• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.4
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• pp.436-443
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• 2015

In order to develop the PHEV(plug-in hybrid electric vehicle), the specific power transmission systems considering the PHEV system characteristics should be applied. A PHEV applied to series-parallel type hybrid power transmission system is a typical example. In this paper, the novel hybrid power systems are proposed by analyzing the existing PHEV system. The backward simulation program is developed to analyze the fuel efficiency of hybrid power system. Quasi-static models for each components such as engine, motor, battery and vehicle are included in the developed simulation program. To obtain an optimal condition for hybrid systems, an optimization approach called the dynamic programming is applied. The simulation is performed in various driving cycles. A weakness for the existing system is found through the simulation. To compensate for a discovered weakness, novel hybrid power systems are proposed by adding or moving the clutch to the existing system. Comparing the simulation results for each systems, the improved fuel efficiency for proposed systems are verified.

• 한국전산유체공학회:학술대회논문집
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• 2008.08a
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• pp.60.6-61
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• 2008

• Transactions of Materials Processing
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• v.16 no.8
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• pp.582-589
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• 2007

This paper is related to an analysis on the surface expansion in backward can extrusion process using spherical punches. It is generally known that the backward can extrusion process usually experiences severe normal pressure and heavy surface expansion. This is a reason why the backward can extrusion process is one of most difficult operations among many forging processes. Different punch nose radii have been applied to the simulation to investigate the effect of punch nose radius on the surface expansion, which is a major effort in this study. AA 2024 aluminum alloy is selected as a model material for investigation. Different frictional conditions have also been selected as a process parameter. The pressure applied on the punch has been also investigated since heavy surface expansion as well as high normal pressure on the tool usually leads to severe tribological conditions along the interface between material and tool. The simulation results are summarized in terms of surface expansion at different reduction in height, deformation patterns including strain distributions and maximum pressure exerted on the workpiece and punch, the effect of punch nose radius and the frictional condition on the surface expansion and the location and magnitude of maximum pressure exerted, respectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.11a
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• pp.1-12
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• 2001

In cold forging of piston-pin for automobile parts, the flow defect appears by the dead metal zone. This appearance evidently happens in products with a thin piercing thickness for the dimension accuracy and the decrease of material loss. The best method that can prevent flow defect is removing dead metal zone. The purpose of this study is to investigate the material flow behavior of forward-backward extruded piston-pin through the relative velocity ratio and the stroke control of upper moving punch & container using the flow control forming technique. The finite element simulations are applied to analyse the flow defect, then the results are compared with the plasticine model material experiments. Finally, the model experiment results are in good agreement with the FE simulation ones.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.347-350
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• 2003

The metal forming behavior and defect formation in Ti-6Al-4V tube during hot backward extrusion were investigated. To predict the forming-defects such as shear band, inner cracks or surface cracks, dynamic material model(DMM) including Ziegler's instability criterion and modified Cockcroft-Latham fracture criterion(C-L model) were used. These models were coupled to the internal variables generated from FE analysis. The chilling effect and friction indicated a great influence on the deformation mode of the tube and the formation of surface cracks. The simulation results for the backward extrusion were compared with the experimental observations.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.1147-1156
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• 1993

In order to analyze lateral control in the backward maneuver of a tractor -trailer combination , a kinematic vehicle model and a human operator model with time delay were utilized for the operator/vehicle system. The analysis was carried out using the frequency domain approach. The open-loop stability of the vehicle motion was analyzed through the transfer functions. The sensitivity of the stability of the vehicle motion. to a change in the steering angle, was also analyzed. A mathematical model of the closed -loop operator/vehicle system was then formulated. The closed -loop stability of the operator /vehicle system was then analyzed. The effect of the delay time on the system was also analyzed through computer simulation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1366-1375
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• 2002

In cold forging of piston-pin for automobile parts, the flow defect appears by the dead metal zone. This appearance evidently happens in products with a thin piercing thickness for the dimension accuracy and the decrease of material loss. The best method that can prevent flow defect is removing dead metal zone. The purpose of this study is to investigate the material flow behavior of forward-backward extruded piston-pin through the relative velocity ratio and the stroke control of upper moving punch & container using the flow control forming technique. The finite element simulations are applied to analyse the flow defect, then the results are compared with the plasticine model material experiments. The model experiment results are in good agreement with the FE simulation ones.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.8 s.179
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• pp.2042-2049
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• 2000

This paper is concerned with the comparison of forging characteristics between forward and backward processes, through the three-dimensional finite element simulation, for the aluminum powder forging of engine pistons. Starting from the theoretical formulation of velocity and temperature fields in the sintered preform during the process, we examine the comparative distributions of relative density, effective stress and temperature as well as the variations of total forging load and total volume reduction. Through the comparative results, we find out that the forward method provides better forging characteristics than the backward method.

• Transactions of Materials Processing
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• v.12 no.8
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• pp.693-701
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• 2003

In this paper, the influence of frictional conditions on the backward impact extrusion of aluminum battery casing with large aspect ratio has been investigated. In the simulation, MSC.Superforge, a package based on the finite volume method, is used for the extrusion analysis. The formability and earing problem during the production have been evaluated by studying the sensitivity to frictional effects. During the sensitivity analysis, the friction factor was varied from 0.02 to 0.24. As the friction factor is increased, the forming height of the narrow edge is decreased, and the forming height of the wide edge is increased. When the friction factor becomes 0.2, the earing problem does not occur The experimental results show a good agreement with analytical results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.03b
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• pp.130-137
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• 1996

Several cold extrusion processes to produce an axisymmetric steel piston-pin are investigated for comparing each other. Two methods among four conventinal ones are selected to be simulated using the rigid-plastic finite element method. One of the both methods using a mechanical press has one stage process and the other utilizing a cold header applies a multi-stage process to produce a final product. Because the main process is a backward extrusion, the design criteria such as the backward extrusion ration and punch diameter to depth rationare ocnsidered. FEM analysis is performed mainly for strain distributin and load-stroke relationshis. Based on the results of preliminary simulatin, both process sequences are proved to have proper charicteristics suitable for each production method in terms of maximum load. Those simulation results will be a good design criteria in the future work to advance the manufacturing process.