• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.353-356
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• 2003

Acoustic holography is adopted in identifying the noise sources of a vehicle's underbody. Wind noise from a vehicle's underbody accounts for a large portion of the overall noise level due to the complex flow structure. Current study presents the development process of acoustic holography in the vehicle underbody, and discusses the results obtained using the method. Difficulties associated with using acoustic holography as well as the implication of the results regarding future noise reduction possibilities are discussed.

• 한국철도학회논문집
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• 제8권5호
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• pp.454-459
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• 2005

In this study, the relationship between tie shape and underbody train gust of high-speed train is numerically investigated. To this end, complex train underbody/railroad model is replaced by simple plate/tie model. And it is tried to find a most important parameter for reduction of underbody train gust through the Taguchi method and orthogonal array. As a result, it is verified that the height of tie is most sensitive to the underbody train gust because of the cavity effect between ties. When the width and distance between ties are decreased, underbody train gust is also reduced. Consequently, the heighter is examined which can give the similar effect of higher tie without replacement of tie. The 5cm heighter can reduce underbody train gust about $73\%$, which value is only $7\%$ less than the higher tie.

• 한국자동차공학회논문집
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• 제4권1호
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• pp.134-146
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• 1996

Numerical and experimental studies are performed to investigate the effect of the underbody shape of the simplified road vehicle on drag and life. Four different vehicle models with front and rear slanted variations at the lower surface are used in this study. Cases with a slanted underbody surface at front have smaller drag than those without a slanted surface. Also, cases with a slanted underbody surface at rear have smaller lift than those without a slanted surface. Pressure distributions along the model surfaces and velocity fields at the wake region are examined in detail. In general, numerical solutions are in agreement with experimental results.

• 한국철도학회논문집
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• 제12권1호
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• pp.39-44
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• 2009

차륜이나 기타 궤도주변의 구조물에 동에 충돌하여 유험을 초래할 수 있는 자갈비산 현상은 고속으로 달리는 열차의 하부에 유도되는 돌풍에 의해 발생 가능하다. 자갈비산을 방진하기 위한 방법 하나로 선로상의 자갈표면 유속을 감소시키는 높임침목이 사용되고 있다. 본 연구에서는 다양한 높임침목의 형상에 대하여 전산해석을 이용하여 그 공력특성을 분석하였다. 높임침목의 높이가 높아질수록 유도되는 유속은 감소하였으며 폭의 변화는 큰 영향이 없음을 확인하였다. 또한 높임침목의 형상 변화에 따라 자갈궤도면에 유도되는 유속을 검토하여 유동방향에 대하여 뾰족하고 각진 높임침목 형상이 효과적임을 알 수 있었다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.1241-1247
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• 2005

The ballast-flying, induced by strong underbody train gust, may damage train underbody, wheel and even cause the safety problems. For this reason, a heighter is being used to prevent the ballast-flying phenomenon through underbody now reduction. In this research, flow field around a heighter is numerically simulated. And the parametric study of various heighter shapes is performed to find out more effective heighter shape. Also the ballast-flying probabilities are calculated for various ballast types and train speeds.

• Elastomers and Composites
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• 제53권3호
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• pp.136-140
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• 2018

In this study, research was conducted into the manufacture of thermally expandable microspheres for automotive underbody coatings and applications in industry. In particular, the relationship between heat resistance and the ratio of crosslinking agents and initiators in the manufacture of the thermally expandable microspheres was investigated. We focused on the results with various cross-linking agents; our aim was to make the walls of the microspheres thicker to solve the problem of reductions in size caused by shrinkage when the microspheres are heated to $T_m$ ($T_{max}$). We observed the sectional thickness and surface of the samples with thicker walls. The thick thermally expandable microspheres showed reduced shrinkage and excellent stability in spite of prolonged exposure to heat.

• EDISON SW 활용 경진대회 논문집
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• 제4회(2015년)
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• pp.518-520
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• 2015

Automotive aerodynamic drag coefficient is important variable for vehicle's driving performance and fuel economy. In this research, we applied genetic algorithm to determine the geometrical figure which can optimize Carr's automotive aerodynamic underbody coefficient. And it's verified by previous research.

• 한국자동차공학회논문집
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• 제4권4호
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• pp.140-146
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• 1996

A large portion(above 70%) fo the hydrocorbon and NOx emissions for a typical vehicle occur mainly before the conventional underbody catalyst reaches activation temperature. To meet the stringent regulation as EC stage 2, the emissions produced during this period must be reduced. One of alternative techniques is to place CCC(Close-Coupled Catalyst) near the exhaust manifold. In this study, the characteristics of CCC are observed through EEC mode.

• 한국철도학회논문집
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• 제12권6호
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• pp.829-834
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• 2009

자갈비산에 대한 위험성을 평가하는 한 방법으로 열차 하부 각 지점에서 다양한 자갈 종류 및 열차 속도에 따라 자갈 비산 확률을 파라메타로 제시하였다. 이를 위하여 풍동실험 결과를 바탕으로 한 확률계수 BFPF를 이용하였으며, 다양한 조건의 열차 하부 영역에 대한 수치해석을 수행하여 각 조건에 따른 각 지점의 자갈비산확률을 검토하였다. 열차 속도증가에 따라 비산확률이 급격히 증가하고, 속도가 350 km/h가 되면 자각비산 확률이 87%로 증가하였다. 또한 높힘침목을 적용하였을 경우와 비교를 통해, 다양한 조건에서의 자갈비산 확률에 대한 민감도를 분석하여 자갈형태 및 높힘침목 형태에 따른 변화 특성을 분석하고 높힘침목이 자갈비산 위험을 억제할 수 있음을 확인하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.1579-1580
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• 2013