• 한국해양공학회지
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• 제20권2호
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• pp.16-21
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• 2006

This paper discusses the behavior of post-tensioned and shaped hypar space truss, with consideration of the influence of removing some web members. Hypar space truss is post-tensioned at the bottom chords of one diagonal on the ground; the essential behavior characteristic of shape formation is discussed by using a small-scale test model. Results of experiments and nonlinear finite-element analysis indicate that a planar, rectangular- arranged structure can be deformed to a predicted hyper shape, by the proposed shape formation method. Also the feasibility of the proposed method for furnishing of a hypar shaped face truss has been presented, under the condition of both non-removed and partially removed web members. It follows that a nonlinear finite element analysis method can be used in predicting the behavior of the space shape and the post-tensioning force in sharing of hypar space truss. Further, in comparison to the other cases, the results of test and analysis show that the active diagonal shaping in the non-removed web members and passive diagonal shaping of partially removed web members are in relatively good agreement.

• Structural Engineering and Mechanics
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• 제52권5호
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• pp.919-935
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• 2014

In this study, the control of the shape of pre-stressed cable structures and the effective control element were examined. The process of deriving the displacement control equations using the force method was explained, and the concurrent control scheme (CCS) and the sequence control scheme (SCS) were proposed. To explain the control scheme process, the quadrilateral cable net model was adopted and classified into a regular model and an irregular model for the analysis of the control results. In the control analysis of the regular model, the CCS and SCS analysis results proved reliable. For the SCS, the errors occur in the control stage and varied according to the control sequence. In the control analysis of the irregular model, the CCS analysis result also proved relatively reliable, and the SCS analysis result with the correction of errors in each stage was found nearly consistent with the target shape after the control. Finally, to investigate an effective control element, the Geiger cable dome was adopted. A set of non-redundant elements was evaluated in the reduced row echelon form of a coefficient matrix of control equations. Important elements for shape control were also evaluated using overlapping elements in the element sets, which were selected based on cable adjustments.

• 한국재료학회지
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• 제30권11호
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• pp.589-594
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• 2020

Many electronic applications require magnetic materials with high permeability and frequency properties. We improve the magnetic permeability of soft magnetic powder by controlling the shape magnetic anisotropy of the powders and through the preparation of amorphous nanoparticles. For this purpose, the effect of the shape magnetic anisotropy of amorphous Fe-B-P nanoparticles is observed through a magnetic field and the frequency characteristics and permeability of these amorphous nanoparticles are observed. These characteristics are investigated by analyzing the composition of particles, crystal structure, microstructure, magnetic properties, and permeability of particles. The composition, crystal structure, and microstructure of the particles are analyzed using inductively coupled plasma optical emission spectrometry-, X-ray diffraction, scanning electron microscopy and focused ion beam analysis. The saturation magnetization and permeability are measured using a vibrating sample magnetometer and an LCR meter, respectively. It is confirmed that the shape magnetic anisotropy of the particles influences the permeability. Finally, the permeability and frequency characteristics of the amorphous Fe-B-P nanoparticles are improved.

• 한국유체기계학회 논문집
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• 제18권2호
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• pp.5-13
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• 2015

The aim of this study is to investigate the feasibility of a new type of casing for the inline Francis hydro turbine. Comparing with the traditional turbine with spiral casing, this turbine is unique for its flow passage shape at the first stage of flow to the turbine, very similar to a pipe, called inline casing. Before the commercialization of this new type of casing, a global investigation of the inline casing must be conducted. Preserving the structural characteristics of simple, compact-size and convenient for manufacture, different shapes of the belt passage, vertical corner and stay vanes are applied to investigate the influence of flow passage shape on the turbine performance. Stable and relatively high efficiency is achieved regardless of flow passage shape difference proving the feasibility of the inline casing used in a hydro turbine.

• EDISON SW 활용 경진대회 논문집
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• 제5회(2016년)
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• pp.203-208
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• 2016

In this paper, vibration characteristics in terms of the airfoil cross-sectional shape was examined by using the EDISON co-rotational plane beam-transient analysis. Assuming aircraft wing as a cantilevered beam with a constant cross-sectional shape, natural frequencies of each airfoil shape was compared while varying airfoil maximum thickness and maximum camber length, using Fast Fourier Transformation(FFT). When the airfoil maximum thickness was varied, natural frequency showed peak value at 18% chord, and decreased afterwards. When the airfoil maximum camber length was varied, natural frequency either increased or decreased at 6% chord, while at 8% the natural frequency showed its maximum. Applying such trends to B-737 wing airfoil, an improved B-737_mod airfoil shape was obtained with regard to the vibration characteristics.

• Structural Engineering and Mechanics
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• 제68권5호
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• pp.519-526
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• 2018

In this article, experimental training of the commercial available shape memory alloy fibre (SMA) fibre under the combined thermomechanical loading is reported. SMA has the ability to sense a small change in temperature (${\geq}10^{\circ}C$) and activated under the external loading and results in shape change. The thermomechanical characteristics of SMA at different temperature and mechanical loading are obtained through an own lab-scale experimental setup. The analysis is conducted for two types of the medium using the liquid nitrogen (cold cycle) and the hot water (heat cycle). The experimental data indicate that SMA act as a normal wire for Martensite phase and activated behavior i.e., regain the original shape during the Austenite phase only. To improve the confidence of such kind of behavior has been verified by inspecting the composition of the wire. The study reveals interesting conclusion i.e., while SMA deviates from the equiatomic structure or consist of foreign materials (carbon and oxygen) except nickel and titanium may affect the phase transformation temperature which shifted the activation phase temperature. Also, the grain structure distortion of SMA wire has been examined via the scanning electron microscope after the thermomechanical cycle loading and discussed in details.

• 항공우주시스템공학회지
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• 제9권2호
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• pp.7-12
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• 2015

In this paper, we report a non-explosive separation device for a small satellite which utilize a shape memory alloy actuator and spring clamp. In order to increase the preload, the proposed device employs spring clamp that can generate high toque when the shape memory alloy actuator makes the cylinder key unlatch a holding ball effectively. Owing to simple design of separation device configuration, we could obtain good repeatability(up to 30 times activation). Conclusively, we could develop a non-explosive separation device which can reliably activate within 1.2 sec under high preload(up to 300kgf).

• 한국전산유체공학회지
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• 제17권3호
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• pp.93-98
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• 2012

The injection molding process is suitable for manufacturing complicated plastic products. As the customer request higher quality products increase, realization of the precise dimensional and shape controls is getting more important. For this purpose it is important to obtain uniform cooling procedure over the whole surface of the high temperature molded plastic. Failure to this may lead to different shrinkage speed, internal stresses and unwanted shape deformations. It is necessary to distribute coolant flow rates to the main channel and to the sub-channels properly to insure uniform cooling process when there are parallel cooling channels. In this study, three-dimensional turbulent flow simulations for representative parallel cooling channels were performed. To insure the intended flow rate to each sub-channels, various shape designs for the channel system were investigated. The results show that as the Reynolds number increases the effect of shape design is more profound. Through the proper flow distribution, uniform cooling effects would be expected.

• 한국재료학회지
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• 제8권11호
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• pp.993-998
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• 1998

본 연구는 형상기억합금을 이용하여 제조한 신소재 중의 하나인 형상기억복합재료를 소개하고자 한다. 이 복합재료는 TiNi 섬유의 형상기억효과로 금속복합재료의 취약점이라 할 수 있는 기지와 섬유간의 열팽창차이로 인한 인장잔류응력을 제거하고 기지내에 압축잔류응력을 발생시켜 높은 인장강도를 갖는다. 따라서 본 연구에서는 용탕단조법으로 복합재료를 제조한 후 미세조직을 관찰하고 TiNi 섬유의 역변태온도 이상에서 피로실험을 수행하여 복합재료의 피로특성을 검토하였다. 이 결과 363K에서의 피로균열전파제어효과는 섬유체적률과 예변형에 의하여 증가된다.

• Elastomers and Composites
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• 제42권4호
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• pp.217-223
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• 2007

결정성을 갖는 에틸렌프로필렌디엔 고무($Nordel^{(R)}$ IP)를 과산화물로 가교시키고 열적, 기계적특성과 형상기억거동을 조사하였다. 겔함량 측정결과 가교도는 DCP 함량에 따라 증가되었으며, DSC 분석결과 가교된 고무는 결정상이 존재하고 있음을 알 수 있었다. 인장시험 결과가교도가 증가함에 따라 고무의 모듈러스는 증가되며 파단신율은 감소되었다. 이와 같이 가교구조 내에 결정상을 함유하는 고무는 우수한 형상기억 특성을 나타내었다. 즉, 이러한 고무는 결정상의 용융온도 이상에서 쉽게 원하는 형태로 변형되고, 변형된 상태에서 냉각시키면 변형된 형태로 잘 고정되었으며, 또한 이렇게 변형된 형상의 시료를 용융온도 이상으로 가열하면 원래의 모양으로 신속히 되돌아오는 것을 관찰할 수 있었다.