평판 감육 측정 성능향상을 위한 IDT 기반 SLDV의 모드 선정 방안

국문 초록 (Abstract)

레이저 진동계를 이용하는 정상파응답영상화(Steady-state ultrasonic imaging technique) 기법을 활용한 평판 구조물의 결함 영상화 기법은 측정된 진동 신호의 주파수(wavenumber) 응답에 따라 구조물의 두께를 정량적으로 파악할 수 있기에 최근 활발하게 이용되어 왔다. 하지만, 두꺼운 구조물의 경우 저차 모드인 A0 모드가 두께 변화에 대한 파수 민감도가 낮아 측정에 어려움이 있으며 이러한 어려움을 해결하기 위해 높은 파수 민감도(wavenumber sensitivity)를 가진 할 수 있는 IDT(Interdigital transducer) 기반 SLDV(Scanning Laser Doppler Vibrometer)를 사용하였다. 하지만 기존 방법에서도 파수 민감도를 유한차분으로 구했을 뿐만 아니라 측정 모드가 전체 주파수 및 파수 민감도의 응답곡선을 통해 정성적으로 결정되었다. 본 연구에서는 파수 민감도를 해석적으로 구하였으며 이것을 최저임계값을 포함한 제약조건으로, 그리고 측정모드 개수를 목적함수로 하여 최적설계 문제로 정식화 하여 최적의 측정 모드를 선정하였고, 이를 예제를 통해 검증하였다.

다국어 초록 (Multilingual Abstract)

Defect imaging of plate structures using a Scanning Laser Doppler Vibrometer (SLDV) is a widely used technique because the thickness of such structures can be quantitatively identified. However, for thick structures, the low-dimensional mode A0 performs poorly due to low wavenumber sensitivity with respect to change in thickness. Interdigital transducer (IDT)-based SLDVs with high wavenumber sensitivity have been adopted to resolve this problem. However, using this method, not only was the wavenumber sensitivity obtained as a finite difference, but the measurement mode was also determined empirically through the response curve of the total frequency and wavenumber sensitivity. In this study, wavenumber sensitivity was obtained analytically and was used as a constraint together with the lowest threshold value and the inspection mode. Using the number of inspection modes as the objective function, an optimal design problem was formulated, and the optimal inspection mode was selected. This was verified through numerical examples.

목차 (Table of Contents)

• 초록
• Abstract
• 1. 서론
• 2. 최적설계 정식화를 통한 주파수 측정 모드 선정
• 3. 정식화된 설계문제를 통한 다양한 평판 문제에 대한 주파수 모드 선정
• 4. 결론
• References

참고문헌 (Reference)

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