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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 25, Issue 6 - Dec 2005
Volume 25, Issue 5 - Oct 2005
Volume 25, Issue 4 - Aug 2005
Volume 25, Issue 3 - Jun 2005
Volume 25, Issue 2 - Apr 2005
Volume 25, Issue 1 - Feb 2005
Selecting the target year
Bending Characteristics Change of Long-Period fiber Grating due to Co-doping of Boron for Optical fiber Sensors
Moon, Dae-Seung ; Chung, Young-Joo ;
Journal of the Korean Society for Nondestructive Testing, volume 25, issue 5, 2005, Pages 339~342
In long-period fiber grating (LPFG) to be made up optical fiber sensors, resonance coupling occurs between the forward-propagating core mode and cladding modes at the wavelength that satisfy the Phase matching condition. The resonance wavelength and the coupling strength depends strongly on the external environment like temperature, strain, and ambient index. These characteristics can be utilized for various applications as optical fiber sensors. fabrication of optical fiber gratings is typically based on the photosensitivity effect, i.e. the permanent change of the refractive index upon irradiation of the UV beam, and therefore, fabrication of the optical fiber with high phososensitivity is an important part of the research on optical fiber gratings. In this work, we measured the effort of to-doping of boron on the index difference between the core and cladding of the optical fiber and the sensitivity of the LPFC to the temperature and bending changes. We observed that the index difference between the core and the cladding decreased by
and the temperature sensitivity of the resonance wavelength shirt decreased by
. The dependence or the bending-induced changes or the transmission characteristics of LPFG on the tore-cladding index difference was investigated experimentally. The measurement results indicate that the bending sensitivity increases as the index difference decreases.
A Study on the Measurement and Application of Long Gauge fiber Brags Grating Sensors
Kim, Ki-Soo ;
Journal of the Korean Society for Nondestructive Testing, volume 25, issue 5, 2005, Pages 343~349
In this research, the fiber Bragg grating sensors with long gauge for displacement measurement in the long distance is developed and tested. The sensors show an accuracy and a capability for displacement measurement oin long distance. Monitoring using static logger of system of FBG sensor with strained optical fiber shows the capability of measurement in the harsh environment such as strong wind. Measurement of long distance displacement by optical fiber sensor if use
optical fiber and impose some strong pre-tension shows possibility in monitoring of nuclear containment structure.
A Probe of Fiber Optic OTDR Displacement Sensor
Kwon, Il-Bum ; Kim, Chi-Yeop ; Seo, Dae-Cheol ;
Journal of the Korean Society for Nondestructive Testing, volume 25, issue 5, 2005, Pages 350~355
The probes of fiber optic OTDR (Optical Time Domain Reflectometry) sensor was developed to measure displacements of social infrastructures. This probe was simply constructed with two conventional optical fiber connectors, and a fiber bending part, which transforms displacement to optical loss. When the displacement was affected on the bending loss part, the reflected light intensity of one optical connector was changed. The displacement was determined from this reflected light intensity change of the connector. fiber optic OTDR displacement sensor was developed as the multiplexed type of one fiber line with 5 sensor probes. Multiplexing operation was tested by these 5 sensor probes.
Fabrication of a Temperature-Compensating FBB Sensor for Measurement of Mechanical Strain
Jung, Dal-Woo ; Kwon, Il-Bum ; Choi, Nak-Sam ;
Journal of the Korean Society for Nondestructive Testing, volume 25, issue 5, 2005, Pages 356~361
A temperature-compensating double fiber Bragg grating(FBG) sensor having two different FBGs in one fiber line was proposed for real time measurement of mechanical normal strain in structures. Measurement of mechanical strains of the aluminum beam surface by the double FBG sensor was performed under various thermal conditions, and the results were compared with those of electrical resistance strain gage. The FBG sensor fabricated in this study was able to measure accurately the mechanical strains without containing any thermal strain component.
Spectral Backward Radiation Profile
Kim, Hak-Joon ; Kwon, Sung-Duk ;
Journal of the Korean Society for Nondestructive Testing, volume 25, issue 5, 2005, Pages 362~367
Ultrasonic backward radiation profile is frequency-dependent when the incident region has deptional gradient of acoustical properties or multi-layers. Until now, we have measured the profiles of principal frequencies of an used transducers so that it was not easy to characterize the frequency dependence of the SAW(surface acoustic wave) from the backward radiation profile. We tried to measure the spectral backward radiation profiles using DFP(digital filer package) in a Lecroy DSO(digital storage oscilloscope). The measured spectral profiles showed that the steel specimen of #1200 surface treatment have 2% SAW velocity dispersion of the loaded case and the severly rusty steel specimen have the very big changes in the shape and pattern of the spectral profile. It is concluded that the spectral backward radiation profiles could be very effective tool to evaluate the frequency dependence of surface area.
Nondestructive Characterization of Degradation of EPDM Rubber for Automotive Radiator Hoses
Kwak, Seung-Bum ; Choi, Nak-Sam ; Choi, Youn-Joung ; Shin, Sei-Moon ;
Journal of the Korean Society for Nondestructive Testing, volume 25, issue 5, 2005, Pages 368~376
Coolant rubber hoses for automobile radiators can be degraded and thus failed due to the influence of contacting stresses of air and coolant liquid under thermal and mechanical loadings. In this study, for EPDM(ethylene-propylene diene monomer) rubber conventionally used as a radiator hose material the aging behaviors of the skin part due to thermo-oxidative and electro-chemical stresses were nondestructively evaluated. Through the thermo-oxidative aging test, it was shown that the surface hardness IRHD(International Rubber Hardness Degrees) of the rubber increased with a considerable reduction of failure strain. On account of the penetration of coolant liquid into the skin part the weight of rubber specimens degraded by electro-chemical degradation(ECD) test increased, whereas their. failure strain and IRHD hardness decreased largely. The penetration of coolant liquid seemed to induce some changes in inner structure and micro hardness distribution of the rubbers. Consequently, EPDM rubbers degraded by thermo-oxidative aging and ECD could be characterized nondestructively by micro-hardness and chemical structure analysis methods.
Degradation Evaluation of High Pressure Reactor Vessel in field Using Electrical Resistivity Method
Park, Jong-Seo ; Baek, Un-Bong ; Nahm, Seung-Hoon ; Han, Sang-In ;
Journal of the Korean Society for Nondestructive Testing, volume 25, issue 5, 2005, Pages 377~383
Because explosive fluid is used at high temperature or under high pressure in petrochemistry and refined oil equipment, the interest about safety of equipments is intensive. Specially, the safety of high pressure reactor vessel is required among them. The material selected in this study is 2.25Cr-1Mo steel that is widely used for high pressure reactor vessel material of petrochemical plant. Eight kinds of artificially aged specimens were prepared by differing from aging periods under three different temperatures. The material was iso-thermally heat treated at higher temperatures than
that is the operating temperature of high pressure reactor vessel. Vickers hardness properties and electrical resistivity properties about artificially aged material as well as un-aged material were measured, and master curves were made out from the correlation with larson-Miller parameter. And electrical resistivity properties as well as Victors hardness properties measured at high pressure reactor vessel of the field were compared with master curves made out in a laboratory. Degradation evaluation possibility in the field of high pressure reactor vessel by using electrical resistivity method was examined. Electrical resistivity property measured in the field is similar with that of artificially aged material in similar aging level.
Characteristic Analysis of Eddy Current Testing According to the finite Element formulations
Lee, Hyang-Beom ;
Journal of the Korean Society for Nondestructive Testing, volume 25, issue 5, 2005, Pages 384~390
In the numerical analysis of En (eddy current testing) using 3-dimensional FEM (finite element method), MVP (magnetic vector potential) and electric scalar potential are used as variables in conductor region. Three dimensional modeling makes number of unknowns increase, and the degree of freedom of variables also makes number of unknowns increase. Because of this reason, modified UP is used to reduce the number of unknowns. Gauge condition is enforced artificially on existing FEM formulations to insure the uniqueness of MVP. So in this paper the effects of these FEM formulation procedures on ECT are investigated and the appropriate FEM formulation is suggested for accurate ECT simulation.
Development of a Laser-Generated Ultrasonic Inspection System by Using Adaptive Error Correction and Dynamic Stabilizer
Park, Seung-Kyu ; Baik, Sung-Hoon ; Park, Moon-Cheol ; Lim, Chang-Hwan ; Ra, Sung-Woong ;
Journal of the Korean Society for Nondestructive Testing, volume 25, issue 5, 2005, Pages 391~399
Laser-generated ultrasonic inspection system is a non-contact scanning inspection device with high spatial resolution and wide bandwidth. The amplitude of laser-generated ultrasound is varied according to the energy of pulse laser and the surface conditions of an object where the CW measuring laser beam is pointing. In this paper, we correct the generating errors by measuring the energy of pulse laser beam and correct the measuring errors by extracting the gain information of laser interferometer at each time. h dynamic stabilizer is developed to stably scan on the surface of an object for an laser-generated ultrasonic inspection system. The developed system generates ultrasound after adaptively finding the maximum gain time of an laser interferometer and processes the signal in real time after digitization with high speed. In this paper, we describe hardware configuration and control algorithm to build a stable laser-generated ultrasonic inspection system. Also, we confirmed through experiments that the proposed correction method for the generating errors and measuring errors is effective to improve the performance of a system.
Structural Health Monitoring Using fiber Optic Sensors
Kwon, Il-Bum ;
Journal of the Korean Society for Nondestructive Testing, volume 25, issue 5, 2005, Pages 400~404