• 비파괴검사학회지
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• 제5권2호
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• pp.12-21
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• 1986

Generally, butt welds with plate thickness $30{\sim}40mm$ are welded with groove angle $40^{\circ},\;60^{\circ},\;70^{\circ}$, etc. In the detection of internal weld defects, oblique testing with single probe has been mainly used. But, recently, in acccordance with enlargement of welded structure, thick plate with 100-200mm are frequently required. Thus I-groove welding method was lately developed and often used. In this case, most frequently generated defects are the lack of weld penetration and incomplete fusion between base metal and welding material. If we would detect by oblique testing with single probe, detecting flaw is occassionally impossible or very underestimated. In this study, the limit for applying tandem method was studied in dise and band type flaws. The estimation of flaw size could be within 10% error compared to real flaws.

• 한국가스학회지
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• 제12권2호
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• pp.53-56
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• 2008

용접 부위의 결함을 비파괴적으로 탐지하기 위하여 홀센서에 의해 누설자속을 측정할 수 있는 시스템과 4 종류의 용접결함을 갖는 기준시편을 제작하였다. 제작한 시스템으로 시편에 생성시킨 4 종류의 결함에서 누설된 자속을 측정하였고, 신호의 피크-피크 크기와 피크-피크 간의 간격에서 결함의 종류를 구분할 수 있는 가능성을 확인하였다.

• 방사성폐기물학회지
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• 제15권1호
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• pp.91-99
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• 2017

국내에서 개발중인 콘크리트 저장용기는 방사성 물질의 격납 건전성을 유지하기 위하여 내부에 캐니스터를 포함하고 있다. 본 논문에서는 콘크리트 저장용기 내부 캐니스터의 뚜껑 용접시, 용접시간 저감과 이에 따른 캐니스터 용접부의 구조적 건전성을 확보하기 위한 방안으로, 정상, 비정상 및 사고조건에서 캐니스터 용접부 균열을 진전시키는 하중에 의해 발생되는 균열 깊이를 분석하여, 용접부의 최대 허용결함깊이를 평가하였다. 정상, 비정상 및 사고조건에서의 구조해석은 범용 유한요소해석 프로그램인 ABAQUS를 사용하였으며, 허용결함깊이는 ASME B&PV Code Section XI에 따라 막응력과 조합하중에 대해 평가하였다. 평가결과 콘크리트 저장용기의 캐니스터 용접부의 허용결함깊이는 18.75 mm로 평가되었으며, 이는 NUREG-1536에서 권고하고 있는 임계결함깊이를 만족하고 있는 것으로 나타났다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.304-309
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• 2003

In this study, natural flaws in welding parts are classified using the signal pattern classification method. The storage digital oscilloscope including FFT function and enveloped waveform generator is used and the signal pattern recognition procedure is made up the digital signal processing, feature extraction, feature selection and classifier design. It is composed with and discussed using the distance classifier that is based on euclidean distance the empirical Bayesian classifier. Feature extraction is performed using the class-mean scatter criteria. The signal pattern classification method is applied to the signal pattern recognition of natural flaws.

• 비파괴검사학회지
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• 제23권1호
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• pp.38-44
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• 2003

원자력발전소의 안전성등급 기기에 적용되는 비파괴검사는 실제 결함을 실현한 시험편을 사용하여 결함탐지능력을 검증하도록 하는 기량검증이 요구되고 있다. 가동중인 원전에서 발생 가능한 균열으로는 기계적 피로균열, 열 피로균열 및 입계부식균열 등이 있으나 본 연구에서는 기계적 피로균열을 대상으로 하였다. 인장 피로하중을 사용하여 기계적 피로결함을 제조하기 위해서 시험편을 설계하였고 원하는 피로결함 파면의 조도를 얻기 위해서 인가하중의 크기 및 사이클 수를 조절하여 피로결함을 발생시켰다. 발생된 결함에 대한 정확한 크기와 위치에 대한 물리적 정보를 얻은 후에 결함이 설계된 크기와 위치에 존재하도록 기밀용접을 실시하였다. 기밀용접 후 잔여 용접 흠은 가스 텅스텐 아크용접 및 플럭스 코어드 아크용접으로 채워졌다. 최종 완성된 피로결함 시험편을 방사선투과검사 및 초음파탐상검사를 통하여 검사한 결과, 설계된 길이와 깊이로 피로결함이 형성되었음을 확인하였다.

• 비파괴검사학회지
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• 제27권3호
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• pp.231-238
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• 2007

Ultrasonic inspection of austenitic steel weldments is a truly difficult task due to complicated wave propagation phenomena such as beam skewing, splitting and distortion. In order to understand these phenomena and design proper inspection procedures, simulation is increasingly paid more attention to. This article addresses a ray tracing based approach to determine incident angle and position of optimal wave mode ultrasonic beam for flaw detection in anisotropic and inhomogeneous austenitic steel weldments. Specially, the optimal mode of ultrasonic wave wave is selected by ray tracing simulation, and an optimization approach based on ray tracing and bi-section search is proposed in order to find the ray path connecting two given points in weldments. With help of this approach, the optimal incident angle and position of ultrasonic beam can be determined for a given flaw position.

• Journal of Welding and Joining
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• 제31권6호
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• pp.107-111
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• 2013

The welding distortion is caused by welding heat in the structures which are widely used in shipbuilding and automotive industries, thus many researchers have proposed such methods to control the welding distortion through trials and numerical studies. The welding distortion has been the main cause of low productivity due to the structural strength degradation, apparent flaw, additional deformation caused by the process followed the current assembly step, and the increase of correction workload. The deformation of fillet welding is investigated in this study, and the influence of the rib height on the welding distortion is verified through the actual experiment. And the numerical analysis model using the FE software MSC.marc for analysis of welding distortion is proposed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.393-396
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• 1995

In this syudy, the researches classifying the artificial and natural flaws in welding parts are performed using the smart pattern recognition technology. For this purpose the smart signal pattern recognition package including the user defined function was developed and the total procedure including the digital signal processing,feature extraction , feature selection and classifier selection is treated by bulk. Specially it is composed with and discussed using the statistical classifier such as the linear disciminant function classifier, the empirical Bayesian classifier. Also, the smart pattern recognition technology is applied to classification problem of natural flaw(i.e multiple classification problem-crack,lack of penetration,lack of fusion,porosity,and slag inclusion, the planar and volumetric flaw classification problem). According to this results, if appropriately learned the neural network classifier is better than ststistical classifier in the classification problem of natural flaw. And it is possible to acquire the recognition rate of 80% above through it is different a little according to domain extracting the feature and the classifier.

• 한국압력기기공학회 논문집
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• 제11권2호
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• pp.20-24
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• 2015

During refueling Outage, In-service inspections(ISIs) for the Nuclear Power Plant components are mandatory requirement in accordance with ASME Code Sec. XI. Especially, in current ultrasonic testing is one of the most important NDT techniques that are used for volumetric examination methods for nuclear power plant components, and accurate sizing of flaw indication by UT is essential to assure the integrity of the components. However, ASME code specifies minimum requirement for vessel examination procedure, and so far many different flaw sizing approaches have been tried to apply. Through the Round Robin Test(RRT), the accuracy of ultrasonic flaw sizing using DAC techniques was measured with the mock-ups simulating typical pressure vessel welds. These mock-ups contain artificially introduced flaws of known size and location. This paper shows experimental comparison data on the accuracy of techniques using such as 6dB drop, 50%DAC, 20%DAC and 20%DAC with beam spread correction, and also shows that diverse DAC techniques can be effectively applied to the assessment of the flaw sizing for pressure vessel welds in the stage of welding and fabrication.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.287-292
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• 2004

In this study, we made a comparative study of backpropagation neural network and probabilistic neural network and bayesian classifier and perceptron as shape recognition algorithm of welding flaws. For this purpose, variables are applied the same to four algorithms. Here, feature variable is composed of time domain signal itself and frequency domain signal itself, Through this process, we confirmed advantages/disadvantages of four algorithms and identified application methods of few algorithms.