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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 21, Issue 6 - Dec 2001
Volume 21, Issue 5 - Oct 2001
Volume 21, Issue 4 - Aug 2001
Volume 21, Issue 3 - Jun 2001
Volume 21, Issue 2 - Apr 2001
Volume 21, Issue 1 - Feb 2001
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Multi-Point Optical Fiber Grating Strain Sensor System
Lee, Yong-Wook ; Jung, Jae-Hoon ; Chung, Seung-Hwan ; Lee, Byoung-Ho ; Kim, Nam-Sik ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 2, 2001, Pages 147~151
An optical fiber sensor is capable of nondestructive measurement of a structure and it has an advantage of the immunity to electromagnetic interference because light is not affected by electromagnetic wave. In addition, if optical fibers are buried in an object like a concrete, this sensor tan analyze defects and physical status of the object without disassembling it. Especially, the fiber Bragg grating sensor is a promising optical fiber sensor capable of nondestructive test of such an object. A fiber Bragg grating has the characteristics of reflecting or blotting light of a specific wavelength. If we apply physical quantity like strain to the fiber Bragg grating, the center wavelength of the reflected light is shifted and then we can find the physical quantity applied to the fiber Bragg grating by measuring the center wavelength shift of the reflected light. The fiber Bragg grating sensor capable ot static and dynamic strain measurement is being used in health-monitoring of buildings, structures, etc. Recently increasing is interest in dynamic strain measurement inevitable to the civil structures such as roads and bridges. In this study we implemented the optical fiber sensor system which can measure dynamic strain at multiple points using Fabry-Perot wavelength demodulation. And we measured the static and dynamic strain using this sensor system with a test structure(cantilever). Measurement results were similar to those obtained with the conventional electrical measurement methods.
Evaluation of Surface-Breaking Crack Based on Laser-Generated Ultrasonics and Wavelet Transform
Lee, Min-Rae ; Choi, Sang-Woo ; Lee, Joon-Hyun ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 2, 2001, Pages 152~162
Laser-generated ultrasonic technique which is one of the reliable nondestructive evaluation techniques has been applied to evaluate the integrity of structures by analyzing the characteristics of signal obtained from surface crack. Therefore, the signal analysis of the laser-generated ultrasonics is absolutely necessary for the accurate and quantitative estimation of the surface defects. In this study, one-sided measurement by laser-generated ultrasonic has been applied to evaluate the depth of the surface-breaking crack in the materials. However, since the ultrasonic waveform excited by pulse laser is very difficult to distinguish the defect signals, it is necessary to consider the signal analyses of the transient waveform. Wavelet Transform(WT) is a powerful tool for processing transient signals with temporally varying spectra that helps to resolve high and low frequency transient components effectively. In this paper, the analyses of the surface-breaking crack of the ultrasonic signal excited by pulse laser are presented by employing the WT analyses.
Non-Contact Ultrasonic Testing of Aircraft Joints using Laser Generated Lamb Wave
Jhang, Kyoung-Young ; Kim, Hong-Joon ; Ceringlia, Donatella ; Djordjevic, Boro ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 2, 2001, Pages 163~168
Due to aging, adhesively bonded and riveted aircraft lap joints can contain distends, cracks around rivet holes, fatigue induced flaws, and corrosion. It is required for the safety of aircraft to inspect these defects through the whole region of mint in rapid speed. Bond quality or adhesively bonded and riveted aluminum lap splice joints is investigated using non-contact remote ultrasonic nondestructive evaluation (NDE). Non-contact ultrasonic tests are performed using laser generation and air-coupled transducer detection. A Q-switched Nd:YAG laser and a periodic transmission mask are used to generate a selected Lamb mode. The Lamb wave is generated on one side of the lap splice joint, propagates along the plate, interacts with the joint and is detected on the other side by a micromachined air-coupled capacitance transducer. Analysis of recorded signals allows to evaluate the condition of the bond.
A Study on 3-Dimensional Surface Measurement using Confocal Principle
Kang, Young-June ; Song, Dae-Ho ; You, Weon-Jae ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 2, 2001, Pages 169~176
In modern industry, the accuracy and the sulfate-finish requirements for machined parts have been becoming ever more stringent. In addition, the measurement and understanding of surface topography is rapidly attracting the attention of the physicist and chemist as well as the engineer. Optical measuring method is used in vibration measurement, crack and defect detection with the advent of opto-mechatronics, and it is expected to play an important role in surface topography. In this study, the principle of confocal microscope is described, and the advanced 3-D surface measuring system that has better performance than the traditional confocal microscope is developed. Suitable fixtures arc developed and integrated with the computer system for generating 3-D surface and form data. Software for data acquisition and analysis of various parameters in surface geometrical features has been developed.
Nondestructive Testing with Shearography
Chang, Seog-Weon ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 2, 2001, Pages 177~181
Nondestructive testing(NDT) is one of the fundamental tools to improve the quality of commercial and industrial products. NDT is potentially a major application of interferometry. Interferometry(ESPI, Shearography, ect) has successfully been applied in various industrial environments such as high performance aircraft, home appliance, automotive, and laminates on engine structures, etc. Today's industry demands high performance components with toughest mechanical features and ultimate safety standards. Especially in automotive and aircraft industry the development process focuses on tailor-made design and solutions to meet customer specifications. To reconcile economy, ligh-weight construction has become a key issue. Many companies are looking for new advanced NDT techniques to archive cost efficiency over the limitations of classical methods. ESPI and shearography allow a rapid, full field and 3D-measurement without contact. In this paper recent applications of ESPI and shearography for NDT are described. Advanced features of classical techniques are specified and new applications in material and component testing are presented.
A Study on the Vibration Characteristics of Thin Plate with Crack under Tension using ESPI
Kim, Koung-Suk ; Kang, Ki-Soo ; Choi, Ji-Eun ; Park, Chan-Ju ; Hong, Jin-Who ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 2, 2001, Pages 182~188
This paper presents the vibration characteristics of a rectangular plate with
oblique crack subjected to a uniaxial tension. The experiment is adopted by the time-average Electronic Speckle Pattern Interferometry(ESPI) method. The natural frequency and mode shape are considered accurately according to the increase of tensile load. When tensile load is zero, the vibration modes we agreed with the smooth and the
obliquely cracked plate. But according to the increasement of load it is shown that vibration modes are extremely varied. The effects of the crack under the vibration are discussed in detail. It is indicated that the increase of load makes the variation of the frequencies and modes complicate in the range of even a small load. The results are agreed with the FEM analysis within 5%.
Simulation of Separating Isoclinics and Isochromatics from Photoelastic Fringes of a Disk using 8-step Phase Shifting Methodology
Baek, Tae-Hyun ; Kim, Myung-Soo ; Cho, Sung-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 2, 2001, Pages 189~196
Photoelasticity is one of the most widely used methods for whole field stress analysis. In photoelasticity, the difference and the directions of the principal stresses we given isochromatic and isoclinic fringe patterns. Conventionally, principal stress directions are measured manually by relating the polarizer and analyzer of a plane polariscope at the same time. This is known to be the Tardy compensation method. This measurement can be very tedious and time consuming in whole field analysis. It is not possible to separate isoclincs from photoelastic fringes by conventional photoelastic technique. In this study, photoelastic theory is represented by Jones matrices and 4-steps and 8-steps phase shifting methods are described A feasibility study using computer simulation is done to separate isoclincs and isochomatics from photoelastic fringes of a circular disk under diametrical compression. Fringe patterns of the disk are generated using stress optic law. The magnitudes of isoclincs and isochromatics obtained from 8-step phase shifting method are compared with those of theories. From computer simulation, it is verified to separate isoclincs and isochomatics from photoelastic fringes.
Application of a New NDI Method using Magneto-Optical Film for Inspection of Micro-Cracks
Lee, Hyoung-No ; Park, Han-Ju ; Shoji, Tetsuo ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 2, 2001, Pages 197~203
Micro-defects induced by design and production failure or working environments are known as the cause of SCC(Stress Corrosion Cracking) in aged structures. Therefore, the evaluation of structural integrity based on micro-cracks is required not only a manufacturing step but also in-service term. So we introduce a new nondestructive inspection method using the magneto-optical film to detect micro-cracks. The method has some advantage such as high testing speed, real time data acquistion and the possibility of remote sensing by using of a magneto-optical film that takes advantage of the change of magnetic domains and domain walls. This paper introduces the concept of the new nondestructive inspection method using the magneto-optical film, also proves the possibility of this method as a remote testing system under oscillating load considering application on real fields by applying the method to four types of specimens.
Identification of Structural Damages in a Plate Structure: An FRF-Based Method
Kim, Nam-In ; Lee, U-Sik ; Kwon, Oh-Yang ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 2, 2001, Pages 204~212
In this study, an FRF-based structural damage identification method (SDIM) is proposed for plate structures. The present SDIM is derived from the partial differential equation of motion of the damaged plate, in with damages we characterized by using a damage distribution function. The appealing features of the present SDIM include the followings. First, the modal data of the damaged structure are not required. Secondly, a sufficient number of information can be generated from the measured FRFs by simply varying excitation frequencies and response measurement points. The feasibility of the present SDIM is verified through some numerically simulated damage identification tests.
Nondestructive Evaluation using Optical Methods
Kang, Young-June ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 2, 2001, Pages 213~226