteristics of ultrasonic wave in the specimen.
        The A. sound source generates ultrasonic waves and uses certain means to make the ultrasonic wave into the specimen;
        The B. ultrasonic wave propagates in the specimen and interacts with the specimen material and its defects so that its propagation direction or characteristics are changed;
        The C. The modified ultrasonic wave is received by the detecting device and can be processed and analyzed;
        The D. based on the characteristics of the received ultrasonic wave, the defects and defects in the specimen itself and its interior are evaluated.