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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 32, Issue 6 - Dec 2012
Volume 32, Issue 5 - Oct 2012
Volume 32, Issue 4 - Aug 2012
Volume 32, Issue 3 - Jun 2012
Volume 32, Issue 2 - Apr 2012
Volume 32, Issue 1 - Feb 2012
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Frequency Characteristics of Surface Wave Generated by Single-Line Pulsed Laser Beam with Two Kinds of Spatial Energy Profile Models: Gaussian and Square-Like
Seo, Ho-Geon ; Kim, Myung-Hwan ; Choi, Sung-Ho ; Kim, Chung-Seok ; Jhang, Kyung-Young ;
Journal of the Korean Society for Nondestructive Testing, volume 32, issue 4, 2012, Pages 347~354
DOI : 10.7779/JKSNT.2012.32.4.347
Using a single-line pulsed laser beam is well known as a useful noncontact method to generate a directional surface acoustic wave. In this method, different laser beam energy profiles produce different waveforms and frequency characteristics. In this paper, we considered two typical kinds of laser beam energy profiles, Gaussian and square-like, to find out a difference in the frequency characteristics. To achieve this, mathematical models were proposed first for Gaussian laser beam profile and square-like respectively, both of which depended on the laser beam width. To verify the theoretical models, experimental setups with a cylindrical lens and a line-slit mask were respectively designed to produce a line laser beam with Gaussian spatial energy profile and square-like. The frequency responses of the theoretical models showed good agreement with experimental results in terms of the existence of harmonic frequency components and the shift of the first peak frequencies to low.
Nonlinear Time Reversal Focusing and Detection of Fatigue Crack
Jeong, Hyun-Jo ; Barnard, Dan ;
Journal of the Korean Society for Nondestructive Testing, volume 32, issue 4, 2012, Pages 355~361
DOI : 10.7779/JKSNT.2012.32.4.355
This paper presents an experimental study on the detection and location of nonlinear scattering source due to the presence of fatigue crack in a laboratory specimen. The proposed technique is based on a combination of nonlinear elastic wave spectroscopy(NEWS) and time reversal(TR) focusing approach. In order to focus on the nonlinear scattering position due to the fatigue crack, we employed only one transmitting transducer and one receiving transducer, taking advantage of long duration of reception signal that includes multiple linear scattering such as mode conversion and boundary reflections. NEWS technique was then used as a pre-treatment of TR for spatial focusing of reemitted second harmonic signal. The robustness of this approach was demonstrated on a cracked specimen and the nonlinear TR focusing behavior is observed on the crack interface from which the second harmonic signal was originated.
Imaging of Harmonic Wave Generated by Contact Acoustic Nonlinearity in Obliquely Incident Ultrasonic Wave
Yun, Dong-Seok ; Choi, Sung-Ho ; Kim, Chung-Seok ; Jhang, Kyung-Young ;
Journal of the Korean Society for Nondestructive Testing, volume 32, issue 4, 2012, Pages 362~368
DOI : 10.7779/JKSNT.2012.32.4.362
The objective of this study is to image the harmonic wave generated by contact acoustic nonlinearity in obliquely incident ultrasonic wave for early detection of closed cracks. A closed crack has been simulated by contacting two aluminum block specimens producing solid-solid contact interfaces and then acoustic nonlinearity has been imaged with contact pressure. Sampling phased array(SPA) and synthetic aperture focusing technique(SAFT) are used for imaging techniques. The amplitude of the fundamental frequency decreased with appling pressure. But, the amplitude of second harmonic increased with pressure and was a maximum amplitude at the simulation point of closed crack. Then, the amplitude of second harmonic decreased. As a result, harmonic imaging of contact acoustic nonlinearity is possible and it is expected to be apply for early detection of initial cracks.
Detection of Micro-Crack Using a Nonlinear Ultrasonic Resonance Parameters
Cheong, Yong-Moo ; Lee, Deok-Hyun ;
Journal of the Korean Society for Nondestructive Testing, volume 32, issue 4, 2012, Pages 369~375
DOI : 10.7779/JKSNT.2012.32.4.369
In order to overcome the detection limit by the current nondestructive evaluation technology, a nonlinear resonant ultrasound spectroscopy(NRUS) technique was applied for detection of micro-scale cracks in a material. A down-shift of the resonance frequency and a variation of normalized amplitude of the resonance pattern were suggested as the nonlinear parameter for detection of micro-scale cracks in a materials. A natural-like crack were produced in a standard compact tension(CT) specimen by a low cycle fatigue test and the resonance patterns were acquired in each fatigue step. As the exciting voltage increases, a down-shift of resonance frequency were increases as well as the normalized amplitude decrease. This nonlinear effects were significant and even greater in the cracked specimen, but not observed in a intact specimen.
Analysis of Harmonic Wave Generation in Nonlinear Oblique Crack Surface
Kim, Noh-Yu ; Yang, Seung-Yong ;
Journal of the Korean Society for Nondestructive Testing, volume 32, issue 4, 2012, Pages 376~387
DOI : 10.7779/JKSNT.2012.32.4.376
Based on the nonlinear spring model coupled with perturbation method, 2nd harmonic waves generated by oblique incident ultrasound on nonlinear crack interface were calculated and investigated. Reflected and transmitted waves from the interface were determined and analyzed at various angle of incidence for the cracks with different interfacial stiffness in order to estimate the 2nd harmonic generation of incident ultrasound. It was shown in computer simulation that the 2nd harmonic components changed much with the increase of incidence angle in both reflected and transmitted wave, but became very small when the incident angle approached toward 90 degree. It can be concluded that the 2nd harmonic component of reflected wave has a meaningful amplitude as much as the transmitted 2nd harmonic wave from partly closed crack.
Fully Non-Contact Assessment of Acoustic Nonlinearity According to Plastic Deformation in Al6061 Alloy
Lee, Hyeon ; Chung, Cheon ; Kim, Chung-Seok ; Jhang, Kyung-Young ;
Journal of the Korean Society for Nondestructive Testing, volume 32, issue 4, 2012, Pages 388~392
DOI : 10.7779/JKSNT.2012.32.4.388
This study proposes a fully non-contact measurement method to assess acoustic nonlinearity of narrowband surface waves generated by a line-arrayed laser beam by using a laser-ultrasonic detector in the way of two-wave mixing (TWM) method. This method was applied to figure out a relationship between plastic deformation and nonlinearity characteristics of a plastically deformed aluminum specimens. The experimental results showed that the acoustic nonlinearity of the laser-generated surface wave increased proportionally to the level of tensile deformation. This tendency is in good agreement with the result of measurement by contact method with PZT-transducer.
Evaluation of Adhesive Strength for Nano-Structured Thin Film by Scanning Acoustic Microscope
Park, Tae-Sung ; Kwak, Dong-Ryul ; Park, Ik-Keun ; Miyasaka, Chiaki ;
Journal of the Korean Society for Nondestructive Testing, volume 32, issue 4, 2012, Pages 393~400
DOI : 10.7779/JKSNT.2012.32.4.393
In recent years, nano-structured thin film systems are often applied in industries such as MEMS/NEMS device, optical coating, semiconductor or like this. Thin films are used for many and varied purpose to provide resistance to abrasion, erosion, corrosion, or high temperature oxidation and also to provide special magnetic or dielectric properties. Quite a number of articles to evaluate the characterization of thin film structure such as film density, film grain size, film elastic properties, and film/substrate interface condition were reported. Among them, the evaluation of film adhesive to substrate has been of great interest. In this study, we fabricated the polymeric thin film system with different adhesive conditions to evaluate the adhesive condition of the thin film. The nano-structured thin film system was fabricated by spin coating method. And then V(z) curve technique was applied to evaluate adhesive condition of the interface by measuring the surface acoustic wave(SAW) velocity by scanning acoustic microscope(SAM). Furthermore, a nano-scratch technique was applied to the systems to obtain correlations between the velocity of the SAW propagating within the system including the interface and the shear adhesive force. The results show a good correlation between the SAW velocities measured by acoustic spectroscope and the critical load measured by the nano-scratch test. Consequently, V(z) curve method showed potentials for characterizing the adhesive conditions at the interface by acoustic microscope.
Analysis of Ultrasonic Resonance Signal in Multi-Layered Structure
Kim, Dong-Ryun ; Kim, Jae-Hoon ;
Journal of the Korean Society for Nondestructive Testing, volume 32, issue 4, 2012, Pages 401~409
DOI : 10.7779/JKSNT.2012.32.4.401
Ultrasonic testing are far superior to other nondestructive tests for detecting the disbond interface which occurred in adhesive interface. However, a solid rocket motor consisting of a steel case, rubber insulation, liner, and propellant poses many difficulties for analyzing ultrasonic waves because of the superposition of reflected waves and large differences in acoustic impedance of various materials. Therefore, ultrasonic tests for detecting the disbond interface in solid rocket motor have been applied in very limited areas between the steel case and rubber insulation using an automatic C-scan system. The existing ultrasonic test cannot detect the disbond interface between the liner and propellant of a solid rocket motor because most of the ultrasonic waves are absorbed in the rubber material which has low acoustic impedance. This problem could be overcome by analyzing the resonance frequency from the frequency spectrum using the ultrasonic resonance method. In this paper, a new technique to detect the disbond interface between the liner and propellant using ultrasonic resonance characteristics is discussed in detail.
Study on the Property of Guided Wave Signal Analysis according to Defect Shape of Small Size
Gil, Doo-Song ; Ahn, Yeon-Shik ; Jung, Gye-Jo ; Park, Sang-Gi ; Kim, Yong-Gun ;
Journal of the Korean Society for Nondestructive Testing, volume 32, issue 4, 2012, Pages 410~417
DOI : 10.7779/JKSNT.2012.32.4.410
Currently domestic thermal and nuclear power plants are comprised of many type's condenser and steam generator tubes to produce the electricity of good quality. There are some methods to inspect these tubes in the event that several defects were discovered in these facilities. Among many non-destructive methods, we used guided wave to inspect the soundness of tubes, because this method is very fast to detect the defect and very simple to install the equipment and also, can inspect up to the long range at a fixed point. Also, this method has a drawback that does not detect a very small size defect. So, we made an effort to overcome this drawback through the experimentation and signal analysis according to the size and shape of the defect through the manufacture of various artificial cracks capable to generate within the small size tube in the study and we anticipate that these detect limits can be overcome along with the development of the signal processing and manufacturing technology of the sensor for the inspection.
Review of Micro/Nano Nondestructive Evaluation Technique (II): Measurement of Acoustic Properties
Kim, Chung-Seok ; Park, Ik-Keun ;
Journal of the Korean Society for Nondestructive Testing, volume 32, issue 4, 2012, Pages 418~430
DOI : 10.7779/JKSNT.2012.32.4.418
The present paper reviews the micro and nano nondestructive evaluation(NDE) technique that is possible to investigate the surface and measure the acoustic properties. The technical theory, features and applications of the ultrasonic atomic force microscopy(UAFM) and scanning acoustic microscopy(SAM) are illustrated. Especially, these technologies are possible to evaluate the mechanical properties in micro/nano structure and surface through the measurement of acoustic properties in addition to the observation of surface and subsurface. Consequently, it is thought that technique developments and applications of these micro/nano NDE in advanced industrial parts together with present nondestructive industry are widely possible hereafter.
Correction of Focal Law of Curved Wedge for Phased Array Ultrasonic Testing of Pipe
Kim, Ki-Bok ;
Journal of the Korean Society for Nondestructive Testing, volume 32, issue 4, 2012, Pages 431~438
Under-Sodium Viewing Techniques in Sodium-Cooled Fast Reactors
Joo, Young-Sang ;
Journal of the Korean Society for Nondestructive Testing, volume 32, issue 4, 2012, Pages 439~447