• Journal of Navigation and Port Research
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• v.39 no.3
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• pp.179-184
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• 2015

The purpose of this study is to provide appropriate methodology to ensure the safety and integrity of the production riser in offshore structure. In order to select integrity estimation methodology for production riser, level I and II Non-destructive Damage Evaluation (NDE) methods that were applied to existing structures are classified and reviewed. Numerical analysis is performed to verify the applicability and capability on damage detection of reviewed methods. As a result, the damage detection methodology using modal strain energy is more sensitive in detection of the damage than other methods. In practice, the number of sensors is limited due to the environmental and financial conditions. The impact on damage detection performance by reducing the number of sensors is systematically investigated through a series of numerical analyses and the results are discussed. The optimal number of sensor for the integrity estimation of production riser is recommended.

• Proceedings of the Acoustical Society of Korea Conference
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• 1985.10a
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• pp.47-49
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• 1985

In most of ultrasonic NDT(Non-Destructive Testing) equipments using A-scan display technic, it is one of the inconveniences that the user must be proficient in reading the displayed signals for the accurate decisions. In this study, a simple microprocessorized NDT machine for the flaw detection was developed. The operation of system is based on the conventional NDT system. The microprocessor detects the time delay between transmitted pulse and echos by counter-measure method. Then according to the scanning position, the location of flaw orthe other side of testing object is plotted on the CRT. The main advantages of the developed system are simplicity in handling, recording capability of measured data, and low cost.

• Journal of Power System Engineering
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• v.8 no.3
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• pp.52-57
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• 2004

A new non-destructive inspection technique has been developed. One characteristic of the technique is that defects are visualized by laser ray. Magnetic domains and domain walls of a magneto-optical sensor(MO sensor) are varied by the magnetic flux leaked by defects, and the variations are observed by the reflected light of the laser ray. The information of defect can remotely be inspected by this technique in a real time. This paper describes the results estimated on the 2-dimensional surface defects and opposite-side defects in a ferromagnetic material and the natural surface defect in a clutch disk wheel. The light region of a visible image and the magnitude of a reflected light increases as the input current of the magnetizer increases. The natural surface defect, that has not the width of crack's open mouth, can be also visualized like as 2-dimensional artificial defects.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.2
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• pp.111-117
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• 2011

Vibration monitoring is required for reliable thermosonic testing to decide whether sufficient vibration is achieved in each test for the detection of cracks. From a practical point of view, a cheaper and convenient monitoring method is better for the application to real tests. Therefore, the performance of different sensors for vibration monitoring was investigated and compared in this study to find a convenient and acceptable measurement method for thermosonics. Velocity measured by a laser vibrometer and strain provide an equivalent HI when measured at the same position. The microphone can provide a cheaper vibration monitoring device than the laser and the heating index calculated by a microphone signal shows similar characteristics to that calculated from velocity measured by the laser vibrometer. The microphone frequency response shows that it underestimates high frequency components but it is applicable to practical tests because it gives a conservative value of HI.

• Journal of the Korean Society of Safety
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• v.9 no.1
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• pp.28-30
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• 1994

Ultrasonic for MoSi$_2$/Y. C. Kim, C. K. Namkoong/MoSi$_2$in the silicides has excellence in the oxidation and corrosion resistence. When the solid state bonding sintered-MoSi$_2$/metal or the thermal sprayed coating by powder-MoSi$_2$on the metal are carried out, the defects may be occured at the bonded surface. So, the method for evaluating the existence of the defects by non-destructive inspection is strongly desired. Here, the characteristics of ultrasonic for sintered-MoSi$_2$are elucidated and the possibility of the detection of defects using by ultrasonic is investigated.

• Agricultural and Biosystems Engineering
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• v.2 no.2
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• pp.75-80
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• 2001

This paper describes method to diagnose abiotic stresses such ad low root temperature, low light intensity and high salinity in cucumber plants with several physiological instruments. The stresses could be detected by measuring and analyzing the differences in chlorophyll content, temperature difference between leaf and atmosphere and light absorptance at wavelengths of 480, 560, 710, 1420 and 1650nm. It was concluded that the stresses could be first diagnosed from the 3rd to 10th day after treatment and the overall accuracy of diagnosis was estimated between 25 and 75%. near-infrared spectrometer showed better and earlier detection than the other instruments investigated.

• Proceedings of the Korean Society of Computer Information Conference
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• 2013.07a
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• pp.271-273
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• 2013

본 논문에서는 비파괴 검사를 통하여 얻은 세라믹 영상에 퍼지 기법과 ART2 기법을 적용하여 결함을 검출하는 방법을 제안한다. 제안된 방법은 세라믹 소재로 얻어진 영상에서 결함의 구간을 설정하기 위해 퍼지 스트레칭 기법을 적용하여 명암도를 대비시킨다. 명암 대비가 강조된 영상에서 퍼지 이진화 기법을 적용한 후, 상/하 경계선에 가장 많이 분포된 곳을 Max, Min으로 설정하고, Max+20, Min-20을 결함 구간으로 설정한다. 설정한 결함 구간 내의 비파괴 세라믹 영상에서 ART2 알고리즘 기법을 적용하여 세라믹 영상의 결함을 검출한다. 본 논문에서 제안된 방법을 비파괴 세라믹 영상을 대상으로 실험한 결과, 제안된 방법이 기존의 세라믹 결함 검출 방법보다 비파괴 세라믹 영상에서 다양한 형태의 결함이 검출되는 것을 확인하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.429-436
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• 2004

For the in-situ health monitoring of critical members in civil infra-structures, ultrasonic guided Lamb waves-based non-destructive evaluation (NDE) is very suitable. However, a chief drawback of the Lamb wave techniques is that multiple modes exist at all frequencies and the modes are generally dispersive, which means that the received signals may be very complicated. To overcome these complications, selective transmitting and receiving of a single A/sub 0/ mode within a frequency range can be adopted. Furthermore, a wavelet technique can be utilized to decompose the Lamb wave response into wavelet coefficients as a tool for signal processing. The changes in the Lamb waves interacting with damages in the steel plates are successfully characterized by this wavelet technique, through the amplitude change of the wavelet coefficients. In this paper, the feasibility of detecting a line crack on the surface of a steel plate and loosened bolts in a joint steel specimen using the Lamb waves and the wavelet technique is investigated.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.193-195
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• 2010

본 논문에서는 비파괴 검사를 통하여 얻어진 항공 갑판 영상에서, 조직의 이상이나 결함의 정도를 자동으로 검출하는 방법을 제안한다. 비파괴 검사를 통하여 얻어진 항공 갑판 영상에서 감마상관 변환과 $7{\times}7$ 소벨 마스크와 $13{\times}13$ 소벨 마스크를 각각 적용하여 윤곽선을 추출한다. 추출된 윤곽선 영역을 평활화와 평균 이진화 기법을 적용하여 영상을 보정한다. 보정된 영상에서 침식 연산과 팽창 연산을 이용하여 잡음을 제거한 후, 라벨링 기법을 적용하여 항공 갑판의 결함 영역을 추출한다. 본 논문에서 제안한 방법을 다양한 항공 갑판 영상을 대상으로 실험한 결과, 기존의 방법보다 항공 갑판에서 결함을 추출하는데 효과적인 것을 확인하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1538-1541
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• 2005

For reliability evaluation of AC-PDP, one of the most important factor is sealing property. In this paper, the reliability evaluation test method of the commercialized sealing glass frit in AC-PDP was studied. 6 inch AC-PDP panels were tested for evaluation of sealing glass frit by vibration shock test, thermal shock test, non -destructive X-ray inspection, residual stress inspection and residual gas detection. These test methods are proposed as a standard for testing the reliability of sealing glass frit. The main failure mode of sealing glass frit in AC-PDP seems to be the crack propagation from thermal cycling rather than mechanical factor.