• 비파괴검사학회지
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• 제24권4호
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• pp.378-383
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• 2004

국내 원자력발전소의 Class1과 Class2 배관검사에 적용할 수 있는 초음파탐상 검사자, 장비 그리고 절차서에 대한 한국형 기량검증(KPD) 시스템을 구축하였다. PD 방법을 적용한 검사결과와 전통적인 dB-drop 방법을 이용한 검사결과를 상호 비교하기 위하여 Round Robin Test(RRT)를 수행하였다. RRT 결과는 PD 방법의 신뢰성이 dB Drop 방법보다 우수한 것으로 나타났다. 이러한 결과로부터 원자력발전소 가동중검사에 PD 방법을 적용함으로써 초음파탐상검사 결과의 신뢰성이 더욱 향상될 것으로 기대된다.

• 비파괴검사학회지
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• 제20권1호
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• pp.46-53
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• 2000

석유화학 설비 등과 같은 노출 배관의 결함을 검출하는데 효율적으로 이용될 수 있는 자왜형 초음파 센서를 제작하였다. 최대의 초음파 발생 효율을 얻기 위한 최적 조건을 설정하였으며, 실험에 사용된 배관의 경우 $250{\sim}350Oe$의 정자기장이 최적이었으며, 180kHz의 주파수를 갖는 초음파를 발생시키기 위해서는 15mm 폭의 코일을 사용하는 것이 가장 좋았다. 최적의 조건에서 발생된 초음파는 50m 이상을 충분히 진행할 수 있으며, 결함의 단면적이 증가함에 따라 수신된 결함 신호는 직선적으로 증가함을 확인하였다.

• 비파괴검사학회지
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• 제20권6호
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• pp.501-510
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• 2000

초음파 에코파형의 시간-주파수해석법으로 Wigner 분포와 웨이브렛 변환 등과 같은 새로운 신호처리 기법이 비파괴평가 분야에 널리 응용되고 있다. 본 연구에서는 웨이브렛 변환(wavelet transform)에 의한 음속과 감쇠계수의 주파수의존성과 초음파 결함신호의 잡음제거의 유용성 유무를 실험적으로 검증하였다. Gabor 함수를 웨이브렛의 기본함수로 사용하였다. 초음파의 에코파형에 포함된 각 주파수성분의 속도와 감쇠계수의 주파수의존성을 추정할 수 있었으며, 초음파탐상에서 결함의 검출능 향상과 결함크기 산정의 정량화에 접근하기 위해 웨이브렛 변환에 의한 S/N비 신호처리 시뮬레이션 결과를 오스테나이트강 스테인레스 용접부에 가공한 EDM 노치의 초음파 결함신호에 적용한 결과 임상에코를 저감하고 S/N비를 개선하는 것이 가능하였다.

• 비파괴검사학회지
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• 제28권3호
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• pp.263-272
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• 2008

Many technical methods are used for nondestructive testing field for solid materials. Among those, ultrasonic inspection methods are widely used and one of the popular methods involves the extraction of an appropriate set of features followed by the use of a neural network for the classification of the signals in the feature space. This paper describes an approach which uses LMS method to determine the coordinates of the ultrasonic probe followed by the use of SAFT with centroid technique to estimate the location of the ultrasonic reflector. The method is employed for classifying UT-NDE signals from the steam generator tubes in a nuclear power plant. The classification results are presented for the ultrasonic signals from cracks and deposits within steam generator tubes.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 추계학술대회 논문집
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• pp.60-65
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• 1998

Recently, It is gradually raised necessity that thickness of thin film is measured accuracy and managed in industrial circles and medical world. Ultrasonic Signal processing method is likely to become a very powerful method for NDE method of detection of microdefects and thickness measurement of thin film below the limit of Ultrasonic distance resolution in the opaque materials, provides useful information that cannot be obtained by a conventional measuring system. In the present research, considering a thin film below the limit of Ultrasonic distance resolution sandwiched between three substances as acoustical analysis model, demonstrated the usefulness of ultrasonic Signal processing technique using information of ultrasonic frequency for NDE of measurements of thin film thickness, sound velocity, and step height, regardless of interference phenomenon

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.585-590
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• 2000

Recently, It is gradually raised necessity that thickness of thin film is measured accuracy and managed in industrial circles and medical world. Ultrasonic Signal processing method is likely to become a very powerful method for NDE method of detection of microdefects and thickness measurement of thin film below the limit of Ultrasonic distance resolution in the opaque materials, provides useful information that cannot be obtained by a conventional measuring system. In the present research, considering a thin film below the limit of ultrasonic distance resolution sandwiched between three substances as acoustical analysis model, demonstrated the usefulness of ultrasonic Signal processing technique using information of ultrasonic frequency for NDE of measurements of thin film thickness, sound velocity, and step height, regardless of interference phenomenon. Numeral information was deduced and quantified effective information from the image. Also, pattern recognition of a defected input image was performed by neural network algorithm. Input pattern of various numeral was composed combinationally, and then, it was studied by neural network. Furthermore, possibility of pattern recognition was confirmed on artifical defected input data formed by simulation. Finally, application on unknown input pattern was also examined.

• International Journal of Reliability and Applications
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• 제5권1호
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• pp.25-36
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• 2004

Ultrasonic inspection system consist of the examination procedures, equipment, and operators. The reliability of nondestructive testing is influenced by the inspection environment, materials and types of defect. It is very difficult to estimate the reliability of NDT due to the various factors. Piping inspection round robin was conducted to quantify the capability of ultrasonic inspection during in-service. In this study, the models for predicting the ultrasonic NDE reliability by logistic model and linear regression model are discussed. The utility of the NDT reliability assessment is verified by the analysis of the data from round robin test with these models.

• 한국생산제조학회지
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• 제5권4호
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• pp.38-46
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• 1996

This paper discusses the feasibility of Ultrasonic Nondestructive Evaluation (UNDE) technique for sport weld quality. Ultrasonic c-scan image assisted by image processing technique was used for Nondestructive Evaluation(NDE) of spot weld quality. Ultrasonic testing results obtained were confirmed and compared by Optical Microscope and SAM(Scanning Acoustic Mircroscope) observation of the spot-weld cross section, The results show that the nugget dinameter can be successfully measured with the accuracy of 0.5mm. It was ascertained that ultrasonic c-scan technique is very effective method for the sake of the approach to the quantitative measurement of nugget diameter and the discrimination of the corona bond from nugget. Additional support for the above conclusions is provided by the results for galvanized steel. The ultrasonic results for galvanized welds generally correspond to the results for uncoated steel. Finally, it was found that the above-mentioned technique can be sufficiently applied to NDE method for securing the Quality Assurance(QA) of spot welded products in production line.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.123-127
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• 1997

Recently, it is gradually raised necessity that interface is measured accurately and managed in industrial circles and medical world, An Ultrasonic wave transmitted from a focused beam transducer is being expected as a powerful tool for NDE of micro-defect. The ultrasonic NDE of the defect is based on the form of the wave reflected form the interface In this study, regarding to the thickness of film which is in opaque object and thickness measurement was done by MEM-cepstrum analysis of received ultrasonic wave. In measument results, film thickness which is beyond distance resolution capacity was measured accurately. Also, automatically repeated discrimination analysis method can be decided in the category of all kinds of defects on semiconductor package.

• 비파괴검사학회지
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• 제14권3호
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• pp.172-176
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• 1994

핀-핑거형 터빈 동익 루트의 사각 초음파탐상에서의 기하신호가 해석된다. 동익루트의 기하가 설명되고, 기하신호가 형성되기 위한 반사조건들이 제시된다. 그리고, 이 기하신호의 빔경로에 관한 일반식들이 유도되고 검증된다. 이 기하신호는 리가먼트 모서리 신호이며, 그 위치와 진폭은 핀홀과 리가먼트의 크기 및 탐촉자의 빔지향 특성으로부터 결정될 수 있다는 것이 보여진다.