• Steel and Composite Structures
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• v.29 no.3
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• pp.319-332
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• 2018

This paper investigates the free vibration of geometrically imperfect functionally graded car-bon nanotube-reinforced composite (FG-CNTRC) beams that are integrated with two sur-face-bonded piezoelectric layers and subjected to a combined action of a uniform temperature rise, a constant actuator voltage and an in-plane force. The material properties of FG-CNTRCs are assumed to be temperature-dependent and vary continuously across the thick-ness. A generic imperfection function is employed to simulate various possible imperfections with different shapes and locations in the beam. The governing equations that account for the influence of initial geometric imperfection are derived based on the first-order shear deformation theory. The postbuckling configurations of FG-CNTRC hybrid beams are determined by the differential quadrature method combined with the modified Newton-Raphson technique, after which the fundamental frequencies of hybrid beams in the postbuckled state are obtained by a standard eigenvalue algorithm. The effects of CNT distribution pattern and volume fraction, geometric imperfection, thermo-electro-mechanical load, as well as boundary condition are examined in detail through parametric studies. The results show that the fundamental frequency of an imperfect beam is higher than that of its perfect counterpart. The influence of geometric imperfection tends to be much more pronounced around the critical buckling temperature.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.1
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• pp.59-65
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• 2017

A seat track product is a car seat part that provides a base for vehicle seats. An ultra-high strength steel sheet is used to reduce the weight of vehicle body parts. However, the formability of an ultra-high strength steel sheet is poor because of its very low elongation and very high elastic deformation. For this reason, a new forming technology of an ultra-high strength steel sheet is required. The influence of spring-back of seat track parts on the shape freeze in forming processes was investigated to be solved by adjusting the appropriate tool design such as minus clearance between punch and die, and punch angle. This paper describes how to apply the spring-back prevention technique for improving shape freeze by using the ultra-high strength steel sheet with 980MPa to develop lightweight seat tract parts.

• Journal of Energy Engineering
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• v.11 no.3
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• pp.254-261
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• 2002

The fabrication method for the main components of the polymer electrolyte membrane fuel cell stack such as electrodes, membrane-electrode assemblies, and bipolar plates was established for the effective electrode area of 240 ㎠. A counter-flow type 100-cell stack was fabricated by using the above components and then a maximum power of 7.44 kW for H$_2$/O$_2$ and 5.56 kW for H$_2$/air could be obtained at 70$\^{C}$ and 1 atm. It was seen that the distribution of the OCV for unit cells in the stack was uniform but the voltage deviation increased as the load increased due to the IR drop and the electrode polarization. The stack was applied to the power source of the fuel cell/battery hybrid electric golf car. It produced about 1 kW at a room temperature operation during the test run, which occupied about 43% of the total power required by the 2.3 kW motor.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.868-869
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• 2011

Domestic Foreign automaker's are focused on the high-efficiency, low emission cars development. On the way, the hybrid car is the first priority. Hybrid electric vehicle battery pack configurations, EV Relay one of the key components of the engine driving, to assist in the drive motor to supply electrical energy to the battery is a device for opening and closing of the output device. EV Relay determine the longevity and the replacement cycle, The EV Relay environmental conditions and duty cycle considering the reliability tests are essential requirements of many automotive companies to respond to RFQ, this test is essential. This paper using Maxwell Software for Prediction of the Ev Relay impulse, the theoretical data to obtain the impulse to develop methods for mechanical testing after to take advantage of it.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.1
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• pp.59-64
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• 2014

Integrated Starter Generator (ISG) system improves the fuel economy of hybrid electric vehicles by using idle stop and go function, and regenerative braking system. To obtain the high performance and durability of ISG motor under continuously high load condition, the motor needs to properly design the cooling system (cooling fan and cooling structure). In this study, we suggested the enhanced design by modifying the thermal design of the ISG motor and then analyzed the improvement of the cooling performance under high-speed condition and generating mode by CFD simulation. The temperatures at the coil and the magnet of the enhanced model were decreased by about $4^{\circ}C$ and $6^{\circ}C$, respectively, compared to those of the conventional model. Therefore, we verified the cooling performance enhancement of the novel thermal design in the case of core loss increment due to the higher speed condition.

• Transactions of Materials Processing
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• v.17 no.3
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• pp.170-181
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• 2008

The shape of rectangular cup used for Ni-MH(Nickel-coated Metal Hydrogen) battery for hybrid car looks quite simple, but the forming process of extruding and setting up process design are highly difficult. Furthermore, there are few concrete reports on the rectangular deep drawn cup as part of hybrid vehicles till now. In this study, process design for rectangular cup in the multi-stage deep drawing process is carried out, and FE analysis is also preformed based on the result of the process design. From the simulation result, some unexpected problems such as earing, wrinkling and excessive thickness changes of the intermediate blank occurred. To overcome these failures, a series of modification for punch shape in the forming process design are completed and applied. Considering the modified punch shape in the multi-stage deep drawing process, additional FE analysis is also carried out and the simulation result is verified in view of the deformed shape, thickness change and effective strain distribution. The result of FE analysis with the improved process design confirmed not only reducing thinning of wall and possibilities of failure but also improving the quality of drawing product through the modification of punch shape.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.10
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• pp.1204-1209
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• 2011

In this study, fatigue life is evaluated by comparing with lighter car body through the experiment on SPR joints. An experimental activity on sheet metal samples of Aluminum 5J32 and Steel SPRC440 has been conducted to achieve better understanding of the process. In addition, SPR joint used less than the existing Spot Welding improves joint strength and fatigue life is evaluated by using SPR and adhesive joining Hybrid. Joining(bonding) strength and fatigue life on SPR and Hybrid (SPR + adhesive) are evaluated throughout the experiment. With joining strength than 20 % of the aluminum material, dissimilar materials has improved over 2 times as large as the strength In case of dissimilar materials, the fatigue life of aluminum is increased by 1.6 to 2.5 times as large as the life.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.152.1-152.1
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• 2011

This study analyzes transitions to a green path in transportation system in South Korea. We develop transportation system model with four new technology options, green cars; Hybrid electric vehicle, plug-in hybrid vehicle, electric vehicle and fuel cell vehicle. Among those technologies fuel cell vehicle is the best option assuming no GHG emissions when driving. We use MESSAGE model to get an optimal solution of pathway for high deployment of fuel cell vehicles under the Korea BAU transportation model. Among hydrogen production sources, off gas hydrogen is most economic since it is hardly used to other chemical sources or emits in South Korea. According to off gas hydrogen projection it can run 1.8 million fuel cell vehicles in 2040 which corresponds to 10% of all passenger cars expected in Korea in 2040. However, there are concerns associated with technology maturity, cost uncertainty which has contradictions. But clean pathway with off gas and renewable sources may provide a strong driving force for energy transition in transportation in South Korea.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.122-125
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• 2006

The Substructure Synthesis means the technology to predict the dynamic properties of an assembly from the properties of its components, or to predict the effect of a modification on a structure. The FRF Based Substructuring method is a kind of the Substructure Synthesis and very useful to predict the efficiency of the product in the early stage of development. Especially, the Hybrid FBS method is very useful to predict the vehicle NVH characteristics after modifying some components of the vehicle. Target components can be established on the basis of test models and FE models of the prototype constructed in the early stage of development. In this study, the Hybrid FBS method was applied to vehicle subframe and car-body in order to reduce vehicle interior noise induced by engine exciting force.

• Environmental and Resource Economics Review
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• v.22 no.1
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• pp.3-29
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• 2013

The purpose of this study is to estimate consumer preferences on hybrid cars and electric cars by employing a choice experiment reflecting the various market conditions, such as different projected market shares of green vehicles and $CO_2$ emission regulations. Depending on different market scenarios, we examine as to which attribute and individual characteristic affect the preferences of potential consumers on green vehicles and further, forecast the potential market shares of green cars. The primary results, estimated by a conditional logit and panel probit models, indicate that sales price, fuel cost, maximum speed, emission of air pollutants, fuel economy, and distance between fuel stations can significantly affect consumer's choice of environment-friendly cars. The second finding is that the unique features of electric cars might better appeal to consumers as the market conditions for electric cars are improved. Third, education, age, and gender can significantly affect individual preferences. Finally, as the market conditions become more favorable toward green cars, the forecasted market shares of hybrid and electric vehicles will increase up to 67% and 14%.