• 한국해양공학회지
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• 제24권5호
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• pp.1-7
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• 2010

Offshore, sub-sea pipelines that transport oil and gas experience thermal expansion induced by the temperature of the transported medium during operation. The expansion of the pipeline can induce overload and cause damage to offshore platforms or sub-sea structures that are connected to the pipelines. To mitigate and prevent these incidents, expansion spools are installed between offshore, sub-sea pipelines and risers on the platform. This paper presents the results of the study and development of a simplified design method for expansion spools, using the slope deflection method for the purpose of preliminary design or front-end engineering and design (FEED).

• 한국산업융합학회 논문집
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• 제25권5호
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• pp.827-833
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• 2022

In this study, the prediction of the bending angle for the 350 A bellows-type expansion joints and the structural stability according to the load were determined. The stability of the 2km piping system was predicted by applying the allowable bending angle of the expansion pipe joint obtained from the analysis. The maximum bending angle was calculated through bending analysis of the bellows-type expansion joints, and the maximum bending angle by numerical calculation was about 1.8°, and the maximum bending angle of the bellows obtained by comparing the allowable strength of the material was about 0. 22°. This angle was very stable compared to the allowable bending angle (3°) of the expansion pipe joint regulation. By applying the maximum bending angle, the allowable maximum deflection of the 2 km pipe was about 3.8 m. When the seismic load was considered using regression analysis, the maximum deflection of the 2km pipe was about 142.3mm, and it was confirmed that the bellows-type expansion joints and the deflection were stable compared to the allowable maximum deflection of the pipe system. These research results are expected to present design and analysis guidelines for the construction of piping and the development of bellows systems, and to be used as basic data for systematic research.

• Structural Engineering and Mechanics
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• 제58권6호
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• pp.949-966
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• 2016

The second order analysis taking place due to non-linear behavior of the structures under the mechanical and geometric factors through implementing exact and approximate methods is an indispensible issue in the analysis of such structures. Among the exact methods is the slope-deflection method that due to its simplicity and efficiency of its relationships has always been in consideration. By solving the differential equations of the modified slope-deflection method in which the effect of axial compressive force is considered, the stiffness matrix including trigonometric entries would be obtained. The complexity of computations with trigonometric functions causes replacement with their Maclaurin expansion. In most cases only the first two terms of this expansion are used but to obtain more accurate results, more elements are needed. In this paper, the effect of utilizing higher order terms of Maclaurin expansion on reducing the number of required elements and attaining more rapid convergence with less error is investigated for the Bernoulli beam with various boundary conditions. The results indicate that when using only one element along the beam length, utilizing higher order terms in Maclaurin expansion would reduce the relative error in determining the critical buckling load and kinematic parameters in the second order analysis.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.679-681
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• 2017

듀얼 벨 노즐에 확장-굴절 노즐 개념을 적용한 기초 전산수치해석 연구를 수행하였다. CEA 코드를 이용하여 노즐 내부 유동의 화학조성을 계산한 8 화학종 동결유동 해석을 진행하였고, 난류 모델은 $k-{\omega}$ SST 모델을 선정하였다. 듀얼 벨 노즐에 확장-굴절 노즐 개념을 적용함에 따라 변화된 천이고도 및 성능 계산을 수행하였다. 해석 결과 확장-굴절 노즐 개념을 적용함에 따라 과대팽창 조건이 형성되었고, 그에 따라 천이고도가 상승하였다.

• 한국생산제조학회지
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• 제9권3호
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• pp.123-129
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• 2000

To make high accuracy cutting of long materials and a piston for the engines it must be necessary to keep the thermal stability of spindle and tail stock in CNC lathe. If a object is clamped at the ends the thermal expansion and cutting process generate the deflection of cutting objects. Especially in the case of a piston ring piston ovality and piston profile the influences of deflection are very serious. In order to solve the problems most of piston cutting are worked under simply support. However the prob-lems exist yet. Therefore this paper proposes the new structure of tail stock which can compensates the deflection.

• 비파괴검사학회지
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• 제31권5호
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• pp.543-551
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• 2011

Steam generator tubes for nuclear power plants contain the local shape transitions on their inner or outer surface such as dent, bulge, over-expansion, eccentricity, deflection, and so on by the application of physical force during the tube manufacturing and steam generator assembling and by the sludge (that is, corrosion products) produced during the plant operation. The structural integrity of tubes will be degraded by generating the corrosive crack at that location. The profilometry using the traditional bobbin probes which are currently applied for measuring the profile change of tubes gives us basic information such as axial locations and average magnitudes of deformations. However, the three-dimensional quantitative evaluation on circumferential locations, distributional angle, and size of deformations will have to be conducted to understand the effects of residual stresses increased by local deformations on corrosive cracking of tubes. Steam generator tubes of Korean standard nuclear power plants expanded within their tube-sheets by the explosive expansion method and suffered from corrosive cracks in the early stage of power operation. Thus, local deformations of steam generator tubes at the top of tube-sheet were measured with an advanced rotating probe and a laser profiling system for the two cases where the tubes expanded by the explosive expansion method and hydraulic expansion. Also, the trends of eccentricity, deflection, and over-expansion of tubes were evaluated. The advanced eddy current profilometry was confirmed to provide accurate information of local deformations compared with laser profilometry.

• 한국정밀공학회지
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• 제23권9호
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• pp.76-83
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• 2006

Machining accuracy is closely related with tool deflection induced by cutting forces. In this research, cutting forces and tool deflection in end milling are expressed as a closed form of tool rotational angle and cutting conditions. The discrete cutting fores caused by periodic tool entry and exit are represented as a continuous function using the Fourier series expansion. Tool deflection is predicted by direct integration of the distributed loads on cutting edges. Cutting conditions, tool geometry, run-outs and the stiffness of tool clamping part are considered together far cutting forces and tool deflection estimation. Compared with numerical methods, the presented method has advantages in prediction time reduction and the effects of feeding and run-outs on cutting forces and tool deflection can be analyzed quantitatively. This research can be effectively used in real time machining error estimation and cutting condition selection for error minimization since the form accuracy is easily predicted from tool deflection curve.

• 한국추진공학회지
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• 제26권5호
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• pp.11-23
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• 2022

길이를 단축한 ED(Expansion Deflection) 노즐의 설계를 위해 길이 단축 방안에 따른 ED 노즐의 수치적 연구를 수행하였다. 첫 번째 방안은 80% 벨 노즐 길이를 갖는 ED 노즐의 확장부 길이를 10%, 20%와 30%씩 단축하는 것이다. 두 번째 방안은 노즐 목 각도를 증가시켜 확장부 길이를 단축하는 것이다. 길이 단축에 따른 윤곽선의 곡률 증가로 인해 80% 벨 노즐 길이인 ED 노즐과 첫 번째 방안의 ED 노즐의 출구 유동 속도의 감소폭이 줄어들어 추력이 유사해졌다. 두 번째 방안의 ED 노즐은 80% 벨 노즐 길이인 ED 노즐보다 출구 유동 속도가 증가하여 추력이 증가하였다.

• 대한치과교정학회지
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• 제24권3호
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• pp.721-733
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• 1994

Orthodontic tooth movement is closely related to the stress on the periodontal tissue. In this research the finite element method was used to observe the stress distribution and to find the best condition for effective tooth movement in the case of unilateral molar expansion. The author constructed the model of lower dental arch of average Korean adult and used $.032'\times.032'\times60mm$ TMA wire. The wire was deflected in the horizontal and vertical direction to give the 16 conditions. The following results were obtained ; 1. When the moment and force were controlled properly the movement of anchor tooth was minimized and the movement of moving tooth was maximized. 2. As the initial horizontal deflection increased the buccal displacement of both teeth was also increased. As the initial horizontal deflection increased the lingual movement of anchor tooth and the buccal movement of moving tooth increased. 3. When the initial horizontal and vertical deflection rate was 1.5 the effective movement of moving tooth was observed with minimal displacement of anchor tooth.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.781-785
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• 2005

Cutting forces and tool deflection in end milling are represented as the closed form of tool rotational angle and cutting conditions. The discrete cutting forces caused by tool entry and exit are continued using the Fourier series expansion. Tool deflection is predicted by direct integration of the distributed loads on cutting edges. Cutting conditions, tool geometry, run-outs and the stiffness of tool clamping pan are considered for cutting forces and tool deflection estimation. Compared to numerical methods, the presented method has advantages in short prediction time and the effects of feeding and run-outs on cutting forces and tool deflection can be analyzed quantitatively. This research can be effectively used in real time machining error estimation and cutting condition selection for error minimization since the ferm accuracy is easily predicted by tool deflect ion curve.