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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society for Nondestructive Testing
Journal Basic Information
Journal DOI :
The Korean Society for Nondestructive Testing
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Volume & Issues
Volume 20, Issue 6 - Dec 2000
Volume 20, Issue 5 - Oct 2000
Volume 20, Issue 4 - Aug 2000
Volume 20, Issue 3 - Jun 2000
Volume 20, Issue 2 - Apr 2000
Volume 20, Issue 1 - Feb 2000
Selecting the target year
Inspection of Heat Exchanger Tubing Defects with Ultrasonic Guided Waves
Shin, Hyeon-Jae ; Rose, Joseph L. ; Song, Sung-Jin ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 1, 2000, Pages 1~9
This study shows the defect detection and sizing capability of ultrasonic guided waves in the nondestructive inspection of heat exchanger and steam generator tubing. Phase and group velocity dispersion curves for the longitudinal and flexural modes of a sample Inconel tube were presented for the theoretical analysis. EDM(Electric Discharge Machining) wears in tubing under a tube support plate and circumferential laser notches in tubing were detected by an axisymmetric and a non-axisymmetric transducer set up, respectively. EDM wears were detected with L(0, 2), L(0, 3) and L(0, 4) modes and among them L(0, 4) mode was found to be the most sensitive. It was also found that the flexural modes around L(0, 1) mode could be used for the detection and sizing of laser notches in the tubing.
Creep Damage Evaluation of High-Temperature Pipeline Material for Fossil Power Plant by Frequency Spectrum Analysis Method
Lee, Sang-Guk ; Lee, In-Cheol ; Chang, Hong-Keun ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 1, 2000, Pages 10~17
In boiler high-temperature pipelines such as main steam pipe, header and steam drum in fossil power plants, conventional measurement techniques(replica method, electric resistance method, and hardness test method) for measuring creep damage have such disadvantages as complex preparation and measurement procedures, too many control parameters. And also, these techniques have low practicality and applied only to component surfaces with good accessibility. It needs to apply a reliable and quantitative ultrasonic nondestructive evaluation method that can be replaced for these equipment. In this study, both artificial creep degradation test using life prediction formula and frequency analysis by ultrasonic tests for crept specimens were carried out for the purpose of nondestructive evaluation for creep damage. As a result of ultrasonic tests for crept specimens, we conformed that the high frequency side spectra decrease and central frequency components shift to low frequency band, and also their bandwidth decreases as increasing creep damage in backwall echos.
Creep Damage Evaluation of Cr-Mo Steel High-Temperature Pipeline Material for Fossil Power Plant Using Ultrasonic Test Method
Lee, Sang-Guk ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 1, 2000, Pages 18~26
Boiler high-temperature pipelines such as main steam pipe, header and steam drum in fossil power plants are degraded by creep damage due to severe operating conditions such as high temperature and high pressure for an extended period time. Conventional measurement techniques(replica method, electric resistance method, and hardness test method) for measuring creep damage have such disadvantages as complex preparation and measurement procedures, too many control parameters. And also these techniques have low practicality and applied only to component surfaces with good accessibility. In this paper, artificial creep degradation test and ultrasonic measurement for their creep degraded specimens(Cr-Mo alloy steels) were carried out for the purpose of evaluation for creep damage. Absolute measuring method of quantitative ultrasonic measurement for material degradation was established, and long term creep degradation tests using life prediction formula were carried out. As a result of ultrasonic tests for crept specimens. we conformed that both the sound velocity decreased and attenuation coefficient linearly increased in proportion to the Increase of creep life fraction(
Detection of Laser Generated Ultrasonic Wave Using Michelson Interferometer
Kim, Kyung-Cho ; Yamawaki, Hisashi ; Jhang, Kyung-Young ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 1, 2000, Pages 27~32
In this paper, ultrasonic wave in the thermoelastic regime was generated in a steel disk by illuminating a pulse laser (Q-switched Nd:YAG) on the surface of the sample and was detected on the other side by Michelson interferometer which was stabilized by feed back control. The experimentally detected displacement waveform of the ultrasonic wave showed good agreement with the theoretically expected one. Also it was shown that sound speeds of longitudinal and shear wave were similar to ones measured by pulse-echo method using a contact transducer. As an application of the noncontact ultrasonic measurement by using laser based ultrasonics, the sound speed in the sample was monitored while the sample was heated in a furnace, and the result showed that it decreased according to the increase of sample temperature.
Characteristics of The 1-3 Piezoelectric Composite Transducer Manufactured by Dicing-Filling Method
Kim, W.S. ; Yun, U.H. ; Ok, C.I. ; Kim, S.B. ; Lee, J.K. ; Lee, J.O. ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 1, 2000, Pages 33~37
The 1-3 piezoelectric composite transducer with 75 volume percents PZT was fabricated by the dicing-filling method. The resonance modes of the 1-3 transducer have been studied with electric impedance measurement as a function of frequency. The fundamental frequencies of the planar and thickness mode were observed at 0.95MHz and 1.63MHz respectively, but the lateral mode was not observed. In the thickness mode, the electromechanical coupling coefficient of the 1-3 piezoelectric composite transducer, 0.54, was very closed to that of the single phase PZT(0.52). The pulse-echo response by exciting the 1-3 transducer with an electric pulse was observed from the water/reflector interface, and analyzed bandwidth by the spectrum of the impulse response. The quality factor Q for the 1-3 transducer was observed as 1.5 smaller than that of the single phase(80) and then the 1-3 transducer may be used to the broad band type transducer applications.
Corrosion Assessment of Storage Tank Floor using Magnetic Flux Leakage Technique
Won, Soon-Ho ; Cho, Kyung-Shik ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 1, 2000, Pages 38~45
In this research, MFL technique has been studied for the inspection of storage tank floor. The reference specimens having 20%, 40%, 60% and 80% slot's are fabricated using the carbon steel plates of a 6mm and 10mm thick. Powerful permanent magnets and Hall effect sensors are used to this application. It is shown that our system is able to detect metal loss like a slot. Also, it is possible that slot diameter is measured using transverse type of Hall generator. It is demonstrated that MFL can not differentiate between the response from top side and bottom side slot. Flux leakage response from a bottom side indication is significantly lower in amplitude than that from an equivalent top side slot. It is essential to know this sensor lift-off distance because the MFL signal also changes considerably with the sensor lift-off distance.
Characteristics of Magnetostrictive Sensor for Detecting the Flaws in Pipe
Ahn, Bong-Young ; Kim, Young-Joo ; Kim, Young-Gil ; Lee, Seung-Seok ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 1, 2000, Pages 46~53
Magnetostrictive sensors which can be used effectively to detect flaws in pipe were fabricated. The optimal conditions to obtain the maximum generation efficiency of the ultrasonic wave were established. In case of the used steel pipe the optimal magnetic field was
and the coil width of 15mm showed the best efficiency for generating a wave with the frequency of 180 kHz. In the best condition, the wave can propagate further than 50m without serious attenuation. The amplitude of the ultrasonic wave reflected from artificial flaw had a good linear relationship to the cross-sectional area of the flaw.
Nondestructive Evaluation of Fatigue Damage
Kwon, Oh-Yang ;
Journal of the Korean Society for Nondestructive Testing, volume 20, issue 1, 2000, Pages 54~61
In order to determine the mode I stress intensity factor (
) by means of the alternating current potential drop(ACPD) technique, the change in potential drop due to load for a paramagnetic material containing a two-dimensional surface crack was examined. The cause of the change in potential drop and the effects of the magnetic flux and the demagnetization on the change in potential drop were clarified by using the measuring systems with and without removing the magnetic flux from the circumference of the specimen. The change in potential drop was linearly decreased with increasing the tensile load and was caused by the change in conductivity near the crack tip. The reason of decreasing the change in potential drop with increasing the tensile load was that the increase of the conductivity near the crack tip due to the tensile load caused the decreases of the resistance and internal inductance of the specimen. The relationship between the change in potential drop and the change in
was not affected by demagnetization and was independent of the crack length.