• 한국시뮬레이션학회논문지
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• 제19권4호
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• pp.123-128
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• 2010

본 논문에서는 우주방사능 환경에서 우주방사능/총 누적 방사선량(TID) 및 이에 대한 시스템 영향과 정지궤도 위성 시스템 설계를 Spenvis 를 사용하여 분석하였다. 우주환경에서 정지궤도 위성 시스템이 겪게 될 우주방사선 환경을 포획된 입자, 태양 양성자 그리고 우주선으로 구분하여 각각 NASA AP8, JPL91 그리고 NRL CREME 모델을 사용하여 전산모사하였다. 임무수명기간 동안 전자부품에 계속적으로 피폭되는 전체 방사량을 알루미늄 차단두께의 함수로 나타내었으며, 이 값들은 디지털채널 처리부의 전자부품의 선택기준 및 위성체 또는 구성품의 구조물 두께를 설정할 수 있는 기준으로 제시한다.

• Advances in aircraft and spacecraft science
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• 제10권1호
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• pp.19-49
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• 2023

The present study proposes a theoretical and numerical investigation on the dynamic response behaviour of a functional graded (FG) ceramic-metal tapered rotor shaft system, by the differential quadrature finite elements method (DQFEM) to identify the natural frequencies for modelling and analysis of the structure with suitable validations. The purpose of this paper is to explore the influence of heat gradients on the natural frequency of rotation of FG shafts via three-dimensional solid elements, as well as a theoretical examination using the Timoshenko beam mode, which took into account the gyroscopic effect and rotational inertia. The functionally graded material's distribution is described by two distribution laws: the power law and the exponential law. To simulate varied thermal conditions, radial temperature distributions are obtained using the nonlinear temperature distribution (NLTD) and exponential temperature distribution (ETD) approaches. This work deals with the results of the effect on the fundamental frequencies of different material's laws gradation and temperature gradients distributions. Attempts are conducted to identify adequate explanations for the behaviours based on material characteristics. The effect of taper angle and material distribution on the dynamic behaviour of the FG conical rotor system is discussed.

• Advances in aircraft and spacecraft science
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• 제10권3호
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• pp.203-222
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• 2023

The detonation combustion is a supersonic combustion process follows on shock wave oscillations in detonation tube. In this paper numerical studies are carried out combined effect of blockage ratio and spacing of obstacle on detonation wave propagation of hydrogen-air mixture in pulse detonation combustor. The deflagration to detonation transition of stoichiometric (ϕ=1)fuel-air mixture in channel has been analyzed for effect of blockage ratio (BR)=0.39, 0.51, 0.59, 0.71 with spacing of 2D and 3D. The reactive Navier-Stokes equation is used to solve the detonation wave propagation mechanism in Ansys Fluent platform. The result shows that fully developed detonation wave initiation regime is observed near smaller vortex generator ratio of BR=0.39 inside the combustor. The turbulent rate of reaction has also a great significance role for shock wave structure. However, vortices of rapid detonation wave are appears near thin boundary layer of each obstacle. Finally, detonation combustor demonstrates the superiority of pressure gain combustor with turbulent rate of reaction of 0.6 kg mol/m3 -s inside the detonation tube with obstacle spacing of 12 cm, this blockage enhanced the turbulence intensity and propulsive thrust. The successful detonation wave propagation speed is achieved in shortest possible time of 0.031s with a significance magnitude of 2349 m/s, which is higher than Chapman-Jouguet (C-J) velocity of 1848 m/s. Furthermore, stronger propulsive thrust force of 36.82 N is generated in pulse time of 0.031s.

• Advances in aircraft and spacecraft science
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• 제10권4호
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• pp.347-368
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• 2023

In the first part of this study, a numerical simulation model was developed using the mechanical APDL software to validate the results of the 3D-elastisity theory on the laminated sandwich plate developed by Panago. The numerical simulation model showed a good agreement to the results of Pagano's theory in terms of deflection, normal stresses, and shear stresses. In the second part of this study, the developed numerical simulation model was used to define different plates dimensions and fibers layup orientations to examine the load response in terms of deflection and stresses. Further analysis was implemented on the natural frequencies of laminated xxx plates of the plates. The layup configurations include Unidirectional (UD), Cross-Ply (CP), Quasi-Isotropic (QI), the linear bio-inspired known as Linear-Helicoidal (LH), and the nonlinear bio-inspired known as Fibonacci-Helicoidal (FH). The following numerical simulation model can be used for the design and study of novel, sophisticated bio-inspired composite structures in a variety of configurations subjected to sinusoidal or constant loads.

• Advances in aircraft and spacecraft science
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• 제5권1호
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• pp.1-19
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• 2018

The present work shows many aspects concerning the use of a numerical wave-based methodology for the computation of the structural response of periodic structures, focusing on cylinders. Taking into account the periodicity of the system, the Bloch-Floquet theorem can be applied leading to an eigenvalue problem, whose solutions are the waves propagation constants and wavemodes of the periodic structure. Two different approaches are presented, instead, for computing the forced response of stiffened structures. The first one, dealing with a Wave Finite Element (WFE) methodology, proved to drastically reduce the problem size in terms of degrees of freedom, with respect to more mature techniques such as the classic FEM. The other approach presented enables the use of the previous technique even when the whole structure can not be considered as periodic. This is the case when two waveguides are connected through one or more joints and/or different waveguides are connected each other. Any approach presented can deal with deterministic excitations and responses in any point. The results show a good agreement with FEM full models. The drastic reduction of DoF (degrees of freedom) is evident, even more when the number of repetitive substructures is high and the substructures itself is modelled in order to get the lowest number of DoF at the boundaries.

• 항공우주산업기술동향
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• 제7권2호
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• pp.59-67
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• 2009

항공우주산업과 관련된 항공기, 인공위성, 발사체 등의 구조체 개발을 위해서는 설계단계에서부터 해석 및 제작에 이르기까지 다양한 전산기술(CAD/CAE/CAM)이 널리 적용되고 있다. 이 중 구조해석을 위해서는 NASTRAN, ABAQUS, ANSYS와 같은 유한요소법에 기반을 둔 CAE 소프트웨어가 개발되어 산업현장에 널리 보급되어 있으며, 정적해석, 동적해석, 진동해석, 충돌해석 등 해석목적에 맞게 모듈화가 되어있다. 최근에는 해 석알고리즘 및 컴퓨터성능의 발달에 힘입어 다중물리해석, 최적설계와 같은 난해하며 높은 계산량을 요구하는 문제의 적용과 및 다자유도문제의 해결이 진행되고 있는 추세이다. 본 논문에서는 항공우주산업분야에 주로 사용되는 구조해석 소프트웨어의 최신기술동향을 살펴본다.

• 한국항공우주학회지
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• 제42권8호
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• pp.629-639
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• 2014

강성이 우수하고, 경량으로 제작이 가능한 격자강화 복합재 구조체를 다기능 구조체의 기층구조로 적용함으로써, 전기전자회로를 용이하게 내장할 수 있으며 방사차폐 특성을 갖춘 다기능 구조체에 대한 설계 및 제작을 수행하였다. 피치계열 탄소섬유 복합재료의 적용을 통해 열전달특성을 향상시키고, 전자회로의 하우징 구조물이 없어도 우주방사환경에 충분한 내구성을 갖도록 경량 국부 강화 방사차폐 방법을 제안하고, 양성자 조사시험을 통하여 선택적 방사차폐의 효과를 검증하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.376-379
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• 2006

Reaction Wheel Assembly (RWA) is one of the major disturbance sources that have influence upon the Line of Sight (LOS) of payload. A micro-vibration induced by RWA is propagated through the satellite structure and decrease the LOS stability performance of payload. This effect shall be analyzed through the jitter analysis. If a requirement or specification of payload jitter level is found to be not satisfied according to the jitter analysis campaign, some modification or redesign should be done on the satellite structure or a couple of isolator should be attached on the RWA interface in order to reduce the transmitted vibration level of RWA. The purpose of ???RWA isolator test? is to roughly evaluate the performance of vibration suppression level with a passive RWA isolator made of rubber. For this test, actual RWA is used as a vibration source and a couple of cube-shaped rubber mount designed for satellite is used as a passive isolator. There may be several considerations in order to accommodate RWA isolator to spacecraft such as not only vibration reduction performance but also thermal conduction problem, mechanical size, RWA alignment problem, etc. But in this report the feasibility of RWA isolator is analyzed only in a vibration suppression point of view. As a result, high frequency vibration of RWA above 50Hz is perfectly attenuated with isolators, however, first harmonic components below 50Hz became larger due to the additional low frequency resonance modes of roll, pitch, yaw rigid body motion of RWA+bracket.

• Advances in aircraft and spacecraft science
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• 제5권3호
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• pp.363-383
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• 2018

One-dimensional (1D) models of incompressible flows, can be of interest for many applications in which fast resolution times are demanded, such as fluid-structure interaction of flows in compliant pipes and hemodynamics. This work proposes a higher-order 1D theory for the flow-field analysis of incompressible, laminar, and viscous fluids in rigid pipes. This methodology is developed in the domain of the Carrera Unified Formulation (CUF), which was first employed in structural mechanics. In the framework of 1D modelling, CUF allows to express the primary variables (i.e., velocity and pressure fields in the case of incompressible flows) as arbitrary expansions of the generalized unknowns, which are functions of the 1D computational domain coordinate. As a consequence, the governing equations can be expressed in terms of fundamental nuclei, which are invariant of the theory approximation order. Several numerical examples are considered for validating this novel methodology, including simple Poiseuille flows in circular pipes and more complex velocity/pressure profiles of Stokes fluids into non-conventional computational domains. The attention is mainly focused on the use of hierarchical McLaurin polynomials as well as piece-wise nonlocal Lagrange expansions of the generalized unknowns across the pipe section. The preliminary results show the great advantages in terms of computational costs of the proposed method. Furthermore, they provide enough confidence for future extensions to more complex fluid-dynamics problems and fluid-structure interaction analysis.

• 항공우주시스템공학회지
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• 제18권2호
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• pp.104-116
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• 2024

인공위성은 발사체 모델과 연성하중해석을 수행하여 설계를 최종 검증하게 된다. 연성하중해석 결과의 정확도를 높이기 위해서는 유한요소모델 정확도가 매우 중요하며, 이를 위해 모델 보정은 필수적이다. 일반적으로 모델 보정은 재료 물성치와 두께 등을 하나씩 바꿔가며 수행하게 되는데, 이는 매우 많은 시간과 비용이 소요된다. 따라서 본 논문에서는 최적화 기법을 이용하여 탑재체 유한요소모델의 보정작업을 보다 효율적으로 수행하였다. 분산분석을 통해 중요 변수를 선정하고, 크리깅 대체 모델을 이용하여 해석과 최적화에 필요한 시간과 비용을 절감하였다. 본 논문에서 제안한 보정 방법은 진동 시험 결과만 있으면 적용할 수 있으며, 수치적인 계산 비용과 소요 시간을 대폭 줄일 수 있다는 점에서 효율성 측면에서 큰 장점이 있다.