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Aircraft integrated structural health monitoring using lasers, piezoelectricity, and fiber optics
Choi, Yunshil,Abbas, Syed Haider,Lee, Jung-Ryul Elsevier 2018 MEASUREMENT -LONDON- Vol.125 No.-
<P><B>Abstract</B></P> <P>Various structural health monitoring (SHM) systems that have been developed based on laser ultrasonics and fiber optics are introduced in this paper. The systems are used to realize the new SHM paradigm for ground SHM, called the Smart Hangar. Guided wave ultrasonic propagation imaging (G-UPI) technology is implemented in the Smart Hangar in the form of built-in and mobile G-UPI systems. The laser-induced guided waves generated by pulsed beam scanning in the wings and fuselage of an aircraft are captured by a fiber optic, piezoelectric, or laser ultrasonic sensor, and their propagation is visualized. The wave propagation video is further processed to visualize damage in the presence of multiple sources using a multi-time-frame ultrasonic energy mapping (mUEM) method. For in-flight SHM, laser scanning-based smartification of the structure with sensors is presented, and an event localization method based on fiber optics and piezoelectric sensing is also introduced. Optic sensors are also utilized to reconstruct the wing deformation from the measured strain. The wing deformation and impact localization information is transferred to a ground pilot in the case of unmanned aerial vehicles (UAV), and the ground pilot can feel the wing deformation and impact by using a pilot arm-wearable haptic interface, which makes it possible to achieve human-UAV interactive decision making.</P>
Q-switched 레이저와 다중센서/단일채널 신호수집을 이용한 복합재 구조 음향방출 트레이닝 및 위치탐지 기법 개발
최윤실 ( Yunshil Choi ),이정률 ( Jung-ryul Lee ) 한국복합재료학회 2018 Composites research Vol.31 No.4
항공우주산업에서 구조물의 수명연장과 경제적 측면에서의 효율적인 운용을 위해 다양한 구조건전성모니터링(Structural Health Monitoring, SHM) 기법들이 제시되어왔다. 금속재 구조물의 경우, 수분이나 염분 등에 의한 부식이나 쉽게 응력집중이 발생하는 타공, 노치, 볼트 등과 같은 위치에서의 균열이 주된 관심사였으나, 항공우주산업에서의 복합재 사용비율이 증가함에 따라 손상 메커니즘이 더욱 복잡한 복합재 구조물에 적용이 가능한 고도화된 SHM 시스템의 필요성이 강조되고 있다. 본 논문에서는 Q-switched 레이저와 다수의 압전센서를 이용한 복합재에서의 AE(Acoustic emission) 위치탐지 기법을 제시한다. 제시되는 기법은 10 mm 이내의 거리오차로 방출위치 탐지를 목표로 하며 복합재 구조에서 수행된 AE 모사실험 및 위치탐지 시도 결과를 제시하여 기법이 유효함을 증명한다. Various structural health monitoring (SHM) systems have been suggested for aerospace industry in order to increase its life-cycle and economic efficiency. In the case of aircraft structure madden with metal, a major concern was hot spots, such as notches, bolts holes, and where corrosion or stress concentration occurs due to moisture or salinity. However, with the increasing use of composites in the aerospace industry, further advanced SHM systems have been being required to be applied to composite structures, which have much complex damage mechanism. In this paper, a method of acoustic emission localization for composite structures using Q-switched laser and multiple Amplifier-integrated PZTs have been proposed. The presented technique aims at localization of the AE with an error in distance of less than 10 mm. Acoustic emission simulation and the localization attempt were conducted in the composite structure to validate the suggested method. Localization results, which are coordinates of detected regions, grid plots and color intensity map have been presented together to show reliability of the method.
Shin, Hye-Jin,Choi, Yunshil,Lee, Jung-Ryul ELSEVIER 2019 MEASUREMENT -LONDON- Vol.147 No.-
<P><B>Abstract</B></P> <P>Recently, composite lattice structures are attracting significant attention owing to their high specific stiffness and specific strength and are mainly used in aerospace applications. However, the composite lattice structure also exhibits damage occurrence probability during operation as well as defects in the filament winding manufacturing process. Thus a non-destructive evaluation (NDE) technique for defect and damage evaluation is essential although its complexity is not desirable, especially with respect to in-situ NDE. In this study, we propose a pulse-echo ultrasonic propagation imaging (PE UPI) system for in-situ NDE of cylindrical composite lattice-skin specimen and develop a VTWAM (Variable time window amplitude mapping)-based curvature-compensating algorithm that eliminates the curved surface effect of the PE UPI system. As a result of the actual application to a damaged lattice cylindrical specimen, the damage position, size, and shape are clearly visualized by effectively suppressing the curved surface effect in the inspection region via the VTWAM-based curvature-compensating algorithm. We demonstrate the capability of the linear scan PE UPI to inspect a curved and complex lattice-skin structure with a curved surface compensation algorithm and propose the same as a tool for in-situ health management of composite lattice structures for manufacturing to in-service stages.</P> <P><B>Highlights</B></P> <P> <UL> <LI> NDE using a PE UPI was performed to visualize damage in a lattice-skin structure. </LI> <LI> Cylindrical lattice-skin structures cause a curvature effect in the PE UPI results. </LI> <LI> Curvature-compensating algorithm was developed to reduce the curvature effect. </LI> <LI> Delaminations were clearly visualized by effectively reducing the curvature effect. </LI> </UL> </P>
Corrosion visualization under organic coating using laser ultrasonic propagation imaging
Jung-Ryul Lee,An Seob Shin,Jin Hwan Park,Hee-Soo Lee,Yunshil Choi 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.2
Protective coatings are most widely used anticorrosive structures for steel structures. The corrosion under the coating damages the host material, but this damage is completely hidden. Therefore, a field-applicable under-coating-corrosion visualization method has been desired for a long time. Laser ultrasonic technology has been studied in various fields as an in situ nondestructive inspection method. In this study, a comparative analysis was carried out between a guided-wave ultrasonic propagation imager (UPI) and pulse-echo UPI, which have the potential to be used in the field of under-coating-corrosion management. Both guided-wave UPI and pulse-echo UPI were able to successfully visualize the corrosion. Regarding the field application, the guided-wave UPI performing Q-switch laser scanning and piezoelectric sensing by magnetic attachment exhibited advantages owing to the larger distance and incident angle in the laser measurement than those of the pulse-echo UPI. Regarding the corrosion visualization methods, the combination of adjacent wave subtraction and variable time window amplitude mapping (VTWAM) provided acceptable results for the guided-wave UPI, while VTWAM was sufficient for the pule-echo UPI. In addition, the capability of multiple sensing in a single channel of the guided-wave UPI could improve the field applicability as well as the relatively smaller size of the system. Thus, we propose a guided-wave UPI as a tool for undercoating- corrosion management.