• Journal of Welding and Joining
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• v.23 no.5
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• pp.25-29
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• 2005

Steel has been mainly used in the automotive industry, because of good mechanical properties, weldability and so on. However, there has been increase in using aluminum to reduce the weight of vehicle. This leads to improve fuel efficiency and to reduce air pollution. A steel-aluminum hybrid body structure is recently used not only to reduce the weight of vehicle but also to increase safety. In this paper, the laser beam joining method is suggested to join steel and aluminum. To avoid making brittle intermetallic compounds(IMC) that reduce mechanical properties of the joint area, only aluminum is melted by laser irradiation and wetted on the steel surface. The brittle IMC layer is formed with small thickness at the interface between steel and aluminum. By controlling the process parameters, brittle IMC layer thickness is suppressed under 10 micrometers which is a criterion to maintain good mechanical properties.

• Journal of Mechanical Science and Technology
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• v.19 no.6
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• pp.1304-1312
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• 2005

The ride and noise characteristics of a vehicle are significantly affected by the vibration transferred to the body through the chassis mounting points in the engine and suspension. It is known that body attachment stiffness is an important factor of idle noise and road noise for NVH performance improvement. The body attachment stiffness serves as a route design aimed at isolating the vibration generated inside the car due to the exciting force of the engine or road. The test result of the body attachment stiffness is shown in the FRF curve data; the stiffness level and sensitive frequency band are recorded by the data distribution. The stiffness data is used for analyzing the parts that fail to meet the target stiffness at a pertinent frequency band. The analysis shows that the target frequency band is between 200 and 500 Hz. As a result of the comparison in a mounted suspension, the analysis data is comparable to the test data. From these results, there is a general agreement between the predicted and measured responses. This procedure makes it possible to find the weak points before a proto car is produced, and to suggest proper design guidelines in order to improve the stiffness of the body structure.

• Journal of Mechanical Science and Technology
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• v.19 no.6
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• pp.1321-1328
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• 2005

The characteristics of the diesel spray have affected certain aspects of engine performance, such as the power, fuel consumption, and emissions. Therefore, this study was performed to investigate the effects of various injection parameters. In order to obtain the effect of injection parameters on diesel spray characteristics, the experiment is performed by using a high temperature and pressure chamber. The behaviors of the spray are visualized by using a high speed video camera, spray angle, penetration, and various other things. The results of the experiment are summarized as follows. (1) The correlation of the spray penetration can be expressed as follows. $$0< t $$t_{b} (2) The correlation of the spray angle can be expressed as follows $$T_a=293K\;tan({\theta}/2)=0.59({\rho}a/{\rho}f)^{0.437}$$ $$T_a=473K\;tan({\theta}/2)=0.588({\rho}a/{\rho}f)^{0.404}$$ (3) The measured macro characteristics that include the spray tip penetration and spray angle corresponded with the established correlations.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.1
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• pp.237-243
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• 1996

Current low head and small scale hydroturbines have limitations in the minimum required head and flow rate for efficient operation. This study attempts to develop a new concept hydroturbine which is expected to run efficiently even in very low head and small flow rate, so that the limitations on the conventional small scale hydropower could be alleviated and competition with other alternative energy sources in the economic respect could be attained. A small scale catapillar track- hydroturbine was fabricated and the performance test was carried out in a water tunnel over the head range of H = 0.8 m ~ 1.26 m. The peak turbine efficiency was 41.3% at the speed ratio of 0.6, and the turbine loss was mostly due to the friction at the chain drive used for power transmission from the runner to the shafts. This type of turbine is expected to become competitive when some improvement in the power transmission mechanism is made.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.5
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• pp.261-268
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• 2013

Technologies for preventing contaminants deposition are a key issue in a modern duct system. When particulate matters deposit inside the exhaust pipes, which are widely used in the Urea-SCR system to reduce $NO_x$ emission from heavy duty diesel engines, many problems arise associated with increased flow resistance and corrosion. Therefore, the development of the urea deposition avoidance technologies is being treated as an important issue of the Urea-SCR system. An analytical study was carried out to investigate the effects of the wall flow around the mixer with the variation of the mixer housing surrounding and supporting the mixer, which is designed to increase the wall flow and then to reduce droplet deposition. The housing angles and the position of the mixer were changed：angles of $0^{\circ}$, $1^{\circ}$, $2^{\circ}$, and $3^{\circ}$, and mixer positions of 0 L, 0.5 L, and 1 L. The axial velocity distributions, maximum velocity, the half-width, and momentum distribution of the wall flow were investigated to examine the effect of the mixer-housing assembly geometry.

• Journal of Climate Change Research
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• v.8 no.1
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• pp.41-50
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• 2017

As serious consequences of climate change became indisputable, vehicles based on fossil fuel has to be shifted toward more sustainable way to drastically reduce carbon emissions. Eco-friendly vehicles contribute mitigating climate change through reducing the greenhouse gas emissions. The goal of this research is to find ways to promote the eco-friendly vehicle industry in Korea. In order to achieve this goal, surveys are collected from the professionals of eco-friendly vehicle industry, and analyzed through Delphi method. Results show that the first thing is to promote the eco-friendly vehicle market by introducing the economic incentives. The second thing is to allow more emission credit for eco-friendly vehicle manufacturers. The third thing is to build more concrete infrastructure for the eco-friendly vehicles. The increase of the number of the electric or hydrogen charging system would be one of the good examples of the infrastructure. The fourth thing is that the government supports the research & development of eco-friendly vehicles. The fifth is to regulate that the government agency is mandatory to use the eco-friendly vehicles. The sixth thing is to provide the low-carbon certification for eco-friendly vehicles. The seventh thing is to support advertising the eco-friendly vehicles. The results from this research can be used as a guideline to make policies to stimulate the eco-friendly vehicle industry in Korea.

• Korean Chemical Engineering Research
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• v.56 no.6
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• pp.779-783
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• 2018

In this work, Mathematical modeling was carried-out to predict the charging/discharging characteristics of VRLA (Valve regulated lead acid) battery, which is mainly used as a 12 V lead acid battery for automobile. And It also carried-out how it's characteristics would be changed due to aging. A mathematical modeling technique, which has been mainly used to predict behavior of Lithium-ion batteries, is applied to commercial 70 Ah VRLA battery. The modeling result of Voltage was compared with result of constant current charge / discharge test. From this, it can be seen that the NTGK model can be applied to the lead acid battery with high accuracy. It was also found that the aging of lead-acid battery can be predicted by using it.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.6
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• pp.117-123
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• 2018

Automotive headlamps have been continuously developed as one of the most important devices for securing the driver's view, and the LED lamps are getting popular in recent years. However, in case of the LED lamps, because the heat generated by the LED lamps are too high, it shorten the product life and lower the LED efficiency. Therefore, this study was investigated the cooling characteristics of the LED lamp heat sink for automobile by forced convection for LED heat generation control. In order to analyze the cooling characteristics of the heat sink, the temperature distribution results were investigated through the experiment and computational analysis under the increase of the air flow velocity, and the convective heat transfer coefficient was obtained. Also, convective heat transfer coefficient was calculated by the theoretical formula under the same condition and compared with experimental and computational results. From the result of this study, as the air flow velocity around the heat sink fins increased, the convective heat transfer coefficient significantly increased, confirming the improvement in the cooling effect.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.4
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• pp.69-75
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• 2019

Since gasoline engines are based on a combination of a cast iron liner and an aluminum block, which have different thermal properties and stiffnesses, bore shape distortion is likely to occur during honing due to uneven thermal deformation. To solve this problem, many tests and evaluations are needed to support the development of a high-performance honing stone with low heat generation. Moreover, performance evaluation, which depends on inspection and observation after work, often requires much trial and error to optimize tool design, due to challenges in the accurate interpretation of results. This study confirmed that the assessment of grinding capability was clarified by evaluating performance under severe work conditions and by in-situ measurement and recording of current consumption (workload) and heat generation during operation. As a result of using a honing stone with excellent grinding performance in engine block manufacture-in which cylinder bore distortion caused by thermal deformation during manufacture is a problem-a noticeable improvement in the degree of cylindricity was observed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.12
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• pp.34-41
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• 2020

Ready-mixed concrete is unconsolidated concrete typically transported to construction sites by using mixer trucks. A proper rotation of concrete is necessary to prevent its solidification in mixer trucks during transport: in accordance with the manufacturing method and quality inspection prescribed in KSF4009, this movement is maintained after the manufacturing of concrete in professional production plants and the addition of water, solid materials, and admixtures. Unfortunately, mixer truck parts wear out over long periods of time. In order to improve the wear resistance of the main part of mixer trucks, we used a steel plate with good wear resistance or partially added a reinforcement plate. In this study, we first tested the properties of concrete (as required for the DEM), and then carried out mixing and discharge simulations to define the actual operating conditions of mixer trucks. For each condition, we calculated the amount and location of wear. The reliability of our results was finally verified by comparing them with the measurement values. Overall, this study provided basic data for an optimal design of mixer trucks: one that would reduce the vehicles' weight and production costs.