Abstract
In this paper, we regard the ultrasonic wave as an oscillatory waveform and detect the minute degradation by means of the slight modulation of the ultrasonic frequency. In the experiment, we use epoxy resin adhesive which bonds two acrylic plates and detect the defect in adhesion. A new technique is employed to evaluate the frequency modulation of ultrasonic wave. A significant difference is observed in the ultrasonic frequency by means of the proposed method. By simulation, the cause of the observed difference is made known.
