벨로우즈에 대한 유한요소해석 프로그램 및 간편식의 개발과 형상최적설계

고병갑,박경진,Koh, Byung-Kab,Park, Gyung-Jin 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.8

Bellows is a component in piping systems which absorbs mechanical deformation with flexibility. Its geometry is an axial symmetric shell which consists of two toroidal shells and one annular plate or conical shell. In order to analyze bellows, this study presents the finite element analysis using a conical frustum shell element. A finite element analysis is developed to analyze various bellows. The validity of the developed program is verified by the experimental results for axial and lateral stiffness. The formula for calculating the natural frequency of bellows is made by the simple beam theory. The formula for fatigue life is also derived by experiments. The shape optimal design problem is formulated using multiple objective optimization. The multiple objective functions are transformed to a scalar function by weighting factors. The stiffness, strength and specified stiffness are considered as the multiple objective function. The formulation has inequality constraints imposed on the fatigue limit, the natural frequencies, and the manufacturing conditions. Geometric parameters of bellows are the design variables. The recursive quadratic programming algorithm is selected to solve the problem. The results are compared to existing bellows, and the characteristics of bellows is investigated through optimal design process. The optimized shape of bellows is expected to give quite a good guideline to practical design.

에어컨 임펠러의 파손 거동에 관한 실험 및 수치적 연구

고병갑,이성철,Koh, Byung-Kab,Lee, Sung-Chul 한국산학기술학회 2009 한국산학기술학회논문지 Vol.10 No.12

An air conditioner impeller has been used to suck the warm air and to blow the chilled air by the centrifugal force induced from the rotation of it. To check the possibility of the fracture due to resonance, both numerical and experimental approach was carried out. For the structural analysis, the commercial code ANSYS based on the Finite Element Method was employed. The possibility of the fracture is the resonance between the natural frequency of impeller and characteristic frequency due to the aerodynamic forces. Experiment was carried out to see the natural frequency and numerical analysis based on the Vortex Element Method is performed to get the characteristic frequency. Comparing the natural frequencies that are calculated as described, we believe that resonance occurs. 에어컨 임펠러는 에어컨에 장착되어지는 부품으로서 모터 구동에 의하여 차가운 바람을 실내로 유입되도록 해주는 부분이다. 본 연구에서는 임펠러의 파손 원인을 수치적인 방법에 의하여 규명하고, 공진에 의한 파손 여부를 평가한다. 임펠러의 공진 여부를 판단하기 위하여 임펠러의 고유진동수와 Aerodynamic force에 의한 특성 주파수를 비교한다. 먼저, 임펠러의 고유진동수를 알기 위하여 모드 실험과 수치 계산을 병행한다. 즉, 구조 해석용 상용 소프트웨어인 ANSYS를 이용하여 고유진동수와 모드 형을 계산하고, 이를 확인하기 위하여 실험적 주파수 분석을 수행한다. 공진 현상의 원인이 되는 외력에 대하여 임펠러 Blade에 작용하는 Aerodynamic force를 구하여야 하며, 본 연구에서는 V.E.M.(Vortex Element Method)에 근거한 유동 해석 프로그램을 수행하여 Aerodynamic force에 의한 특성 주파수를 얻는다.

EJMA에 기초한 벨로우즈 설계 소프트웨어의 개발

고병갑(Byung Kab Koh) 한국생산제조학회 2008 한국생산제조학회지 Vol.17 No.1

Bellows are commonly used in piping systems to absorb expansion and contraction in order to reduce stress. Unlike most piping components, bellows consist of a thin-walled shell of revolution with a corrugated meridian, in order to provide the flexibility needed to absorb mechanical movements. It is a composite shell structure consisting of at least one toroidal shell, an annular plate or conical shell. It is difficult to analyze the behavior of bellows because of its complex geometry. Simplified formulas for variable mechanical behaviors of bellows are provided by a standard called EJMA. An automatic design software for bellows is programming by using VBA(Visual Basic for Application) based on EJMA. Bellows engineers can effectively make a decision for bellows geometries because this software provides graphically design results in its post-processor. Bellows design software is expected to give quite a good guidance to practical design. The characteristics of bellows are also investigated through the automatic design process in bellows design software.

마그네트론 구조의 열특성에 관한 해석

고병갑(Koh, Byung-Kab) 한국산학기술학회 2011 한국산학기술학회논문지 Vol.12 No.3

마그네트론은 마이크로파를 발진하기 위한 부품으로써 전자레인지 등에 사용되는 부품이다. 이러한 마그네트 론은 열이 많이 발생하며, 따라서 열특성을 고려한 방열 설계가 반드시 수반되어야 한다. 본 연구에서는 마그네트론 을 구성하는 부품에 대하여 열전달 해석을 수행하여 마그네트론의 열특성을 파악하였다. 이를 위하여 상용 소프트웨 어인 ANSYS를 이용하여 전도 및 대류를 고려한 열전달 해석을 수행하였다. 마그네트론 부품을 하나씩 추가하면서 해석을 수행하였고 각각의 해석 결과를 실험 결과와 비교하였다. Magnetron is applied in microwave ovens for generating microwaves. It is composed of r-fin, yoke, A/F seals, gasket base, filter box. The temperature is occurred highly, when magnetron operate in its systems. Therefore the thermal characteristics must be considered in the design of magnetron. Because of its geometric complex, it is difficult to analysis the thermal characteristics. In this paper, temperature analysis is performed for all components. The commercial software ANSYS is used to consider both conduction and convection. The analysis is carried out by adding each component. An experiment on the thermal characteristics is performed to verify the reliability for simulation.

레이저 용접물 결함 평가에 대한 화상처리의 이용

이정익(Jeong-ick Lee),고병갑(Byung-kab Koh) 한국생산제조학회 2007 한국생산제조학회지 Vol.16 No.4

The welded defects are usually called user's unsatisfaction for appearance and functional usage. For checking these defects effectively without time loss, setup of weldability estimation system is an important for detecting whole specimen quality. In this study, after catching a rawdata on welded specimen profiles and treating vision processing with these data, the qualitative defects are estimated from getting these information by laser vision camera at first. At the same time, the weldability estimation for whole specimen is produced. For user friendly, the weldability estimation results are shown each profiles, final reports and visual graphics method. So, user can easily determined weldability. By applying these system to welding fabrication, these technologies are contribution to on-line setup of weldability estimation system.

접촉을 고려한 터보 압축기 로터의 안정성 해석

이승표(Seung-Pyo Lee),고병갑(Byung-Kab Koh) 한국생산제조학회 2007 한국생산제조학회지 Vol.16 No.3

It is necessary to analyze the contact phenomena in order to effectively design the machine components with contact surfaces. In general, the contact action is highly nonlinear and irreversible because we cannot predict the contact regions and conditions. Recently, the finite element method is used to analyze the contact problem. In this paper, the contact element method is applied to avoid the mesh refinement and iterative calculation of general contact algorithms. By use of it, the deformation and stress concentration of turbo compressor rotor are computed. It shown that the contact element is convenient analysis and the results are relatively accurate.

용접 이음 추적시스템의 응용

이정익(Jeong-ick Lee),고병갑(Byung-kab Koh) 한국생산제조학회 2007 한국생산제조학회지 Vol.16 No.2

Welding fabrication invariantly involves three district sequential steps: preparation, actual process execution and post-weld inspection. One of the major problems in automating these steps and developing autonomous welding systems, is the lack of proper sensing strategies. Conventionally, machine vision is used in robotic arc welding only for the correction of pre-taught welding paths in single pass. In this paper, novel presented, developed vision processing techniques are detailed, and their application in welding fabrication is covered. The software for joint tracking system is finally proposed.

아크 용접의 이면비드 예측 비교

이정익(Jeong-ick Lee),고병갑(Byung-kab Koh) 한국생산제조학회 2007 한국생산제조학회지 Vol.16 No.3

It is important to investigate the relationship between weld process parameters and weld bead geometry for adaptive arc robot welding. However, it is difficult to predict an exact back-bead owing to gap in process of butt welding. In this paper, the quantitative prediction system to specify the relationship external weld conditions and weld bead geometry was developed to get suitable back-bead in butt welding which is widely applied on industrial field. Multiple regression analysis and artificial neural network were used as the research methods. And, the results of two prediction methods were compared and analyzed

위상최적설계를 통한 가공의치의 해석

이정익(Lee, Jeongick),고병갑(Koh, Byung Kab) (사)한국CDE학회 2006 한국CDE학회 논문집 Vol.11 No.5

실험을 이용한 전기보온압력밥솥 오븐의 안전도 평가

이승표(Lee, Seung-Pyo),고병갑(Koh, Byung-Kab),하성규(Ha, Sung-Kyu) 한국산학기술학회 2008 한국산학기술학회논문지 Vol.9 No.6

유도가열 방식의 전기보온압력밥솥은 밥솥 전체를 가열하기 때문에 밥맛이 좋고, 빠르게 밥을 지을 수 있는 장점이 있어서 많이 사용되고 있다. 특별히 전기보온압력밥솥의 오븐은 내부에 압력이 작용하기 때문에 안전성 검토가 반드시 필요하다. 본 연구에서는 변형률을 평가하기 위하여 스트레인 게이지를 이용한 실험을 수행하였고, 그 결과를 유한 요소법을 이용한 구조 해석 결과와 비교하였다. 또한, 영구 변형량을 평가하기 위하여 수부하 실험을 수행 하였고, 그 결과를 구조 해석 결과와 비교하였다. 이들 실험과 해석 결과를 통하여 오븐의 안전도를 평가하는 방법을 제시하였다. Because of good taste and quick cooking, the induction heating type pressure rice cooker is widely used. Since pressure is applied to oven structure, it should be necessary to check the safety evaluation. In this paper, strain gauge experiment is performed in order to evaluate the oven's strain and its result is compared with that of structural analysis. And water test is performed to evaluate the oven’s permanent deformation. The result is also compared with that of structural analysis. By using these experiments and analyses the safety evaluation method of the oven is suggested.