• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.1
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• pp.46-53
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• 2010

A Compton X-ray backscatter technique has been developed to quantitatively assess impact damage in quasi-isotropic laminated composites made by a drop-weight tester. X-ray backscatter imaging system with a slit-type camera is constructed to obtain a cross-sectional profile of impact-damaged laminated composites from the electron-density variation of the cross section. A nonlinear scattering model based on Boltsman equation is introduced to compute Compton X-ray backscattering field for the defect assessment. An adaptive filter is also used to reduce noises from many sources including quantum noise and irregular distributions of fibers and matrix in composites. Delaminations masked or distorted by the first delamination are detected and characterized effectively by the Compton X-ray backscatter technique, both in width and location, by application of error minimization algorithm.

• Journal of the Korean Society for Nondestructive Testing
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• v.37 no.1
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• pp.29-36
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• 2017

Recently, KTX (Korean Train Express) train stoppage accidents were mainly caused by malfunctioning equipment, aging and cracking of railway vehicles, crack breakages of brake disks, and breakages of brake disks. Breakage of brake disk can cause large-scale casualties such as high-speed collision and concern about derailment by hitting lower axle and wheel. Therefore, in this study, a brake disk with solid and ventilation type, which is the brake disk of a KTX train was modeled, and a dynamometer system was constructed to operate the disk. A Rayleigh wave was used to inspect the surface of the brake disk. An ultrasonic inspection module was developed for the brake disk by using a local immersion method due to the difficulty involved in ultrasonic inspection using an existing immersion method. In addition, the surface defects of the brake disk were evaluated using a dynamometer mock-up system and an ultrasonic inspection module of the brake disk.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.4
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• pp.307-314
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• 2004

A circumferential guided wave method was developed to detect the axial crack on the bent feeder pipe. Dispersion curves of circumferential guided waves were calculated as a function of curvature of the pipe. In the case of thin plate, i.e. infinite curvature, as the frequency increases, the $S_0$ and $A_0$ mode coincide and eventually become Rayleigh wave mode. In the case of pipe, however, as the curvature increases, the lowest modes do not coincide even in the high frequencies. Based on the analysis, a rocking technique using angle beam transducer was applied to detect an axial defect in the bent region of PHWR feeder pipe. Based on the analysis of experimenal data for artificial notches, the vibration modes of each signal were identified. It was found that the notches with the depth of )0% of wall thickness can be detected with the method.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.1229-1232
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• 2001

코일에 고주파전압을 걸면 교류자계가 발생하며 이 자게 내의 금속재료에 와전류가 발생하는데 와전류는 재료의 재질, 결함, 이종금속, 형상변화 등에 의해 그 발생상태가 다르기 때문에 검출용 코일에서 얻어진 신호성분을 해석함으로써 재료의 비파괴검사가 가능하다. 원자력발전소에서는 증기발생기와 열교환기를 정기적으로 이 와전류 탐상검사를 수행하고 결함상태를 평가하여 그 결과를 대용량 Media에 저장한다. 본 논문에서는 평가결과 정보를 추출하고 변환 처리하여 RDBMS에 입력 관리하는 과정과 다양한 형태의 열교환기 Tubesheet를 편집하는 기능, 사용자의 검색조건 선택에 따라 데이터베이스를 Query하여 Tubesheet에 Mapping 처리하는 기능, 검사주기 및 기기별로 평가결과를 비교 분석할 수 있는 통계/보고서 기기사양정보 및 검사정보관리 등 제반 Application 시스템 구현 결과를 소개한다.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.3
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• pp.275-283
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• 2002

To detect the position and depth of buried underground utilities, method of Ground Penetrating Radar(GPR) survey is the most commonly used. However, the skin-depth of GPR is very shallow, and in the places where subsurface materials are not homogeneous and are compose of clays and/or salts and gravels, GPR method has limitations in application and interpretation. The aim of this study is to overcome these limitations of GPR survey. For this purpose the site where the GPR survey is unsuccessful to detect the underground big pipes is selected, and soil tests were conducted to confirm the reason why GPR method was not applicable. Non-destructive high-frequency electromagnetic (HFEM) survey was newly developed and was applied in the study area to prove the effectiveness of this new technique. The frequency ranges $2kHz{\sim}4MHz$ and the skin depth is about 30m. The HFEM measures the electric field and magnetic field perpendicular to each other to get the impedance from which vertical electric resistivity distribution at the measured point can be deduced. By adopting the capacitive coupled electrodes, it can make the measuring time shorter, and can be applied to the places covered by asphalt an and/or concrete. In addition to the above mentioned advantages, noise due to high-voltage power line is much reduced by stacking the signals. As a result, the HFEM was successful in detecting the buried underground objects. Therefore this method is a promising new technique that can be applied in the lots of fields, such as geotechnical and archaeological surveys.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.4
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• pp.361-367
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• 2013

Many of the nuclear power plant pipe is used in high temperature and high pressure environment. Wall thinning frequently caused by the corrosion. These wall thinning in pipe is expected gradually increase as nuclear power become superannuated. Therefore there is need to evaluate wall thinning in pipe and corrosion defect by non-destructive method to prevent the accident of the nuclear power facility due to pipe corrosion. Especially for real-time assessment of the wall thinning that occurs in nuclear power plant pipe, the laser ultrasonic technology can be measured even in hard-to-reach areas, beyond the limits of earlier existing contact methods. In this study, the optical method using laser was applied for non-destructive and non-contact evaluation. Ultrasonic signals was acquired through generating ultrasonic by pulse laser and using laser interferometer. First the ultrasonic signal was detected in no wall thinning in pipe, then a longitudinal wave velocity was measured inside of pipe. Artificial wall thinning specimen compared to 20, 30, 40 and 50% of thickness of the pipe was produced and the longitudinal wave velocity was measured. It was possible to evaluate quantitatively the wall thinning area(internal defect depth) cause it was able to calculate the thickness of each specimen using measured longitudinal wave velocity.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.5
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• pp.465-471
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• 2013

A steam generator in nuclear power plant is a heatexchager which is used to convert water into steam from heat produced in a nuclear reactor core, and the steam produced in steam generator is delivered to the turbine to generate electricity. Because of damage to steam generator tubing may impair its ability to adequately perform required safety functions in terms of both structural integrity and leakage integrity, eddy current testing is periodically performed to evaluate the integrity of tubes in steam generator. This assessment is normally performed during a reactor refueling outage. Currently, the eddy current testing for steam generator of nuclear power plant in Korea is performed in accordance with KEPIC & ASME Code requirements, the eddy current testing system is consists of remote data acquisition unit and data analysis program to evaluate the acquired data. The KEPIC & ASME Code require that the electrical properties of remote data acquisition unit, such as total harmonic distortion, input & output impedance, amplifier linearity & stability, phase linearity, bandwidth & demodulation filter response, analog-to-digital conversion, and channel crosstalk shall be measured in accordance with the KEPIC & ASME Code requirements. In this paper, the measurement requirements of electrical properties for eddy current testing instrument described in KEPIC & ASME Code are presented, and the measurement results of newly developed eddy current testing instrument by KHNP(Korea Hydro & Nuclear Power Co., LTD) are presented.

• Proceedings of the Korean Magnestics Society Conference
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• 2004.12a
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• pp.181-182
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• 2004

• Proceedings of the KWS Conference
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• 2006.10a
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• pp.289-291
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• 2006

• Proceedings of the Korean Magnestics Society Conference
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• 2009.12a
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• pp.224-225
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• 2009