• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.151-154
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• 2001

Shape memory alloy (SMA) has demonstrated its potentials for various smart structure applications. SMA wires undergo a reversible phase transformation from martensite to austenite as temperature increases. This transformation leads to shape recovery and associated recovery strains. If SMA actuators are embedded off the neutral surface and are oriented in arbitrary angles with respect to a beam axis, then the beam bends and twists due to the coupling effects of recovery strains activated. In this study, the bending and twisting of a SMA/Composite beam were controlled by both electric resistive heating and passive elastic tailoring. 3-dimensional finite element formulations were derived and validated to analyze the responses of the SMA/Composite beam. Numerical results show that the shape of the SMA/Composite beam can be controlled by judicious choices of control temperatures, SMA angles, and elastic tailoring.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.575-580
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• 2004

In this work, the effect of composite couplings and mass distributions on hub loads of a hingeless rotor in forward flight is investigated. 1'he hingeless composite rotor is idealized as a laminated thin-walled box-beam. The nonclassical effects such as transverse shear and torsion warping are considered in the structural formulation. The nonlinear differential equations of motion are obtained by applying Hamilton's principle. The blade responses and hub loads are calculated using a finite element formulation both in space and time. The aerodynamic forces acting on the blade are calculated using the quasi-steady strip theory. The theory includes the effects of reversed flow and compressibility The magnitude of elastic couplings obtained by MSC/NASTRAN is compared with the classical pitch-flap($\delta$$_{3}$) coupling. It is observed that the elastic couplings and mass distributions of the blade have a substantial effect on the behavior of $N_{b/}$rev hub loads. About 40% hub loads is reduced by tailoring or redistributing the structural properties of the blade.f the blade.

• 한국소음진동공학회논문집
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• 제14권8호
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• pp.734-740
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• 2004

In this work, the effect of composite couplings and mass distributions on hub loads of a hingeless rotor in forward flight is investigated. The hingeless composite rotor is idealized as a laminated thin-walled box-beam. The nonclassical effects such as transverse shear and torsion warping are considered In the structural formulation. The nonlinear differential equations of motion are obtained by applying Hamilton’s principle. The blade responses and hub loads are calculated using a finite element formulation both in space and time. The aerodynamic forces acting on the blade are calculated using the quasi-steady strip theory. The theory includes the effects of reversed flow and compressibility. The magnitude of elastic couplings obtained by MSC/NASTRAN is compared with the classical pitch-flap($\delta$$_3$) coupling. It Is observed that the elastic couplings and mass distributions of the blade have a substantial effect on the behavior of $N_{b}$ /rev hub loads. About 40％ hub loads is reduced by tailoring or redistributing the structural properties of the blade.e.

• Advances in materials Research
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• 제9권2호
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• pp.115-131
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• 2020

Limit elastic speed analysis of Al/SiC-based functionally graded annular disk of uniform thickness has been carried out for two cases, namely: metal-rich and ceramic rich. In the present study, the unknown field variable for radial displacement is solved using variational method wherein the solution was obtained by Galerkin's error minimization principle. One of the objectives was to identify the variation of induced stress in a functionally graded disk of uniform thickness at limit elastic speed using modified rule of mixture by comparing the induced von-Mises stress with the yield stress along the disk radius, thereby locating the yield initiation. Furthermore, limit elastic speed has been reported for a combination of varying grading index (n) and aspect ratios (a/b).Results indicate, limit elastic speed increases with an increase in grading indices. In case of an increase in aspect ratio, limit elastic speed increases up to a critical value beyond which it recedes. Also, the objective was to look at the variation of yield stress corresponding to volume fraction variation within the disk which later helps in material tailoring. The study reveals the qualitative variation of yield stress for FG disk with volume fraction, resulting in the possibility of material tailoring from the processing standpoint, in practice.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.368-369
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• 2013

• Journal of Mechanical Science and Technology
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• 제16권5호
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• pp.666-675
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• 2002

Piezoelectric Fiber Composites with Interdigitated Electrodes (PFCIDE) were previously introduced as an alternative to monolithic wafers with conventional electrodes for applications of structural actuation. This paper is an investigation into the performance improvement of piezoelectric fiber composite actuators by changing the matrix material. This paper presents a modified micro-electromechanical model and numerical analyses of piezoelectric fiber/piezopolymer matrix composite actuator with interdigitated electrodes (PFPMIDE). Various concepts from different backgrounds including three-dimensional linear elastic and dielectric theories have been incorporated into the present linear piezoelectric model. The rule of mixture and the modified method to calculate effective properties of fiber composites were extended to apply to the PFPMIDE model. The new model was validated when compared with available experimental data and other analytical results. To see the structural responses of a composite plate integrated with the PFPMIDE, three-dimensional finite element formulations were derived. Numerical analyses show that the shape of the graphite/epoxy composite plate with the PFPMIDE may be controlled by judicious choice of voltages, piezoelectric fiber angles, and elastic tailoring of the composite plate.

• 한국항공우주학회지
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• 제32권7호
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• pp.29-36
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• 2004

본 연구에서는 전진비행시 무힌지 로터 블레이드의 허브하중에 대한 복합재료 연성의 영향을 고찰하였다. 무힌지 복합재료 로터 블레이드를 단일 상자형 보로 모델링 하였으며, 전단 변형 및 비틀림 워핑과 같은 비고전적 효과를 고려하였다. 운동방정식은 해밀턴의 원리를 이용하여 구성하였으며, 로터 블레이드의 공간 및 시간차원에서의 유한요소법을 적용하여 완전평형해석을 수행하였다. 블레이드에 작용하는 공기력은 2 차원 준정상 공기력 이론을 바탕으로 하여 역류 및 압축성 효과를 고려하였다. MSC/NASTRAN을 이용하여 피치 -플랩 및 피치-래그와 같은 탄성 연성의 크기를 구하고, 고전적인 기하학적 연계와 비교하였다. 탄생 연성은 $N_b/rev$ 허브하중의 특성에 적지 않은 영향을 미침을 확인하였다 블레이드 복합재료의 적층각을 적절히 변화시킬 경우 약 10-40%의 허브하중을 감소시킬 수 있음을 보였다.

• Journal of Chest Surgery
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• 제40권7호
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• pp.485-491
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• 2007

배경: 비록 흉강의 용적을 감소시키는 과정으로 100여 년 동안 광범위하게 이용하였지만 흉곽성형수술은 현재로는 희귀하게 되었다. 그러나 현재에도 저자는 20명의 환자에서 폐부분절제와 더불어 또는 후에 변형흉곽성형수술을 시행하였다. 이 연구의 목적은 변형흉곽성형수술의 조기와 만기 임상결과와 의의를 평가하기 위해서 시행하였다. 대상 및 방법: 1995년 3월부터 2005 6월까지, 감소된 폐 용적을 받아들일 수 있도록 흉강을 개형하거나 폐부분절제에 이어서 발생한 지속적인 공기누출에 의한 빈 공간을 폐쇄하기 위해서 총 298 폐부분절제술 환자 중 20명에서 폐부분절제술과 더불어서 또는 이어서 변형흉곽성형수술을 시행하였다. 20명의 환자 중 14명은 폐부분절제와 더불어서 변형흉곽성형수술을 시행하였고, 나머지 6명의 환자는 폐부분절제 후에 시행하였다. 나이는 24세에서 77세까지 (평균 $59.1{\pm}6.4$세)였고 남자가 17 : 3으로 많았고 좌우는 동수였다. 술 전 최초의 기저질환은 폐암이 7예, 거대 수 포성변화를 보이는 기흉 6예, 기관지확장증 2예, 또한 과거 폐결핵력을 갖고 있는 국균증 2예 그리고 농흉과 섬유흉을 보이는 2예, 나머지 1예는 이전의 흥부좌상에 의한 다발성 폐 농양과 폐 파손 1예였다. 수술방법은 폐상부박리수술과 첫 번째 늑골을 보존하고, 2, 3, 4번 늑골의 골막하절제술(늑골의 늑연골 접합부터 후부까지)그리고 전 흉부의 탄력붕대와 솜 뭉치에 의한 압박이었다. 결과: 흉곽성형수술 후 평균 공기누출은 $16{\pm}0.2$일($0{\sim}7$일), 흉관 거치기간은 7일($5{\sim}11$일)이었으며 평균 입원 일은 $19{\pm}2.8$일($8{\sim}47$일)이었다. 수술의 합병증은 폐부분절제와 더불어 흉곽성형수술환자에서는 상처감염 2예, 폐염 2예, 재개흉 1예였으며, 폐부분절제 후 흉곽성형수술환자에서 상처감염 1예이었다. 사망은 조기사망 1예 그리고 만기사망은 4예였다. 결론: 변형흉곽성형수술은 선택된 환자에서 폐부분절제와 함께 또는 이어서 시행함으로써 받아들일 만한 미용결과와 더불어서 감소된 폐용적을 적응하기 위해서나 지속적인 늑막의 공간이 기대되는 환자에서 빈 공간을 폐쇄하기 위해서 시행할 수도 있다고 결론을 내렸다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.53-56
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• 2001

Piezoelectric Fiber Composites with Interdigitated Electrodes (PFCIDE) were previously introduced as an alternative to monolithic wafers with conventional electrodes for applications of structural actuation. This paper is an investigation into the performance improvement of piezoelectric fiber composite actuators by changing the matrix material and actuator shape. This paper presents a modified micro-electromechanical model and numerical analyses of piezoelectric fiber/piezopolymer matrix composite actuator with interdigitated electrodes (PFPMIDE). Numerical analyses show that the shape of the graphite/epoxy composite plate with the PFPMIDE may be controlled by judicious choice of voltages, piezoelectric fiber angles, and elastic tailoring of the composite plate.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.108-111
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• 2007

It's important to measure quantitative properties about thermal-nano variation conduct of polymer for producing high quality components using NIL process. NanoScale indents can be used ad cells for molecular electronics and drug deliver, slots for integration into nanodevices, and defects for tailoring the structure and properties. In this study, it's to evaluate mechanical characteristic of polymer such as PMMA and PC at high temperature for manufacture of nano/micro size of polymer using indenter at high temperature. At high temperature mechanical properties of polymer have extreme variation. Because heating the polymer, it becomes softer than room temperature. In this case it is especially important to study for mechanical properties of polymer at high temperature.