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2차원 곡면형 전극에서 정전기 흡착력의 아이소-지오메트릭 해석
오명훈,김재현,김현석,조선호,Oh, Myung-Hoon,Kim, Jae-Hyun,Kim, Hyun-Seok,Cho, Seonho 한국전산구조공학회 2021 한국전산구조공학회논문집 Vol.34 No.4
본 논문에서는 정전기 흡착패드를 구성하는 곡면형 전극의 기하학적 엄밀성을 고려하기 위해 정전기 문제에 대하여 CAD에서 사용하는 NURBS 기저함수를 직접 사용하는 아이소-지오메트릭 해석 기법을 도입하였다. 정전기 흡착력을 곡선 접촉면에서 구하는데 법선 벡터의 영향이 크므로 엄밀한 기하형상을 고려하는 아이소-지오메트릭 해석이 강점을 갖는다. 수치 예제를 통해 곡면과 평면에서 반복 구조의 유무에 따른 파라메터 연구를 수행하여 곡면형 전극의 흡착력이 좋은 성능을 가짐을 보였다. 정전기 흡착력의 성분을 분석하였을 때 정전기 흡착력의 차이는 법선 성분 전기장의 증가로 인한 것으로 파악되었다. 결론적으로 곡면형 전극에서도 전극 사이 거리가 가까워지는 아래로 볼록인 경우가 가장 성능이 좋고, 위로 볼록인 경우에는 성능이 가장 낮음을 보였다. In this study, an isogoemetric analysis (IGA) method that uses NURBS (Non-Uniform Rational B-Spline) basis functions in computer-aided design (CAD) systems is employed to account for the geometric exactness of curved electrodes constituting an electro-adhesive pad in electrostatic problems. The IGA is advantageous for obtaining precise normal vectors when computing the electro-adhesive forces on curved surfaces. By performing parametric studies using numerical examples, we demonstrate the superior performance of the curved electrodes, which is attributed to the increase in the normal component of the electro-adhesive forces. In addition, concave curved electrodes exhibit better performance than their convex counterparts.
지자기센서 기반의 스마트폰 사용자 인터페이스를 통한 메니퓰레이터의 직관적 작업구현
오명훈(Myung-Hoon Oh),김동헌(Dong Hun Kim) 제어로봇시스템학회 2017 제어·로봇·시스템학회 논문지 Vol.23 No.11
In this paper, the intuitive operation to control a robot manipulator based on a compass sensor embedded in a smart-phone is proposed. When a user rotates the smart-phone in a desired direction, the manipulator rotates according to the rotation angle of the smart-phone, which is rotated by the user. The proposed smart-phone control using a compass sensor provides more convenient and intuitive operation than the existing button operations. Thus, it is possible to easily control the robot without considering the user"s posture, position and proficiency. The paper shows that the experimental results can effectively and intuitively operates a robot manipulator via the smart-phone’s user interface based on a compass sensor.
극대화된 밴드갭을 갖는 켈빈 격자 구조의 아이소-지오메트릭 최적 설계
최명진,오명훈,조선호,구본용,Choi, Myung-Jin,Oh, Myung-Hoon,Cho, Seonho,Koo, Bonyong 한국전산구조공학회 2019 한국전산구조공학회논문집 Vol.32 No.4
밴드갭은 기계적 파동의 전파가 금지되는 특정 주파수 범위를 의미한다. 본 연구는 경사도 기반의 설계 최적화 방법을 사용하여 낮은 가청 주파수 범위에서 밴드갭을 갖는 3차원 켈빈 격자를 설계하는 것을 목적으로 하고 있다. 블로흐 이론을 이용하여 무한주기 격자에서의 탄성파 전파를 해석하고, 기하학적으로 엄밀한 빔 이론에서 선형화를 통해 얻은 전단 변형 가능한 빔 모델을 사용하여 격자 구조 연결선을 모델링하였다. 주어진 격자 구성에서 중립 축 및 단면 두께를 B-spline 함수를 이용한 아이소-지오메트릭 매개화를 통해 설계 변수로 정의하고, 격자 구조의 밴드갭의 크기를 극대화하는 최적 설계를 수행하였다. A band gap refers to a certain frequency range where the propagation of mechanical waves is prohibited. This work focuses on engineering three-dimensional Kelvin lattices having external band gaps at low audible frequency ranges using a gradient-based design optimization method. Elastic wave propagation in an infinite periodic lattice is investigated by employing the Bloch theorem. We model the ligaments using a shear-deformable beam model obtained by consistent linearization in a geometrically exact beam theory. For a given lattice topology, we enlarge band gap sizes by controlling the configuration of the beam neutral axis and cross-section thickness that are smoothly parameterized by B-spline basis functions within the isogeometric analysis framework.
마찰용접을 적용한 Cu-Al Busbar의 전기적 물성 연구
김기영,최인철,오명훈,Kim, Ki-Young,Choi, In-Chul,ITO, Kazuhiro,Oh, Myung-Hoon 한국열처리공학회 2020 熱處理工學會誌 Vol.33 No.6
Since the dissimilar bonded interface usually consists of intermetallic compounds (IMCs) layer and cracks, their mechanical and electrical properties can be influenced by microstructure at interface between two different metals. In this study, the friction welded Cu-Al busbar, which is widely used to connect a secondary battery and their component, is selected to analyze the influence of interfacial characteristic on their tensile strength and electric conductivity. Then, the electrical characteristics of Cu busbar and Cu-Al busbar were investigated by thermal flow analysis and temperature rise test. In addition, the relationship between the maximum saturation temperature and the electrical conductivity were discussed in terms of interfacial characteristics of the friction welded Cu-Al busbar.
압축-비틀림이 결합된 격자구조의 아이소-지오메트릭 해석
강세현,최명진,오명훈,윤민호,조선호,Kang, Se-Hyeon,Choi, Myung-Jin,Oh, Myung-Hoon,Yoon, Min-Ho,Cho, Seonho 한국전산구조공학회 2021 한국전산구조공학회논문집 Vol.34 No.5
We utilized the isogeometric analysis (IGA) method that uses NURBS basis functions in CAD systems, to account for the geometric exactness of a geometrically exact beam deformation, on a new type of metamaterial, twist-translation coupled structure showing a large twist angle. A two-dimensional unit cell structure was embedded in a cylindrical wall, using free-form deformation and an appropriate interpolation scheme. A parametric study on the effects of the dimensions of the cylinder and the number of cells, on the twisting angle was performed. Furthermore, the mechanism of the twist-translation coupled metamaterial was explored through numerical examples. 본 논문에서는 CAD 시스템에서 사용하는 NURBS 기저함수를 사용하는 아이소-지오메트릭 해석(Isogeometric analysis) 방법과 기하학적으로 엄밀한 빔 모델링(geometrically exact beam model)을 활용하여 회전과 병진 운동이 결합된 새로운 형태의 메타물질(metamaterial)에 대한 해석을 진행하였다. 이차원 셀 구조는 자유형상변환(Free-form deformation) 법과 적절한 내삽법(Interpolation)을 통해 원통 위에 입혀졌다. 원통의 치수와 셀 개수가 비틀림 각도에 미치는 영향이 매개변수 연구(parametric study)를 통해 확인되었다. 비틀림과 병진 운동이 결합된 구조의 메커니즘에 대해 수치 예제를 통해 알아보았다.
Characteristics Studies of Waste Tire Rubber Powders using the Different Grinding Methods
박종문,안주영,방대석,김봉석,오명훈,Park, Jong-Moon,An, Ju-Young,Bang, Daesuk,Kim, Bong-Seok,Oh, Myung-Hoon The Korean Institute of Resources Recycling 2014 資源 리싸이클링 Vol.23 No.3
본 연구에서는 기존의 cutting 분쇄방식 대신 여러 가지 문제점을 개선한 shear방식 및 2단 disk mill 방식으로 폐타이어를 미분화시켰다. 각 파쇄 또는 분쇄 단계별로 다양한 크기의 고무 칩을 얻을 수 있었다. Shear방식 및 2단 disk mill 방식은 회전 속도와 방향이 다른 두 개의 드럼형의 칼날로 이루어져 있어서 기존의 cutting 방식보다 거친 표면의 미분화 폐타이어 분말을 얻을 수 있었다. 본 연구에서는 주로 shear방식으로 미분화된 폐타이어 분말의 형상을 SEM을 통해 비교하였다. 추가적으로 적절한 크기의 폐타이어 분말이 얻어졌는지를 확인하기 위해 입도분석을 수행하였다. In this study, a method of shear crushing and a two-stage disk mill were introduced to grind the waste tire powder. Rubber chips with various size were obtained during the crushing or grinding step. The two-stage disk mill was composed of two drum-type blades rotating at various speed and in opposite directions. Therefore, more roughly surfaced particles of micronized waste tire powder were obtained using shear crushing rather than using conventional cutting crushing. In this study, the shape of shear-crushed waste tire particles was compared with conventional cutting crushing particles by scanning electron microscope. In addition, the particle size analyzer was employed to determine the appropriate particle size of waste ground tire powders obtained in this study.
삽입금속 Cu를 이용한 TiAl 합금과 SCM440의 마찰용접 계면 특성
박성현,김기영,박종문,최인철,오명훈,Park, Sung-Hyun,Kim, Ki-Young,Park, Jong-Moon,Choi, In-Chul,Ito, Kazuhiro,Oh, Myung-Hoon 한국재료학회 2019 한국재료학회지 Vol.29 No.4
Since the directly bonded interface between TiAl alloy and SCM440 includes lots of cracks and generated intermetallic compounds(IMCs) such as TiC, FeTi, and $Fe_2Ti$, the interfacial strength can be significantly reduced. Therefore, in this study, Cu is selected as an insert metal to improve the lower tensile strength of the joint between TiAl alloy and SCM440 during friction welding. As a result, newly formed IMCs, such as $Cu_2TiAl$, CuTiAl, and $TiCu_2$, are found at the interface between TiAl alloy and Cu layer and the thickness of IMCs layers is found to vary with friction time. In addition, to determine the relationship between the thickness of the IMCs and the strength of the welded interfaces, a tensile test was performed using sub-size specimens obtained from the center to the peripheral region of the friction-welded interface. The results are discussed in terms of changes in the IMCs and the underlying deformation mechanism. Finally, it is found that the friction welding process needs to be idealized because IMCs generated between TiAl alloy and Cu act to not only increase the bonding strength but also form an easy path of fracture propagation.
CP-Ti 분말로부터 스파크 플라즈마 소결한 타이타늄의 미세구조와 기계적 성질에 미치는 소결 온도의 영향
조경식,송인범,장민혁,윤지혜,오명훈,홍재근,박노광,Cho, Kyeong-Sik,Song, In-Beom,Jang, Min-Hyeok,Yoon, Ji-Hye,Oh, Myung-Hoon,Hong, Jae-Keun,Park, Nho-Kwang 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.5
The evolution of sinterability, microstructure and mechanical properties for the spark plasma sintered(SPS) Ti from commercial pure titanium(CP-Ti) was studied. The densification of titanium with 200 mesh and 400 mesh pass powder was achieved by SPS at $750{\sim}1100^{\circ}C$ under 10 MPa pressure and the flowing $H_2$+Ar mixed gas atmosphere. The microstructure of Ti sintered up to $800^{\circ}C$ consisted of equiaxed grains. In contrast, the growth of large elongated grains was shown in sintered bodies at $900^{\circ}C$ with the 400 mesh pass powder and the lamella grains microstructure had been developed by increasing sintering temperature. The Vickers hardness of 240~270 HV and biaxial strength of 320~340 MPa were found for the specimen prepared at $950^{\circ}C$.