• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.7-10
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• 2007

In case of large steel water pipe, it have been observed that its fracture mostly occurs due to the complicated outside fatigue load on the pipe in the underground. It is also well known that its damage and leakage happen mainly in a weld zone. In this study we evaluated the fatigue characteristics based on size effect and residual stress by comparing the test results on the standard specimen collected from real pipe with those on full scale pipe.

• Journal of Welding and Joining
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• 제32권5호
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• pp.13-20
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• 2014

A brief overview is given of the corrosion and hydrogen diffusion behaviors of high strength pipe steel in sour environment. Firstly, hydrogen adsorption and diffusion mechanism of the pipe steel is introduced. Secondly, the effect of iron sulfide film precipitated as a result of the corrosion reaction on the steel surface on hydrogen reduction reaction and subsequent hydrogen permeation through the steel is discussed. Moreover, the hydrogen diffusion behavior of the pipe steel under tensile stress in both elastic and plastic ranges is reviewed based on a number of experimental permeation data and theoretical models describing the hydrogen diffusion and trapping phenomena in the steel. It is hoped that this paper will result in significant academic contributions in the field of corrosion and hydrogen related problems of the pipe steel used in sour environment.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.699-704
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• 2002

The pipe with a long-neck flange is widely used in power plants, chemical plants, and shipbuilding companies. New the pipe with a long-neck flange is manufactured by welding a thick flange to a pipe. But this long-neck flange pipe has some deflects in the welding region such as unfitting and local thermal fatigue, which weaken the strength around the neck of the flange. Moreover, after welding the flange, the contacting surfaces of the flange have to be machined flat. So, that is uneconomical. Therefore, to solve the above problems of the long-neck flange pipe, a new process, which has no defects around the flange neck, is required. In this study, three forming processes are suggested to get an enhanced long-neck flange. First suggested process consists of conical terming and flange forming. Second and third suggested processes consist of the bulging of a long pipe locally heated by induction coils and the flange forming. The differences between second and third suggestions are the thickness and local heating area of the pipe. That is, the thickness of the initial pipe of third suggestion is larger than that of the final product, and the local heating area is smaller than that of second suggestion. These three suggestions fur forming a long-neck flange are simulated by FE analyses with a commercial cede DEFORM 2D. Especially, the theoretical result of FE analysis on the first suggestion fur forming a long-neck flange is verified by the experiment with aluminum 6063 pipes. From the theoretical and experimental results, it is concluded that three suggested processes are very useful in order to manufacture the pipe with a long-neck flange without any deflects.

• 한국정밀공학회지
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• 제19권8호
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• pp.212-219
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• 2002

The pipe with a long-neck flange is widely used in power plants, chemical plants, and shipbuilding companies. Now the pipe with a long-neck flange is manufactured by welding a thick flange to a pipe. But this long-neck flange pipe has some defects in the welding region such as unfitting and local thermal fatigue, which weaken the strength around the neck of the flange. Moreover, after welding the flange, the contacting surfaces of the flange have to be machined flat. So, that is uneconomical. Therefore, to solve the above problems of the long-neck flange pipe, a new process, which has no defects around the flange neck, is required. In this study, three forming processes are suggested to get an enhanced long-neck flange. First suggested process consists of conical forming and flange forming. Second and third suggested processes consist of the bulging of a long pipe locally heated by induction coils and the flange forming. The differences between second and third suggestions are the thickness and local heating area of the pipe. That is, the thickness of the initial pipe of third suggestion is larger than that of the final product, and the local heating area is smaller than that of second suggestion. These three suggestions for forming a long-neck flange are simulated by FE analyses with a commercial code DEFORM 2D. Especially, the theoretical result of FE analysis on the first suggestion for forming a long-neck flange is verified by the experiment with aluminum 6063 pipes. From the theoretical and experimental results, it is concluded that three suggested processes are very useful in order to manufacture the pipe with a long-neck flange without any defects.

• 한국정밀공학회지
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• 제12권9호
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• pp.86-94
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• 1995

Bead shape in high frequency electric resistance (HER) pipe welding gives useful information on judging current welding conditon. In most welding process, heat input is controlled by skilled operators observing color and shape of bead. In this paper, a visual monitoring system is designed to observe bead shape in HERW pipe welding process by using structured light beam and a C.I.D(Charge injection device) camera. To avoid some difficul- ties arising in extracting stable features of stripe pattern and classifying the extracted features, Kohonen neural network is used to classify such bead shapes. The experimental results show accurate classification performance of the proposed method.

• 한국해양공학회지
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• 제21권5호
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• pp.39-46
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• 2007

The sea water pipe of a ship's engine room is a severely corrosive environment caused by fast flawing sea water containing chloride ions and high conductivity. Therefore, leaking of sea water may occur as a result of local corrosion of the welded zone. Leaking is usually controlled by various welding methods. In this study, when the sea water pipe is welded with certain welding methods and welding electrodes, the corrosion resistance of WM (Welding metal) and HAZ (Heat affected zone) was investigated using electrochemical methods. Although the corrosion potential of the HAZ is higher than that of WM, the corrosion resistance of WM is superior to HAZ. However, when WM and HAZ are both opened to the sea water, the WM part with the anode was more seriously corroded than was the HAZ of the cathode by performance of a galvanic cell due to difference of the corrosion potential between HAZ and WM. In particular TIG welding showed relatively good results in corrosion resistance of both HAZ and WM compared to other welding methods.

• 한국지반공학회논문집
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• 제16권1호
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• pp.235-241
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• 2000

기존의 장대강관말뚝 공법들은 말뚝의 용접이음이나 관내토의 제거 작업으로 인하여 공비와 공기가 증가하고 이들 작업이 진행되는 동안 시간효과에 의하여 말뚝의 관입 저항이 증가하여 타입이 어려워지는 등 각종 비경제적인 문제점들을 갖고 있다. 이러한 문제들을 해결하기 위하여 본 연구에서는 새로운 장대강관말뚝 공법을 제안하였으며, 제안된 공법의 시공성과 경제성을 분석하기 위하여 모형말뚝시험을 행하였다. 시험결과 새로 제안된 장대말뚝공법은 기존 공법에 비해 공기와 공비는 절감되고 지지력은 증가시키는 것으로 나타났다.

• 에너지공학
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• 제24권1호
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• pp.1-9
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• 2015

Welding defects affect the performance of welded pipe joints. In this study, a three point bend test of welded steel and medium density polyethylene (MDPE) pipe joints with defects of various defect locations and defect materials was studied using the finite element method. The defect was assumed to be located at 12 o'clock, 3 o'clock or 6 o'clock direction. The results showed that pipes failed more easily on the compression side due to stress or local buckling. The air defect was more dangerous than the steel defect if the defect was located in the compression side; otherwise, the defect material effect on the integrity of pipes was ignorable. It is argued that the integrity of pipes with defects in the compression side is weaker than that in other regions, and the defect should be located in the compression side or the 12 o'clock position in the three point bend test to maximize the effect of defect existence on the pipe structural integrity.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1997년도 특별강연 및 추계학술발표 개요집
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• pp.179-183
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• 1997

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1997년도 특별강연 및 추계학술발표 개요집
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• pp.224-228
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• 1997