• Corrosion Science and Technology
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• 제9권1호
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• pp.16-19
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• 2010

Application of ultra-high strength steel sheets is one of the most important methods to satisfy weight reduction and crash safety of a vehicle. Recently, there has been a trend to apply ultra-high strength steel sheets widely to underbody parts in which corrosion resistance is required. In this work, ultra-high strength galvannealed steel sheets with a tensile strength of 1180 MPa were developed. Newly developed ultra-high strength galvannealed steel sheets have comparable properties, such as mechanical properties, spot weldability, crashworthiness and adhesion of coatings, to conventional steel sheets.

• 한국자동차공학회논문집
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• 제13권3호
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• pp.80-86
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• 2005

In this study, we investigated the characteristics of the conversion efficiency and the effect of ageing Diesel Oxidation Catalyst (DOC). The DOC was composed of Warm-up Catalytic Converter (WCC) and Underbody Catalytic Converter (UCC). As the result, the conversion efficiency of THC was 10$\~$50$\%$ on WCC and 30$\~$40$\%$ on UCC .The conversion efficiency of CO was 80$\~$90$\%$ on WCC and remained 10$\~$20$\%$ of CO was purified on UCC. The WCC shows high conversion efficiency on CO. After 20 hours aging process of engine bench, conversion efficiencies of THC and CO were improved a little, because it was activated catalyst surface by 20 hours aging. In case of 80 hours aging, the conversion efficiencies of THC and CO were decreased on WCC. However, the UCC was not affected by aging process .

• 한국자동차공학회논문집
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• 제19권4호
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• pp.99-106
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• 2011

This paper deals with engine room layout design optimization of fuel cell electric vehicle (FCEV), which has been proposed as a potential alternative to fossil fuel depletion. Investing the great R&D efforts, the global vehicle manufacturers, especially Honda motor corporate, have shown not prototype vehicle but commercial vehicle using fuel cell in the market recently. In this paper, we analyze cooling performance and flow characteristic in the engine room of newly FCEV, in addition we suggest the optimization process for engine room layout design optimization. The two radiators in the vehicle for fuel cell stack and electronic components cooling have been analyzed and their performance are obtained in terms of cooling performance ratio (CPR). The value of CPR should always be less than one and based on criteria, we have achieved the optimum cooling performance of radiators for stack and electronic components. Aerodynamic performance is evaluated in terms of drag coefficient, improved through underbody modification using air devices.

• 한국자동차공학회논문집
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• 제18권1호
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• pp.131-138
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• 2010

Because real flow of engine exhaust is very hot and highly transient, it may cause thermal and inertial loads on catalyzed filters in DPF. Transient and detailed flow and thermal simulations are necessary in this field. To assess the importance of time dependent phenomena, typical cone-type configuration such as an underbody DPF is selected for steady and transient analysis. User defined functions of FLUENT by sinusoidal inlet velocities are written and integrated with main solver for realistic simulation. Also, 4-cylinder and 6-cylinder engines for 3,000 L class are considered for the dynamic exhaust effect of engine type. Key parameters to understanding of catalyst performance and durability issues such as flow uniformity index and peak velocity are investigated. Also, pressure drop for engine power are considered. From the simulation results for three different cases, proper approach is recommended.

• 동력기계공학회지
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• 제19권2호
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• pp.15-21
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• 2015

Bollard installed on the street is a facility that protects pedestrians by restraining cars from entering on the sidewalk. It is basically classified into manual, semiautomatic, automatic type and mostly manual type is widely used because the automatic type is imported and much expensive. However, in case of manual handling type in practice, it is very troublesome and difficult to remove it whenever cars are permitted, and in case of automatic type, since underbody of a bollard is very long, it is difficult to dig a deep hole in the ground because a pipe, a hose or a cable is under the surface. In order to reduce these difficulties, this paper proposed new design of the multistage bollard that moves up and down automatically by using hydraulic system. This is developed by 6 step creativity of TRIZ inventive problem solving and structural analysis. The developed bollard can be installed in shallow hole and allow entry of vehicles through up-and-down movement without its removal manually. Finally, we could see smoothly motion through the manufactured bollard.

• 한국자동차공학회논문집
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• 제17권4호
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• pp.24-31
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• 2009

This paper has been focused on the development of integrated automotive muffler system to meet getting more stringent sound quality target. Typically, muffler system consists of resonator and main muffler. The many varieties in exhaust pipe routing and the flexibility in muffler design make it possible to design an exhaust system to deliver tailpipe sound for specific sound quality requirement. In recent, it is strongly recommended that the function of resonator be merged into that of main muffler due to severe space limitation of underbody. The main objective of the paper is to study the effects of various geometrical parameters on the muffler performance. This work has succeeded in eliminating resonator without loss of muffler performance. This work has also investigated the effect of diameter of hole, geometries of pipes and location of muffler on the sound quality.

• 한국기계가공학회지
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• 제16권3호
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• pp.24-29
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• 2017

In this study, a seat cross member was fabricated by optimizing the resin transfer molding processing of CFRP (Carbon Fiber Reinforced Plastics) materials. This seat cross member is used in automotive underbody parts and provides side impact support. The seat cross was manufactured via vacuum resin transfer molding. The process included 1min of resin injection, 8 mins of heating, and 1 min of cooling, for a total molding time of 10mins. Tensile test results showed an average breaking load of 21.50kN, a tensile strength of 404 MPa, and an elastic modulus of 46.2 GPa. As a result, the CFRP seat cross provides the same strength as a similar steel part, but weighs 42% less.

• Wind and Structures
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• 제34권5호
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• pp.451-467
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• 2022

The flow around a high-speed train with three underbody structures in the bogie area is numerically investigated using the improved delayed detached eddy simulation method. The vortex structure, pressure distribution, flow field structure, and unsteady velocity of the wake are analyzed by vortex identification criteria Q, frequency spectral analysis, empirical mode decomposition (EMD), and Hilbert spectral analysis. The results show that the structures of the bogie and its installation cabin reduce the momentum of fluid near the tail car, thus it is easy to induce flow separation and make the fluid no longer adhere to the side surface of the train, then forming vortices. Under the action of the vortices on the side of the tail car, the wake vortices have a trend of spanwise motion. But the deflector structure can prevent the separation on the side of the tail car. Besides, the bogie fairings do not affect the formation process and mechanism of the wake vortices, but the fairings prevent the low-speed fluid in the bogie installation cabin from flowing to the side of the train and reduce the number of the vortices in the wake region.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.369-373
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• 2005

To investigate the mechanism of ballast-flying phenomena by strong wind induced by high-speed trains, wind velocity in the vicinity of the track has been measured using 16-channel Kiel-probe array and detailed flow structure near the surface of the track has been analyzed. The position at which the underflow fully develop has been examined in order to assess the driving force of the turbulent flow under train and the results yields that the turbulent flow owing to the cavity of the inter-car as well as the friction force at the underbody of the train is the main reason of the strong wind under high-speed train. The preceding wind tunnel test results has been introduced to assess the probability of ballast-flying during the passage of the high-speed train by comparing the results from field-measuring. The results shows that when the G7 train as well as the KTX train runs at 300km/h, about 25m/s wind gust is induced just above the tie and the probability for small ballast under 50g to fly is about 50% when it is on the tie. If the G7 train runs at 350km/h, the wind gust just above the tie increases to 30m/s, therefore more radical countermeasure seems to be needed.

• 한국의류학회지
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• 제41권1호
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• pp.184-195
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• 2017

Baseball is a life sport that gives vitality to people. However, currently available leg guards do not have a variety of sizes and it is very difficult to purchase a leg guard that is suitable for the size of a specific consumer. Therefore, this study investigated the size system of a leg guard sold in the market and suggested a grading deviation suitable for the legs of Korean males. The results of the study were as follows. First, most brands were sold only in three size systems as children's, teenagers, and adults. Adult size systems were not subdivided. Second, Korean male legs were classified into Group 1 (large girth and height and lower body muscle) and Group 2 (small girth and height and low underbody muscle). Third, the size system is based on vertical items such as height and mid-thigh circumference. Each group produced 10 sizes. The smallest height or the largest height was also found to be about 4.5 to 5.0cm smaller or larger than the sample size for each group. The total length of the leg guard was about 2.5cm when the height was increased or decreased by one size. It was confirmed that the deviation of the circumference of the mid-thigh should be about 2.0cm larger or smaller than the sample size even if the height is the same. The deviation of the knee circumference and ankle circumference was smaller than the other circumference. In conclusion, the dimension combinations of the leg guard must be set differently to provide a leg guard with high size suitability according to leg type.