• 전산구조공학
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• 제10권4호
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• pp.117-130
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• 1997

본 논문에서는 등방성판의 인장이나 전단변형은 물론 굽힘문제에도 적용할 수 있는 3차원 고체요소들 중에서 최소의 자유도를 갖는 수정 10절점 상당요소를 제안하였다. 제안된 수정 10절점 상당요소는 Q11요소나 20절점요소로부터 자유도가 줄어듬에 기인한 과대한 굽힘강성을 나타낸다. 이러한 상대적 강성과잉 현상을 수정하기 위한 효과적인 방법으로 가우스 적분점 수정 방법을 제안하였다. 수정량은 포아송 비의 함수이다. 수정 10절점 상당요소의 효과를 여러 가지 예에 적용하여 검증하였다. 제안된 수정 10절점 상당요소에 의한 등방성판의 정적해석과 자유진동 해석의 결과들은 20절점요소를 사용한 결과들과 잘 일치하였다.

• 터널과지하공간
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• 제18권6호
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• pp.418-426
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• 2008

인도네시아 파시르탄광에서 적용되고 있는 전형적인 발파방법은 지표면을 유일한 자유면으로 하는 일자유면 노천발파 공법이다. 일반적으로 일자유면 발파방법은 자유면이 하나뿐이므로 구속이 커서 큰 지반진동을 일으키게 된다. 큰 지반진동은 다시 채광장의 경계를 이루는 사면의 안정성에 나쁜 영향을 미칠 수 있다. 이런 측면에서 발파로 인한 지반진동으로부터 파시르탄광의 채광장 사면과 폐석장의 안전을 확보할 수 있는 발파지침을 마련하기로 하였다 먼저, 파시르탄광에서 발파로 발생될 수 있는 지반진동 수준을 예측할 수 있는 예측식을 유도하였다. 다음으로, 채광장 사면과 폐석장의 폐석더미를 관리하기 위한 지반진동 허용수준을 PPV 측정치로 각각 120mm/s 및 60mm/s로 설정하였다. 도출된 예측식과 설정된 허용수준으로부터 현장에서 사용할 수 있는 안전발파를 위한 환산거리 조건식을 설정하였다. 설정된 환산거리 조건식은 채광장 사면과 폐석더미에 대해 각각 $D_s{geq}5$ 및 $D_s{geq}10$이다. 또한, 환산거리 조건식을 만족시킬 수 있도록 천공장 $3.3{sim}8.8m$에 대하여 몇 가지 표준발파패턴을 제안하였다.

• 한국컴퓨터정보학회논문지
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• 제28권8호
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• pp.111-118
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• 2023

본 논문에서는 비행 시뮬레이터와 VR분야에서 사용될 수 있는 가속도 센서와 진동 센서를 적용한 와이파이 기반의 조이스틱을 제안한다. 비행시뮬레이터는 ICT 및 SW 응용분야에 속하는 기술로 항공기의 환경을 재현하는 시뮬레이션 환경을 제공한다. 비행시뮬레이터의 일반적인 조종 장치는 고정식으로 특정 장치에 부착되어 사용되어 사용자의 활동 영역의 한계성을 가진다. 본 논문에서는 자유로운 공간 활용성을 위하여 3차원 공간 조종 장치를 구현하였다. 또한, 제안하는 조종 장치는 기존 VR장비의 컨트롤러에 비해 정확하고 정교한 조종을 위하여 3축 센싱과 정보를 표시하는 디스플레이 및 와이파이 통신을 위한 보드를 설계하고 유니티 기반의 가상 환경을 구현하여 적용 가능성을 확인하였다. 구현된 장치는 통신 인터페이스를 통해 조종 장치가 정상적으로 동작하는 것을 확인하였으며, 게임 내 센싱 값과 구현된 보드에서 측정한 센싱 값이 일치하는 것을 확인하였다. 연구의 결과물은 비행시뮬레이터 외에도 VR 및 다양한 메타버스 관련 콘텐츠에 활용될 수 있을 것이다.

• Advances in nano research
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• 제13권3호
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• pp.207-216
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• 2022

In this paper, a novel model is developed for frequency behavior of single walled carbon nanotubes. The governing equation of motion is constructed method based on the Sander theory using Rayleigh-Ritz's method The frequencies enhances on increasing the power law index using simply supported, clamped and clamped free end conditions. The frequency curve for C-F is less than other conditions. It is due to the physical constraints which are applied on the edge of the CNT. It is observed that the C-F boundary condition have less frequencies from the other two conditions. The frequency phenomena for zigzag are insignificant throughout the aspect ratio. Moreover when index of power law is increased then frequencies increases for all boundary conditions. The natural frequency mechanism for the armchair (10, 10) for various values of power law index with different boundary conditions is investigated. Here frequencies decrease on increases the aspect ratio for all boundary conditions. The frequency curves of SS-SS edge condition is composed between the C-C and C-F conditions. The curves of frequency are less significant from small aspect ratio (L/d = 4.86 ~ 8.47) and decreases fast for greater ratios. It is found that the frequencies via aspect ratios, armchair (10, 10) have higher values from zigzag (10, 0). It is due to the material structure which is made by the carbon nanotubes. The power law index have momentous effect on the vibration of single walled carbon nanotubes. The present frequency result is also compared numerically experimentally with Raman Spectroscopy.

• 대한조선학회논문집
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• 제51권5호
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• pp.409-418
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• 2014

Simulation of flow past a complex marine structure requires a fine resolution in the vicinity of the structure, whereas a coarse resolution is enough far away from it. Therefore, a lot of grid cells may be wasted, when a simple Cartesian grid system is used for an Immersed Boundary Method (IBM). To alleviate this problems while maintaining the Cartesian frame work, we adopted an Adaptive Mesh Refinement (AMR) scheme where the grid system dynamically and locally refines as needed. In this study, We implemented a moving IBM and an AMR technique in our basic 3D incompressible Navier-Stokes solver. A Volume Of Fluid (VOF) method was used to effectively treat the free surface, and a recently developed Lagrangian Dynamic Subgrid-scale Model (LDSM) was incorporated in the code for accurate turbulence modeling. To capture vortex induced vibration accurately, the equation for the structure movement and the governing equations for fluid flow were solved at the same time implicitly. Also, We have developed an interface by using AutoLISP, which can properly distribute marker particles for IBM, compute the geometrical information of the object, and transfer it to the solver for the main simulation. To verify our numerical methodology, our results were compared with other authors' numerical and experimental results for the benchmark problems, revealing excellent agreement. Using the verified code, we investigated the following cases. (1) simulating flow around a floating sphere. (2) simulating flow past a marine structure.

• 동력기계공학회지
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• 제21권1호
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• pp.57-62
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• 2017

The flexible joint with bellows and flange is made by welding bellows and flange in general. The welded parts cause a crack or demage in the flexible joint due to continuous vibration and fatigue limit. This paper is concerned with development of flexible joint with non-welded, free rotation of flange and non-packing to improve fatigue failure condition between bellows and flange. The support box and support plate that are components of press part are designed to compress fore-end of bellows only without demage of bellows. The production system of flexible joint is designed with piston attached on the compression side. The simulation is performed using Deform 3D software. As the result of simulation, the shape of compressed bellows was most proper in the compression power of $157kg{\cdot}f$ and any deformation has not occurred at a part besides fore-end. The result show that the production possibility of the designed flexible joint.

• 한국분말재료학회지
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• 제16권4호
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• pp.249-253
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• 2009

3-D shape soft magnetic composite parts can be formed by general compaction method of powder metallurgy. In this study, the results on the high density nanostructured Fe-Si/Fe composite prepared by a warm compaction method were presented. Ball-milled Fe-25 wt.%Si powder, pure Fe powder and Si-polymer were mixed and then the powder mixture was compacted at various temperatures and pressures. Pore free density of samples up to 95% theoretical value has been obtained. The warm compacted sample prepared at 650 MPa and 240$^{\circ}C$ had highest compaction properties in comparison with other compacts prepared at 300, 400 MPa and room temperature and 120$^{\circ}C$. The magnetic properties such as core loss, magnetization saturation and coercivity were measured by B-H curve analyzer and vibration sample magnetometer.

• 한국정밀공학회지
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• 제25권5호
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• pp.103-111
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• 2008

This study proposes a technique to estimate the material property of a paper by using an experimental methods and commercial CAE software. Under gravitation, if one side of the paper is attached to the ground, the opposite side of paper is largely deformed, and vibrates freely. Since the paper has an orthotropic characteristic due to its treatment, the deformations in two orthogonal directions of the dry paper are different. An experimental method to measure the static deformation of the paper introduces this phenomenon. And dynamic behavior, frequency of free vibration is measured. And then. virtual prototypes that can represent the static and dynamic behavior are modeled by using the commercial CAE software $RecurDyn^{MT}$/MTT3D, which has been widely used by the printer makers. While comparing the deformation and frequency from the experiment and simulation, a design optimization technique in the commercial CAE software of R-INOPL, $RecurDyn^{TM}$/AutoDesign is used to estimate the material property such as Young's modulus, shear modulus and density of the paper.

• Steel and Composite Structures
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• 제46권3호
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• pp.367-383
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• 2023

In this investigation, an improved integral trigonometric shear deformation theory is employed to examine the vibrational behavior of the functionally graded (FG) sandwich plates resting on visco-Pasternak foundations. The studied structure is modelled with only four unknowns' variables displacements functions. The simplicity of the developed model being in the reduced number of variables which was made with the help of the use of the indeterminate integral in the formulation. The current kinematic takes into consideration the shear deformation effect and does not require any shear correction factors as used in the first shear deformation theory. The equations of motion are determined from Hamilton's principle with including the effect of the reaction of the visco-Pasternak's foundation. A Galerkin technique is proposed to solve the differentials governing equations, which enables one to obtain the semi-analytical solutions of natural frequencies for various clamped and simply supported FG sandwich plates resting on visco-Pasternak foundations. The validity of proposed model is checked with others solutions found in the literature. Parametric studies are performed to illustrate the impact of various parameters as plate dimension, layer thickness ratio, inhomogeneity index, damping coefficient, vibrational mode and elastic foundation on the vibrational behavior of the FG sandwich plates.

• Journal of the Korean Wood Science and Technology
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• 제43권3호
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• pp.364-373
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• 2015

본 연구는 밀도와 귤박첨가율이 다른 톱밥-귤박 파티클보드의 동적 정적탄성계수와 휨강도를 측정, 비교하여 밀도와 귤박의 첨가율이 파티클보드의 역학적 성능에 주는 영향과 동적탄성계수와 정적 휨강도 성능사이의 관계를 조사하였다. 톱밥-귤박 파티클보드의 밀도가 0.4에서 $0.6g/cm^3$로 증가할수록 휨성능은 증가하여, 밀도가 휨성능에 크게 영향하였으며, 밀도 $0.4g/cm^3$와 $0.5g/cm^3$의 톱밥-귤박 파티클보드에서 귤박의 첨가량이 증가할수록 휨성능은 감소하는 경향을 나타내었다. 톱밥-귤박 파티클보드의 동적탄성계수, 정적탄성계수 그리고 휨강도 사이에 높은 상관관계가 확인되었으며 양단 자유 휨진동시험에 의한 동적탄성계수로부터 비파괴적으로 정적 휨강도 성능의 예측이 가능할 것으로 사료되었다.