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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 27, Issue 6 - Dec 2007
Volume 27, Issue 5 - Oct 2007
Volume 27, Issue 4 - Aug 2007
Volume 27, Issue 3 - Jun 2007
Volume 27, Issue 2 - Apr 2007
Volume 27, Issue 1 - Feb 2007
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FBG Sensor Demodulation Using a Double-Pass Mach-Zhender Interferometer
Park, Hyoung-Jun ; Song, Min-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 4, 2007, Pages 285~290
A wavelength-demodulation algorithm for FBG sensor is proposed by using a double-pass Mach-Zehnder interferometer. Zero-crossing points of double-passed interference signal are used to trigger the accurate
phase difference positions in the sensor signal, which is an essential condition in the subsequent arctangent and phase unwrapping signal processing. With the proposed method, we could efficiently measure various measurands, such as dynamic-, static-strain, and temperature, and
of wavelength resolution was obtained.
Signal Processing Algorithm for Controlling Dynamic Bandwidth of Fiber Optic Accelerometer
Kim, Dae-Hyun ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 4, 2007, Pages 291~298
This paper presents a signal processing algorithm to control the dynamic bandwidth of a single-degree-of-freedom (SDF) dynamic sensor system. An accelerometer is a representative SDF sensor system. In this paper, a moire-fringe-based fiber optic accelerometer is newly used for the test of the algorithm. The accelerometer is composed of one mass, one damper and one spring as a SDF dynamic system. In order to increase the dynamic bandwidth of the accelerometer, it is needed to increase the spring constant or decrease the mass. However, there are mechanical difficulties of this adjustment. Therefore, the presented signal processing algorithm is very effective to overcome the difficulties because it is just adjustment in the signal processing software. In this paper, the novel fiber optic accelerometer is introduced shortly, and the algorithm is applied to the fiber optic accelerometer to control its natural frequency and damping ratio. Several simulations and experiments are carried out to prove the performance of the algorithm. As a result, it is shown that the presented signal processing algorithm is a good way to broaden the dynamic bandwidth of the fiber optic accelerometer.
Fiber Optic Bragg Grating Sensor for Crack Growth Detection of Structures
Kwon, Il-Bum ; Seo, Dae-Cheol ; Kim, Chi-Yeop ; Yoon, Dong-Jin ; Lee, Seung-Seok ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 4, 2007, Pages 299~304
There are to be some cracks on the material degradation part or the stress concentration parts of the main members, which carry on over-loads, of structures. Because these cracks can be used to evaluate the structural health status, it is important to monitor the crack growth for maintaining the structural safety. In this study, the fiber Bragg grating sensor with a drop ball was developed as a sensor for crack growth detection of an existing crack. The crack growth detection sensor was constructed with three parts: a probe part, a wavelength controling light source and receiver part, and an impact part. The probe part was just formed with a fiber Bragg grating optical fiber The wavelength controling light source part was composed of a current supplying circuit, a DFB laser diode, and a TEC controling circuit for wavelength control. Also, the impact part was just implemented by dropping a steel ball. The performance of this sensor was confirmed by the experiments of the crack detection with an aluminum plate having one existing crack. According to these experiments, the difference of the sensor signal outputs was correlated with the crack length. So, it was confirmed that this sensor could be applied to monitor the crack growth.
Serviceability Assessment of a K-AGT Test Bed Bridge Using FBG Sensors
Kang, Dong-Hoon ; Chung, Won-Seok ; Kim, Hyun-Min ; Yeo, In-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 4, 2007, Pages 305~312
Among many types of light rail transits (LRT), the rubber-tired automated guide-way transit (AGT) is prevalent in many countries due to its advantages such as good acceleration/deceleration performance, high climb capacity, and reduction of noise and vibration. However, AGT is generally powered by high-voltage electric power feeding system and it may cause electromagnetic interference (EMI) to measurement sensors. The fiber optic sensor system is free from EMI and has been successfully applied in many applications of civil engineering. Especially, fiber Bragg grating (FBG) sensors are the most widely used because of their excellent multiplexing capabilities. This paper investigates a prestressed concrete girder bridge in the Korean AGT test track using FBG based sensors to monitor the dynamic response at various vehicle speeds. The serviceability requirements provided in the specification are also compared against the measured results. The results show that the measured data from FBG based sensors are free from EMI though electric sensors are not, especially in the case of electric strain gauge. It is expected that the FBG sensing system can be effectively applied to the LRT railway bridges that suffered from EMI.
Study on Ultrasonic Transducer for Non-Destructive Evaluation of Highly Attenuative Material Using PMN-PT Single Crystal
Kim, Ki-Bok ; Ahn, Bong-Young ; Kim, Young-Gil ; Park, Sang-Ki ; Ha, Jeong-Soo ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 4, 2007, Pages 313~320
Recently, a new class of single-crystal piezoelectric materials such as lead metanibobate doped with lead titanate (PMN-PT) has been synthesized and were found to further enhance the electro-mechanical coupling factor compared to piezo-ceramic materials. This paper describes fabrication and evaluation of PMN-PT single crystal ultrasonic transducers for contact measurement of stainless steel that is one of the highly attenuative materials. The design conditions for ultrasonic transducer such as front matching layer between test materials and piezo-material and backing materials were investigated based on the simulation results by KLM model. The PMN-PT single crystal ultrasonic transducers with centre frequencies at 1 and 2.25 MHz were fabricated and their performances were evaluated.
Defect Sizing and Location by Lock-in Photo-Infrared Thermography
Choi, Man-Yong ; Kang, Ki-Soo ; Park, Jeong-Hak ; Kim, Won-Tae ; Kim, Koung-Suk ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 4, 2007, Pages 321~327
In lock-in thermography, a phase difference between the defect area and the healthy area indicates the qualitative location and size of the defect. To accurately estimate these parameters, the shearing-phase technique has been employed which gives the shearing-phase distribution. The shearing-phase distribution has maximum, minimum, and zero points that help determine quantitatively the size and location of the subsurface defect. In experiment, the proposed technique is verified with artificial specimen and these related factors are analyzed.
An Application of Smart Composite for Health Monitoring
Lee, Jin-Kyung ; Ha, Young-Joon ; Park, Young-Chul ; Lee, Joon-Hyun ; Lee, Sang-Pill ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 4, 2007, Pages 328~338
One of main advantages of composite using smart material as reinforcement can be controlled cracks behavior inside the composite. If the smart composite is applied as part of the structure, the use of the shape memory effect of the smart material is the best way to protect the propagation of cracks generated in the structure while use. In this study, the optical manufacturing conditions for the smart composite were derived. In order to evaluate the shape memory effect by shape memory alloy, the tensile load was applied to the smart composite and stress distribution was inspected. And then, the smart composite was heated to a certain temperature and the shape memory alloy would shrink to the original shape. Finally, at this point the recovering status of stress using photoelastic instrument was discussed.
Development of Magnetic Sensor for Measurement of the Cable Tension of Large Scale Bridge
Park, Hae-Won ; Ahn, Bong-Young ; Lee, Seung-Seok ; Kim, Jong-Woo ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 4, 2007, Pages 339~344
Safety of large scale cable in bridge is very important because it may cause the unwanted catastrophic failure. Although the proof load were considered at the design stage, its soundness must be monitored continuously because the cable may be broken out without warning by the variable external load. The cable tension of in-use structures has been mainly measured by the resonance method and its use has been limited because of relatively large measurement uncertainty. Recently a new magnetic method was developed and its reliability is known to be good for evaluating the cable tension. In this study a system which can deliver the calibrated load to the cable was developed and the measurement reliability of developed magnetic sensor according to the change of external load was analyzed quantitatively. The effect of magnetization frequency, bias magnetic field, and temperature on the sensor output was also evaluated.
A Study for a Near-Field Microwave Microscope Using a Tuning Fork Distance Control System in liquid Environment
Kim, Song-Hui ; Yoo, Hyung-Keun ; Babajanyan, Arsen ; Kim, Jong-Chul ; Lee, Kie-Jin ;
Journal of the Korean Society for Nondestructive Testing, volume 27, issue 4, 2007, Pages 345~353
We have obtained a topographical image nondestructively for a Cu thin film in liquid using a near-field scanning microwave microscope (NSMM), its operating frequency was 3.5 to 5.5 GHz. We have kept a distance of 10 nm between tip and sample using a quartz tuning fork shear force feedback system. As an end of tip was attached to one prong of the quartz tuning fork has a length of 2 mm, the only tip of tuning fork was immersed in water tank. A loss cause by evaporation in water tank is regulated with actuator was connected to a supplementary tank. Moreover, using a revise program of LabView, we could increase the accuracy of a measurement in liquid.