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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society for Nondestructive Testing
Journal Basic Information
Journal DOI :
The Korean Society for Nondestructive Testing
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Volume & Issues
Volume 26, Issue 6 - Dec 2006
Volume 26, Issue 5 - Oct 2006
Volume 26, Issue 4 - Aug 2006
Volume 26, Issue 3 - Jun 2006
Volume 26, Issue 2 - Apr 2006
Volume 26, Issue 1 - Feb 2006
Selecting the target year
Ambient Vibration-Measurement of Real Building Structure by Using Fiber Optic Accelerometer System
Kim, Dae-Hyun ;
Journal of the Korean Society for Nondestructive Testing, volume 26, issue 6, 2006, Pages 373~379
Vibration-based structural health monitoring is one of non-destructive evaluation (NDE) techniques for civil infrastructures. This paper presents a novel fiber optic accelerometer system to monitor civil engineering structures and a successful application of the novel sensor system for measuring ambient vibration of a real building structure. This sensor system integrates the Moire fringe phenomenon with fiber optics to achieve accurate and reliable measurements. The sensor system is immune to electromagnetic (EM) interference making it suitable for difficult applications in such environments involving strong EM fields, electrical spark-induced explosion risks, and cabling problems, prohibiting the use of conventional electromagnetic accelerometers. A prototype sensor system has been developed, together with a signal processing software. The experimental studies demonstrated the high-performance of the fiber optic sensor system. Especially, the sensor was successfully used for monitoring a real building on UCI (University of California Irvine, USA).
Novel Laser Ultrasonic Receiver for Industrial NDE
Pouet, B. ; Breugnot, S. ; Clemenceau, P. ;
Journal of the Korean Society for Nondestructive Testing, volume 26, issue 6, 2006, Pages 380~389
A new laser-based ultrasonic receiver that is based on multi-channel interferometry is shown to be well suited for robust and sensitive detection of ultrasound in industrial environment. The proposed architecture combines random-quadrature detection with detector arrays and parallel multi-speckle processing. The high sensitivity is reached, thanks to the random phase distribution of laser speckle caused by surface roughness. High-density parallel signal processing is achieved by using a simple demodulation technique based on signal rectification. This simple detection scheme is also demonstrated for rejection of the laser intensity noise, making possible the use of lower cost laser without reduction in performances. Results demonstrating this new principle of operation and its performances are presented.
Inspection of Ceramic Coatings Using Nanoindentation and Frequency Domain Photoacoustic Microscopy
Steen, T.L. ; Basu, S.N. ; Sarin, V.K. ; Murray, T.W. ;
Journal of the Korean Society for Nondestructive Testing, volume 26, issue 6, 2006, Pages 390~402
The elastic properties and thickness of mullite environmental barrier coatings grown through chemical vapor deposition (CVD) on silicon carbide substrates were measured using frequency domain photoacoustic microscopy. In this technique, extremely narrow bandwidth surface acoustic waves are generated with an amplitude modulated laser source. A photorefractive crystal based interferometer is used to detect the resulting surface displacement. The complex displacement field is mapped as a function of source-to-receiver distance in order to extract the wavelength of the surface acoustic wave at a given excitation frequency, and the phase velocity is determined. The coatings tested exhibited spatial variations in thickness and mechanical properties. The measured surface wave dispersion curves were used to extract an effective value for the elastic modulus and the coating thickness. Nanoindentation was used to validate the measurements of the effective elastic modulus. The average elastic modulus measured through the coating thickness using nanoindentation is compared to the effective modulus found using the photoacoustic system. Optical microscopy is used to validate the thickness measurements. The results indicate that the photoacoustic microscopy technique can be used to estimate the effective elastic properties in coatings exhibiting spatial inhomogeneities, potentially providing valuable feedback for the optimization of the CVD growth process.
Simulation of ECT Bobbin Coil Probe Signals to Determine Optimum Coil Gap
Kong, Young-Bae ; Song, Sung-Jin ; Kim, Chang-Hwan ; Yu, Hyung-Ju ; Nam, Min-Woo ; Jee, Dong-Hyun ; Lee, Hee-Jong ;
Journal of the Korean Society for Nondestructive Testing, volume 26, issue 6, 2006, Pages 403~410
Eddy current testing (ECT) signals produced by a differential bobbin coil probe vary according to probe design parameters such as the number of turns, geometry and coil gap size. In the present study, the characteristics of a differential bobbin coil probe signals are investigated by numerical simulation in order to determine the optimum coil gap. For verification of numerical simulation accuracy, a specially designed bobbin probe of which the coil gap can be adjusted is fabricated and a series of experiments to acquire signals from two kinds of standard tubes with the variation in coil gap is performed. Then, the experimental signals are compared to the simulation results. Based on this investigation, a decision on the optimum range of coil gap is made. The theoretically predicted signals agree very well to the experimental signals. In fact, this excellent agreement demonstrates a high potential of the simulation as a design optimization tool for ECT bobbin probes.
A Feasibility Study of Guided Wave Technique for Rail Monitoring
Rose, J.L. ; Lee, C.M. ; Cho, Y. ;
Journal of the Korean Society for Nondestructive Testing, volume 26, issue 6, 2006, Pages 411~416
The critical subject of transverse crack detection in a rail head is treated in this paper. Conventional bulk wave ultrasonic techniques oftenfail because of shelling and other surface imperfections that shield the defects that lie below the shelling. A guided wave inspection technique is introduced here that can send ultrasonic energy along the rail under the shelling with a capability of finding the deleterious transverse crack defects. Dispersion curves are generated via a semi analytical finite element technique along with a hybrid guided wave finite element technique to explore the most suitable modes and frequencies for finding these defects. Sensor design and experimental feasibility experiments are also reported.
Detection of Second-Layer Corrosion in Aging Aircraft Fuselage
Kim, Noh-Yu ; Achenbach, J.D. ;
Journal of the Korean Society for Nondestructive Testing, volume 26, issue 6, 2006, Pages 417~426
A Digital X-ray imaging system using Compton backscattering has been developed to obtain a cross-sectional profile and mass loss of corroded lap-splices of aging aircraft from density variation. A slit-type camera was designed to focus on a small scattering volume inside the material, from which the backscattered photons are collected by a collimated scintillator detector for interpretation of material characteristics. The cross section of the lap-joint is scanned by moving the scattering volume through the thickness direction of the specimen. The mass loss of each layer has been estimated from a Compton backscatter A-scan to obtain the thickness of each layer including the aluminum sheet, the corrosion layer and the sealant. Quantitative information such as location and width of planar corrosion in the lap splices of fuselages is obtained by deconvolution using a nonlinear least-square error minimization method(BFGS method): A simple reconstruction model is also introduced to overcome distortion of the Compton backscatter data due to attenuation effects attributed to beam hardening and quantum noise.
Experimental Investigation of Impact-Echo Method for Concrete Slab Thickness Measurement
Popovics John S. ; Cetrangolo Gonzalo P. ; Jackson Nicole D. ;
Journal of the Korean Society for Nondestructive Testing, volume 26, issue 6, 2006, Pages 427~439
Accurate estimates of in place thickness of early age (3 to 28 days after casting) concrete pavements are needed, where a thickness accuracy of
is desired. The impact-echo method is a standardized non-destructive technique that has been applied for this task. However, the ability of impact-echo to achieve this precision goal is affected by Vp (measured) and
(assumed) values that are applied in the computation. A deeper understanding of the effects of these parameters on the accuracy of impact-echo should allow the technique to be improved to meet the desired accuracy goal. In this paper, the results of experimental tests carried out on a range of concrete slabs are reported. Impact-echo thickness estimation errors caused by material property gradients and sensor type are identified. Correction factors to the standard analysis method are proposed to correct the identified errors and to increase the accuracy of the standard method. Results show that improved accuracy can be obtained in the field by applying these recommendations with the standard impact-echo method.
Ultrasonic Phased Array Techniques for Detection of Flaws of Stud Bolts in Nuclear Power Plants
Lee, Joon-Hyun ; Choi, Sang-Woo ;
Journal of the Korean Society for Nondestructive Testing, volume 26, issue 6, 2006, Pages 440~446
The reactor vessel body and closure head are fastened with the stud bolt that is one of crucial parts for safety of the reactor vessels in nuclear power plants. It is reported that the stud bolt is often experienced by fatigue cracks initiated at threads. Stud bolts are inspected by the ultrasonic technique during the overhaul periodically for the prevention of failure which leads to radioactive leakage from the nuclear reactor. The conventional ultrasonic inspection for stud bolts was mainly conducted by reflected echo method based on shadow effect. However, in this technique, there were numerous spurious signals reflected from every oblique surfaces of the thread. In this study, ultrasonic phased array technique was applied to investigate detectability of flaws in stud bolts and characteristics of ultrasonic images corresponding to different scanning methods, that is, sector and linear scan. For this purpose, simplified stud bolt specimens with artificial defects of various depths were prepared.