지원사업
학술연구/단체지원/교육 등 연구자 활동을 지속하도록 DBpia가 지원하고 있어요.
커뮤니티
연구자들이 자신의 연구와 전문성을 널리 알리고, 새로운 협력의 기회를 만들 수 있는 네트워킹 공간이에요.
이용수
초록· 키워드
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Closed cracks are difficult to detect using conventional ultrasonic testing because most incident ultrasound passes completely through these cracks. Nonlinear ultrasound inspection using sub-harmonic frequencies a promising method for detecting closed cracks. To implement this method, a sub-harmonic phased array (PA) is proposed to visualize the length of closed cracks in solids. A sub-harmonic PA generally consists of a single transmitter and an array receiver, which detects sub-harmonic waves generated from closed cracks. The PA images are obtained using the total focusing method (TFM), which (with a transmitter and receiving array) employs a full matrix in the observation region to achieve fine image resolution. In particular, the receiving signals are measured using a laser Doppler vibrometer (LDV) to collect PA images for both fundamental and sub-harmonic frequencies. Oblique incidence, which is used to boost sub-harmonic generation, inevitably produces various surface waves that contaminate the signals measured in the receiving transducer. Surface wave interference often degrades PA images severely, and it becomes difficult to read the closed crack’s position from the images. Various methods to prevent or eliminate this interference are possible. In particular, enhancing images with signal processing could be a highly cost-effective method. Because periodic patterns distributed in a PA image are the most frequent interference induced by surface waves, spatial frequency filtering is applicable for removing these waves. Experiments clearly demonstrate that the spatial frequency filter improves PA images.
목차
Abstract
1. Introduction
2. Sub-Harmonic Phased Array Imaging
3. Surface Wave Interference
4. 2-D Signal Processing for Image Enhancement
5. Image Enhancement by Removing Interference
6. Conclusions
References
참고문헌 (17)
참고문헌 신청
1. [학술지(정기간행물)] - K. Yamanaka. / 2003 / Evaluation of closed cracks by model analysis of sub-harmonic ultrasound / Japanese Journal of Applied Physics 43 (5B) : 3082 ~ 3087
2. [학술지(정기간행물)] - O. Buck. / 1978 / Acoustic harmonic generation at unbonded interfaces and fatigue cracks / Applied Physics Letters 33 (5) : 371 ~ 373
3. [학술지(정기간행물)] - J. M. Richardson / 1979 / Harmonic generation at an unbonded interface-I. Planar interface between semi-infinite elastic media / International Journal of Engineering Science 17 (1) : 73 ~ 85
4. [학술대회논문] - K. Yamanaka. / 2003 / Evaluation of nanoscale cracks by lowpass filter effect in nonlinear ultrasound / Proc. 2003 IEEE Ultrasonics Symposium : 972 ~ 977
5. [학술대회논문] - M. Akino. / 2004 / Fatigue crack closure analysis using nonlinear ultrasound / Review of Quantitative Nondestructive Evaluation, Green Bay, Wisconsin, USA : 1256 ~
2. [학술지(정기간행물)] - O. Buck. / 1978 / Acoustic harmonic generation at unbonded interfaces and fatigue cracks / Applied Physics Letters 33 (5) : 371 ~ 373
3. [학술지(정기간행물)] - J. M. Richardson / 1979 / Harmonic generation at an unbonded interface-I. Planar interface between semi-infinite elastic media / International Journal of Engineering Science 17 (1) : 73 ~ 85
4. [학술대회논문] - K. Yamanaka. / 2003 / Evaluation of nanoscale cracks by lowpass filter effect in nonlinear ultrasound / Proc. 2003 IEEE Ultrasonics Symposium : 972 ~ 977
5. [학술대회논문] - M. Akino. / 2004 / Fatigue crack closure analysis using nonlinear ultrasound / Review of Quantitative Nondestructive Evaluation, Green Bay, Wisconsin, USA : 1256 ~
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UCI(KEPA) : I410-ECN-0101-2015-500-001677170