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초음파의 에코 높이를 이용한 미소(微小) 박리(剝離) 두께 측정에 관한 연구
한응교,장경영,황병일,이범성,박익근,Han, E.K.,Jang, K.Y.,Hwang, B.I.,Lee, B.S.,Park, I.G. 한국비파괴검사학회 1993 한국비파괴검사학회지 Vol.13 No.1
If the infinitesimal delamination exists and the two waves can hardly be distinguished from each other on account of being much closer, we cannot measure the thickness of delamination by the time difference method. On this study, we calculated the thickness of infinitesimal delamination model by means of measuring echo height due to the deflection of material particles and utilized Newton Ring for optical measurement as a delamination model. From the result of Newton Ring expressed in the delamination model, we can calculate the infinitesimal delamination thickness up to $0.2{\sim}0.3{\mu}m$ due to the difference of acoustic impedance by the ratio of the echo height to the total reflection.
高分子 PVDF 振動子를 利用한 点集束超音波探觸子의 특성
韓應敎,黃汐泰,李範成,朴俊緖,小倉幸夫 한국비파괴검사학회 1992 한국비파괴검사학회지 Vol.12 No.2
In this study, we examine the characteristics of beam and the effect of these characteristics on the flaw detection by using different type of two transducers, which are PZT and PVDF film transducer. Consequently, the detection of infinitesimal flaw is more possible than PZT, since it has beam width at focus of 60%∼65% in contrast with PZT's. Moreover we can know PVDF transducer has superiority in detecting ability for sub-suface flaw detection in view of its acoustic impedance is near to water's and its focusing range is narrower than PZT's as 65%∼85% because it has spherical surface.