• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.401-404
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• 2007

Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint face, and energy required for welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy, amount of upset, working time, and residual stresses in the joint. Inertia welding was conducted to make the large rotor shaft for low speed marine diesel engine, alloy steel for shaft of 140mm. Due to different material characteristics, such as, thermal conductivity and flow stress, on the two sides of the weld interface, modeling is crucial in determining the optimal weld geometry and parameters. FE simulation was performed by the commercial code DEFORM-2D. A good agreement between the predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.1
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• pp.17-24
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• 2011

TMED(Transmission Mounted Electric Device) parallel hybrid configuration can realize EV(Electric Vehicle) mode by disengaging the clutch between an engine and a transmission-mounted motor to improve efficiencies of low load driving and regenerative braking. In the EV mode, however, jerk can be induced since there are insufficient damping elements in the drive-train. Though the jerk gives demoralizing influence upon driving comport, adding a physical damper is not applicable due to constraints of the layout. This study suggests the jerk reduction control, composed of active damping method and torque profiling method, to suppress the jerk without hardware modification. The former method creates a virtual damper by generating absorbing torque in the opposite direction of the oscillation. The latter method reduces impulse on the mated gear teeth of the drive-train by limiting the gradient of traction torque when the direction of the torque is reversed. To validate the effectiveness of the suggested strategy, a series of vehicle tests are carried out and it is observed that the amplitude of the oscillation can be reduced by up to 83%.

• Journal of ILASS-Korea
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• v.23 no.3
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• pp.136-148
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• 2018

Major countries have tighten their NOx regulation of diesel passenger cars. In the case of the EU, the regulation has been toughen up to 6.25 times since 2000. Despite the regulation the NOx concentration of the ambient has not been reduced proportionally. As these issues, to reduce NOx emission practically, Korea and the EU introduced the real-world driving emission (RDE) regulation and the test method that will be applied after 2017. In this paper, for the regulation to make a soft landing in Korea, 6 diesel passenger cars which met Euro 6a~6d regulation and were equipped with LNT/SCR were tested at a chassis dynamometer with environmental chamber applying the off-cycles (FTP, US06, SC03, HWFET and CADC) and several ambient conditions (-7 and $14^{\circ}C$) as well as certification modes (NEDC, WLTC@ $23^{\circ}C$). The result of the test showed that the ambient temp. and the engine load as a test mode impacted the NOx emission of the cars while the vehicles with SCR emitted NOx lower than with LNT. Additionally, to propose an effective RDE test method, the above result was compared with the results of the other papers which tested RDE using the same cars.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.285-288
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• 2001

Hypereutectic Al-25Si-X alloys, expected to be applied to the cylinder-liner-part of the engine-block of an automobile due to the excellent wear resistance, low density and low thermal expansion coefficient has been fabricated through a spray forming process. The obtained microstructure of the hypereutectic Al-25Si-X alloy appeared to consist of Al matrix and equiaxed Si particles of average diameter of $5-7{\mu}m$. To characterize the deformation behavior of this alloy, a series of load relaxation and compression tests have been conducted at temperatures ranging from RT to $500^{\circ}C$. The strain rate sensitivity parameter (m) of this alloy has been found to be very low (0.1) below foot and reached 0.2 at $500^{\circ}C$. During the deformation above 300'c in compression, strain softening has been observed. The diagram of extrusion pressure vs. ram-speed has been constructed, providing the extrusion condition of Al-25Si-X alloys.

• Proceedings of the Society of Korea Industrial and System Engineering Conference
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• 2002.05a
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• pp.237-242
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• 2002

The sales activity of most of small manufacturing companies is based on orders of buyers. The process of promotion, receipt and selection of orders of the manufacturers is closely coupled with the load status of the production lines. The decision on whether to accept an order or not, or the selection of optimal order set among excessive orders is entirely dependent on the schedule of production lines. However, in the real world, since the production scheduling activity is mainly performed by human experts, most of small manufacturers are suffer from being unable to meet due dates, lack of rapid decision on the acceptance of new order. To cope with this problem, this paper deals with the development of an agent for selecting an optimal order set automatically. The main engine of selection agent is based on the typical job-shop scheduling model since our target domain is the injection molding company. To solve the problem, we have formulated it as IP (Integer Program) model, and it has been successfully implemented by ILOG and selection agent. And we have suggested an architecture of an agent for tackling web based order selection problems.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.89-94
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• 2006

The tire delivering power generated from engine to the ground pulls a vehicle to move. Radius of tires is changeable due to elasticity that depends on the speed of vehicle and traction force. The main objectives on this study are real time measurement of dynamic radius and slip ratio according to the speed and traction force. The dynamic radius is proportional to speed and traction force. According to measurement, the dynamic radius is increased about 3mm under 100km/h compared to stop. It is also increased about 1.5mm when a traction force is supplied as much as 4kN compared to no load state at low speed. There is no strong relationship between slip ratio and vehicle speed. The slip ratio is measured up to 4% under WOT at first stage gear. Through this research, the method of measuring dynamic radius and slip ratio is set up and is expected to be applied to the measurement of traction force in chassis dynamometer or accelerating and climbing ability.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.25 no.5
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• pp.1-8
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• 2002

The sales activity of most of small manufacturing companies is based on orders of buyers. The process of promotion, receipt and selection of orders of the manufacturers is closely coupled with the load status of the production lines. The decision on whether to accept an order or not, or the selection of optimal order set among excessive orders is entirely dependent on the schedule of production lines. However, in the real world, since the production scheduling activity is mainly performed by human experts, most of small manufacturers are suffer from being unable to meet due dates, lack of rapid decision on the acceptance of new order. To cope with this problem, this paper deals with the development of an agent for selecting an optimal order set automatically. The main engine of selection agent is based on the typical job-shop scheduling model since our target domain is the injection molding company. To solve the problem, we have formulated it as IP (Integer Program) model, and it has been successfully implemented by ILOG and selection agent. And we have suggested an architecture of an agent for tackling web based order selection problems.

• Journal of Ocean Engineering and Technology
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• v.31 no.5
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• pp.352-356
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• 2017

We performed thermal and structural analyses to evaluate the structural integrity of a semi-metal gasket for a flange with increases in the internal fluid temperature and pressure using a commercial FEA program. As a thermal analysis result, the temperature distribution of the gasket body increased with an increase in the internal fluid temperature until the maximum fluid temperature of $600^{\circ}C$. In addition, the structural analysis showed that contact pressures of more than 35 MPa occurred uniformly in the graphite seal regions. It was found that no fluid leakage occurred under the load conditions for the structural analysis because the contact pressure in the graphite seal region was greater than the maximum internal fluid pressure of 35 MPa. Therefore, we demonstrated the structural integrity of the semi-metal gasket by performing the thermal and structure analyses under the maximum fluid temperature of $600^{\circ}C$ and the internal fluid pressure of 35 MPa.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.1831-1838
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• 1991

The deformation of coil spring with noncircular section, which is used in the engine valve of automobiles under the applied load is usually accompanied by sectional warping and additional displacements of geometric center. In this study the isoparametric beam element formulations are modified and expanded to consider these two effects. To verify these formulations, simple torsion tests are made and compared with the analysis results. For the case of the zero-pitch spring, the stress distributions of oval and circular section are coincided with those of the analysis using the solid elements. Cylindrical coil springs with oval section are analyzed. These results are agreed with those of Nagaya.

• International Journal of Automotive Technology
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• v.2 no.4
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• pp.157-164
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• 2001

The vehicle electric power system, which consists of two major components: a generator and a battery, which have to provide numerous electrical and electronic systems with enough electrical energy. A detailed understanding of the characteristics of the electric power system, electrical load demands, and the driving environment such as road, season, and vehicle weight is required when the capacities of the generator and the battery are to be determined for a vehicle. An easy-to-use and inexpensive simulation program may be needed to avoid the over/under design problem of the electric power system. A vehicle electric power simulator is developed in this study. The simulator can be utilized to determine the optimal capacities of generators and batteries. To improve the expandability and easy usage of the simulation program, the program is organized in modular structures, and is run on a PC. Empirical electrical models of various generators and batteries, and the structure of the simulation program are presented. For executing the vehicle electric power simulator, data of engine speed profile and electric loads of a vehicle are required, and these data are obtained from real driving conditions. In order to improve the accuracy of the simulator, numerous driving data of a vehicle are logged and analyzed.