• 대한기계학회논문집A
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• 제22권1호
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• pp.1-15
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• 1998

In this paper, thermo-viscoplastic finite element analysis of the effect of tool edge radius on cutting process are performed. The thermo-viscoplastic cutting model is capable of dealing with free chip geometry and chip-tool contact length. The coupling with thermal effects is also considered. Orthogonal cutting experiments are performed for 0.2% carbon steel with tools having 3 different edge radii and the tool forces are measured. The experimental results are discussed in comparison with the results of the FEM analysis. From the study, we confirm that this cutting model can well be applied to the cutting process considered the tool edge radius and that a major causes of the "size effect" is the tool edge radius. With numerical analysis, the effects of the tool edge radius on the stress distributions in workpiece, the temperature distributions in workpiece and tool, and the chip shape are investigated.estigated.

• 한국소음진동공학회논문집
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• 제21권4호
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• pp.374-383
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• 2011

A numerical model based on a mode method coupling beams and a rectangular plate is proposed to estimate radiation characteristics of an edge-clamped rectangular plate. The radiation efficiency and radiation power in the audio frequency range including the critical frequency can be predicted. The proposed model is rather simple and straightforward and gives reliable results comparing to the previous studies. The estimated radiation characteristics are compared to those of the pinned condition plates and also to those based on the formulae proposed by Maidanik. The radiation efficiency of the clamped plate seems a little higher than that of the pinned plate in the frequency range of corner and edge modes. It is explicitly shown that the power as well as efficiency at high frequencies is not influenced by these edge boundary conditions.

• Tribology and Lubricants
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• 제36권6호
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• pp.359-364
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• 2020

Numerical investigation of the groove trap effect with variation in the groove-edge radius of curvature is presented here. The trap effect is evaluated in a two-dimensional sliding bearing using computational fluid dynamics (CFD). This simulation is based on the discrete phase model (DPM) and standard k - ε turbulence model using commercial CFD software, FLUENT. The numerical results are evaluated by comparisons with streamlines and particle trajectories in the grooves. Grooves are applied to various lubrication systems to improve their lubrication characteristics, such as load carrying capacity increment, leakage reduction, frictional loss reduction, and preventing three-body abrasive wear due to trapping effect. This study investigates the grove trapping effect for various groove-edge radius of curvature values and Reynolds numbers. The particle is assumed to be made of steel, with a circular shape, and is injected as a single particle in various positions. One-way coupling is used in the DPM model because the single particle injection condition is applied. Further, the "reflect" condition is applied to the wall boundary and "escape" condition is used for the "pressure inlet" and "pressure outlet" boundaries. From the numerical results, the groove edge radius is found to influence the groove trap effect. Moreover, the groove trap effect is more effective when applying the groove edge radius.

• 대한전자공학회논문지TC
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• 제47권6호
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• pp.26-34
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• 2010

기판 크기가 유한하면 두 패치안테나간의 상호결합은 기판 가장자리에서 회절되어 들어오는 표면파에 의해 영향을 받는다. 상호결합이 최소가 되는 패치안테나 중심과 기판 가장자리까지의 거리는 접지된 기판의 유효 유전상수에 의해 결정됨을 알 수 있었다. 상호결합이 최소화되는 기판 크기는 이미지 방법을 사용하여 쉽게 계산 할 수 있다. 이미지 방법으로 계산한 최적화된 기판 크기와 전산모의 결과로 얻어진 최적화된 기판 크기가 잘 일치하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.967-972
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• 2008

This paper presents the free vibration analysis of a circular plate with a concentric square hole. The present problem deals with the numerical calculation of the natural frequencies and mode shapes of vibration of the structure by means of Independent Coordinate Coupling Method (ICCM). In this study, the boundary condition is the edge of the square hole is free and the outer circular plate is simply supported. Due to the geometric abnormality, this analysis does not permit an exact solution. Since the ICCM employs coordinate systems corresponding to each domain independently, the kinetic and potential energy expressions necessary for the Rayleigh-Ritz method can be easily obtained. Lastly, the kinematic relation is imposed. In this way, the eigenvalue problem can be easily set up. The numerical results show the efficacy of the ICCM and changes in natural frequencies and modes due to the square hole size.

• 한국소음진동공학회논문집
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• 제19권2호
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• pp.192-199
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• 2009

This paper presents the free vibration analysis of a circular plate with a concentric square hole. The boundary condition is the edge of the square hole is free and the outer circular plate is simply supported. Due to the geometric abnormality, this analysis does not permit an exact solution. The present problem deals with the numerical calculation of the natural frequencies and mode shapes of vibration of the structure by independent coordinate coupling method(ICCM). The numerical results show the efficacy of the ICCM and changes in natural frequencies and modes due to the square hole size.

• 한국전자파학회논문지
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• 제13권10호
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• pp.1078-1082
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• 2002

두 스텁이 커플된 마이크로스트립 계단 임피던스 저역통과 필터의 전송선로의 폭과 edge 캐패시턴스의 변화에 따른 삽입손실 특성을 연구하였다. 이 구조에서 커플링효과는 전송선로의 폭과 스텁의 갭 간격에 의존하며 적절한 조건에서 3개의 감쇄폴이 생겨 넓은 저지대역을 가진다. 또한, 두 스텁 사이에 존재하는 edge 캐패시턴스는 3개의 감쇄폴을 가지기 위해서 중요한 역할을 한다. 이것을 [S] 파라피터를 구하여 확인했다.

• 한국정보통신학회논문지
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• 제26권7호
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• pp.1032-1039
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• 2022

이동통신 중계기에 사용하는 SAW(Surface Acoustic Wave) 방식의 대역통과필터를 대체할 수 있는 5G 이동통신 중계기용 군 지연 특성이 개선된 크로스 커플링 등화기 구조를 결합한 캐비티 대역통과필터를 설계하고 이를 구현하였다. 3D EM 시뮬레이션 툴 (HFSS)을 이용하여 공진 주파수, 공진기 간 결합 계수와 공진기 사이 외부 품질 계수를 계산하였고, 이를 바탕으로 메탈 캐비티 구조로 주파수대역 3500MHz~3600MHz, 대역폭 97.85MHz로 대역 양쪽 가장자리 주파수(edge)단에서 20dB 이상의 감쇄 특성을 가지도록 12차 대역 통과 필터를 제작 하였다. 설계 제작한 대역통과필터는 5G 이동통신 표준에 요구하는 군 지연 시간 조건과 인-밴드, 아웃-밴드 주파수 응답을 만족하였다.

• Wind and Structures
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• 제34권5호
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• pp.437-450
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• 2022

Vortex-induced vibration (VIV) is a significant concern when designing slender structures with square cross sections. VIV strongly depends on structural dynamics and flow states, which depend on the conditions of the approaching flow and shape of a structure. Therefore, the effects of the angle of attack on the coupling effects of VIV for a square cylinder are expected to be significant in practice. In this study, the aerodynamic forces for a fixed and elastically mounted square cylinder were measured using wind pressure tests. Aerodynamic forces on the stationary cylinder are firstly discussed by comparisons of variation of statistical aerodynamic force and wind pressure coefficient with wind angle of attack. The coupling effect between the aerodynamic forces and the motion of the oscillating square cylinder by VIV is subsequently investigated in detail at typical wind angels of attack with occurrence of three typical flow regimes, i.e., leading-edge separation, separation bubble (reattachment), and attached flow. The coupling effect are illustrated by discussing the onset of VIV, characteristics of aerodynamic forces during VIV, and interaction between motion and aerodynamic forces. The results demonstrate that flow states can be classified based on final separation points or the occurrence of reattachment. These states significantly influence coupling effects of the oscillating cylinder. Vibration enhances vortex shedding, which creates strong fluctuations in aerodynamic forces. However, differences in the lock-in range, aerodynamic force, and interaction process for angles of attack smaller and larger than the critical angle of attack revealed noteworthy characteristics in the VIV of a square cylinder.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.561-564
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• 1999

The uniform state of prestress in a fully prestressed concrete members shows reductions of more than half of the initial prestress in the construction and coupling joint vicinity. Especially, at a zone x/d=0.2 above the construction joint where at the edge of the member, a quite localized reduced stress state of 1/3 of uniform stress is encountered. Five full-scale test specimens were segmentally constructed and post-tensioned and analytic models is used to verify and validate measured test results. The encountered highly nonuniform stress/strain state in the coupling joint vicinity requires special design consideration for the successful application of tendon couplers.