• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.5
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• pp.356-361
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• 2014

The eddy current testing performance directly affects the results of a steam generator tube integrity assessment because the integrity assessment of defected tubes is conducted based on eddy current testing results. This means that it may not be possible to accurately discriminate between adjacent flaws. This paper presents an investigation on the resolution of rotating pancake coils with multiple cracks and the effects on the structural integrity assessment of steam generator tubes.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.5
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• pp.321-328
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• 2006

In this study, the deformation oi wall thinning elbow is measured and the position of the internal thinning defect is found out by shearography. Shearography is an optical method which has applied to nondestructive testing (NDT) and the strain/stress and deformation analysis. This technique has the merit of the directly measuring the first derivative of displacement with sensitivity which can be adjusted by handling the tilt mirror in the interferometer. In this paper, we tested carbon steel pipe locally wall thinned and loaded internal pressure and the shearography was applied to measure the out-of-plane deformation of wall thinning elbow and to investigate the internal thinning defect of it. From the results, it was confirmed that this technique is proper to the practical application on the pipe line system with internal defect.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.4
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• pp.369-375
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• 2012

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.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.10a
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• pp.144-145
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• 2003

감자는 전세계 대부분의 국가에서 재배되고 있는 세계 4대 주곡 작물인 동시에 스낵류 시장에서도 중요한 부분을 차지하고 있다. 우리나라의 감자 가공산업은 1990년대 초부터 활기를 띠기 시작여하 현재 2,000억불의 매출을 달성하고 있다. 이중 우리나라 농민이 직접 생산한 감자를 원료로 사용하는 천연칩 감자 가공산업은 매출액을 기준으로 144억 (1997년)에서 700억 (2001년)으로 과거 10년 동안 괄목할 만한 성장을 하였다. 우리나라의 연간 감자 칩 원료용 가공용 감자 소요량은 총 51,600톤 (2002 년)으로 그중 40,600톤은 국내생산량으로 충당하고 나머지는 냉동감자를 수입하여 처리하고 있다. 가공원료용 감자는 괴경의 크기나 모양과 같은 외부품질과 환원당이나 고형분 함량과 같은 내부품질이 좋아야 한다. 하지만 가공용 감자의 내·외부품질이 좋게 판정되어도 내부갈색반점이나 중심공동과 같은 괴경 생리장해가 발생하면 원료용 감자로서의 상품 가치가 상실된다. 국내 칩 가공원료용 감자는 봄재배에서는 약 5 ∼ 7 ％, 여름재배에서는 10 ∼ 15 ％의 괴경 생리장해가 발생되고 있다. 현재 위와 같은 생리장해는 가공공장에서 감자를 잘라서 골라내거나 감자 칩을 만든 후 제거하는 방법을 쓰고 있다. 이에 감자를 수확 후 감자칩으로 가공하기 전에 생리장해가 발생한 감자를 제거하여 생산 공정에서의 불필요한 가공을 줄일 수 있는 방법이 개발되어야 할 필요성이 증대되고 있다. 최근, 농산물의 비파괴적 품질 평가와 선별에 있어서 가장 실용적이고 성공적인 기술 중의 하나는 농산물의 광학적 성질을 이용한 전기-광학 기술이다. 그중 X-선과 같이 파장이 짧은 방사 에너지는 대부분의 농산물을 투과하여 내부의 질량 밀도의 변화와 상관관계를 갖는 품질 인자를 비파괴적으로 평가하는데 적합하나 아직 국내에선 X-선을 이용한 가공용 감자의 내부 결함특성에 대한 연구는 이뤄지지 않고 있다. 이에 본 연구에서는 가공용 감자의 내부결함 특성중 하나인 내부동공의 X-선에 의한 특성을 본 연구소에 있는 X-선 발생장비로 측정해 보고 비파괴적인 방법으로 실시간 가능성을 시험하였다. 감자는 수원 농산물 도매시장에서 2003년산 가공용 감자 (품종:선농)를 구매하여 사용하였다. 감자내 내부동공은 35 ∼ 40 kV와 5.25 mA값으로 발생된 X-선에 의해 잘 검출되는 것으로 나타나, 현장에서 충분히 활용가능 할 것으로 판단되었다. 금후, 실시간으로 내부동공을 검출할 수 있는 시스템을 개발할 계획이다.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.6
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• pp.545-554
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• 2000

Compton X-ray backscatter technique has been used to quantitatively assess the impact damage in quasi-isotropic laminated composites and to obtain a cross-sectional profile of impact-damaged laminated composites from the density variation of the cross section. An adaptive filter is applied to the Compton backscattering data for the reconstruction and noise reduction from many sources including quantum noise, especially when the SNR(signal-to-noise ratio) of the image is relatively low. A nonlinear reconstruction model is also proposed to overcome distortion of the Compton backscatter image due to attenuation effects, beam hardening, and irregular distributions of the fibers and the matrix in composites. Delaminations masked or distorted by the first few delaminations near the front surface are detected and characterized both in width and location, by application of an error minimization algorithm.

• Journal of the Korean Professional Engineers Association
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• v.33 no.6
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• pp.23-29
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• 2000

The nondestructive tests(NDT) are widely applied at various industrial job sites to detect defects and flaws early and thus to diagnose the quality and integrity of components, structures and systems. This paper discusses the R&MD history of various nondestructive testing techniques, their applications and many technical as well as safety issues identified, particularly in the performance of radiography. Also discussed are the principles of inspection methods and NDT qualifications that should be applied at the industrial job sites. As a result, this paper provides suggestions for improvement in Government programs to promote th NDT industry, for more systematic operation through a direct with the owner, and also for improvement in working conditions for NDT workers.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.321-323
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• 2004

전자 제품에 사용되는 부품 ㆍ소재의 신뢰성 품질 평가를 위해 정밀한 모터의 제어기술, 첨단신호처리 기술, 압전소자 기술의 발달로 미세변화 계측의 재현성, 고분해능, 표면과 내부의 이미지관찰, 또한 미소부위에서 재료의 누설탄성표면파의 음속측정이 가능한 초음파현미경에 대한 연구가 최근 들어 활발히 진행되고 있다. (중략)

• Proceedings of the KAIS Fall Conference
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• 2005.05a
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• pp.151-154
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• 2005

In this paper, we present a ultrasonic speckle suppression method for centrifugal-casted stainless steel sample by computer simulations of a flaw enhancement algorithm. Because of their practical importance in welds, the ultrasonic signal obtained from heat-affected zone or welds are investigated for computer simulation. The results for computer simulation present the more enhanced flaw-visibility and speckle suppression than the compared two techniques.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.5
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• pp.494-499
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• 2011

This paper presents the biomechanical analysis and evaluation technology of musculoskeletal system by multi-body human dynamic model and 3-D motion capture data. First, medical image based geometric model and material properties of tissue were used to develop the human dynamic model and 3-D motion capture data based motion analysis techniques were develop to quantify the in-vivo joint kinematics, joint moment, joint force, and muscle force. Walking and push-up motion was investigated using the developed model. The present model and technologies would be useful to apply the biomechanical analysis and evaluation of human activities.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.6
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• pp.504-509
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• 2016

Defects in dissimilar metal welds are reported to be on the increase during the operating lifespan and aging of nuclear power plants. In Korea, reported cases of defects due to dissimilar metal welds include the drain nozzle of a steam generator and RCS hot tube sampling nozzles. Therefore, there is an urgent need to develop a reliable automated nondestructive inspection technique and a system for the inspection of dissimilar metal welds of small diameter nozzles in a high radiation area of a nuclear power plant. In this study, to ensure effective defect inspection of small diameter nozzles (RCS high-temperature tube sampling nozzle) of a nuclear power plant, three different methods were developed. These include: (1) optimum inspection probe design by beam simulation, (2) multi-directions UT optimum inspection technique for the inspection of small diameters of different welded parts, and (3) remote control automatic inspection system. The developed technique and systems have been verified to be suitable for use in the inspection of defects in smaller diameter nozzles in nuclear power plants.