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Imaging of Harmonic Wave Generated by Contact Acoustic Nonlinearity in Obliquely Incident Ultrasonic Wave

경사입사 초음파에서 계면 접촉 음향 비선형성에 의해 발생한 고조파의 영상화

  • 윤동석 (한양대학교 자동차공학과) ;
  • 최성호 (한양대학교 자동차공학과) ;
  • 김정석 (한양대학교 자동차공학과) ;
  • 장경영 (한양대학교 기계공학부)
  • Received : 2012.06.11
  • Accepted : 2012.08.10
  • Published : 2012.08.30

Abstract

The objective of this study is to image the harmonic wave generated by contact acoustic nonlinearity in obliquely incident ultrasonic wave for early detection of closed cracks. A closed crack has been simulated by contacting two aluminum block specimens producing solid-solid contact interfaces and then acoustic nonlinearity has been imaged with contact pressure. Sampling phased array(SPA) and synthetic aperture focusing technique(SAFT) are used for imaging techniques. The amplitude of the fundamental frequency decreased with appling pressure. But, the amplitude of second harmonic increased with pressure and was a maximum amplitude at the simulation point of closed crack. Then, the amplitude of second harmonic decreased. As a result, harmonic imaging of contact acoustic nonlinearity is possible and it is expected to be apply for early detection of initial cracks.

본 연구에서는 닫힘균열의 조기발견을 위해서 경사입사 초음파를 이용하여 계면 접촉 음향 비선형성에 의해 발생한 고조파를 영상화하고자 한다. 알루미늄 시편 두 개를 접촉하여 고체-고체 접촉계면을 만들어 닫힘균열을 모사하였고, 접촉계면 압력에 따른 초음파의 음향 비선형을 영상화하였다. 영상화 기법으로는 sampling phased array(SPA)와 synthetic aperture focusing technique(SAFT) 기법을 사용하였다. 접촉계면 압력이 증가하면서 기본 주파수의 성분은 감소하였고 2차 고조파 성분은 증가하다가 닫힘균열로 모사된 부분에서 가장 큰 값을 나타내고 이후에는 감소하였다. 결과적으로 접촉계면에서 음향 비선형성에 의해 발생한 고조파를 영상화 하는 것이 가능하며 이는 초기균열의 조기발견에 적용 가능할 것으로 기대 된다.

Keywords

References

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