• 한국신뢰성학회지:신뢰성응용연구
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• 제18권3호
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• pp.240-249
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• 2018

Purpose: The purpose of this research is to find which technique, between the PAUT (Phased array ultrasonic test) that has been used widely in practice and RT (Radiographic test) that was used widely in the past, has the higher reliability as a non-destructive testing of welding points in water wall tubes. Methods: To evaluated the reliability of non-destructive testing, eleven test pieces that were fabricated intentionally, which have the most frequently occurred defect types in water wall tubes and then both the PAUT and RT were performed on those eleven test pieces to compare their reliability. Results: The differences of type of defect, length are occurred due to the characteristics of nondestructive testing. The RT could not detect the lack of fusion defect type in specimen #4 and #8 while PAUT could not detect the lateral crack and 1 mm size small porosity in specimen #11. Conclusion: It is concluded that applying both the RT and PAUT result the best reliability rather than applying only one test method, if it is possible, in nondestructive testing of weld water wall tube in thermal power plant boiler case.

• 한국컴퓨터정보학회논문지
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• 제21권9호
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• pp.45-49
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• 2016

In this study, an image processing algorithm was developed to increase readability of the images of specific parts of a KTX train acquired by using a mobile digital radiographic testing device in a situation where a running train is stopped. The image processing algorithm was realized by using a Visual C++ development tool. The algorithm developed in this study allows to select an interested region in the acquired images when the interested region is suspected to cause a problem, and applies a thinning process based Sobel operators to the selected region. The experimental results show that the readability of defect parts that are not visible to naked eyes was increased through edge detector. Application of the algorithm developed in this study may help to accurately read non-destructive inspection images.

• 한국산업융합학회 논문집
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• 제25권4_2호
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• pp.687-697
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• 2022

An automated system is needed for the effectiveness of non-destructive testing. In order to utilize the radiographic testing data accumulated in the film, the types of welding defects were classified into 9 and the shape of defects were analyzed. Data was preprocessed to use deep learning with high performance in image classification, and a combination of one-stage/two-stage method and convolutional neural networks/Transformer backbone was compared to confirm a model suitable for welding defect detection. The combination of two-stage, which can learn step-by-step, and deep-layered CNN backbone, showed the best performance with mean average precision 0.868.

• Journal of Electrical Engineering and Technology
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• 제7권6호
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• pp.1001-1008
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• 2012

Non-destructive testing (NDT) is a technique used in science and industry to evaluate the properties of a material without causing damage. In this paper we propose a method for segmenting radiographic images of welding in order to extract the welding defects which may occur during the welding process. We study different methods of level set and choose the model adapted to our application. The methods presented here take the property of local segmentation geodesic active contours and have the ability to change the topology automatically. The computation time is considerably reduced after taking into account a new level set function which eliminates the re-initialization procedure. Satisfactory results are obtained after applying this algorithm both on synthetic and real images.

• 보존과학회지
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• 제36권3호
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• pp.197-212
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• 2020

울산 하대유적에서 출토된 민고리자루칼을 방사선 비파괴조사와 미세조직 분석으로 환두부의 제작 방법과 재질 특성을 살펴보았다. 방사선 비파괴 조사법으로(X-ray, CT) 내부 구조를 확인한 결과, 제작 방법의 기본형식은 철 단일 소재로 칼 끝부터 환두부까지 일체형으로 제작한 단조품임을 확인하였다. 또한 미세조직 분석을 통해 살펴 본 제작기술은 '순철-형태가공, 순철-형태가공-침탄, 강-형태가공-담금질'의 세 가지 유형으로 분류할 수 있었다. 민고리자루칼 5점 중 4점의 환두부는 약 0.7% 내외인 공석강 정도의 탄소 함량을 가진다. 특히 환두부에서는 손잡이보다 증가된 탄소함량을 보이는데, 이는 손잡이 끝 부분을 세장한 형태로 만들고 둥글게 구부리는 과정에서 인성을 부여하기 위한 침탄 처리의 결과로 추정된다. 길이 60 cm 이하의 민고리자루칼 1점은 날 부위에 집중시킨 담금질을 통해 강한 인성을 부여하여 무기로서의 용도를 극대화시켰다. 반면 75 cm를 넘는 4점의 날 부위에서는 담금질 조직인 마르텐사이트가 관찰되지 않았다. 하지만 칼등 대비 날 부위의 탄소함량 증가나 결정립의 미세화는 실용기로서 사용이 가능했음을 보여준다. 2C말에서 4C초로 편년되는 울산 하대고분군 출토 민고리자루칼은 단조기술을 통해 일체형으로 제작하였으며, 사용 목적에 따라 제강, 열처리 기술을 적용하여 칼이 가지는 용도의 효과를 극대화시켜 제작하였다.

• 보존과학회지
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• 제37권3호
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• pp.220-231
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• 2021

문화재 방사선 비파괴 투과 조사 방식은 이미지플레이트(Image Plate, IP)를 사용하는 디지털 방사선영상시스템(Computed Radiography, CR)이 도입되면서 필름방식의 아날로그 이미지에서 점차 디지털 이미지로 교체되고 있다. 방사선 비파괴 투과 조사의 이미지 품질은 촬영 조건(관전압, 관전류, 노출시간), 영상 획득 매체, 촬영 거리, 유물의 두께 등이 영향을 미친다. 이 논문에서는 목재 문화재에 주로 사용되는 수종(소나무, 밤나무, 은행나무, 상수리나무)에 X선 선원의 투과 특성을 GE사(社)의 CR 영상 시스템을 통해 획득된 이미지의 그레이 스케일(Gray Scale)을 분석한 후 신호 대 잡음비(signal to noise ratio) 및 대조도를 평가하고, 이중-선 상질계(Duplex-wire image quality indicator), 구형파 차트(line-pair gauges), 선형 식별계(Image Quality Indicator)를 이용하여 이미지를 분석하였다.

• 비파괴검사학회지
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• 제33권1호
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• pp.63-68
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• 2013

Some essential components in nuclear power plants are periodically inspected using non-destructive examinations, for example ultrasonic, eddy current and radiographic examinations, in order to determine their integrity. These components include nuclear power plant items such as vessels, containments, piping systems, pumps, valves, tubes and core support structure. Steam generator tubes have an important safety role because they constitute one of the primary barriers between the radioactive and non-radioactive sides of the nuclear power plant. There is potential that if a tube bursts while a plant is operating, radioactivity from the primary coolant system could escape directly to the atmosphere. Therefore, in-service inspections are critical in maintaining steam generator tube integrity. In general, the eddy current testing is widely used for the inspection of steam generator tubes due to its high inspection speed and flaw detectability on non-magnetic tubes. However, it is not easy to analyze correctly eddy current signals because they are influenced by many factors. Therefore, the performance of eddy current data analysts for steam generator tubing should be demonstrated comprehensively. In Korea, the performance of steam generator tubing analysts has been demonstrated using the Qualified Data Analyst program. This paper describes the performance demonstration program for steam generator tubing analysts and its implementation results in Korea. The pass rate of domestic analysts for this program was 71.4%.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.171-173
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• 2005

To evaluate the applicability of dissimilar metal friction stir welding in automobile manufacturing process, friction stir welding trials were carried out for typical 5000 and 6000 series aluminum alloy sheets with 2mm thickness. The sound joints of A15052 and A16061-T6 alloys were successfully formed under a wide range of welding condition. Excellent weld ability has been obtained at a condition of rotating speed 2000rpm and travel speed 100mm/min, while a radiographic test also confirmed defect free joint for this condition. Through the Erichsen cup test, the plastic formability of the FSWelded joints was found to be about 83% of base metal.

• 한국기계가공학회지
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• 제19권1호
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• pp.43-48
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• 2020

At present, 24 nuclear power plants are in operation nationwide as the main power source responsible for about 27% of Korea's electricity, and five nuclear power plants are currently under construction. Issues of nuclear safety and reliability have always existed, but after the Fukushima accident, ensuring reliability has become an even more important issue for safety. Compared to other kinds of accidents, the initial response after a nuclear accident is more important than any other accident. Prior to accidents, it is important to be able to predict and judge the accident in advance for the sake of prevention. In this research, non-destructive inspection methods for existing pipe welds include radiographic, ultrasonic, magnetic particle practice, and liquid penetration testing. For this experiment, carbon steel pipes like that of the material used in nuclear pipes were adopted, and specimen welded to the flange (Flange) were manufactured. After testing, the weld specimen were not damaged through the infrared thermography (IRT) experiment. This study attempted to improve the safety of carbon steel pipes through a comparative analysis of finite element analysis.

• 비파괴검사학회지
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• 제29권5호
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• pp.485-492
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• 2009

열피로균열은 원자력발전소의 운영 과정에서 구조물의 수명을 결정짓는 문제로 정량적인 탐지가 어렵다. 현재 산업현장에서 구조물에 대한 건전성을 정량적으로 평가하기 위해서 radiographic탐상 및 초음파탐상, eddy current 등 다양한 종류의 비파괴검사 기술이 사용되고 있지만, 위에 열거한 비파괴탐상법의 경우 균열이 일정부분 진행된 이후에나 검출이 가능하다는 제한 사항이 있다. 이러한 이유로 구조물에 대한 연속적인 모니터링이 가능한 장점을 가진 음향방출탐상법(acoustic emission testing)이 대안적인 검사방법으로 제시되고 있다. 일반적으로 구조물이나 장비의 건전성에 영향을 미치는 모든 요인들이 음향방출 신호의 발생을 일으키기 때문에, 음향방출을 이용한 결함 탐상시 함께 발생하는 노이즈를 구분하는 일은 음향방출을 연구하는 대부분의 연구원의 주요 업무중 하나라고 할 수 있다. 이에 본 연구에서는 열피로 사이클 조건에서의 배관에 대한 음향방출 신호를 수집하여 유효한 균열 신호를 노이즈로부터 구분하고자 하는 목적으로 진행되었다. 그 방법으로 유사한 조건에서 실시한 결과를 이용하여 노이즈 필터링 조건을 설정하였으며, 균열의 신호를 찾아내기 위한 방법으로 음향파형(waveform) 구분법을 제시하였다. 이 실험에서 도출된 결과는 구조물의 결함을 탐지하는 실시간 연속적 모니터링 기술 개발에 대한 기초자료로 사용될 수 있을 것으로 기대된다.