• 대한기계학회논문집A
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• 제27권8호
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• pp.1295-1302
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• 2003

In order to evaluate a failure behavior of pipe with notch-type wall thinning, the present study performed full-scale pipe tests using the 102mm, Schedule 80 pipe specimen simulated notch- and circular-type thinning defects. The pipe tests were conducted under the conditions of both monotonic and cyclic bending moment at a constant internal pressure of 10 MPa. From the results. of experiment the failure mode, load carrying capacity, deformation ability, and fatigue life of a notch-type wall thinned pipe were investigated, and they were compared with those of a circular-type wall thinned pipe. The failure mode of notched pipe was similar to that of circular-type thinned pipe under the monotonic bending load. Under the cyclic bending load, however, the mode was clearly distinguished with variation in the shape of wall thinning. The load carrying capacity of a pipe containing notch-type wall thinning was about the same or slightly lower than that of a pipe containing circular-type wall thinning when the thinning area was subjected to tensile stress, whereas it was higher than that of a pipe containing circular-type thinning defect when the thinning area was subjected to compressive stress. On the other hand, the deformation ability and fatigue life of a notch-type wall thinned pipe was lower than those of a circular-type wall thinned pipe.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 추계학술대회 논문집
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• pp.329-330
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• 2008

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.310-313
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• 2007

This paper covers finite element simulations to evaluate the bending limit of double pipe for tube-hydroforming. The tube-hydroforming process starts with a straight precut tube. The tube is often prebent in a rotary draw bending machine to fit the hydroforming tool. During the bending the tube undergoes significant deformation. So forming defects such as wrinkling, thinning and flattening are generated in the tube. Consequently we analyzed the effect of process parameters in rotary draw bending process and searched the optimized combination of process parameters to minimize the forming defects using orthogonal arrays. The characteristic to evaluate the effects of the process parameters is the bending angle which wrinkling is generated, we define the bending angle at that time as bending limit. Of many process parameters, the process parameters of the bending process such as gab between inner and outer tube, boosting force, dimensions of mandrel were analyzed. And we observed the deformation modes of bent double pipe at specific bending angle in each parameter combination.

• 한국가스학회지
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• 제8권3호
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• pp.1-7
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• 2004

최근 가스관용으로 압력손실이 큰 동관의 사용은 점차 줄어들고 있는 추세이며, 한편으로는 폴리에틸렌관이 신소재배관재료로서 사용되어 지고 있다. 폴리에틸렌관은 화학적으로 안정성이 높아 부식에 강하고 반영구적으로 사용할 수 있으며, 유연성이 좋아 설치와 유지관리가 편한 장점이 있다. 그러나 외부에 노출되었을 때 쉽게 열화되므로, 주로 저압가스용 매설배관으로서 사용하고 있는 실정이다 그러나 매설배관으로 사용되는 폴리에틸렌관의 사용 중에 발생하는 결함에 대한 비파괴적 평가에 대한 연구는 거의 없다. 본 연구에서는 폴리에틸렌 배관의 건전성을 평가하기 위해 다양한 결함을 상정하여 볼 베어링 충격시험에 따른 음향방출에 의한 신호특성을 평가하였다. 폴리에틸렌 배관의 결함 형상에 따라 파형 및 중심주파수의 구별이 가능하였다. 특히, 노치결함이 있는 경우 노치의 각도와 깊이에 따라 AE신호의 특성이 다르게 나타났다.

• 비파괴검사학회지
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• 제33권4호
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• pp.323-329
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• 2013

위상잠금 적외선 열화상 기법을 이용하여 원전 배관의 결함 검출 및 각도별 결함 검출 조건에 관한 연구를 수행하였다. 결함의 가공은 감육 길이, 원주방향 각도, 감육 깊이를 변화시켜 결함조건을 가공하였다. 사용된 장비는 적외선 열화상 카메라와 1 kW용량의 halogen lamp 2개를 사용하였으며, halogen lamp와 대상 배관과의 거리는 2 m로 고정시켜 실험을 수행하였다. 실험결과의 분석을 위하여 온도분포, 위상 데이터를 확보하고, 이를 분석하여 결함 길이를 측정하였다. 이 연구를 통해 각도별로 나타나는 감육 결함의 검출 형태를 파악함으로서 실제 발전소의 배관에 나타나는 다양한 각도의 결함의 분석이 가능하다. 적외선 열화상 데이터보다 위상잠금 적외선 열화상 데이터가 측정 결과의 신뢰도가 높았다.

• 비파괴검사학회지
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• 제29권5호
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• pp.442-449
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• 2009

스테인레스 스틸 배관의 결함에 대한 MsS의 비틀림모드 신호와 BEM 모델링의 SH모드 신호의 특성을 살펴보았다. 비틀림모드 신호와 SH모드신호의 비교를 위해 스테인레스 스틸 배관의 결함은 깊이와 폭을 달리하면서 원주방향으로 360도 가공하였다. MsS의 비틀림모드 신호분석 결과 원주방향 결함을 모두 탐지하였으며 깊이 변화에 따라 신호 진폭의 변화가 확인되었다. 하지만 원주방향 결함의 폭 변화는 일정한 경향이 나타나지 않았다. BEM 모델링의 SH 모드 신호 분석 결과 깊이 변화의 경우 비틀림모드 신호와 유사한 결과가 나타났지만, 폭 변화는 신호 진폭의 변화가 일어났다. 본 연구를 통하여 배관의 원주방향 결함에 대한 비틀림모드와 SH모드의 비교 분석을 통하여 신호 특성을 확인하였고 배관의 축대칭 결함에 대해 SH모드 모델링으로도 신호 예측이 가능함을 알 수 있었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.219-219
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• 2000

A Plate type pipe is used for heat exchange in radiator of a vehicle. The pipe has several rooms through which water flows and heat is dissipated into outside . In the case that there are small holes, cracks or some scratches on the plate, the radiators lost their functions due to Leakage. This may result in overheating of engine in a car. Thus, we need to perform the entire inspection of the plate type pipe in advance before assembling the radiator. In manufacturing process of the plate type pipe, the productive speed is very high and that may be performed continuously. So, there is no room to perform the outlook inspection by typical image processing techniques. This paper proposes a new method to inspect the outlook surface of the plate type pipe automatically with high speed. Especially, the sequential processing technique of an algorithm which detects defects on the surfaces of the plate type pipe is proposed for line scan camera which captures line image. To evaluate the inspection performance, a series of experiments is performed.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.500-502
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• 2008

In generally, a high pressure fuel injection pipe has been often used as a fuel supply line in automobiles or other diesel engines. Such conventional high pressure fuel injection pipe, however, has suffered from the problem that is folding and hair cracks created therein. The defects can be locally formed in the inner wall surface of the pipe at the connecting head leading to a flow path when the pipe is deformed by the heading process. In the study, in order to prevent the folding in the inner wall surface of the pipe during the heading process, FE-analysis has been used in the die design.

• 한국지진공학회논문집
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• 제27권6호
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• pp.283-291
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• 2023

Unlike other facilities, maintaining processes is essential in industrial facilities. Pipe racks, which support pipes of various diameters, are important structures used in industrial facilities. Since the transport process of pipes directly affects the operation of industrial facilities, a fragility curve should be derived based on considering not only the pipe racks' structural safety but also the pipes' transport process. There are several studies where the fragility curves have been determined based on the structural behavior of pipe racks. However, few studies consider the damage criteria of pipes to ensure the transportation process, such as local buckling and tensile failure with surface defects. In this study, an analysis model of a typical straight pipe rack used in domestic industrial facilities is constructed, and incremental dynamic analysis using nonlinear response history analysis is performed to estimate the parameters of the fragility curve by the maximum likelihood estimation. In addition, the pipe rack's structural behavior and the pipe's damage criteria are considered the limit state for the fragility curve. The limit states considered in this paper to evaluate fragility curves are more reasonable to ensure the transportation process of the pipe systems.

• 한국기계가공학회지
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• 제7권3호
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• pp.47-49
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• 2008

The brake pipe is important part in automobile. The brake pipe have to prevent crack, fracture and defects for braking in safety. Especially, shape of ends of pipe has influence on ability of brake. Based on the procedure of process design, in this paper, the forming operation is designed by finite element method. Design variable and response value was selected shape of die and damage factor. To improve die that performed FEM and compared results of two types of die.