• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.514-518
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• 2000

Micro wave seeker consists of a gimbal structure, a antenna and many RF parts. And Missile's propelling powers excite a gimbal structure, a antenna and many RF parts. Therefore, We must inquire into external forces to act on a micro wave seeker before everything. We must inquire into design parameters and then estimate dynamic characteristics of a gimbal structure with a finite element model to reflect part's characteristics for design for a gimbal structure in consideration of vibration features. In this paper, a gimbal structure of a micro wave seeker is modeled in finite element method and then updated by using the experimental modal data. Before we make a finite element model of a gimbal structure of a micro wave seeker, we make a finite element model of a sub-structure and compare with the experimental modal data.

• 한국정밀공학회지
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• 제21권8호
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• pp.34-42
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• 2004

A new polishing technique for three dimensional micro/meso-scale parts is suggested using a micro quill and a magnetic chain structure. The principle of this method is to polish the target surface with the collected magnetic brushes at a micro tool by the non-uniform magnetic field generated around the tool. In a typical magnetic abrasive finishing process magnetic particles and abrasive particles are unbonded each other. But, to finish the three dimensional small parts bonded magnetic abrasive have to be used. Bonded magnetic abrasives are made from direct bonding, and their polishing characteristics are also examined. Alumina, silicon carbide and diamond micro powders are used as abrasives. Base metal matrix is carbonyl iron powder. It is found that bonded magnetic abrasives are superior to unbonded one by experiment. finally, the polished surface roughness is evaluated by atomic force microscope.

• 콘크리트학회논문집
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• 제29권1호
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• pp.101-107
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• 2017

본 연구는 시멘트계 재료의 프랙탈 특성에 관한 기초적 연구로써, 고로슬래그 미분말 혼입 시멘트 페이스트의 공극 구조를 수은압입법을 이용하여 측정하였고, 측정된 결과를 프랙탈 모델에 적용하여 그 특성을 분석하였다. 분석 결과, 고로슬래그미분말 혼입 시멘트 페이스트의 공극 구조는 그 범위가 나노미터부터 밀리미터 단위까지 다양하게 분포하는 불규칙한 조직이기 때문에, 전체 영역에 대한 프랙탈 차원을 산정했을 때 각 공극 영역의 특성을 반영할 수 없다. 따라서 프랙탈 차원 산정 시 공극 영역을 나누어서 분석하였다. Zhang and Li (1995) model을 적용했을 때, 시멘트와 GGBFS의 수화반응 결과 생성된 C-S-H 내의 gel pores 및 small capillary pores에 해당하는 micro 영역과 large capillary pores에 해당하는 macro 영역에서 각각 프랙탈 특성이 나타나는 결과를 보였다. 또한 macro 영역보다 micro 영역의 공극 표면이 더 불규칙한 형상을 나타내었다. Ji et al. (1997) model을 적용할 경우, micro 영역이 C-S-H 내의 gel pores에 해당하는 micro I과 small capillary pores에 해당하는 micro II로 구분되었으며, 각각의 프랙탈 특성이 산정되었다. 또한 Zhang and Li (1995) model을 결과와 유사하게, macro, micro II, micro I의 순서대로 공극 크기가 작아질수록 VFD 결과 값이 감소하였으며, 이는 곧 공극의 복잡성이 증가함을 나타낸다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.508-513
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• 2000

Micro wave seeker detects micro wave signal reflecting from a object and modifies the angle of a antenna in the direction of a reflecting signal. Gimbal structure makes a motion in the direction of an elevation axis and an azimuth axis and change the direction of a missile toward a object. As before, Micro wave seeker is a important part of a missile. Especially, gimbal structure is designed to resist a external force generated by a strong propelling power. For that reason, it is essential to analyze a vibration feature of gimbal structure. In this paper, we analyze dynamic characteristics of a gimbal structure of a micro wave seeker. And we measure frequency response functions of a gimbal structure in order to investigate the effect of a pre-load on bearing.

• 한국분말재료학회지
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• 제22권3호
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• pp.169-174
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• 2015

The optical film for light luminance improvement of BLU that is used in LCD/LED and retro-reflective film is used as luminous sign consist of square and triangular pyramid structure pattern based on V-shape micro prism pattern. In this study, we analyzed machining characteristics of Cu-plated flat mold by shaping with diamond tool. First, cutting conditions were optimizing as V-groove machining for the experiment of micro prism structure mold machining with prism pattern shape, cutting force and roughness. Second, the micro prism structure such as square and triangular pyramid pattern were machined by cross machining method with optimizing cutting conditions. Burr and chip shape were discussed with material properties and machining method.

• 소성∙가공
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• 제15권2호
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• pp.158-163
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• 2006

The demand for the miniaturization and high-precision of machine part has recently increased in new technology like biotechnology(BT) and nanotechnology(NT). The purpose of this study is to analyze the molding characteristics according to injection conditions by measuring the filling height in micro injection molding of the polypropylene(PP) and cyclic olefin copolymer(COC). The result shows that the filling effect of COC is better than that of PP in micro rib structure with injection molding process.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계합동학술대회 논문집
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• pp.197-201
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• 2002

This paper presents optimized design, fabrication and thermal characteristics of micro-heaters for thermal MEMS (micro electro mechanical system) applications using SOI and trench structures. The micro-heaters are based on a thermal measurement principle and contains thermal isolation regions of 10 ${\mu}m$-thick Si membranes consisting of oxide-filled trenches in the SOI membrane rim. The micro-heaters were fabricated with Pt-RTD on the same substrate via MgO buff layer between Pt thin-film and $SiO_2$ layer. The thermal characteristics of micro-heater with trench-free SOI membrane structure was $280^{\circ}C$ at input power 0.9 W; in the presence of 10 trenches, it was $580^{\circ}C$ due to reduction of the external thermal loss. Therefore, a micro-heater with trenches in SOI membrane rim structure provides a powerful and versatile alternative technology for enhancing the performance of micro-thermal sensors and actuators.

• Steel and Composite Structures
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• 제26권4호
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• pp.421-437
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• 2018

Free vibration analysis of a three-layered microbeam including an elastic micro-core and two piezo-magnetic face-sheets resting on Pasternak's foundation are studied in this paper. Strain gradient theory is used for size-dependent modeling of microbeam. In addition, three-unknown shear and normal deformations theory is employed for description of displacement field. Hamilton's principle is used for derivation of the governing equations of motion in electro-magneto-mechanical loads. Three micro-length-scale parameters based on strain gradient theory are employed for prediction of vibrational characteristics of structure in micro-scale. The results show that increase of three micro-length-scale parameters leads to significant increase of three natural frequencies especially for increase of second micro-length-scale parameter. This result is according to this fact that stiffness of a micro-scale structure is increased with increase of micro-length-scale parameters.

• 한국공작기계학회논문집
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• 제16권5호
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• pp.77-83
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• 2007

The study on damaged layer is necessary for machinability improvement in micro machining. The damaged layer in metal cutting is derived from plastic deformation and transformation of metal structure. The damaged layer affects micro mold life and micro machine parts. In this study, the damaged layer of micro machined surface of copper is evaluated according to various machining condition. The damaged layer structure and metallurgical characteristics are measured by optical microscope, and evaluated by cutting forces and surface roughness. The scale of this damaged layer depends on cutting process parameters and machining environments. By experimental results, depth of damaged layer was increased with increasing of cutting depth, also the damaged layer is less occurred in down-milling compared to up-milling during micro endmilling operation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.1003-1007
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• 2002

Micro-EDM is generally used far machining micro 3-D structure. For micro-EDM, first of all, micro-electrode fabrication is needed and WEDG system is proposed for tool electrode fabrication method. When tool electrode is fabricated using WEDG system, its characteristics are under the control of many EDM parameters. Also relations between the parameters affect electrode fabrication. In this study, experiments are carried out to analyze effects of EDM parameters on micro-electrode fabrication. Experimental method and analysis are used to experimental design method. Factors used in experiments are composed of applied voltage, capacitance, wire feed rate, spindle rotating speed, machining time. As a result of experiments, wire feed rate, machining time and capacitance is proportional to gap distance(material removal), the other parameters(applied voltage, spindle rotating speed) and relations between the parameters have little influence on machining.