서지주요정보
광섬유 샤냑 간섭계를 이용한 고체 매질 내 레이저-여기 초음파의 비접촉식 측정 및 전파 특성에 관한 연구 = A Study on non-contact measurements of laser-generated ultrasonic waves in a solid medium using fiber optic sagnac interferometer and their propagation characteristics
서명 / 저자 광섬유 샤냑 간섭계를 이용한 고체 매질 내 레이저-여기 초음파의 비접촉식 측정 및 전파 특성에 관한 연구 = A Study on non-contact measurements of laser-generated ultrasonic waves in a solid medium using fiber optic sagnac interferometer and their propagation characteristics / 장태성.
저자명 장태성 ; Jang, Tae-Seong
발행사항 [대전 : 한국과학기술원, 2003].
Online Access 원문보기 원문인쇄

소장정보

등록번호

8014287

소장위치/청구기호

학술문화관(문화관) 보존서고

DME 03010

휴대폰 전송

도서상태

이용가능

대출가능

반납예정일

초록정보

A fiber optic sensor suitable for non-contact detection of ultrasonic waves has been developed in this study. This sensor is based on the fiber optic Sagnac interferometer, which has a path-matched configuration and does not require active stabilization. It is shown that there exists the specific birefringence producing the quadrature point of operation for the maximum sensitivity of the fiber optic Sagnac interferometer for an arbitrary incident polarization state. The quadrature phase bias between two interfering laser beams in the Sagnac loop is achieved by the control of birefringence using a fiber polarization controller. The birefringence can be controlled in low birefringent single mode fiber due to bending; then the fiber may have a fast and a slow axis. As a result, an arbitrary optical phase delay of the light can be obtained between clockwise and counter clockwise beams in the Sagnac loop. A stable quadrature phase bias is confirmed by observing the interferometer output corresponding to the 2π peak-to-peak input signal produced by a fiber-wrapped PZT ring phase modulator. A fiber focuser is attached to the end of the probing optical fiber to focus the laser beam onto the specimen surface and to collect the reflected light back into the optical fiber probe. Harmonic ultrasonic oscillations produced by a PZT disk and ultrasonic pulses produced by conventional ultrasonic PZT transducers are successfully detected; and the performance of the interferometer is investigated by a power spectrum analysis of the output signal. The interference intensity is affected by the frequency of ultrasonic waves and the time delay of Sagnac loop. An additional signal processing is not needed for the detection of ultrasonic waves using the Sagnac interferometer. The configured fiber optic Sagnac interferometer is very effective for the non-contact detection of small displacement with high frequency such as ultrasonic waves used in conventional non-destructive testing, and can be applied for any other ultrasonic measurements. Based on the validation of the fiber optic Sagnac interferometer, the non-contact detection of laser-generated ultrasound is performed. Longitudinal and Rayleigh waves are generated in a steel specimen by a high powered Q-switched Nd:YAG laser pulse, and are detected by the non-contact optical technique using the fiber optic Sagnac interferometer. Surface acoustic waves are generated by line array illumination of a sample surface with a Q-switched Nd:YAG laser pulse. Multiple slits and a cylindrical lens are used to generate the tone-burst like surface waves. The adjustment of the center frequency of surface wave is performed by the change of distance between the sample and the lens; and the narrowband surface acoustic waves are obtained. Surface acoustic waves generated by laser line array illumination and the optical detection of ultrasound by fiber optic Sagnac interferometer can be applied to non-destructive testing and evaluation in a non-contact manner. Symmetric and antisymmetric Lamb modes are also excited in low-frequency-thickness regime by illuminating a thin plate with an array of Q-switched Nd:YAG laser-generated line sources. The propagation of laser-generated Lamb waves is detected by measuring the out-of-plane displacements in a non-contact manner using the fiber optic Sagnac interferometer. Laser line array illumination using multiple slits and a cylindrical lens is effective for the wavelength control of surface waves and Lamb waves. This scheme is very simple to generate the spatially narrow-banded surface waves and Lamb waves by the wavelength control. The laser generation and non-contact detection of narrowband Lamb waves at the selected operating points with relatively small rate of change in group velocity are presented.

서지기타정보

서지기타정보
청구기호 {DME 03010
형태사항 ix, 129 p. : 삽도 ; 26 cm
언어 한국어
일반주기 저자명의 영문표기 : Tae-Seong Jang
지도교수의 한글표기 : 이정주
지도교수의 영문표기 : Jung-Ju Lee
수록잡지명 : "Non-contact detection of laser-generated surface acoustic waves using fiber optic sagnac interferometer". Ultrasonics, v.40 no.1-8, pp. 803-807 (2002)
수록잡지명 : "Non-contact detection of ultrasonic waves using fiber optic Sagnac interferometer". IEEE transactions on ultrasonics, ferroelectrics and frequency control, v.49 no. 6, pp. 767-775 (2002)
학위논문 학위논문(박사) - 한국과학기술원 : 기계공학전공,
서지주기 참고문헌 : p. 124-129
주제 레이저 초음파
광섬유 샤냑 간섭계
램파
초음파
비접촉식 감지
Laser Ultrasonics
Fiber Optic Sagnac Interferometer
Lamb Waves
Ultrasonic Waves
Non-contact Detection
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