NR/EPDM Blend고무의 노방특성 연구

고진환,장동호,박성수 한국고분자학회 1997 한국고분자학회 학술대회 연구논문 초록집 Vol.1997 No.10

대수학 부구조법을 이용한 내부 고유치 계산

고진환,변도영,Ko, Jin-Hwan,Byun, Do-Young 한국전산구조공학회 2007 한국전산구조공학회논문집 Vol.20 No.6

대수학 부구조법은 대형 문제들의 고유치 계산에 최고 성능을 지닌 방법이지만 근본적으로 최소 고유치만을 계산하기 위해 설계되었다. 본 논문에서는 이동값을 이용하여 특정범위 안의 내부 고유치를 계산하기 위해 대수학 부구조법의 갱신된 버전을 제안하고, 이를 이동 대수학 부구조법이라 명명한다. 그리고 구조문제의 유한요소모델에 대한 수치실험을 통해 제안된 방법이 다수의 내부고유치를 계산하는데 란쵸스방법보다 월등한 효율성을 가지고 있음을 보였다. Algebraic substructuring (AS) is a state-of-the-art method in eigenvalue computations, especially for large size problems, but, originally, it was designed to calculate only the smallest eigenvalues. In this paper, an updated version of AS is proposed to calculate the interior eigenvalues over a specified range by using a shift value, which is referred to as the shifted AS. Numerical experiments demonstrate that the proposed method has better efficiency to compute numerous interior eigenvalues for the finite element models of structural problems than a Lanczos-type method.

쥐가오리 모방 진동식 조류 터빈의 출력향상에 대한 실험적 연구

고진환,김지훈 한국해양과학기술원 2017 Ocean and Polar Research Vol.39 No.4

Various approaches have been tried in an effort to improve the power performance of a flapping tidal stream turbine after it was introduced as an alternative to conventional rotary turbines. Among the different approaches, researches on mimicking the morphology and behavior of animals have been conducted. In this study, we utilized a flapper to mimic the multi-joint pectoral fin of a Manta-ray and investigated its effect on power generation. Experiments were conducted by a dual flapping apparatus with rigid and flexible flappers in a towing tank facility. First, in order to determine the conditions that can produce high power generation, the performances of the dual rigid flappers were compared when input arm angles and frequencies are changed, and the two conditions 40ο, 0.2 Hz and 40ο, 0.3 Hz for the input arm angle, frequency were selected. When the mimicked flexible flapper was used instead of the front rigid flapper and the rear one, the power was improved by an average of 22% and 38% in the experimental conditions, respectively. Moreover, it was recognized from the apparent camber observed during the experiment that the flexible flapper had been successfully applied. If the feasibility of the Manta-Ray mimicked flapper is improved through subsequent researches, the flapping tidal turbine can be a viable alternative to rotary turbines in the near future.

효과적인 열응력 해석을 위한 사각형 추가 변형률 요소의 개발

고진환,이병채,Ko, Jin-Hwan,Lee, Byung-Chai 대한기계학회 1999 大韓機械學會論文集A Vol.23 No.7

A new quadrilateral plane stress element is developed for efficient and accurate analysis of thermal stress problems. It is convenient to use the same mesh and the same shape functions for thermal analysis and stress analysis. But, because of the inconsistency between deformation related strain field and thermal strain field, oscillatory responses and considerable errors in stresses are resulted in. To avoid undesired oscillations, strain approximation is enhanced by supplementing several assumed strain terms based on the variational principle. Thermal deformation is incorporated into the generalized mixed variational principle for displacement, strain and stress fields, and basic equations for the modified enhanced assumed strain method are derived. For the stress approximation of bilinear elements, the $5{\beta}$ version of Pian and Sumihara is adopted. The numerical results for several problems show that the present element behaves well and reduces oscillatory responses. it also results in almost the same magnitude of error as compared with the quadratic element.

Aerodynamic analysis of flapping foils using volume grid deformation code

고진환,김지웅,박수형,변도영 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.6

Nature-inspired flapping foils have attracted interest for their high thrust efficiency, but the large motions of their boundaries need to be considered. It is challenging to develop robust, efficient grid deformation algorithms appropriate for the large motions in three dimensions. In this paper, a volume grid deformation code is developed based on finite macro-element and transfinite interpolation, which successfully interfaces to a structured multi-block Navier-Stokes code. A suitable condition that generates the macro-elements with efficiency and improves the robustness of grid regularity is presented as well. As demonstrated by an airfoil with various motions related to flapping, the numerical results of aerodynamic forces by the developed method are shown to be in good agreement with those of an experimental data or a previous numerical solution.

An algebraic substructuring using multiple shiftsfor eigenvalue computations

고진환,Sung Nam Jung,변도영,and Zhaojun Bai 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.3

Algebraic substructuring (AS) is a state-of-the-art method in eigenvalue computations, especially for large-sized problems, but originally it was designed to calculate only the smallest eigenvalues. Recently, an updated version of AS has been introduced to calculate the interior eigenvalues over a specified range by using a shift concept that is referred to as the shifted AS. In this work, we propose a combined method of both AS and the shifted AS by using multiple shifts for solving a considerable number of eigensolutions in a large-sized problem, which is an emerging computational issue of noise or vibration analysis in vehicle design. In addition, we investigated the accuracy of the shifted AS by presenting an error criterion. The proposed method has been applied to the FE model of an automobile body. The combined method yielded a higher efficiency without loss of accuracy in comparison to the original AS.

EPDM / BR 블랜드에서의 상용화제가 물성에 미치는 영향 연구

고진환,노익삼 한국고분자학회 1993 한국고분자학회 학술대회 연구논문 초록집 Vol.1993 No.4

다리우스 터빈 성능에 대한 가변 형상 블레이드의 영향 연구

고진환,Patar Ebenezer Sitorus,김지훈 한국해양환경·에너지학회 2019 한국해양환경·에너지학회지 Vol.22 No.1

The Darius turbine is one of the typical vertical axis flow turbines, but it has disadvantages such as low efficiency, shaking etc. In this study, we implemented a variable shape blade and investigated the per-formance improvement through open water channel experiments. Variable pitch and variable pitch-camber were chosen for the variable shape, and aircraft-flap based mechanism was devised for the variable pitch-camber. Both the variable pitch and the variable pitch-camber showed noticeable differ-ence from the fixed pitch at the limited pitch angle of 10 degrees and the performance was improved by increasing the efficiency and moving to the lower TSR (tip speed ratio). Also, it was indicated that TSRs of the variable pitch-camber shifted to lower values than those of the variable pitch due to the superposition effect of pitch and camber. The experimental results show that the performance of the variable shape blades can be improved and the competitiveness of the Darius turbine is expected to be improved through practical experi-mental validation studies. 다리우스 터빈은 수직축 방식으로 대표적 유동 터빈 중 하나이나 낮은 효율, 흔들림 등 단점을 가지고 있다. 본 연구에서는 가변 형상 블레이드를 구현하고 이를 통한 성능 향상 여부를 개수로 실험을 통해 알아보고자 하였다. 가변 형상의 경우 가변 피치와 가변 피치-캠버가 사용되었고 가변 피치-캠버의 경우는 항공기의 플랩(flap)에 근거한 메커니즘이 고안되었다. 가변 피치와 가변 피치-캠버 두 가지 경우 모두 한계 피치각 10도에서 고정 피치와의 차이점이 두드러졌으며, 효율 증가와 낮은 TSR(tip speed ratio)로의 이동으로 성능이 향상됨을 확인하였다. 또한 가변 피치-캠버의 TSR이 피치와 캠버의 중첩 효과에 기인하여 가변 피치의 TSR보다 더 낮은 값으로 이동하는 것을 확인하였다. 본 실험 연구를 통해 가변 형상 블레이드의 성능 향상 가능성을 볼 수 있었고 향후 이에 대한 실용적인 실험 검증 연구들을 통해 다리우스 터빈의 경쟁력을 높일 수 있을 것으로 기대된다.

고무 특성에 대한 실리카구조와 그의영향

고진환,이석,조축택,박낭국 한국고무학회 1996 엘라스토머 및 콤포지트 Vol.31 No.3

불완전분해법을 전처리로 하는 공액구배법의 안정화에 대한 연구

고진환,이병채 대한기계학회 2003 大韓機械學會論文集A Vol.27 No.2