• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.229-232
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• 2007

In hot strip rolling, the work roll profile is one of the main factors in predicting and correcting the strip profile. Various studies concerning the wear profile and the thermal crown of work roll have been performed, and the results of these studies have shown that the work roll profile must be predicted accurately so as to efficiently control the strip qualities such as thickness, crown, flatness, and camber. Therefore, a precise prediction model of roll profile is called for in a perfect shape control system. In this paper, a genetic algorithm was applied to improve on the roll profile prediction model in hot strip rolling. In this approach, the optimal design problem is formulated on the basis of a numerical model so as to cover the diverse design variables and objective functions. A genetic algorithm was adopted for conducting design iteration for optimization to determine the coefficient of the numerical model for minimization of errors in the result of the calculated value and the measured data. A comparative analysis showed a satisfactory conformity between them..

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권2호
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• pp.406-417
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• 2014

This paper presents a numerical optimization method to improve the performance of the propeller with Turbo-Ring using real-coded genetic algorithm. In the presented method, Unimodal Normal Distribution Crossover (UNDX) and Minimal Generation Gap (MGG) model are used as crossover operator and generation-alternation model, respectively. Propeller characteristics are evaluated by a simple surface panel method "SQCM" in the optimization process. Blade sections of the original Turbo-Ring and propeller are replaced by the NACA66 a = 0.8 section. However, original chord, skew, rake and maximum blade thickness distributions in the radial direction are unchanged. Pitch and maximum camber distributions in the radial direction are selected as the design variables. Optimization is conducted to maximize the efficiency of the propeller with Turbo-Ring. The experimental result shows that the efficiency of the optimized propeller with Turbo-Ring is higher than that of the original propeller with Turbo-Ring.

• 한국산학기술학회논문지
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• 제14권7호
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• pp.3170-3176
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• 2013

본 연구에서는 피치각 가변형 축류팬의 성능(정압별 풍량, 소비전력)과 소음특성을 실험으로 구하였다. 피치각은 $20^{\circ}{\sim}45^{\circ}$로 $5^{\circ}$ 간격으로 6개의 각도를 변화시켜 가면서 측정 하였고 팬 날개는 동일한 에어포일 형상으로 길이는 80 mm, 90 mm, 100 mm, 110 mm, 120 mm로 변경하여 실험을 수행하였다.

• International Journal of Fluid Machinery and Systems
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• 제4권4호
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• pp.360-366
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• 2011

Thin circular-arc blade is often used as a guide vane, a deflecting vane, or a rotating blade of low pressure axial-flow turbomachine because of its easy manufacture. Ordinary design of the blade elements of these machines is done by use of the carpet diagrams for a cascade of circular-arc blades. However, the application of the carpet diagrams is limited to relatively low cambered blade operating under optimum inlet flow conditions. In order to extend the applicable range, additional design data is necessary. Computational fluid dynamics (CFD) is a promising method to get these data. In this paper, two-dimensonal cascade performances of circular-arc blade are widely analyzed with CFD. The results have been compared with the results of experiment and potential theory, and useful information has been obtained. Turning angle and total pressure loss coefficients are satisfactorily predicted for lowly cambered blade. For high camber angle of $67^{\circ}$, the CFD results agree with experiment for the angle of attack less than that for shockless inlet condition.

• 한국항공우주학회지
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• 제30권4호
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• pp.44-52
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• 2002

비정상, 비압축성 Navier-Stokes 코드를 이용하여, 저 레이놀즈수 유동에서 flapping 운동을 하는 익형의 공력특성을 수치해석적인 방법으로 연구하였다. 비정상 유동장의 효율적인 계산을 위하여, 개발된 코드는 MPI 프로그래밍 기법을 이용하여 병렬처리 되었으며, 난류 유동장의 계산을 위해 2방정식 난류모델의 하나인 k-$\omega$ SST 모델을 적용하였다. 익형의 3가지 운동모드 즉, pitching, plunging, flapping과 주파수 및 진폭의 변화 그리고 두께와 캠버의 변화에 의한 공력특성을 살펴보았고, 이를 위해 NACA4자 계열의 익형을 이용하였다. 해석 결과는 실험치와 비교하여 보았을 때 잘 일치하였으며, 각 운동모드에서의 공기역학적 특성을 파악할 수 있었다.

• International Journal of Precision Engineering and Manufacturing
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• 제2권2호
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• pp.38-47
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• 2001

This paper decribes the development of computer-aided design of a very precise progressice die for lead frame of semiconductor chip. The approach to the system is based on knowledgr-based rules. Knowledge of fie이 experts. This system has been written in AutoLISP using AutoCAD ona personal computer and the I-DEAS drafting programming Language on the I-DEAS mater series drafting with on HP9000/715(64) workstation. Data exchange between AutoCAD and I-DEAS master series drafting is accomplished using DXF(drawing exchange format) and IGES(initial graphics exchange specification) files. This system is composed of six main modules, which are input and shape treatment, production feasibility check, strip layout, data conversion, die layout, and post processing modules. Based on Knowledge-based rules, the system considers several factors, such as V-notches, dimple, pad chamfer, spank, cavity punch, camber, coined area, cross bow, material and thickness of product, complexities of blank geometry and punch profiles, specifications of available presses, and the availability of standard parts. As forming processes and the die design system using 2D geometry recognition are integrated with the technology of process planning, die design, and CAE analysis, the standardization of die part for lead frames requiting a high precision process is possible. The die layout drawing generated by the die layout module s displayed in graphic form. The developed system makes it possible to design and manufacture lead frame of a semiconductor more efficiently.

• 한국유체기계학회 논문집
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• 제14권1호
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• pp.48-54
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• 2011

The effect of channel cutback on three-dimensional flow fields and aerodynamic losses downstream of a cavity squealer tip has been investigated in a turbine rotor cascade for the squealer rim height-to-chord ratio and tip gap height-to-chord ratio of $h_{st}/c$ = 5.51% and h/c = 2.0% respectively. The cutback length-to-camber ratio is changed to be $CB/c_c$ = 0.0, 0.1, 0.2 and 0.3. The results show that longer cutback delivers not only stronger secondary flow but also higher aerodynamic loss in the tip leakage vortex region, meanwhile it leads to lower aerodynamic loss in the passage vortex region. The discharge of cavity fluid through the cutback opening provides a beneficial effect in the reduction of aerodynamic loss, whereas there also exists a side effect of aerodynamic loss increase due to local wider tip gap near the trailing edge. With increasing $CB/c_c$ from 0.0 to 0.3, the aerodynamic loss coefficient mass-averaged all over the measurement plane tends to increase slightly.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2007년도 추계학술대회 및 제23회 정기총회
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• pp.25-26
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• 2007

Ship are typically thin-walled structures and consists of stiffened plate structure by purpose of required design load and weight reduction etc. Also, a hull structural characteristics are often used in structures with curvature at deck plating with camber, side shell plating at fore and aft parts and bilge circle parts, It have been believed that these structures can be modelled fundamentally by a part of cylinder. Structural component with curvature subjected to combined loading regimes and complex boundary conditions, which can potentially collapse due to buckling. Hence, for more rational and safe design of ship structures, it is crucial importance to better understand the interaction relationship of the buckling and ultimate strength for cylindrically curved plate under these load components. In this study, the ultimate strength characteristic of curved plate under combined load(lateral pressure load + axial compressive load) are investigated through using FEM series analysis with varying geometric panel properties.

• 한국강구조학회 논문집
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• 제17권2호통권75호
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• pp.183-194
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• 2005

기존의 연속 프리플렉스 거더교는 내측지점부 바닥판 콘크리트에 압축력을 도입시키기 위해 내측지점을 상승시키고 부모멘트 구간만큼의 바닥판 콘크리트를 타설하고 하강시키는 시공법을 사용하였다. 그러나 상기의 시공법은 장시간의 내측지점 상승 작업과 종곡선의 굴곡 문제 등 여러 가지 시공상 문제점을 가지고 있다. 따라서 본 논문은 이러한 문제점을 해소하기 위해 내측지점 및 외측지점을 하강시키는 공정만을 이용한 개선된 연속 프리플렉스 합성형 거더교의 시공법을 제시하였으며, 특정화된 연속 프리플렉스 거더교의 설계 프로그램에만 의존하지 않고 프리플렉스 거더교의 단면을 쉽게 추정할 수 있는 체계화된 설계식을 제시하였다.

• 수산해양기술연구
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• 제22권4호
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• pp.41-48
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• 1986

To investigate the midwater trawl gear available for the Korean near sea trawlers, the authors carried out a field experiment on the attitude and the opening efficiency of the otter board with the Pusan 404 (160GT, 750ps), a training ship of National Fisheries University of Pusan. The experimental trawl gear was designed to be operable by the ship and the otter board was made of single iron plate with 12% camber ratio. The special-prepared potentiometric angle detector was used for determining the attitude, and the 50 KHz fish finder for the opening between the otter boards. The results obtained can be summarized as follows: 1. The angle of attack varied by moving the towing point on the towing plate of the otter board. It showed 33 to 36 degrees when the point was set at the outmost position, 25 to 31 degrees at the middle position and 19 to 30 degrees at the inmost position, with a decreasing tendency according to the increase of towing speed in each cases. 2. The heel of the otter board always occured inwards, increasing slightly according to the increase of towing speed. 3. The tilt of the otter board always occured outwards, increasing slightly according to the move of the towing point inwards, and decreasing slightly according to the increase of towing speed. 4. The opening between otter boards showed the largest value when the towing point was set at the outmost position.