• 한국전산구조공학회논문집
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• 제22권1호
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• pp.73-79
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• 2009

본 논문에서는 승객 보호용으로 지하철 역사에 설치된 PSD(승강장 스크린 도어)의 상부 헤더박스 내에 부착되어 개폐용 유리문을 지지하는 알루미늄 구동(레일)부재에 대한 구조해석과 최적설계를 수행하였다. 구동부재의 볼트 체결부에 대한 엄밀한 구조해석을 위하여 물리적 현상과 일치하도록 상세 유한요소 모델링하여 해석의 정확도를 높였다. 또한 유리문이 구동부재에 걸려 있으면서 개폐될 때 발생하는 하중의 이동상태를 고려한 구조해석 결과, 설계 목표치인 내구 수명 20년이 만족되었다. 구동부재 단면의 단면 길이를 설계변수로 하고 설계제약조건(응력의 최소화, 중량의 감소)에 만족할 수 있도록 반응표면법을 적용한 최적화를 수행하여 15%의 감량 결과를 도출하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1303-1306
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• 2005

The mechanical properties of bellows, such as the extensibility and the strength can be changed depending on the shape. For the shipbuilding material, it is favorable that the fatigue life is long due to the elastic property and the reduction of thermal stress in piping system. Nowadays, the domestic production and design of bellows are based on the E.J.M.A Code. Therefore, the design standard is in need because of much errors and lack of detailed analysis. In this study, it is attempted to find out the optimal shape of U-type bellows using the finite element method. The effective factors, mountain height, length, thickness, and number of mountains and the length of joint are considered and the proper values are chosen for the simulation. The results shows that if the number of mountains are reduced, the volume decreases while the stress increases. However, the number of mountains are increased, the volume increases above the standard volume and the stress obviously increases. In addition, the effect of the thickness of bellows on the stress is very large. Both of the volume and stress are decreasing at a certain lower value region.

• Journal of Advanced Marine Engineering and Technology
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• 제38권2호
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• pp.195-201
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• 2014

Flexible risers have been used extensively in recent years for floating and early production systems. Such risers offer the advantage of having inherent heave compliance in their catenary thereby greatly reducing the complexity of the riser-to-rig and riser-to subsea interfaces. Another advantage with flexible risers is their greater reliability. Concerns about fatigue life, gas permeation and pigging of lines have been overcome by extensive experience with these risers in production applications. In this paper, flexible riser analysis results were compared through coupled and uncoupled dynamic analyses methods. A time domain coupled analysis capability has been developed to model the dynamic responses of an integrated floating system incorporating the interactions between vessel, moorings and risers in a marine environment. For this study, SPM (Single Point Mooring) system for an FSU in shallow water was considered. This optimization model was integrated with a time-domain global motion analysis to assess both stability and design constraints of the flexible riser system.

• Ocean Systems Engineering
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• 제3권2호
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• pp.97-122
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• 2013

For the optimization design and strength evaluation of the umbilical cable, the calculation of cross section stress is of great importance and very time consuming. To calculate the cross section stress under combined tension and bending loads, a new integrated analytical model of umbilical cable is presented in this paper. Based on the Hook's law, the axial strain of helical components serves as the tensile stress. Considering the effects of friction between helical components, the bending stress is divided into elastic bending stress and friction stress. For the former, the elastic bending stress, the curvature of helical components is deduced; and for the latter, the shear stress before and after the slipping of helical components is determined. This new analytical model is validated by the experimental results of an umbilical cable. Further, this model is applied to estimate the extreme strength and fatigue life of the umbilical cable used in South China Sea.

• EDISON SW 활용 경진대회 논문집
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• 제6회(2017년)
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• pp.259-269
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• 2017

Gust load is a very important load factor in designing various structures of an aircraft and judging its stability. This is because the blast effect on the aircraft in operation increases the risk of damage to the structure of the aircraft and causes a negative impact such as shortening the fatigue life by generating vibration. Particularly in the case of wing, a change in angle of attack is caused by gust load, and an additional lift acts on the wing, thereby being exposed to various excitational environments. Severe structural damage to the aircraft may occur if the natural frequencies of the aircraft wing are close to or coincident with the frequencies of the gust load applied to the wing. Recent trends of research include flight dynamics analysis considering discontinuous gusts or structural optimization of the blades under gust load. A number of studies have been conducted to interpret gust load response in consideration of irregularities in gusts. In this paper, we tried to imagine the situation of the aircraft subjected to the gust load as realistic as possible, and proposed an algorithm to track back the critical gust profile according to given aircraft characteristics from the viewpoint of preliminary engineering prediction.

• 한국정밀공학회지
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• 제25권5호
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• pp.132-139
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• 2008

To meet demand of big capacity and high speed rotation for washing machine, more stress from bending and twisting are complexly loaded onto the shaft supporting the horizontal drum, causing problems in fracture strength and fatigue life. Also, Vibration occurs due to the frequency of the rotating parts. But, shaft has various design factors such as diameter and distance between bearings according to configuration of shaft, the optimal values can't be easily determined. Using a design of experiment (DOE) based on the FEM (Finite Element Method), which has several advantages such as less computing, high accuracy performance and usefulness, this study was performed investigating the interaction effect between the various design factor as well as the main effect of the each design factor under bending, twist and vibration and proposed optimum design using center composition method among response surface derived from regression equation of simulation-based DOE.

• 한국연안방재학회지
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• 제1권4호
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• pp.149-155
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• 2014

Flexible risers have been used extensively in recent years for floating and early production systems. Such risers offer the advantage of having inherent heave compliance in their catenary thereby greatly reducing the complexity of the riser-to-rig and riser-to subsea interfaces. Another advantage with flexible risers is their greater reliability. Concerns about fatigue life, gas permeation and pigging of lines have been overcome by extensive experience with these risers in production applications. In this paper, flexible riser analysis results were compared through coupled and uncoupled dynamic analyses methods. A time domain coupled analysis capability has been developed to model the dynamic responses of an integrated floating system incorporating the interactions between vessel, moorings and risers in a marine environment. For this study, SPM (Single Point Mooring) system for an FSU in shallow water was considered. This optimization model was integrated with a time-domain global motion analysis to assess both stability and design constraints of the flexible riser system.

• 한국결정성장학회지
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• 제32권6호
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• pp.251-261
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• 2022

본 연구에서는 냉간단조공정에서 성형하중과 금형내 응력집중 감소를 위해 자동차 엔진 밸브 스프링 리테이너 제품의 형상최적화를 위한 금형형상 최적설계를 수행하였다. 기존 생산에 사용되는 각 성형공정별 냉간단조 금형에 대한 유한요소해석 시뮬레이션을 통해 절단공정을 포함해 총 6공정으로 구성되어 있는 냉간단조공정 별 단조 프리폼의 성형 시에 발생하는 성형하중과 성형유동 특성을 분석하였으며, 이를 통해 금형 내 응력집중이 발생하는 주요 설계인자를 확인하였다. 상형금형과 하형금형부의 챔퍼(chamfer) 및 에지필렛(edge fillet) 형상을 대상으로 4인자 3수준 설계인자 및 변수 수준을 설정하고, 성형해석 시뮬레이션과 다구찌법을 활용하여 설계인자별 영향도를 분석하여 최적의 최적설계인자를 결정하였다. 본 연구를 통해 얻어진 최적설계변수를 적용하여 엔진밸브 스프링 리테이너의 최적설계 시뮬레이션 결과, 각 프리폼 성형공정별로 최대 36 %, 전체 공정 평균 20 %의 성형하중 감소 효과를 얻을 수 있었다. 엔진의 고효율, 고출력, 고성능화 목표가 지속적으로 높아짐에 따라 고강도 소재의 활용이 많아지게 되어 이에 대응할 수 있는 성형공정 및 금형설계의 최적화가 필요하며, 향후 연구 결과를 활용하여 현업에 적용하여 제품단조성형성 개선 및 금형수명관리를 위한 기술자료로 활용하고자 한다.

• 한국해양공학회지
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• 제21권5호
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• pp.55-60
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• 2007

Bellows are mechanical components which prevent the damage of system by absorption of the vibration and the displacement of axle and radial direction. Thermal piping system is expanded by the fluid of the high temperature from the heat engine inside. At this time, bellows prevent the damage of the piping due to the thermal expansion. Recently, design of bellows is required to fit some other operational environments which are not suggested in the E.J.M.A code book. And it is difficult to produce and to maintain bellows of high temperature and high pressure bemuse of its complicated shape and this causes the manufacturing cost to rise. The objective of this study is to determine optimum shape of bellows which can endure in the high temperature and high pressure. The maximum stress has an effect on the fatigue life of bellows, therefore it needs to be minimized. This study attempts to find a shape which minimizes the stress occurring in the bellows by the design of experiment. The model used in this study is not presented in the E.J.M.A code book, therefore, from the result of design of experiment we find the factors which give effects on the characteristic value and we presents the recession model using the RSM, which can predict the characteristic values depending on the change of factor values.

• 생명과학회지
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• 제27권2호
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• pp.247-266
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• 2017

동충하초(Cordyceps)는 B.C. 2,000년 이후로부터 지금까지 중국, 한국, 일본 등 아시아 국가에서 잘 알려진 전통적인 불로장생의 비약으로 사용되어져 왔다. 곤충기생 곰팡이균으로서 원조 동충하초로 불리는 Cordyceps속에 속하는 Cordyceps sinensis는 우리나라 한반도에서는 발견되지 않고 있다. 그 이유는 해당 곰팡이균에 특정적인 기주곤충인 박쥐나방(Hepialus armonicanus)이 우리나라에는 존재하지 않기 때문으로 보인다. 따라서 차선책으로서 한국형의 동충하초, 즉 Paecilomyces tenuipes 동충하초균에 대한 곤충생체배지로서 누에(Silkworm, Bombyx mori)를 기주곤충으로 사용하는 누에동충하초의 인공적인 생산방법을 세계 최초로 개발하게 된 것이다. 따라서 본 총설은 누에동충하초를 개발하게 된 역사적 배경과 생산방법 및 약리학적 효능과, 비곤충유래 동충하초인 인공배지 배양동충하초(밀리타리스동충하초: Cordyceps militaris, 붉은자루동충하초: Cordyceps pruinosa 등)의 배양조건과 동충하초 품종육성, 배지배양조건, 동충하초의 식품에의 응용 가능성, 화학적 구성성분 및 약리적 효능 등에 대해 고찰하였다. 곤충유래의 누에동충하초 및 비곤충유래동충하초균사체 및 자실체동충하초의 주요 약리작용은 항종양, 면역증강, 항피로, 항스트레스, 항산화, 항노화, 항당뇨, 항염증, 항혈전, 항지질 및 해충방제 효능으로 요약된다. 동충하초의 주요 생리활성물질들은 단백다당체(헥소스, 헥소사민), 코디세핀, 만니톨, 산성다당체 등이다. 단백다당체와 부타놀 추출물은 매우 강한 항종양 효과를 보이나 세포독성은 나타내지 않았다. 만니톨은 종양유발쥐의 수명을 유의성 있게 연장하였다. 에르고스테롤은 항종양 활성은 보이지 않았으나 왕성한 식세포활성을 보였다. 따라서 우리가 높은 관심을 가지고 있는 누에동충하초의 항종양 활성은 세포독성효과보다는 면역력증강효과에 기인하는 것으로 사료된다[164].