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정밀가공용 고속 자동선반 베드의 정하중 및 공진주파수 해석
하주환,이윤철,주강우,조은정,이영식,이재권,김광선 한국반도체디스플레이기술학회 2017 반도체디스플레이기술학회지 Vol.16 No.2
This paper is about the analysis on the vibration characteristic of tooling units on the precision bed in high-speed automatic lathe for precision machining. An automatic lathe operating at about 25,000 RPM is a critical factor in the self-weight stress and deformation of the bed. Especially, the resonance frequency should be grasped in advance to prevent abnormal vibration that may occur during processing. If the wrong bed is used, the resonant frequency can have a fatal influence on the precision machining and increase the defective rate of precision machined parts such as semiconductor parts. In this paper, vibration characteristics were evaluated through static load and resonance frequency analysis of automatic lathe bed. As a result, the maximum stress was 0.14MPa, the maximum deformation amount was 17.9μm, and the natural frequency was 364.72Hz. The resonance frequency was calculated as 718Hz, and the stability was confirmed by being in the range of 400Hz or more, which is the processing condition.
선삭 및 호빙 가공용 자동선반 베드의 정하중 및 공진주파수 해석
하주환,이윤철,조은정,이영식,이재권,김광선 한국반도체디스플레이기술학회 2018 반도체디스플레이기술학회지 Vol.17 No.1
This paper is about the analysis on the vibration characteristic of tooling units on the precision bed in turning and hobbing automatic lathe for precision machining. An automatic lathe operating at about 12,000 RPM is a critical factor in the self-weight stress and deformation of the bed. Especially, the resonance frequency should be grasped in advance to prevent abnormal vibration that may occur during processing. If the wrong bed is used, the resonant frequency can have a fatal influence on the precision machining and increase the defective rate of precision machined parts such as semiconductor parts. In this paper, vibration characteristics were evaluated through static load and resonance frequency analysis of automatic lathe bed. As a result, the maximum stress was 14.52 MPa, the maximum deformation amount was 12.15 μm, and the natural frequency was 189.43 Hz. The resonance frequency was calculated as 500 Hz, and the stability was confirmed by being in the range of 200 Hz or more, which is the processing condition.
입자추적 유동해석을 이용한 초음파분무화학기상증착 균일도 예측 연구
하주환,박소담,이학지,신석윤,변창우,Ha, Joohwan,Park, Sodam,Lee, Hakji,Shin, Seokyoon,Byun, Changwoo 한국반도체디스플레이기술학회 2022 반도체디스플레이기술학회지 Vol.21 No.3
Mist-CVD is known to have advantages of low cost and high productivity compared to ALD and PECVD methods. It is capable of reacting to the substrate by misting an aqueous solution using ultrasonic waves under vacuum-free conditions of atmospheric pressure. In particular, Ga<sub>2</sub>O<sub>3</sub> is regarded as advanced power semiconductor material because of its high quality of transmittance, and excellent electrical conductivity through N-type doping. In this study, Computational Fluid Dynamics were used to predict the uniformity of the thin film on a large-area substrate. And also the deposition pattern and uniformity were analyzed using the flow velocity and particle tracking method. The uniformity was confirmed by quantifying the deposition cross section with an FIB-SEM, and the consistency of the uniformity prediction was secured through the analysis of the CFD distribution. With the analysis and experimental results, the match rate of deposition area was 80.14% and the match rate of deposition thickness was 55.32%. As the experimental and analysis results were consistent, it was confirmed that it is possible to predict the deposition thickness uniformity of Mist-CVD.
계층적 B-스플라인을 이용한 스플라인 유한요소법의 국부 세분화에 관한 연구
하주환(Zoo-Hwan Hah),김현중(Hyun-Jung Kim),윤성기(Sung-Kie Youn) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.8
본 연구에서는 NURBS 의 국부 세분화 방법 중 하나인 계층적 B-스플라인을 이용해 스플라인 유한요소법의 국부 세분화를 수행하는 방법을 제안한다. 세분화가 필요한 영역에 전역 격자로부터 계층적으로 생성된 국소 격자를 중첩시켜 국부 세분화를 수행한다. 국소 격자의 매듭 벡터와 제어점은 전역 격자로부터 추출된 후 세분화 되는 과정을 거친다. 생성된 국소 격자에 적절한 연속성 조건을 부여 함으로써 전역 격자와 국소 격자의 연속성을 유지 한다. 제안된 방법을 이용해 수치 예제의 해석을 수행하였다. 이를 통해 기존 NURBS 기반 스플라인 유한요소법에 비해 제안된 방법의 효율성을 검증하였다. A new local refinement scheme for spline finite element method has been proposed; this scheme involves the use of hierarchical B-spline. NURBS has been widely used in CAD; however, the local refinement of NURBS is difficult due to its tensor-product property. In this study, we attempted to use hierarchical B-splines as local refinement strategy in spline FEM. The regions of high gradients are overlapped by hierarchically-created local meshes. Knot vectors and control points in local meshes are extracted from global meshes, and they are refined using specific schemes. Proper compatibility conditions are imposed between global and local meshes. The effectiveness of the proposed method is verified on the basis of numerical results. Further, it is shown that by using a proposed local refinement scheme, the accuracy of the solution can be improved and it could be higher than that of the solution of a conventional spline FEM with relatively lower degrees of freedom.
피난 시뮬레이션을 이용한 피난 유도 시스템의 성능 평가
김준영,하주환,주강우 한국화재감식학회 2018 한국화재감식학회 학회지 Vol.9 No.3
In the case of a fire or disaster in a high-rise building, the efficiency of the evacuation and the need for preventive construction are increasing due to various problems. As seen in many large accidents, the damage caused by the maze was complicated by the complicated structure and uncertain distance. The most important thing here is to allow the occupants to evacuate quickly and safely. Therefore, in this study, considering the evacuation guidance system guiding the optimal evacuation route through the fire detection facility and the evacuation guidance light, the high - rise building of the KOREATECH And the time required to evacuate is estimated through simulations.
Ga2O3초음파분무화학기상증착 공정에서 유동해석을 이용한 균일도 향상 연구
변창우,하주환,이학지,박소담,신석윤 한국반도체디스플레이기술학회 2022 반도체디스플레이기술학회지 Vol.21 No.4
Mist-CVD is known to have advantages of low cost and high productivity method since the precursor solution is misting with an ultrasonic generator and reacted on the substrate under vacuum-free conditions of atmospheric pressure. However, since the deposition distribution is not uniform, various efforts have been made to derive optimal conditions by changing the angle of the substrate and the position of the outlet to improve the result of the preceding study. Therefore, in this study, a deposition distribution uniformity model was derived through the shape and position of the substrate support and the conditions of inlet flow rate using the particle tracking method of computational fluid dynamics (CFD). The results of analysis were compared with the previous studies through experiment. It was confirmed that the rate of deposition area was improved from 38.7% to 100%, and the rate of deposition uniformity was 79.07% which was higher than the predicted result of simulation. Particle tracking method can reduce trial and error in experiments and can be considered as a reliable prediction method.