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전자기-구조 상호 작용을 고려한 IPM 모터의 전자기 가진원 해석
남자현(Jahyun Nam),강치호(Chiho Kang),정근수(Geunsu Jeong),장건희(Gungee Jang) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
We investigated the magnetic excitation of an IPM motor considering magnetic and structural interaction through finite element method. The finite element model was developed and the magnetic-structural coupled analysis was performed by using COMSOL, a commercial multiphysics finite element analysis software package. In the coupled analysis, the magnetic force calculated by using the Maxwell stress tensor was applied to the structure, and the magnetic finite element model was rearranged by using the moving mesh method. We showed that coupled analysis predicted the excitation frequency of 667 Hz (the first natural frequency of the rotor) of magnetic force undergoing rotor eccentricity. This paper will contribute the accurate prediction of magnetic excitation in electromechanical machines.
경계윤활에서 기계 부품 소재의 트라이볼로지적 특성에관한 연구
김명구,서국진,남자현,김대은 한국트라이볼로지학회 2019 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.35 No.6
The friction and wear between machine components directly influence the energy loss and failure in various machines. Therefore, there is always a demand for finding methods to reduce friction and wear. Of the possible methods, lubrication is a widely used method for reducing friction and wear. In the case of lubrication, it is important to analyze the tribological behavior in the boundary lubrication because most of friction and wear occurs in the boundary lubrication regime. Cast iron has been regarded as a good material for industrial applications due to the excellent mechanical properties and high productivity. Especially, nodular cast iron is a material that shows better mechanical properties and wear-resistance compared with cast iron due to inclusion of spheroidal graphite. In this work, we investigated the tribological characteristics of nodular cast iron with respect to different counter parts in boundary lubrication regime. Sliding tests were conducted with SUJ2, ZrO2, Si3N4balls as counter parts using a pin-on-disk type tribotester. The results showed different friction and wear behaviors with different counter parts. The case of ZrO2 showed the lowest wear rate in specimen and no significant ball wear. In case of SUJ2, it showed similar wear rate with ZrO2 case in specimen and the highest friction coefficient. The case of Si3N4 showed the lowest friction coefficient, 33% lower than the case of SUJ2. It showed 16.9 times larger wear rate in specimen and 43% larger wear rate in ball compared to that of the SUJ2 case.
공진을 이용한 스마트 디바이스용 S-morph 피에조액츄에이터 개발
한상헌(S. H. Han),남자현(J. H. Nam),장건희(G. H. Jang) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.10
We propose a resonant s-morph piezoelectric actuator (RSPA) with high space efficiency and natural frequency within haptic frequency range for applying to smart device vibrators. RSPA consists of base, connector, cantilevers with two layers and weight. S-morph generates smaller displacement than uni-morph, but it has zero bending angle to generate uniform axial motion without tilting and space efficiency. We confirm the natural frequency and static displacement through the finite element analysis. In order to verify the validity of the analysis, we fabricate the RSPA sample and perform the vibration test. We show that the RSPA generate the axial displacement with zero bending angle, and has a natural frequency of 213.1 Hz within haptic frequency range(180 ~ 240 Hz).
컴프레서 부품의 DLC코팅 적용에 따른 트라이볼로지적 특성 연구
윤주용,서국진,한재호,전지환,송지영,고영덕,남자현,김선교,김대은 한국트라이볼로지학회 2022 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.38 No.1
Amorphous carbon (a-C) has excellent wear resistance and, therefore is used as a coating to protect numerous mechanical components to prolong their lifetimes. Among the a-C coatings, diamond-like carbon (DLC) and DLC-containing silicon (Si-DLC) receive extensive attention owing to their enhanced wear resistance and low frictional characteristics. In this study, the friction and wear characteristics of DLC and Si-DLC coatings are analyzed. For comparative analysis, DLC-coated and Si-DLC-coated vanes are utilized with the counterpart of a roller for the friction tests. Since the lubricated mechanical components are generally vulnerable to wear when a lubricant film does not form properly, friction tests are conducted under boundary lubrication conditions to promote wear. A cylinder-on-cylinder type tribometer is used to perform the friction tests with various normal load conditions. After the friction test, a 3D laser confocal microscope is used for quantifying the wear volume to calculate the wear rate of each specimen. Consequently, the DLC-coated specimen shows a lower coefficient of friction (COF) and wear rate than the specimen without the coating, while the Si-DLC coating shows a higher COF than the bare specimen. The results of this study are expected to contribute to improving the efficiency and reliability of compressors.
연태흠(T. H. Yeon),장건희(G. H. Jang),남자현(J. H. Nam) 한국소음진동공학회 2013 한국소음진동공학회 학술대회논문집 Vol.2013 No.4
This paper analyzes three cantilever-types of piezoelectric actuators of bimorph, unimorph and monomorph in same volume to maximize tip displacement. Tip displacement of each actuator is theoretically derived by using beam theory and numerically verified by FEM. It also investigates the tip displacements of each actuator due to the change of elastic layer. It shows that the piezoelectric actuator of bimorph generates the largest tip displacement among them.