• 한국가스학회지
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• 제16권1호
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• pp.22-25
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• 2012

Welding and/or fusion in polyethylene(PE) system made on site is focused on the control of the welding or fusion process to follow proper procedure. The process control is important, but it is not sufficient for the long term reliability of a pipe system. To achieve the rate of failure close to zero, Non Destructive Testing(NDT) is necessary in addition to joining process control. For electrofusion joints several non-destructive testing methods are available. The ultrasonic phased array technique is possible to detect various defects including wire deviations and regions with lack of fusion. In this studies, testing was carried to detect the defect after electrofusion joining of polyethylene piping is utilized by the ultrasonic phased array technique. From testing data, ultrasonic phased array technique is recommended as a reliable non-destructive testing method.

• 한국정밀공학회지
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• 제26권11호
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• pp.55-61
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• 2009

The wall thinning defect of nuclear power pipe is mainly occurred by the affect of the flow accelerated corrosion (FAC) of fluid. This type of defect becomes the cause of damage or destruction of in carbon steel pipes. Therefore, it is very important to measure defect which is existed not only on the welding part but also on the whole field of pipe. This study use dual-beam Shearography, which can measure the out-of-plane deformation and the in-plane deformation by using another illuminated laser beam and simple image processing technique. And this study proposes Infrared thermography, which is a two-dimensional non-contact nondestructive evaluation that can detect internal defects from the thermal distribution by the inspection of infrared light radiated from the object surface. In this paper, defect of nuclear power pipe were, measured using dual-beam shearography and infrared thermography, quantitatively evaluated by the analysis of phase map and thermal image pattern.

• 한국산학기술학회논문지
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• 제15권10호
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• pp.6282-6288
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• 2014

본 논문은 용접 산업현장에서 많이 사용 되는 $CO_2$ 용접에서는 차량내부 및 탱크내부 용접에서 제어 패널을 볼 수 없는 곳, 작업장이 먼 곳 등에서 용접사가 용접을 하면서 용접조건에 맞는 전류와 전압을 조절할 수가 없고, 전류와 전압을 조절하기 위해 용접을 중단하고 잦은 이동으로 용접 구조물의 순간적인 냉각에 의해 용접결함이 발생된다. 본 연구에서는 기존의 $CO_2$ 용접기 3종류를 각각 사용하여 원격제어 토치의 용접에 대해 SS400 용접구조용 압연강재를 사용하여 원격제어 토치와 기존 $CO_2$ 용접 토치를 V형 맞대기 수직자세로 용접실험을 실시하고 용접 부의 표면비드 상태의 형상을 육안검사 관찰하고 또한 이를 침투탐상검사 및 굽힘 시험을 통해 용접부의 외관품질에 대하여 중점적으로 수행하여 용접결함 감소 및 기존 상용용접기에 교체사용에 대한 성능 및 호환성여부에 미치는 영향에 대해 평가하였다.

• 동력기계공학회지
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• 제14권5호
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• pp.36-40
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• 2010

The ultrasonic guided wave propagates along with the given structure's wall direction. Because of this specific character, the ultrasonic guided waves arc used in many other fields. Especially, it can be readily utilized for nondestructive inspection of various structures that are made up of gas pipes, heat exchanger tubes, and thin plates. Further, the guided wave technology can be readily utilized when inspecting pipes or thin plates which pose high risk of the accident but for which the nondestructive inspection itself is impossible because it is difficult to get to them since they are coated or buried underground. In the other hand, conventional ultrasonic testing such as thickness gauging uses bulk waves and only tests the region of structure immediately below the transducer. As a result of the application about inlet and outlet cooling water line using guided wave test, we conformed that the overall corrosions were in the lower side of the 304.8 mm inlet valve and these corrosions were engaged in not locally but through the lower side of the valve line. In the near future, we can expect that the detectable defect size is smaller than before along with the development of the sensing technology.

• 품질경영학회지
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• 제51권2호
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• pp.283-296
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• 2023

Purpose: The purpose of this study is to actually implement and verify whether welding defects can be detected in real time by utilizing deep learning AI solutions in the welding process of electric vehicle hairpin winding motors. Methods: AI's function and technological elements using synthetic neural network were applied to existing electric vehicle hairpin winding motor laser welding process by making special hardware for detecting electric vehicle hairpin motor laser welding defect. Results: As a result of the test applied to the welding process of the electric vehicle hairpin winding motor, it was confirmed that defects in the welding part were detected in real time. The accuracy of detection of welds was achieved at 0.99 based on mAP@95, and the accuracy of detection of defective parts was 1.18 based on FB-Score 1.5, which fell short of the target, so it will be supplemented by introducing additional lighting and camera settings and enhancement techniques in the future. Conclusion: This study is significant in that it improves the welding quality of hairpin winding motors of electric vehicles by applying domestic artificial intelligence solutions to laser welding operations of hairpin winding motors of electric vehicles. Defects of a manufacturing line can be corrected immediately through automatic welding inspection after laser welding of an electric vehicle hairpin winding motor, thus reducing waste throughput caused by welding failure in the final stage, reducing input costs and increasing product production.

• Journal of Welding and Joining
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• 제18권3호
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• pp.68-75
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• 2000

The incomplete penetration(IP) discontinuity in butt joint weld, which is detected during safety analysis of the steel bridge by nondestructive evaluation(NDE) method, is classified as unacceptable defect according to the NDE codes and standards. In fact, there are a little allowance in butt joint weld in the view point of design criterion, and also detected IP discontinuity should be classified and evaluated for the fatigue strength and residual life estimation. In this study, we performed fatigue test to evaluate the fatigue strength of high strength steel(SWS490A) containing IP discontinuities in various size, the results compared and classified according to the bridge construction standard specification which published by korea administration of construction and traffic. Experimental results could be used to evaluate and estimate the IP discontinuities considering different stress range in butt joint bridge weld during periodic safety inspection.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.194-196
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• 2005

Ultrasonic guided waves are gaining increasing attention for the inspection of platelike and rodlike structures. At the same time, inspection methods that do not require contact with the test piece are being developed for advanced applications. This paper capitalizes on recent advances in the areas of guided wave ultrasonics and noncontact ultrasonics to demonstrate a superior method for the nondestructive detection of thinning defects simulating hidden corrosion in thin aluminum plates. The proposed approach uses EMAT(electro-magnetic acoustic transducer) for the noncontact generation and detection of guided plate waves. Interesting features in the dispersive behavior of selected guided modes are used for the detection of plate thinning. It is shown that mode cutoff measurements provide a qualitative detection of thinning defects. Measurement of the mode group velocity can be also used to quantify of thinning depth.

• 한국지능시스템학회논문지
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• 제22권4호
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• pp.481-486
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• 2012

본 논문은 석유화학 플랜트 등의 결함을 자기자왜센서기술을 활용하여 주기적으로 검사하는 오프라인 모니터링이 가능한 'Health Monitoring System'의 개발과 그 활용성에 대해 확인하였다. 기존의 유도파 검사 방식은 용접부위 검사에는 적용할 수 없고, 일반적인 부위에서도 노이즈 및 반사파 등으로 검사의 정밀도에 한계를 갖고 있다. 본 기술은 주기적인 모니터링을 통해 결함의 진전에 따른 변위정보를 활용할 수 있음으로서, 더 정밀한 검사가 가능하기 때문에 석유화학 플랜트에서 매우 유용하게 활용될 수 있을 것으로 사료된다.

• 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.

• Steel and Composite Structures
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• 제17권6호
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• pp.851-865
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• 2014

Full penetration welded steel moment-resisting frame (SMRF) structures with welded box sections are widely employed in steel bridges, where a large number of steel bridges have been in operation for over fifty years in Japan. Welding defects such as incomplete penetration at the beam-column connections of these existing SMRF steel bridge piers were observed during inspection. Previous experiments conducted by the authors' team indicate that gusset stiffeners (termed fillets in this study) at the beam-web-to-column-web joint of the beam-column connections may play an important role on the seismic performance of the connections. This paper aims to experimentally study the effect of the fillet radius on seismic performance of the connections with large welding defects. Four specimens with different sizes of fillet radii were loaded under quasi-static incremental cyclic loading, where different load-displacement relations and cracking behaviors were observed. The experimental results show that, as the size of the fillet radius increases, the seismic performance of the connections can be greatly improved.