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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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Fracture Behavior Analysis in CFRP Specimens by Acoustic Emission and Ultrasonic Test
Ahn, Seok-Hwan ; Nam, Ki-Woo ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 3, 2001, Pages 251~260
Damage Profess of CFRP laminates under monotonic tensile test was characterized by the correlation between Acoustic Emission(AE) and Ultrasonic Test(UT). The amplitude distribution of AE signal from a specimens is an aid to the determination of the extent of the different fracture mechanism such as matrix crack, debonding, fiber pullout and fiber fracture as load is increased. In addtion, the characteristics of ultrasonic amplitude attenuation are useful lot analysis of the different type of fracture mechanism. Different orientation of carbon fiber reinforced plastic specimens were used to investigate the AE amplitude range and ultrasonic amplitude attenuation. Finally, loading-unloading tests were carried out to check Felicity effect. During the tests, ultrasonic amplitude attenuation was investigated at the same time and compared with AE parameters. The result showed that two parameters of both AE and UT could be effectively used for analysis of fracture mechanism in CFRP laminates.
Analysis of Thermo-Acoustic Emission from Damage in Composite Laminates under Thermal Cyclic Loading
Kim, Young-Bok ; Min, Dae-Hong ; Lee, Deok-Bo ; Choi, Nak-Sam ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 3, 2001, Pages 261~268
An investigation on nondestructive evaluation of thermal stress-nduced damage in the composite laminates (3mm in thickness and
lay-up angles) has been performed using the thermo-acoustic emission technique. Reduction of thermo-AE events due to repetitive thermal load cycles showed a Kaiser effect. An analysis of the thermo-AE behavior determined the stress free temperature of composite laminates. Fiber fracture and matrix cracks were observed using the optical microscopy, scanning electron microscopy and ultrasonic C-sean. Short-Time Fourier Transform of thermo-AE signals offered the time-frequency characteristics which might classily the thermo-AE as three different types to estimate the damage processes of the composites.
Analysis and Simulation of Ultrasonic Wave Propagation and Scattering in Unidirectional Fiber Composites
Lee, Choon-Jae ; Yim, Hyun-June ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 3, 2001, Pages 269~276
Ultrasonic testing of composite materials is much more difficult than that of isotropic materials, because of the beam skew phenomenon caused by their elastic anisotropy. An established analytical method exists for elastic wave propagation in anisotropic media as a result of previous research efforts. Yet, due to the complexity of the analytical method, solution of real problems must resort to the numerical method. In this work, analytical solutions have first been obtained for the wavefield due to a point source in a unidirectional fiber-reinforced composite, which may be modeled as transversely isotropic. Then, the corresponding numerical solutions have been obtained using the mass-spring lattice model(MSLM). The two solutions have agreed well with each other. Other problems such as reflection from free boundaries and scattering from cracks have also been solved numerically, and the results have been investigated from the viewpoint of wave mechanics. The numerical model whose validity has been confirmed by this work will be of great use in simulating ultrasonic testing of composite materials.
AE Source Location of Unidirectional GFRP
Lee, Jong-O ; Won, Soon-Ho ; Yoon, Woon-Ha ; Lee, Jong-Kyu ; So, Cheal-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 3, 2001, Pages 277~280
General source location method that use an arrival time differences among sensors is restricted to the composite material and the complex-shaped material. In this study, a bundle-type acoustic sensor composed of 6 pinducers was utilized to determine wave propagation direction and then to estimate source location of the unidirectional GFRP. For the purpose of the study, slowness curve for the material was obtained and made an assumption that the incident waves on pinducers are propagated as a plane wave. According to the results, measured propagation directions of the wave were coincide with theoretical background, however, it was a hassle to determine the source location exactly. But, it is expected that bundle-type sensor gives more accurate results for zone location than generally used acoustic sensors.
AE Source Location in Anisotropic Plates by Using Nonlinear Analysis
Lee, Kyung-Joo ; Kwon, Oh-Yang ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 3, 2001, Pages 281~287
For the conventional two-dimensional source location of acoustic emission (AE) based on the threshold crossing, wave velocity has to be measured in the actual structure to calculate the arrival-time difference and thus to form the two hyperbolae. Velocity is dependent on the fiber orientation, however, due to the dependence of elastic modulus on fiber orientation in anisotropic materials such as compost#e plates. This tan affect the accuracy of AE source location and make the source location procedure complicated. In this study, we propose a method to reduce the location error in anisotropic plates by using the numerical solution of nonlinear equations, where the velocity term has been removed by employing the fourth sensor. The efficiency and validity of the proposed method has also been experimentally verified.
Ultrasound Wave Propagation in Thick Composites with Uniform Fiber Waviness
Chun, Heoung-Jae ; Jang, Pil-Sung ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 3, 2001, Pages 288~298
There has been a growing interest in thick composite materials especially for primary structures. Fiber waviness is one of the manufacturing defects frequently encountered in thick composite structures and affects the mechanical properties such as stiffness and strength significantly. Therefore, nondestructive evaluation technique that can detect fiber waviness of thick composite is very important for the integrity of structures. In this study, efforts were made to understand ultrasonic wave propagation in thick composites with uniform fiber waviness by adopting the ray and plane wave theories. Both theoretical and experimental investigations were conducted to understand the wave propagation in thick composites with uniform fiber waviness. The experiments were conducted on specially fabricated thick composite specimens with various degrees of uniform fiber waviness using the conventional through-transmission method to verify the predicted results. The experimental results showed good agreement with the theoretical predictions.
Detection of Defects in Composite Structures by using ESPI
Kim, Kyung-Suk ; Cheong, Seong-Kyun ; Kang, Jin-Shik ; Chang, Ho-Seob ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 3, 2001, Pages 299~306
In this paper, artificial and real defects(delamination and debond) in composite structures were detected by using ESPI system. Three types of specimens, that is, composite laminates, honeycomb structures, and adhesive joints, were used to study the applicability of ESPI to composite structures. To detect defects in specimens, we selected thermal loading method that can easily induce the surface deformation of specimen. Experimental results show that defects in composite structures could be easily detected by ESPI. Moreover, it shows that ESPI could be usefully applied to the detection of defects in various composite structures.
The Estimation of Neutron Fluence in Nuclear Reactor Vessel Materials by the Analysis of Ultrasonic Characteristics
Lee, Sam-Lai ; Chang, Kee-Ok ; Kim, Byoung-Chul ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 3, 2001, Pages 307~312
Ultrasonic signals from Charpy impact test specimen have been analyzed in order to evaluate the integrity of reactor pressure vessel. Base and weld metal that were extracted from reactor vessel doting plant outages according to the schedule of the surveillance test required by the related regulations have been used and the ultrasonic test parameters including velocity, attenuation, etc. showed a close correlations with the amount of neutron irradiation for base metal, relatively homogeneous materials. This result showed certain possibility where a nondestructive method could be used to predict the fluence of the Irradiation due to neutron in nuclear reactor vessel materials.
Acoustic Emission Application for Aerospace Composite Materials
Lee, Sang-Ho ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 3, 2001, Pages 313~318
To establish nondestructive test method for aerospace composite materials, various composite specimens were tested and analyzed using acoutic emission. The hit rate of acoustic emission closely was rotated with crack initiation and propagation. This report also presents defection capability of crack initiation pressure, initial crack active location, and crack propagation using acoustic emission.
Research Trend in Smart Structures Using Fiber Optic Sensors
Ryu, Chi-Young ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 3, 2001, Pages 319~329