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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society for Nondestructive Testing
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Journal DOI :
The Korean Society for Nondestructive Testing
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Volume & Issues
Volume 30, Issue 6 - Dec 2010
Volume 30, Issue 5 - Oct 2010
Volume 30, Issue 4 - Aug 2010
Volume 30, Issue 3 - Jun 2010
Volume 30, Issue 2 - Apr 2010
Volume 30, Issue 1 - Feb 2010
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Elastic Wave Detection using Fiber Optic FBG Sensor
Seo, Dae-Cheol ; Kwon, Il-Bum ; Yoon, Dong-Jin ; Lee, Seung-Suk ; Lee, Jung-Ryul ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 1, 2010, Pages 1~5
Acoustic emission(AE) has emerged as a powerful nondestructive tool to detect or monitor preexisting defects and leaks in the vessel structures. A Bragg grating based acoustic emission sensor system is developed. Various type of fiber Bragg grating sensor including the variable length of sensing part was fabricated and prototype sensor system was tested by using PZT pulser and pencil lead break sources. Two types of sensor attachment were used. First, the fiber Bragg grating sensor was attached fully to the surface using bonding agent. Second one is that one part of fiber was attached to the surface partly by bonding and the other part of fiber will be act as a cantilever. That is, the resonant frequency of the fiber Bragg grating sensor will depend on the length of sensing part. The final goal of the sensor system is to provide on-line monitoring of cracks or leaks in reactor vessel head penetration of nuclear power plants.
Reflection Signal Analysis for Time Division Multiplexing of Fiber Optic FBG Sensors
Kim, Geun-Jin ; Kwon, Il-Bum ; Yoon, Dong-Jin ; Hwang, Du-Sun ; Chung, Young-Joo ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 1, 2010, Pages 6~12
Fiber optic sensor using fiber Bragg grating(FBG) probes is used for monitoring strain and temperature distributed on the wide surfaces of large structures. In this paper, in order to use many FBG probes in one optical fiber line, we propose a complex multiplexing technology which is composed of two techniques, one is time division multiplexing and another is wavelength division multiplexing. However, we only investigate the characteristics of time division multiplexing because FBG sensors basically can be operated by wavelength division multiplexing. We calculate the optimal reflectivities and the lengthwise location of five FBG probes in serial connection in order to obtain the unique reflected intensities from the FBG probes. We fabricate five FBG probes with the reflectivities of 13%, 16%, 25%, 40% and 80%, which are determined by the theoretical calculation, and observe the signal reflected from each FBG in the time domain from the experiment. There are differences between experimental and theoretical results caused by the signal noise and the differences of reflectivities of FBG probes. But the experimental results shows the reflected signals of five FBG probes which prove the availability of complex multiplexing.
Performance Evaluation of SG Tube Defect Size Estimation System in the Absence of Defect Type Classification
Jo, Nam-Hoon ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 1, 2010, Pages 13~19
In this paper, we study a new estimation system for the prediction of steam generator tube defects. In the previous research works, defect size estimators were independently designed for each defect types in order to estimate the defect size. As a result, the structure of estimation system is rather complex and the estimation performance gets worse if the classification performance is degraded for some reason. This paper studies a new estimation system that does not require the classification of defect types. Although the previous works are expected to achieve much better estimation performance than the proposed system since it uses the estimator specialized in each defect, the performance difference is not so large. Therefore, it is expected that the proposed estimator can be effectively used for the case where the defect type classification is imperfect.
Development of Tomographic Scan Method for Industrial Plants
Kim, Jong-Bum ; Jung, Sung-Hee ; Moon, Jin-Ho ; Kwon, Taek-Yong ; Cho, Gyu-Seong ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 1, 2010, Pages 20~30
In this paper, a new tomographic scan method with fixed installed detectors and rotating source from gamma projector was presented to diagnose the industrial plants which were impossible to be examined by conventional tomographic systems. Weight matrix calculation method which was suitable for volumetric detector and statistical iterative reconstruction method were applied for reconstructing the simulation and experimental data. Monte Carlo simulations had been performed for two kinds of phantoms. Lab scale experiment with a same condition as one of phantoms, had been carried out. Simulation results showed that reconstruction from photopeak counting measurement gave the better results than from the gross counting measurement although photopeak counting measurement had large statistical errors. Experimental data showed the similar result as Monte Carlo simulation. Those results appeared to be promising for industrial tomographic applications, especially for petrochemical industries.
A Development of Automatic Defect Detection Program for Small Solid Rocket Motor
Lim, Soo-Yong ; Son, Young-Il ; Kim, Dong-Ryun ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 1, 2010, Pages 31~35
This paper presents the development of automatic defect detection program using 3D computed tomography image of small solid rocker motor. We applied the neighbor pixel comparison algorithm with beam hardening correction for the recognition of defect. We made the artificial defect specimen in order to decide a standard CT value of defect. The program was tested with 150 small solid rocket motors and it could detect the disbond, crack, foreign material and void. The program showed more reliable and faster results than human inspector's interpretation.
Development of Multiplexing Model for Moire-Fringe-Based Fiber Optic Sensor
Kim, Dae-Hyun ; Lee, Yeon-Gwan ; Kim, Chun-Gon ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 1, 2010, Pages 36~45
This paper shows a multiplexing technique to maximize the application of a moire-fringe based fiber optic sensor to lots of structure. Especially, a novel fringe-based fiber optic sensor was proposed to overcome the difficulty of multiplexing of a previous moire-fringe-based fiber optic sensor. The novel fringe-based fiber optic sensor is composed of a single reflective fringe and two optical fibers. Therefore, the multiplexing is easily realized because of the simplicity of optic structure inside the sensor. This paper also proposed four models of the multiplexing techniques. The models are based on a wavelength division multiplexing(WDM) technique and a time division multiplexing(TDM) one. Basically, the models would be profitable for a general extrinsic fiber optic sensor such as the fringe-based fiber optic sensor. Finally, the real optic system was manufactured by using the proposed model and successfully examined to prove the feasibility of the model for the application.
Assessment of Multiple Delamination in Laminated Composites for Aircrafts using X-ray Backscattering
Kim, Noh-Yu ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 1, 2010, Pages 46~53
A Compton X-ray backscatter technique has been developed to quantitatively assess impact damage in quasi-isotropic laminated composites made by a drop-weight tester. X-ray backscatter imaging system with a slit-type camera is constructed to obtain a cross-sectional profile of impact-damaged laminated composites from the electron-density variation of the cross section. A nonlinear scattering model based on Boltsman equation is introduced to compute Compton X-ray backscattering field for the defect assessment. An adaptive filter is also used to reduce noises from many sources including quantum noise and irregular distributions of fibers and matrix in composites. Delaminations masked or distorted by the first delamination are detected and characterized effectively by the Compton X-ray backscatter technique, both in width and location, by application of error minimization algorithm.
Structural Health Monitoring Techniques for Composite Aircraft
Choi, Heung-Soap ; Cho, Youn-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 30, issue 1, 2010, Pages 54~59
After the advent of B787(Boeing Co.), a civil aircraft using composite materials more than 50% of it total structural weight for weight savings，best performances and efficiencies, various endeavors to develop and apply the state of art of structural health monitoring(SHM) technologies for composite aircraft have been made for many years. Despite their plentiful advantages composite aircraft structures are susceptible to the hidden or barely visible impact damages(BVID) and excessive loads that if unchecked may lead to lower structural integrity, loss of operational performance and finally a sudden catastrophic failure of the aircraft structure. In this paper background of SHM technology and relevant technologies for application of SHM technology to the composite aircraft in the near future and requirements for certification of SHM system are shortly presented.