• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.4
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• pp.53-63
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• 2002

The high speed wind tunnel test for the study of the basic aerodynamic characteristics of the rocket with twin strap-on boosters was performed using ADD trisonic wind tunnel on the Mach number range of 0.4~4.0. The 6 % scale model of the early design version of Korean sounding rocket was tested. The tested configurations were core only, core/fins, core/boosters and core/boosters/fins. The effects of core length, gap between core and booster, and bank angle were investigated.

• Journal of Korean Association for Spatial Structures
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• v.10 no.2
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• pp.45-60
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• 2010

Nonlinear problems for membrane structures are very sensitive in convergence procedure in nonlinear iterations. Therefore many researchers have suggested a lot of ideas in published papers. In this study, authors are trying to get easier solution for taking membrane shape by initial stresses from substitution of the membrane to line elements. To obtain nonlinear stiffness, the nonlinear finite element method is used for both membrane and cable elements, and only geometric nonlinear terms are taken for shape analysis. By some examined models, we can find that the substituted models show better results to get, initial shape in which the concentrating phenomenon is removed at edge parts.

• Aerospace Engineering and Technology
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• v.11 no.1
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• pp.19-26
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• 2012

The requirement for the aerodynamic hub drag, allocated from the system requirement of development of a bearingless rotor hub, was analyzed and embodied to be substantiated by the methodology assigned from the requirement. Drag prediction for the initial hub configuration was carried out by hand calculation using aerodynamic drag coefficients and the design change about the sectional shape of torque tube was suggested to satisfy the requirement. Finally, drag prediction was performed for the changed hub configuration by using unstructured overset mesh technique and parallel computation and the calculated result satisfied the requirement of the aerodynamic hub drag. It was found that the drag of final hub configuration was also within the range of drag inferred from the trendline of developed helicopter.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.1
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• pp.47-58
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• 2014

In this research, the initial sizing of a HALE(High Altitude Long Endurance) UAV which uses solar power and hydrogen fuel cell as an alternative energy was performed. Instead of a wing box type, a glider type was chosen since it is relatively easy to get a data thanks to many researches abroad. Maximum takeoff weight is around 150Kg and the propulsion system is composed of motor, propeller, solar cell, and hydrogen fuel cell which can be recharged through electrolysis. Maximum takeoff weight was estimated as aspect ratio, wing span, wing area change while considering energy balance of required energy which is necessary for flight during the entire day and available energy which can be taken from the solar cell.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.2587-2593
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• 2014

Ceramic Injection Molding (CIM) is one of wide used processes in industry field and the applications are gradually being expanded to parts of medical and electric devices. In this study, the CIM process were analyzed with FEM and process parameters were studied and analyzed the effect on product quality. The shape of simple flat plate was compared to the shapes with the hole, with the round corner portion or with the side wall portion. If there are holes then the hole around the uneven density distribution and the defects such as weld lines could be occurred. The Large radius of the corners of the product give good formability and fluidity. Not only the shape parameters of product but also the process parameters during CIM are studied. The simulation results showed that the process parameters of temperature, initial fractions and velocity are important design parameters to improve the quality of products.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.1
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• pp.21-29
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• 2016

This paper proposes a method to determine the initial equilibrium state of cable members for preliminary analysis of multi-span suspension bridge under dead load. The proposed method is simpler and more practical than the previous methods used in other studies. The proposed method can be applied to three-span or multi-span suspension bridges. To verify the proposed method, an three-span model as well as four-span models such as New Millenium Bridge in Korea and Yingwuzhou Bridge in China are analyzed. In the verification results, the initial coordinates and tensions of the members calculated by the proposed method are good agreement with those in the previous study for the three-span model and those in the design data of New Millenium Bridge. In addition, the proposed method gives the initial values to keep the initial configuration of Yingwuzhou Bridge.

• Journal of Korean Society of Steel Construction
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• v.30 no.1
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• pp.25-35
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• 2018

Resisting strength of ring-stiffened cylindrical steel shell under uniform external pressure was evaluated by geometrically and materially nonlinear finite element method. The effects of shape and amplitude of geometric initial imperfection, radius to thickness ratio, and spacing of ring stiffeners on the resisting strength of ring-stiffened shell were analyzed. The resisting strength of ring-stiffened cylindrical shells made of SM490 obtained by FEA were compared with design strengths specified in Eurocode 3 and DNV-RP-C202. The shell buckling modes obtained from a linear elastic bifurcation FE analysis were introduced in the nonlinear FE analysis as initial geometric imperfections. The radius to thickness ratios of cylindrical shell in the range of 250 to 500 were considered.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.149-152
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• 2009

A pyrostarter is a sort of gas generator, which supplies the energy to drive turbines by the combustion gas of a solid propellant charged internally. The igniter of the pyrostarter should guarantee the ignition reliability expecially for the solid propellant with a low fame temperature. For the development of the igniter, several closed bomb testes have been performed to decide several design parameters to get a sufficient chamber pressure build-up for the ignition. Moreover, as a result of the firing testes with pyrostarters, the ignition reliability have been verified and the amount of igniter propellants has been reviewed.

• Proceedings of the KAIS Fall Conference
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• 2008.11a
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• pp.101-104
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• 2008

일반적으로 연속경간을 가지는 강합성 I-형강 교량에 있어서 내부 지점 부근에서 상대적으로 큰 부모멘트가 발생하므로, 이에 경제적인 단면 활용을 위하여 변단면을 적용하여 휨강도를 증가시킨다. 본 연구에서는 기존 강도계산식에 관한 연구를 토대로 하여 비탄성 구간에 있는 변단면 I형보의 횡-비틀림 좌굴강도를 유한요소해석프로그램 ABAQUS(2007)를 이용하여 산정하고, 간편한 설계식을 제안하고 있다. 지간 한쪽 끝에 계단식 단면변화를 가지는 보에 대해서 고려하였으며, 플랜지 길이방향 비, 너비방향 비, 두께의 비로 계단식 I형보를 나타내었다. 해석에 사용된 단면매개변수는 36가지 조합이며, 비탄성 횡-비틀림 거동을 고려하기위하여 잔류응력 및 초기결함을 고려한 비선형해석을 실시하였는데, Pi(1995)등이 고려한 잔류응력의 형상과 국내 I형강 표준 치수 허용치에 근거하여 부재 길이의 0.1%를 초기제작오차로 고려하였다. 해석모델의 양쪽 끝단에는 모멘트하중을 재하하였다. 개발 제한된 식은 선형 모멘트 하중이 작용할 때 적용가능한 식으로 경제적이고 합리적인 설계에 적극 활용될 수 있을 것이다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2003.05a
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• pp.21-26
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• 2003

Develop and need design application of carbon sex design concept that consider plasticity in elastic design concept until now. To Place that is representative construction of hull in this research rain deflection pattern analysis technique and grandeur increment method such as general load type increment law and displacement type increment law and Newton-Raphson method increment body law to use jointly compare. Specialty. through analysis by initial deflection pattern. examined closely carbon set conduct of place by initial deflection pattern. Applied thin plate structure which receive compressive load used ANSYS that analysis method is mediocrity finite element analysis program to save complicated conduct that effect that conduct after initial buckling and conduct after secondary buckling get in the whole construction is very big and such and grandeur increment law presumes complicated rain fan shape conduct in bifurcation point specially.