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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 31, Issue 6 - Dec 2011
Volume 31, Issue 5 - Oct 2011
Volume 31, Issue 4 - Aug 2011
Volume 31, Issue 3 - Jun 2011
Volume 31, Issue 2 - Apr 2011
Volume 31, Issue 1 - Feb 2011
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Dynamic Characterization of Sub-Scaled Building-Model Using Novel Optical Fiber Accelerometer System
Kim, Dae-Hyun ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 6, 2011, Pages 601~608
This paper presents the damage assessment of a building structure by using a novel optical fiber accelerometer system. Especially, a sub-scaled building model is designed and manufactured to check up the feasibility of the optical fiber accelerometer for structural health monitoring. The novel accelerometer exploits the moir
fringe optical phenomenon and two pairs of optical fibers to measure the displacement with a high accuracy, and furthermore a pendulum to convert the displacement into acceleration. A prototype of optical fiber accelerometer system has been successfully developed that consists of a sensor head, a control unit and a signal processing unit. The building model is also designed as a 4-story building with a rectangular shape of
mm of edges. Each floor is connected to the next ones by 6 steel columns which are threaded rods. Basically, a random vibration test of the building model is done with a shaker and all of acceleration data is successfully measured at the assigned points by the optical fiber accelerometer. The experiments are repeated in the undamaged state and the damaged state. The comparison of dynamic parameters including the natural frequencies and the eigenvectors is successfully carried out. Finally, the optical fiber accelerometer is proven to be prospective to evaluate dynamic characteristics of a building structure for the damage assessment.
Model-Based Prediction of Pulsed Eddy Current Testing Signals from Stratified Conductive Structures
Zhang, Jian-Hai ; Song, Sung-Jin ; Kim, Woong-Ji ; Kim, Hak-Joon ; Chung, Jong-Duk ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 6, 2011, Pages 609~615
Excitation and propagation of electromagnetic field of a cylindrical coil above an arbitrary number of conductive plates for pulsed eddy current testing(PECT) are very complex problems due to their complicated physical properties. In this paper, analytical modeling of PECT is established by Fourier series based on truncated region eigenfunction expansion(TREE) method for a single air-cored coil above stratified conductive structures(SCS) to investigate their integrity. From the presented expression of PECT, the coil impedance due to SCS is calculated based on analytical approach using the generalized reflection coefficient in series form. Then the multilayered structures manufactured by non-ferromagnetic (STS301L) and ferromagnetic materials (SS400) are investigated by the developed PECT model. Good prediction of analytical model of PECT not only contributes to the development of an efficient solver but also can be applied to optimize the conditions of experimental setup in PECT.
Wireless Impedance Sensor with PZT-Interface for Prestress-Loss Monitoring in Prestressed Concrete Girder
Nguyen, Khac-Duy ; Lee, So-Young ; Kim, Jeong-Tae ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 6, 2011, Pages 616~625
Ensuring the designed prestress force is very important for the safety of prestressed concrete bridge. The loss of prestress force in tendon could significantly reduce load carrying capacity of the structure. In this study, an automated prestress-loss monitoring system for prestressed concrete girder using PZT-interface and wireless impedance sensor node is presented. The following approaches are carried out to achieve the objective. Firstly, wireless impedance sensor nodes are designed for automated impedance-based monitoring technique. The sensor node is mounted on the high-performance Imote2 sensor platform to fulfill high operating speed, low power requirement and large storage memory. Secondly, a smart PZT-interface designed for monitoring prestress force is described. A linear regression model is established to predict prestress-loss. Finally, a system of the PZT-interface interacted with the wireless sensor node is evaluated from a lab-scale tendon-anchorage connection of a prestressed concrete girder.
Calibration of Detection System of Crack in Concrete Structure by Using Image Processing Technology
Kim, Su-Un ; Shin, Sung-Woo ; Park, Jeong-Hak ; Choi, Man-Yong ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 6, 2011, Pages 626~634
The investigation of concrete structure typically relies on visual inspection which is one of the basic inspection techniques. Image processing techniques play a crucial role in the growing field of automatic surface inspection technique. However, kinds of inspection equipment, environmental condition and detection algorithm have much influence on the reliability of inspection result. This paper proposes a verification method and testing procedure for the reliability of inspection results and surveys characteristics of image acquisition systems and crack inspection algorithms.
Simulation of Ultrasonic Beam Focusing on a Defect in Anisotropic, Inhomogeneous Media
Jeong, Hyun-Jo ; Cho, Sung-Jong ; Erdenetuya, Sharaa ; Jung, Duck-Yong ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 6, 2011, Pages 635~641
In ultrasonic testing of dissimilar metal welds, application of phased array technique in terms of incident beam focusing is not easy because of complicated material structures formed during the multi-pass welding process. Time reversal(TR) techniques can overcome some limitations of phased array since they are self-focusing that does not depend on the geometrical and physical properties of testing components. In this paper, we test the possibility of TR focusing on a defect within anisotropic, heterogeneous austenitic welds. A commercial simulation software is employed for TR focusing and imaging of a side-drilled hole. The performance of time reversed adaptive focal law is compared with those of calculated focal laws for both anisotropic and isotropic welds.
Long-Term Aging Diagnosis of Rotor Steel Using Acoustic Nonlinearity
Kim, Chung-Seok ; Park, Ik-Keun ; Jhang, Kyung-Young ; Hyun, Chang-Yong ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 6, 2011, Pages 642~649
The long-term aging of ferritic 2.25CrMo steel was characterized using the acoustic nonlinear effect in order to apply to diagnose the degradation behavior of structural materials. We measured the acoustic nonlinearity parameter for each thermally aged specimen by the higher harmonic-generation technique. The acoustic nonlinearity parameter increased with aging time due to equilibrium M6C carbide precipitation, and has a favorable linear relation with Rockwell hardness. This study suggests that acoustic nonlinearity testing may be applicable to diagnostics on strength degradation in rotor steels.
A Treatment for Truncated Boundary in a Half-Space with 2-D Rayleigh Wave BEM
Ju, Tae-Ho ; Cho, Youn-Ho ; Phan, Haidang ; Achenbach, Jan D. ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 6, 2011, Pages 650~655
Analysis of two-dimensional Rayleigh wave scattering pattern by a surface defect is studied through modified boundary element method. BEM proposed in this paper has special treatment at each end of boundary which should have the Rayleigh wave go away without any generation of virtual reflections. It is shown that treatment for truncated boundary which is used to model two-dimensional Rayleigh waves' behavior in an elastic half-space is successfully implemented. To check numerical results' accuracy, time domain IFFT signal of the displacements is presented. Improvement on getting rid of unwanted influence of truncated boundary induced by 2-D Rayleigh waves on a flat surface of an elastic half-infinite medium is shown. As a final goal, the numerical results of Rayleigh wave scattering trend are plotted and they are compared with theoretical curves to prove its accuracy.
A Numerical Model for Prediction of Residual Stress Using Rayleigh Waves
Yuan, Maodan ; Kang, To ; Kim, Hak-Joon ; Song, Sung-Jin ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 6, 2011, Pages 656~664
In this work, a numerical model is proposed for the relation between the magnitudes and the depth residual stress with the velocity of Rayleigh wave. Three cases, stress-free, uniform stress and layered stress, are investigated for the change tendency of the Rayleigh wave speed. Using the simulated signal with variation of residual stress magnitude and depth, investigation of the parameters for fitting residual stress and velocity change are performed. The speed change of Rayleigh wave shows a linear relation with the magnitude and an exponential relation with the depth of residual stress. The combination of these two effects could be used for the depth profile evaluation of the residual stress.
Contour Integral Method for Crack Detection
Kim, Woo-Jae ; Kim, No-Nyu ; Yang, Seung-Yong ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 6, 2011, Pages 665~670
In this paper, a new approach to detect surface cracks from a noisy thermal image in the infrared thermography is presented using an holomorphic characteristic of temperature field in a thin plate under steady-state thermal condition. The holomorphic function for 2-D heat flow field in the plate was derived from Cauchy Riemann conditions to define a contour integral that varies according to the existence and strength of a singularity in the domain of integration. The contour integral at each point of thermal image eliminated the temperature variation due to heat conduction and suppressed the noise, so that its image emphasized and highlighted the singularity such as crack. This feature of holomorphic function was also investigated numerically using a simple thermal field in the thin plate satisfying the Laplace equation. The simulation results showed that the integral image selected and detected the crack embedded artificially in the plate very well in a noisy environment.
A Noise Reduction Signal Processing for Online Monitoring: Minimum Variance Cepstrum
Park, Choon-Su ; Yoon, Dong-Jin ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 6, 2011, Pages 671~676
Frequency Modulation of Ultrasound by Nonlinear Defects
Kim, No-Hyu ;
Journal of the Korean Society for Nondestructive Testing, volume 31, issue 6, 2011, Pages 677~681