• Journal of the Korea Society for Simulation
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• v.19 no.4
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• pp.123-128
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• 2010

The space radiation/total ionizing Dose(TID) and its effects, and the GEO satellite system design considerations in space radiation environment are studied in this paper using Spenvis(Space Environment Information System). The GEO satellite system in space environment is simulated by NASA AP8/AE8, JPL91 and NRL CREME models, repectively for trapped particle, solar proton and cosmic-ray. The total ionizing Dose which is accumulated continuously to spacecraft electronics has been expressed as the function of aluminum thickness. These values can be used as the criteria for the selection of electronic parts and shielding thickness of the Digital Channel Amplifier(DCAMP) structure.

• Advances in aircraft and spacecraft science
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• v.10 no.1
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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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• v.10 no.3
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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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• v.10 no.4
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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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• v.5 no.1
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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.

• Current Industrial and Technological Trends in Aerospace
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• v.7 no.2
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• pp.59-67
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• 2009

Computer Aided Engineering(CAE) technology as well as Design(CAD) and Manufacturing(CAM) have been widely adopted in the aerospace industry in order to develop the structure of airplanes, satellites and launch vehicles. Among them, CAE softwares based on finite element methods such as NASTRAN, ABAQUS and ANSYS have gained many engineers' interest in various industries such as automobiles, civils, aircraft and spacecraft. The softwares usually consist of several modules: Static, Dynamic, Vibration, Impact etc. that make analysis specific to meet the design goals of the structure systems. Recent enhancement in the computer hardwares and numerical algorithms enables us to perform complex analysis like multi-physics, optimum design. Also, they make it possible to deal with a large scale problem easily. This paper reviews structural analysis softwares in aerospace industry and gives a summary on its recent development.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.8
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• pp.629-639
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• 2014

This paper deals with an alternative multi-functional structures by using grid-stiffened composite structure with excellent bending stiffness and lightweight characteristics which is capable of easy embedding of electrical/electronic circuitry into structure. The enhancement of thermal conduction capability is made by the application of pitch-based carbon fiber. The lightweight radiation spot shielding technique is also proposed for multi-functional structures without conventional housing and the effectiveness of selective radiation shielding is validated through the proton irradiation test.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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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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• v.5 no.3
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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.

• Journal of Aerospace System Engineering
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• v.18 no.2
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• pp.104-116
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• 2024

A satellite is ultimately verified by performing a coupled load analysis with the launch vehicle. To increase the accuracy of the coupled load analysis results, it is important to have good accuracy of the finite element model. Therefore, finite element model correlation is essential. In general, model correlation is performed by changing the material properties and thickness one by one, but this process takes a lot of time and cost. The current paper proposes an efficient model correlation method using optimization. Significant variables were selected through analysis of variance, and the time and cost required for analysis and optimization were reduced by using the Kriging surrogate model. The method proposed in this paper can be applied only with the vibration test results, and it has a great advantage in terms of efficiency in that it can significantly reduce the numerical calculation cost and time required.