• 항공우주시스템공학회지
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• 제1권3호
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• pp.26-31
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• 2007

This paper addresses a method for structural optimum design of composite rotor blade. The basic model of a composite helicopter main rotor blade is designed and its parameters determining the structural/dynamic properties are studied. Through the investigation of flap/lag/torsional stiffness, the structural properties of the model are analyzed. In this study, helicopter rotor blades are analyzed by using VABS. The computer program VABS (Variational Asymptotic Beam Section Analysis) uses the variational asymptotic method to split a three-dimensional nonlinear elasticity problem into a two dimensional cross-sectional analysis and a one-dimensional nonlinear beam problem. This is accomplished by taking advantage of certain small parameters inherent to beam-like structures. In addition, the rotational stability of the blade is estimated by the frequency diagram from FE analysis(MSC.Patran/Nastran) to understand its vibrational property. From the result, design parameters to determine and optimize the properties of the model are presented.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.434-437
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• 2006

Structures tend to become high-rise, large and specialized due to the urban concentration. Technology related to the structure and construction is required to improve, for which the use of high strength concrete(HSC) with better material property, and composite member with the combined advantage of both concrete and steel for better performance, is suggested. Over a half of fires, which increase by over 10% every year recently, come from the architectural structure, causing a loss at national level. However, little study has been conducted on the member at high temperature despite the increase in the use of HSC composite members. In this study, the techniques of modeling for analysing by DIANA (Displacement Analyzer) the fire damaged HSC composite compressive members are researched. We can review the effect of change in the steel ratio, section size and the steel ratio on the residual strength of structural members by parameter analysis study.

• 한국강구조학회 논문집
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• 제16권5호통권72호
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• pp.621-628
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• 2004

본 연구에서는 보강판의 좌굴방지를 위해 기존에 주로 사용되는 보강재를 복합재료를 사용하여 대체하는 새로운 개념을 소개한다. 강재 보강재를 복합재료로 대체함으로써 용접의 불편함과 피로 등에 의한 손상 및 부식을 원천적으로 제거할 수 있다. 강판에 접착되는 복합재료는 강판이 좌굴할 때까지 완전히 접착된 것으로 가정하였다. 이렇게 구성되는 판은 길이와 폭 방향으로 변단면의 형태를 가지며 비등방성의 재료특성을 나타낸다. 이러한 비등방성 변단면 판의 좌굴해석을 위해 범용 유한요소 프로그램인 LUSAS를 사용하였으며 여러 가지 매개변수 변화 해석을 통해 비등방성 변단면 판의 좌굴거동 특성을 살펴보았다.

• 복합신소재구조학회 논문집
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• 제6권2호
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• pp.46-51
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• 2015

Since it is impossible to predict earthquakes, they involve more casualties and property damage compared to meteorological disasters such as heavy snow and heat waves, which can be predicted through weather forecasts. This has highlighted the need for seismic design and reinforcement. Recently, the use of composite materials as reinforcement has surged because steel plate reinforcement and section enlargement are likely to result in increased weight and physical damage to structures. This study evaluates the seismic performance of panels created from composite materials, and their guide systems. The specimens were miniature versions of actual steel structures, and displacement loads were applied in the transverse direction. Seismic performance was found to improve when structures were reinforced with seismic panels.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2607-2612
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• 2020

The present work was aimed to show the possibility of using hydrogel (acrylic/boric acid) for evaluation of the neutron radiation shielding. The influence of acrylic acid concentration, different gamma doses and relative contents of boric acid were studied. The physical properties and the thermomechanical stability of the studied samples were investigated. The shielding property of the composite for neutron was tested by Pu-Be neutron source (5 Ci) under room temperature. The neutron fluence rates and gamma fluxes were measured using a stilbene organic scintillator. The macroscopic effective removal cross-section Σ_R (cm^-1) of fast neutrons and total attenuation coefficient μ (cm^-1) of gamma rays has been studied experimentally. The transmission parameters, the relaxation length (??) and the half-value layer (HVL) were obtained. The obtained results indicated that the addition of boric acid to acrylic acid tends to increase the macroscopic effective removal cross-section Σ_R (cm^-1) to 0.141 compared to 0.094 of ordinary concrete.

• 대한기계학회논문집A
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• 제38권6호
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• pp.691-698
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• 2014

본 논문에서는 복합재료를 이용하여 플렉스빔과 토크튜브를 제작하기 위한 공정과 기본 물리량 시험과정을 소개하였다. 플렉스빔과 토크튜브는 헬리콥터에 적용되는 무베어링 로터 허브 시스템을 구성하기 위한 핵심 구성품이다. 토크튜브는 블레이드의 피치각을 변화시키기 위한 조종력을 전달하며, 플렉스빔은 구조적인 변형을 통해 플랩, 래그 및 페더링 힌지를 구현하는 기능을 담당한다. 지상회전시험을 수행하기에 앞서 플렉스빔과 토크튜브 및 블레이드의 플랩강성, 래그강성 및 토션강성을 측정하기 위한 기본 물리량 시험을 수행하였다. 또한, 해석을 통해 예측된 단면 강성과 기본 물리량을 통해 획득된 강성 값을 비교하였으며, 그 결과를 통해 복합재료로 제작된 플렉스빔과 토크튜브가 구조적인 강성 요구도를 만족함을 확인할 수 있었다.

• Steel and Composite Structures
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• 제44권3호
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• pp.339-351
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• 2022

A mortar-filled rectangular hollow structural section (RHS) can increase a structural section property as well as a compressive buckling capacity of a RHS member. In this study, the tensile performance of newly developed mortar-filled RHS members was experimentally evaluated with various connection details. The major test parameters were the type of end connections, the thickness of cap plates and shear plates, the use of stud bolts, and penetrating bars. The test results showed that the welded T-end connection experienced a brittle weld fracture at the welded connection, whereas the tensile performance of the T-end connection was improved by additional stud bolts inserted into the mortar within the RHS tube. For the end connection using shear plates and penetrating stud bolts, ductile behavior of the RHS tube was achieved after yielding. The penetrating bars increased load carrying capacity of the RHS. Based on the analysis of the load transfer mechanism, the current design code and test results were compared to evaluate the tensile capacity of the RHS tube according to the connection details. Design considerations for the connections of the mortar-filled RHS tubes were also recommended.

• 복합신소재구조학회 논문집
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• 제2권2호
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• pp.20-25
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• 2011

본 논문에서는 2차원 콘크리트 슬래브 철도교량을 특별직교이방성 복합적층판 이론으로 해석하였다. 슬래브의 해석에 있어 단면의 기하학적, 물리적 특성이 중립면에서 휨-연계강성 $B_{ij}$ = 0 이고, $D_{16}=D_{26}=0$임을 고려하였다. 교량상판은 특별직교이방성 판으로 거동한다. 이러한 경계조건을 갖는 단면 혹은 불규칙한 단면을 갖는 시스템은 해석적 해를 구하기가 매우 어렵다. 이러한 문제에 대한 해석을 위해서 유한차분법이 이용되었다. 본 논문에서는 보 이론과 유한차분법이 해석을 위해 사용되었다.

• 헤리티지:역사와 과학
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• 제46권4호
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• pp.108-125
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• 2013

경주 동천동 출토 토제범(土製范)에 대한 실측복원도, 조성광물 분석, 입도 및 물성시험, 미세조직관찰, 색도차 및 주성분 분석결과를 알아보았다. 연구대상 내범과 외범의 단면은 내측(제1층위)과 외측(제2층위)으로 구분되고 외측에는 유기물이 혼합되어 있다. 단면에는 열적 경험과 탈형제로 인한 변화 양상이 확인되며, X-선 촬영에서는 내측인 제1층위가 투과율이 높은 광물로 구성되었고 편광현미경에서 석영만이 관찰되었다. SEM 관찰에서 단면의 내측은 공극이 확대된 양상을 나타내고 중앙은 균열이 발달하였으며 외측에서는 변화를 관찰할 수 없었다. 구성입자의 입도는 내범과 외범이 거의 유사하며 미사질식양토로 구분되고, 미사질과 점토의 구성비는 약 2.7 : 1과 약 2.9 : 1이었다. 물성시험에서 내범과 외범의 밀도와 흡수율은 유사하고 공극률만이 내범이 27.36%와 외범은 31.09%로 다소 차이가 있었다. 단면의 색도차는 제1층위의 표면에 탈형을 위해 그을음을 입히거나 제1층위를 먹물로 수비하였을 가능성이 있다. 조성광물 분석에서는 내범과 외범의 조성광물이 동일하나 내범에서만 자철석이 동정되었다. 주성분 분석에서는 $SiO_2$의 평균함량이 71.64%, $Al_2O_3$는 14.59%이고, 부성분 중 $Fe_2O_3$는 4.51%, $K_2O$는 3.06%이며, $Na_2O$, MgO, CaO, $TiO_2$, $P_2O_5$, MnO는 2% 이하를 나타내었다.

• Steel and Composite Structures
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• 제30권5호
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• pp.471-481
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• 2019

Beam-columns are structural members subjected to a combination of axial and bending forces. Lateral-torsional buckling is one of the main failure modes. Beam-columns that are bent about its strong axis may buckle out of the plane by deflecting laterally and twisting as the values of the applied loads reach a limiting state. Lateral-torsional buckling failure occurs suddenly in beam-column elements with a much greater in-plane bending stiffness than torsional or lateral bending stiffness. This study intends to establish a unique convenient closed-form equation that it can be used for calculating critical elastic lateral-torsional buckling load of beam-column in the presence of a known axial load. The presented equation includes first order bending distribution, the position of the loads acting transversely on the beam-column and mono-symmetry property of the section. Effects of axial loads, slenderness and load positions on lateral torsional buckling behavior of beam-columns are investigated. The proposed solutions are compared to finite element simulations where thin-walled shell elements including warping are used. Good agreement between the analytical and the numerical solutions is demonstrated. It is found out that the lateral-torsional buckling load of beam-columns with mono-symmetric sections can be determined by the presented equation and can be safely used in design procedures.