• 한국산학기술학회논문지
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• 제12권11호
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• pp.5188-5193
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• 2011

본 연구는 변압기 내부에 있는 절연유의 온도제어를 목적으로 열전소자인 펠티어 소자와 무전력 냉각장치인 Heat pipe를 이용한 다양한 시스템을 설계 제작하여, 절연유의 용량별 온도제어에 적용함으로써 최적의 시스템을 구현할 수 있었다. 실험을 통하여 $60^{\circ}C$ 이내의 상태에서는 Heat pipe 100 W + 펠티어 100 W의 조합형이 순수 Heat pipe 300 W보다 탁월한 성능을 확인할 수 있었다. 이를 통하여 조합형의 적정설계 방식이 우수하다는 것을 증명하고, 조합형을 사용함으로써 전기절약 효과와 수배전반의 보다 더 효율적인 관리에 기여하고자 한다.

• 한국해양공학회지
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• 제24권5호
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• pp.88-93
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• 2010

Many pipes that are arranged longitudinally in ships have loops at intervals to prevent the failure of the pipes as they absorb large portions of the axial load caused by the bending of the hull girder and/or thermal loads when the pipes are carrying very hot fluids. Since the loops are curved at corners, an efficient method for conducting the structural analyses of these curved portions is required. In this paper, a pipe loop was analyzed by an analytical method and by the finite-element method in four different ways, i.e., based on straight-beam elements, curved-beam elements, 2-D shell elements, and 3-D solid elements. The results of the five analyses were compared to check the validity of the current curved-beam theory. The paper includes some suggestions on how to analyze the pipe loops efficiently.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.397-402
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• 2003

Fracture resistance curves for concerned materials are required in order to perform elastic-plastic fracture mechanical analyses. Fracture resistance curve is built with J-integral values and crack extension values. The objective of this paper is to apply the load ratio method to the measurement of the crack length for the real scale pipe specimen. For these, the fracture test using the real scale pipe specimen and finite element analyses were performed. A 4-point bending jig was manufactured for the pipe test and the direct current potential drop method and the load ratio method was used to measure the crack extension and the length for the real scale pipe test. Finite element analyses about the compliance of the pipe specimen were executed for applying the load ratio method according to the crack length.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1630-1633
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• 2003

Hair pin bending machine is pipe forming machine consisting of heat exchanger product system. Hair pin produced by these machine is pathway of refrigerant and play a important role improving the performance and productivity of heat exchanger. The core technology of hair pin bending machine is forming the straight pipe into U-type without any defaults. Therefore, this paper study the relation between the pipe bending forming and the shape and position of mandrel using the elastic-plastic finite element analysis and provide a foundation technology for which developing the hair pin bending machine. The results are followed 1. Mandrel located in front of rotating center of bending die minimized the circular shape variation of copper pipe. 2. Diameter change of mandrel hardly effect the pipe shape.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.637-642
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• 2008

Autofrettage analysis of a bend in the fuel injcetion pipe has been performed to investigate the distribution of residual stresses due to pipe bending and autofrettage processes. The pipe bending was simulated by metal forming analysis using finite element method, and residual stress distribution after bending was found. Autofrettage following the pipe bending was performed by applying the hydrostatic internal pressures of 603 MPa, 535 MPa, 500 MPa on the pipe bend, corresponding to theoretical 26 %, 14 %, 9 % overstrain levels, respectively. Residual stress distributions due to bending and autofrettage were evaluated.

• 한국안전학회지
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• 제23권1호
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• pp.1-11
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• 2008

In this study, small punch test and tensile test were performed with specimens directly machined from an ASTM A53 grade B carbon steel pipe at which an explosion accident was occurred in the Heavy Oil Unit. Main damage mechanism of the pipe was known as a high temperature hydrogen attack(HTHA). Effects of HTHA on the mechanical strength change of the A53B steel were studied in detail. Small punch test results have showed that maximum reaction forces, SP energy and ductility were decreased at hydrogen attacked part of the pipe compared with sound part of the pipe. Yield strength and tensile ultimate strength were calculated with the obtained small punch test curve results using different methods and compared the estimation methods. Small punch test simulation has been also performed with the finite element method and then mechanical strength, equivalent strain and fracture toughness were calculated with the obtained numerical analysis results. It was shown that the fracture toughness data calculated from small punch equivalent energy obtained by the finite element analysis for SP test was very low at the hydrogen attacked part.

• 한국지반환경공학회 논문집
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• 제17권12호
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• pp.65-72
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• 2016

There are numerous factors that affect stress distribution in a buried pipe, such as the shape, size, and stiffness of the pipe, its burial depth, and the stiffness of the surrounding soil. In addition, the pipe can benefit from the soil arching effect to some extent, through which the overburden and surcharge pressure at the crown can be carried by the adjacent soil. As a result, the buried pipe needs to support only a portion of the load that is not transferred to the adjacent soil. This paper presents numerical efforts to investigate the stress distribution in the buried concrete pipe under various environmental conditions. To that end, a nonlinear elasto-plastic model for backfill materials was implemented into finite element software by a user-defined subroutine (user material, or UMAT) to more precisely analyze the soil behavior surrounding a buried concrete pipe subjected to surface loading. In addition, three different backfill materials with a native soil were selected to examine the material-specific stress distribution in pipe. The environmental conditions considering in this study the loading effect and void effects were investigated using finite element method. The simulation results provide information on how the pressures are redistributed, and how the buried concrete pipe behaves under various environmental conditions.

• 한국화재소방학회논문지
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• 제21권1호
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• pp.98-105
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• 2007

본 연구에서는 소방 건축분야에 가장 많이 사용되는 배관인 배관용 탄소강관 및 이에 상응하는 스테인리스 강관을 분기배관으로 제작이 가능한지 여부를 상용유한요소프로그램(ABAQUS)을 이용하여 확인하였다. 이러한 배관을 분기배관으로 성형할 경우 심이 없는 배관 사용을 원칙으로 하고 배관에 심이 있는 경우 심과 정반대방향을 성형면으로 하여야 한다. 배관의 성형시 플러그의 경사면과 길이가 성형에 가장 큰 영향을 미치는 요소임을 알 수 있었다. 분기배관의 성형해석결과를 토대로 분기부분의 최소 높이와 두께를 제안했다.

• Steel and Composite Structures
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• 제20권4호
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• pp.931-950
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• 2016

Ratcheting deformation of pressurized Z2CND18.12N stainless steel $90^{\circ}$ elbow pipe with local wall thinning subjected to constant internal pressure and reversed bending was studied using finite element analysis. Chen-Jiao-Kim (CJK) kinematic hardening model, which was used to simulate ratcheting behavior of pressurized $90^{\circ}$ elbow pipe with local wall thinning at extrados, flanks and intrados, was implemented into finite element software ANSYS. The local wall thinning was located at extrados, flanks and intrados of $90^{\circ}$ elbow pipe, whose geometry was rectangular cross-section. The effect of depth, axial length and circumferential angle of local wall thinning at extrados, flanks and intrados on the ratcheting behaviors of $90^{\circ}$ elbow pipe were studied in this paper. Three-dimensional elastic-plastic analysis with Chen-Jiao-Kim (CJK) kinematic hardening model was carried out to evaluate structural ratcheting behaviors. The results indicated that ratcheting strain was generated mainly along the hoop direction, while axial ratcheting strain was relatively small.

• 대한기계학회논문집A
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• 제20권6호
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• pp.1872-1881
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• 1996

LBB(Leak-Before-Break) analysis is performed for the highest stress location of each different type of mateerials in the nuclear piping line. In most cases, the highest stress occurs in the pipe and nozzle interface location. i.e. terminal end. The current finite element analysis approach utilizes the symmetry condition both for locations near the nozzle and for locationa away from the nozzle to minimize the size of the finite element model and to make analysis simple when calculating the J-integral values at the crack tip. In other words, the nozzle is not included in the finite element model. However, in reality, the symmetric condition is not applicable for the pipe-nozzle interface location. Because the pipe-nozzle interface location is asymmetric due to different stiffenss of the pipe and nozzle(both material and dimensions). The simplified analysis approach for pipe-nozzle interface locaiton is too conservative for a smaller diameter piping. In tlhis paper, various analyses are performed for the range of materials and crack sizes to evaluate the nozzle effect for a LBB anlaysis. This paper presents methodology for developing the piping evaluaiton diagram at the pipe-nozzle interface location.