압전소자와 광섬유를 이용한 손상 검출에 관한 연구 = A Study on damage detection using PZT sensor and Optical fiber

다국어 초록 (Multilingual Abstract)

Piezoceramic (PZT) sensors offer special opportunities for the health monitoring of structures. This paper presents work done on developing and utilizing PZT sensors and optical fiber to detect the locations of cracks occurred in beam structures. Beams are a common form in Beam structures, and therefore the real-time condition monitoring and active control of beams will improve the reliability and safety of many structures.
The PZT sensors are conducted particularly to generate the longitudinal wave along the beam specimen, and systematic experiments conducted on statistical samples of incrementally damaged specimens were used to fully understand the method, the cracks with different depth and location are simulated to indicate the feasibility of the detection and assessment.
This paper presents a damage assessment method using guided lamb wave. The guided wave is introduced to accurately localize damages. The improved method provides possibility for more accurately identifying and localization damages compared to that conventional method(Impedance method). A powerful wavelet transform was used to extract the signals efficiently. Additionally, using the arbitrary function generator to excite the PZT patches to generate the guided wave, the guided wave propagates along with the beam structures with PZT patches bonded, and the real-time signals are recorded. Damages are indicated by a change of response signals when compared with a template undamaged condition. The wave attenuation and mode conversion is sufficient to detect various types of defects. The results show considerable ability for identifying and localization of the simulated damages. This paper presents applications of the wavelet transform to reduce the noise signal of the output signal. Also, we developed the methods to detect damages using the method of guided lamb wave detection by PZT sensors and the optical fiber. The transmitted guided lamb wave by PZT sensors propagated through the optical fiber, and the output signal was received by PZT sensors bonded to the aluminum beam. The output signal changed with respect to aluminum specimen condition. This paper presented the characteristics of the optical fiber experimentally. We applied the optical fiber as a medium because the PZT sensor is brittle at common environment and weak at high temperatures, and also the signal can’t be transmitted in fluid.
And this paper presents the detection methods of various damage patterns due to the fracture and fatigue in the structures. The various damage patterns are cracks, loosen bolts, holes, etc. These damages are occurred in real structures usually.

목차 (Table of Contents)

• 제 1 장 서론 = 1
• 1.1 연구 배경 = 1
• 1.2 종래의 연구동향 = 4
• 1.3 연구 목적 = 5
• 제 2 장 이론적 배경 = 7
• 2.1 압전 재료의 정의 = 7
• 2.2 압전세라믹 센서의 응답특성 = 8
• 2.2.1 압전재료의 길이방향 진동모드 = 8
• 2.2.2 FEM을 이용한 압전센서의 고유진동 해석 = 10
• 2.3 유도초음파 계측에 관한 이론적 배경 = 14
• 2.3.1 1차원 파동 방정식을 이용한 손상 검출 = 14
• 2.3.2 1차원 파동 방정식 = 17
• 제 3 장 유도초음파를 이용한 보의 손상 탐지 기법 연구 = 22
• 3.1 유도초음파 계측을 위한 입력 파형 선택 = 22
• 3.2 유도초음파 계측을 위한 프로그램 = 26
• 3.3 유도초음파 계측을 위한 실험 장치 = 30
• 3.4 유도초음파를 이용한 보의 군속도 측정 = 31
• 제 4 장 PZT와 광섬유를 이용한 손상탐지 기법연구 = 35
• 4.1 손상크기에 따른 응답파형 특성 = 36
• 4.2 일자형 보의 손상 위치 탐지 실험 = 42
• 4.3 광섬유의 전파특성 = 48
• 4.4 광섬유 인터페이스를 통한 전파 특성 연구 = 54
• 4.5 광섬유 인터페이스를 통한 손상탐지 기법 연구 = 55
• 4.5.1 PZT 가진 - PZT 수집 = 55
• 4.5.2 PZT가진 - 광센서 수집 = 60
• 4.5.3 광센서 가진 - PZT 수집 = 64
• 4.5.4 PZT 가진 - PZT 수집, PZT가진 - 광센서 수집 파형의 비교 = 66
• 제 5 장 결론 및 고찰 = 67
• 제 6 장 참고문헌 = 69