• 한국디자인학회:학술대회논문집
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• 한국디자인학회 2005년도 춘계 학술발표대회 논문집
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• pp.14-15
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• 2005

• 한국기계가공학회지
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• 제19권1호
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• pp.36-42
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• 2020

In this study, flow analyses of a vehicle at driving were carried out after each installation of a tuning part, specifically the bonnet air ducts, the rear spoiler, and the rear diffuser. The study models were designed to comprise a total of eight cases in which each of the three parts were mounted individually or all together in vehicles. Assuming that the vehicle were driven with an average high speed of 100 km/h, the speed and pressure around the vehicle were obtained using CFD when driving. The rear diffuser that becomes the most effective among the three mounting parts has a major role in reducing air resistance.

• 대한기계학회논문집A
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• 제41권8호
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• pp.729-736
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• 2017

물리모델과 기계학습방법을 이용한 모델지원탐지확률(MAPOD, Model-assisted Probability of Detection) 실험계획법과 운용 중 결함이 발생한 부품을 사용하여 탐지확률을 측정하는 방법을 연구하였다. 검사방법은 와전류탐상검사를 적용하였고 검사대상은 볼트홀 표면에 존재하는 피로균열이다. 모델 지원탐지확률을 이용한 결과 실험요인이 큰 폭으로 감소하였다. 몬테카를로(Monte Carlo) 시뮬레이션을 이용하여 시편 균열길이 측정의 불확실성을 탐지확률에 반영함으로써 사용 중 결함품을 사용하여 비파괴검사정비사의 기량검증을 수행할 수 있었다.

• Elastomers and Composites
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• 제49권4호
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• pp.305-312
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• 2014

대부분 군사용 초음속 전투기는 후기 연소기를 사용한다. 후기 연소기는 초음속 비행, 이륙, 전투 상황에 대해 비상 임무 수행을 가능하게 하는 중요한 역할을 한다. 최근 전투기 J85-GE-21 터보제트 엔진 후기 연소기 연료펌프의 내부 피스톤 패킹고무에서 반복적인 연료 누출 결함이 발생하였다. 이러한 결함은 두 제조사 중 한 제조사의 부품에서만 발생하였다. 따라서, 결함발생 원인을 제조사가 상이한 정상품 및 결함품에 대하여 다양한 비교 분석방법을 통하여 조사하였다. 결함분석에는 팽윤 또는 팽윤도, 총 황함량, 폴리머 확인, 카본블랙 함량 및 표면적, 경도와 같은 분석방법이 적용되었다. 결론적으로, 반복적인 연료 누출 결함의 주요 원인은 보강제 카본블랙의 함량 미달로 확인되었으며, 더불어 표면적이 작은 카본블랙과 함량이 낮은 황 적용이 결함원인에 부가적인 영향을 준 것으로 확인되었다.

• Elastomers and Composites
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• 제54권2호
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• pp.110-117
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• 2019

The characterization of the ozone oxidation for raw natural rubber (NR) was investigated under controlled conditions through image and fourier transform infrared (FT-IR) analysis. The ozone oxidation was performed on a transparent thin film of raw NR coated on a KBr window in a dark chamber at $40^{\circ}C$ under low humidity conditions to completely exclude thermal, moisture, or light oxidation. The ozone concentration was set at 40 parts per hundred million (pphm). Before or after exposure to ozone, the image of the thin film for raw NR was observed at a right or tilted angle. FT-IR absorption spectra were measured in the transmission mode according to ozone exposure time. The ozone oxidation of NR was determined by the changes in the absorption peaks at 1736, 1715, 1697, and $833cm^{-1}$, which were assigned to an aldehyde group (-CHO), a ketone group (-COR), an inter-hydrogen bond between carbonyl group (-C=O) from an aldehyde or a ketone and an amide group (-CONH-) of protein, and a cis-methine group ($is-CCH_3=CH-$, respectively. During ozone exposure period, the results indicated that the formation of the carbonyl group of aldehyde or ketone was directly related to the decrement of the double bond of cis-1,4-polyisoprene. Only carbonyl compounds such as aldehydes or ketones seemed to be formed through chain scission by ozone. Long thin cracks with one orientation at regular intervals, which resulted in consecutive chain scission, were observed by image analysis. Therefore, one possible two-step mechanism for the formation of aldehyde and ketone was suggested.

• Composites Research
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• 제33권5호
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• pp.302-308
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• 2020

본 연구는 탄소 복합소재를 이용하여 오토클레이브와 진공백(Vacuum Bag Only) 공정으로 소재의 열전도 계수를구하고 경화 거동 모델을 통해 표면부와 내부의 경화 거동을 예측 및 비교하였다. 공정에 따른 열전도 계수의 변화로 인해 내부 온도가 표면부와 차이를 보였다. 오토클레이브 공정의 경우 높은 열전도 계수를 통하여 표면부와 내부의 온도는 거의 일치를 하였으며, 경화 거동 역시 유사하게 진행이 되었다. 하지만, 진공백 공정의 경우 표면부와 내부의 경화 거동이 많은 차이를 보였다. 이 차이는 부품 내부의 품질 및 공기 배출에 영향을 준다. 기계적 물성 차이를 확인하고자 0도 단방향 시편으로 압축시험을 수행하였고, 그 결과 진공백 성형이 조금 낮은 물성을 갖는다는 것을 확인하였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.180.2-180.2
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• 2010

Simulation technology for dynamic analysis of wind turbine is developed. The Aerodyn and the DAFUL are chosen for aerodynamic analysis and multi-body and flexible body dynamics respectively. Subroutines and variables of Aerodyn developed by NREL are analyzed with hub-height wind data, full field turbulent wind data and Airfoil data. The interface to perform coupled analysis between AeroDyn and DAFUL, GUI for modeling several parts of wind turbines are developed. The program will be extended to analyze the coupled analysis of aerodynamic and hydrodynamic behavior for floating offshore wind turbines.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1202-1205
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• 2005

Micro hole is one of basic elements for micro device or micro parts. By micro ECM, micro holes less than $50\mu{m}$ in diameter can be machined easily. Machining characteristics of micro ECM were investigated according to machining conditions such as electrolyte concentration and pulse conditions. From the investigation, optimal machining conditions were suggested for micro ECM of stainless steel. For the micro machining with high resolution, the change of machining gap should be predicted. By using electrochemical principle equations, the change of machining gap was simulated.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.134-137
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• 2007

Aero-Heating phenomenon is one of the severe problems occurring in high speed missile flight. in the high speed flight, not only stagnation point but also aft body parts encounter high temperature related structural problems. But the phenomenon is not easy to predict accurately because unsteady calculation according to a flight trajectory is needed, and takes much time. In this Paper, a fast and precise scheme is introduced, which calculates heat flow and temperature by simple pressure field prediction on a missile.

• Journal of Mechanical Science and Technology
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• 제18권11호
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• pp.1923-1931
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• 2004

Manufacturing of complex surface plates in stern and stem is a major factor in cost of a preliminary ship design by computing process. If these hull plate parts are effectively classified, it helps to compute the processing cost and find the way to cut-down the processing cost. This paper presents a new method to classify surface plates effectively in the preliminary ship design using neural network. A neural-network-based ship hull plate classification program was developed and tested for the automatic classification of ship design. The input variables are regarded as Gaussian curvature distributions on the plate. Various applicable rules of network topology are applied in the ship design. In automation of hull plate classification, two different numbers of input variables are used. By observing the results of the proposed method, the effectiveness of the proposed method is discussed. As a result, high prediction rate was achieved in the ship design. Accordingly, to the initial design stage, the ship hull plate classification program can be used to predict the ship production cost. And the proposed method will contribute to reduce the production cost of ship.