• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.2
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• pp.122-129
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• 2006

Shearography is one of optical methods that has been applied to nondestructive testing (NDT) and strain/stress analysis. The technique has the merit of the directly measuring relative displacement, which is insensitive to environmental vibration disturbance. Previous studies about the method have emphasized on extending its application to new fields and lack insufficient research on effective parameters for qualitative and quantitative evaluation of defects. In this paper, the influence of shearing amount on the detection of an internal defect is investigated. In experiment, slender defects along longitudinal direction of pipeline are artificially designed and detection results according to the change of shearing amount are analyzed. Based on the investigation, we propose the technique for the determination of defect size and accurate source location.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.2
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• pp.85-90
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• 2010

The infrared energy is emitted in the infrared wavelength range that corresponds to the surface temperature of a object which has temperature that is over the absolute the temperature(OK). The infrared thermography (IRT) is a non-destrnctive testing method that provides thermal video for the user in real-time by converting the infrared quantity that is detected by the infrared detector into temperature. The pipes of nuclear power plant(NPP) could be thinned by the corrosion and fatigue and the defect could lead to a big accident. For this reason, the effective non-destructive testing method is necessary. In this study, the relationship between the measured temperature and the defect depth or size of NPP pipes were recognized and that was applied to detect the wall thinning defects of NPP pipes.

• Journal of agriculture & life science
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• v.46 no.1
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• pp.35-41
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• 2012

Nondestructive evaluation (NDE) technique method using a resonance frequency mode was carried out for woodceramics made by different carbonizing temperature (600, 800, 1000, $1200^{\circ}C$) for Broussonetia kazinoki Sieb. Dynamic modulus of elasticity increased with increasing carbonizing temperature. There was a close relationship of dynamic modulus of elasticity and static bending modulus of elasticity to MOR. Therefore, the dynamic modulus of elasticity using resonance frequency mode is useful as a nondestructive evaluation method for predicting the MOR of woodceramics made by different carbonizing temperature for B. kazinoki Sieb.

• Journal of the Korean Wood Science and Technology
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• v.31 no.2
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• pp.58-68
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• 2003

Capacity assessment of structural member must be ahead of the safety assessment of wooden traditional building. Capacity assessment of structural member has been dependent on empirical method with visual inspection even now. Safety assessment of building, however, can be more correct and reasonable provided non-destructive evaluation technique that scientific and logic would be used to evaluate the capacity of structural member. For that purpose, non-destructive evaluation technique was applied to column among many structural members of wooden traditional building to examine the possibility of capacity assessment of structural member. And then, those data will be used as a basic data for capacity assessment of structural member in a following study. Specially, deterioration progress levels of column according to exposed condition were measured. Similar results were obtained as compared with results of visual inspection, so there was a good possibility of application for non-destructive evaluation technique.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.3
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• pp.205-210
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• 1998

이미 오래전부터 국내외에서 석유화학공장 등의 보온 배관에서 보온재를 벗기지 않고 배관의 부식 손상 및 잔존두께를 평가하는데 방사선투과시험법을 적용해 오고 있다. 그러나 배관 용접부의 결함 탐상에 관한 방사선투과법에 대한 국제 및 국내 코드는 이미 마련되어 있지만 배관의 두께와 내부에 존재하는 부착물(deposit) 등의 두께를 측정하는 것에 관련한 국제 및 국내 코드는 미비되어 시험 절차 및 시험 결과에 대한 시비가 근본적으로 존재할 수 밖에 없을 뿐만 아니라 표준화된 시험 기술의 미비로 현장에서 많은 시행착오를 동반하였다. 그러나 최근 이 시험법에 대한 관련 원안(protocol)을 확정하기 위해 각국에서 개별적으로 수행되었던 기존의 연구 결과들이 취합되고 있으며 부족한 부분들에 대한 연구가 국제 공동 연구 형식으로 이뤄지고 있다. 따라서 본 연구에서는 tangential radiography를 적용하여 보온된 배관의 잔존 두께를 평가할 수 있는 시험 방법을 제시하고자 하였다.

• Journal of the Korean Society for Nondestructive Testing
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• v.12 no.1
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• pp.9-15
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• 1992

Ultrasonic spectroscopy is likely to become a very powerful NDE method for detection of microfects and thickness measurement of thin film below the limit of ultrasonic distance resolution in the opaque materials, provides a useful information that cannot be obtained by a conventional ultrasonic measuring system. In this paper, we considered a thin film below the limit of ultrasonic distance resolution sandwitched between two substances as acoustical analysis model, demonstrated the usefulness of ultrasonic spectroscopic analysis technique using information of ultrasonic frequency for measurements of thin film thickness, regardless of interference phenomenon and phase reversion of ultrasonic waveform. By using frequency intervals(${\triangle}f$) of periodic minima from the ratio of reference power spectrum of reflective waveform obtained a sample to power spectrum of multiple reflective waves obtained interference phenomenon caused by ultrasonic waves reflected at the upper and lower surfaces of a thin layer, can measured even dimensions of interest are smaller than the ultrasonic wave length with simplicity and accuracy.

• Journal of the Korean Society for Nondestructive Testing
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• v.12 no.4
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• pp.26-31
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• 1993

In this paper, the axial force of high tension bolt is measured by using ultrasonic wave. In the case of the different materials the conclusion obtained are as follows : (1) The relation of the material quality of each high tension bolt and form(diameter or section area), and yield axial force can be observed. (2) As 0.1 is devided by the apparent elongation the measurement accuracy of high tension bolt can be achived. Also, it is founded that the Joint axial force of high tension bolt is determined by the yield force.

• Journal of the Korean Society for Nondestructive Testing
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• v.13 no.1
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• pp.21-28
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• 1993

If the infinitesimal delamination exists and the two waves can hardly be distinguished from each other on account of being much closer, we cannot measure the thickness of delamination by the time difference method. On this study, we calculated the thickness of infinitesimal delamination model by means of measuring echo height due to the deflection of material particles and utilized Newton Ring for optical measurement as a delamination model. From the result of Newton Ring expressed in the delamination model, we can calculate the infinitesimal delamination thickness up to $0.2{\sim}0.3{\mu}m$ due to the difference of acoustic impedance by the ratio of the echo height to the total reflection.

• Journal of the Korean Society for Nondestructive Testing
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• v.8 no.1
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• pp.6-11
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• 1988

The comparison and analysis of flaw detectability, flaw sizing methods and allowable criteria in accordance with the applicable codes, ASME and RCC-M Code, in ultrasonic examination of pressure vessel in nuclear power plants were studied. Accordding to the codes, calibration blocks were made. The artificial flaws such as disc and band types in test specimens were machined. They were detected and evaluated with etch code requirements and measured values were compared with the actual flaws.

• Journal of the Korean Society for Nondestructive Testing
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• v.11 no.2
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• pp.15-21
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• 1991

A wireless acoustic emission (AE) system has been developed for continuous monitoring of rotating structures such as turbine rotors. The cable between preamplifier and signal processing unit of a conventional AE system was replaced by the frequency modulated telemetry. The detected signals were modulated and transmitted as an RF signals by the transmitting module, then received and demodulated by the receiving module. The distance between the transmitting and the receiving antennas could be separated up to 10cm within a reasonable signal-to-noise ratio. The simulated AE signals generated by pencil lead breaks from rotating structures were successfully detected using the developed wireless AE monitoring system.