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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 29, Issue 6 - Dec 2009
Volume 29, Issue 5 - Oct 2009
Volume 29, Issue 4 - Aug 2009
Volume 29, Issue 3 - Jun 2009
Volume 29, Issue 2 - Apr 2009
Volume 29, Issue 1 - Feb 2009
Selecting the target year
Poisson's Ratio Measurement Using a Pair of PVDF Ultrasonic Transducer
Vargas, Enrique ; Toral, Sergio ; Gonzalez, Vicente ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 6, 2009, Pages 519~524
This work presents a simple technique to determine the Poisson's ratio of homogeneous solid material using a pair of low cost PVDF ultrasonic transducers. It is based on transducer's property of generating longitudinal and transversal waves depending on the excitation frequency. Mechanical tests were conducted to validate the proposed method, resulting in a good agreement between ultrasonic and mechanical techniques.
Recent Development in Ultrasonic Guided Waves for Aircraft and Composite Materials
Rose, Joseph L. ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 6, 2009, Pages 525~533
Emphasis in the paper is placed on describing guided wave successes and challenges for applications in aircraft and composite materials inspection. Guided wave imaging methods discussed includes line of sight, tomography, guided wave C-scan, phased array, and ultrasonic vibration methods. Applications outlined encircles lap splice, bonded repair patch, fuselage corrosion, water loaded structures, delamination, and ice detection and de-icing of various structures.
Recent Advances in Scanning Acoustic Microscopy for Adhesion Evaluation of Thin Films
Ju, Hyeong-Sick ; Tittmann, Bernhard R. ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 6, 2009, Pages 534~549
As the thin film technology has emerged in various fields, adhesion of the film interface becomes an important issue in terms of the longevity and durability of thin film devices. Diverse nondestructive methods utilizing acoustic techniques have been developed to assess the interfacial integrity. As an effective technique based on the ultrasonic wave focusing and the surface acoustic wave(SAW) generation, scanning acoustic microscopy(SAM) has been investigated for adhesion evaluation. Visualization of film microstructures and quantification of adhesion weakness levels by SAW dispersion are the recent achievements of SAM. To overcome the limitations in the theoretical dispersion model only suitable for perfectly elastic and isotropic materials, a new model has been more recently developed in consideration of film anisotropy and viscoelasticity and applied to the adhesion evaluation of polymeric films fabricated on semiconductive wafers.
Time Delay Focusing of Ultrasonic Array Transducers on a Defect Using the Concept of a Time Reversal Process
Jeong, Hyun-Jo ; Lee, Jeong-Sik ; Lee, Chung-Hoon ; Jun, Ghi-Chan ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 6, 2009, Pages 550~556
In an application of a time reversal(TR) focusing of array transducer on a defect inside the test material, we employ a new time delay focusing technique based the TR process. In order to realize this idea, a multi-channel ultrasonic system is constructed capable of applying necessary time delays to each channel. The TR-based focusing procedure first measures the backscattered signals after firing one of the array elements. A phase slope method is then used to determine the time-of-flights of the backscattered signals received by all elements of the array. These time delays are used to adjust the time of excitation of the elements for transmission focusing on the defect. In addition to the TR focusing, the classical phased array focusing is also considered for comparison. Experimental results show that the TR-based time delay focusing produces much stronger backscattered signals than the phased array focusing, demonstrating the enhanced capability of the TR focusing.
Comparison of Full-Field Stresses around an Inclined Crack Tip by Using Fringe Data of Finite Element Method with Photoelastic Experiment
Baek, Tae-Hyun ; Kim, Myung-Soo ; Chen, Lei ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 6, 2009, Pages 557~562
Abrupt change of cross-section in mechanical parts is one of significant causes of structural fracture. In this paper, a hybrid method is employed to analyze the stress distribution of a discontinuous plate. The plate with an inclined crack is utilized in our experiment and the stress field in the vicinity of crack tip is calculated through isochromatic fringe order of given points. This calculation can be made handy through least-squares method integrated with complex power series representation(Laurent series) implemented on a computer program for high-speed processing. In order to accurately compare calculated results with experimental ones, both of actual and regenerated photoelastic fringe patterns are doubled and sharpened by digital image processing. The experiment results show that regenerated patterns obtained by hybrid method are quite comparable to actual patterns.
Comparison of Simulated PEC Probe Performance for Detecting Wall Thickness Reduction
Shin, Young-Kil ; Choi, Dong-Myung ; Jung, Hee-Sung ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 6, 2009, Pages 563~569
In this paper, four different types of pulsed eddy current(PEC) probe are designed and their performance of detecting wall thickness reduction is compared. By using the backward difference method in time and the finite element method in space, PEC signals from various thickness and materials are numerically calculated and three features of the signal are selected. Since PEC signals and features are obtained by various types and sizes of probe, the comparison is made through the normalized features which reflect the sensitivity of the feature to thickness reduction. The normalized features indicate that the shielded reflection probe provides the best sensitivity to wall thickness reduction for all three signal features. Results show that the best sensitivity to thickness reduction can be achieved by the peak value, but also suggest that the time to peak can be a good candidate because of its linear relationship with the thickness variation.
Analysis of the Propagation Characteristics of Ultrasonic Guided Waves Excited by Single Frequency and Broadband Sources
Kang, To ; Song, Sung-Jin ; Kim, Hak-Joon ; Cho, Young-Do ; Lee, Dong-Hoon ; Cho, Hyun-Joon ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 6, 2009, Pages 570~578
Excitation and propagation of guided waves are very complex problems in pipes due to their dispersive nature. Pipes are commonly used in the oil, chemical or nuclear industry and hence must be inspected regularly to ensure continued safe operation. The normal mode expansion(NME) method is given for the amplitude with which any propagating waveguide mode is generated in the pipes by applied surface tractions. Numerical results are calculated based on the NME method using different sources, i.e., non-axisymmetric partial loading and quasi-axisymmetric loading sources. The sum of amplitude coefficients for 0~nineth order of the harmonic modes are calculated based on the NME method and the dispersion curves in pipes. The superimposed total field which is namely the angular profile, varies with propagating distance and circumferential angle. This angular profile of guided waves provides information for setting the transducer position to find defects in pipes.
A Study of Frequency Mixing Approaches for Eddy Current Testing of Steam Generator Tubes
Jung, Hee-Jun ; Song, Sung-Jin ; Kim, Chang-Hwan ; Kim, Dea-Kwang ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 6, 2009, Pages 579~585
The multifrequency eddy current testing(ECT) have been proposed various frequency mixing algorithms. In this study, we compare these approaches to frequency mixing of ECT signals from steam generator tubes; time-domain optimization, discrete cosine transform-domain optimization. Specifically, in this study, two different frequency mixing algorithms, a time-domain optimization method and a discrete cosine transform(DCT) optimization method, are investigated using the experimental signals captured from the ASME standard tube. The DCT domain optimization method is computationally fast but produces larger amount of residue.
Material Characterization of Weld-Zone Using Poisson's Ratio Distribution
Park, Jin-Ha ; Kim, Young-H. ; Lee, Seung-S. ; Kim, Young-Gil ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 6, 2009, Pages 586~590
Poisson's ratio, one of elastic constants of elastic solids, has not attracted attention due to its narrow range and difficult measurement. Transverse wave velocity as well as longitudinal wave velocity should be measured for nondestructive measurement of Poisson's ratio. Rigid couplants for transverse wave is one of obstacle for scanning over specimen. In the present work, a novel measurement of Poisson's ratio distribution was applied. Immersion method was employed for the scanning over the specimen. Echo signals of normal beam longitudinal wave were collected, and transverse wave modes generated by mode conversion were identified. From transit time of longitudinal and transverse waves, Poisson's ratio was determined without the information of specimen thickness. Poisson's ratio distribution of the carbon steel weldment was mapped. Heat affected zone of the weldment was clearly distinguished from base and filler metals.
Detection of Second-Layer Corrosion in Aging Aircraft
Kim, Noh-Yu ; Yang, Seun-Yong ;
Journal of the Korean Society for Nondestructive Testing, volume 29, issue 6, 2009, Pages 591~602
The Compton backscatter technique has been applied to lap-joint in aircraft structure in order to determine mass loss due to exfoliative corrosion of the aluminum alloy sheet skin. The mass loss of each layer has been estimated from Compton backscatter A-scan including the aluminum sheet, the corrosion layer, and the sealant. A Compton backscattering imaging system has been also developed to obtain a cross-sectional profile of corroded lap-splices of aging aircraft using a specially designed slit-type camera. The camera is 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 layered structure is scanned by moving the scattering volume through the thickness direction of the specimen. The theoretical model of the Compton scattering based on Boltzmann transport theory is presented for quantitative characterization of exfoliative corrosion through deconvolution procedure using a nonlinear least-square error minimization method. It produces practical information such as location and width of planar corrosion in layered structures of aircraft, which generally cannot be detected by conventional NDE techniques such as the ultrasonic method.