Abstract
The adhesion state of a heat seal used for a cup type container is evaluated only by viewing now. The purpose of this study is a nondestructive evaluation of the adhesive strength of the product using the heat seal. Therefore we evaluate the adhesion state of a heat seal, using ultrasonic wave. The ultrasonic frequency is affected by passing the object inside. We take notice of the frequency modulation of ultrasonic wave. Therefore we apply Hilbert conversion and calculate the frequency modulation of ultrasonic wave. Then, we estimate the state of the adhesion layer from the change by the frequency modulation.
