• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.12
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• pp.1244-1251
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• 2009

In this paper the vibrational behavior of a multi-packet blade system having a cracked blade is investigated. Each blade is assumed as a slender cantilever beam. The coupling stiffness effect that originates from either disc flexibility or shroud is considered in the modeling. Hybrid deformation variables are employed to derive the equations of motion. The flexibility due to crack, which is assumed to be open during the vibration, is calculated basing on a fracture mechanics theory. In the paper, the results of the change in modal parameters due to crack appearance are presented. The influence of the crack parameters, especially of the changing location of the crack is examined.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.6
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• pp.71-77
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• 2001

We have developed the exclusive CAD/CAM system for the machining of impeller blades. This study is about the mod-eling method for the effective machining of impeller blades farmed by ruled surface. As the impeller is consisted of boss part and blade part, the boss is modeled by rotational surface of hub curve on z-axis and the blade is described by ruled- surfaces between hub curve and shroud curve. This modeling process can be carried out on the software developed in this study. And, the developed software can describe the impeller as a solid model through interface with Solid-Works soul- ware. The developed software containing the interface method proposed in this study was very effective fur impeller modeling.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.5
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• pp.314-319
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• 2019

The numerical simulation method was used to analyze the flow velocity change and mechanical coefficient characteristics of the blade in the shroud system that changes with the initial flow velocity and the blade rpm. In the analysis condition, the initial flow velocity was varied from 0.35 m/s to 1.0 m/s, and the blade rpm varied from 50 rpm to 300 rpm. Through this, the mechanical coefficient was estimated. The flow velocity changes tended to increase more than 1.8 times at the middle point compared to the inlet. When the flow velocity ratio was 0.75 m/s compared to the initial flow velocity of 0.5 m/s, the flow velocity ratio decreased. The mechanical coefficient using the torque of the blade also showed the highest coefficient at 0.5 m/s, and the trends were similar. On the other hand, the maximum coefficient was estimated to be about 20.88% in TSR 4.77 when the initial flow velocity was 0.5 m/s. The mechanical coefficient analysis of blades in this study is expected to provide the basic data for hydraulic model experimental.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.266-271
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• 2009

A modeling method for the modal analysis of a multi-packet blade system having a crack undergoing rotational motion is presented in this paper. Each blade is assumed as a slender cantilever beam. The stiffness coupling effects between blades due to the flexibilities of the disc and the shroud are modeled with discrete springs. Hybrid deformation variables are employed to derive the equations of motion. The flexibility due to crack, which is assumed to be open during the vibration, is calculated basing on a fracture mechanics theory. To obtain more general information, the equations of motion are transformed into dimensionless forms in which dimensionless parameters are identified. The effects of the dimensionless parameters related to the angular speed, the depth and location of a crack on the modal characteristics of the system are investigated with some numerical examples.

• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.103-108
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• 2004

The space environment is characterized such a severe condition as high vacuum and very low temperature. Since a satellite will be exposed such a space environment as soon as it goes into the its orbit, thermal vacuum test should be carried out to verify the performance of the satellite on the ground under the space environmental conditions. KARI has a thermal vacuum chamber with useful dimensions of ∮3.6m×L3m, in which KOMPSAT-1 and KOMPSAT-2 satellites were tested. But very large thermal vacuum chamber with useful dimensions of ∮8m×L10m has been needed to meet the future demand of large satellites. Generally, the thermal vacuum chamber can be divided into a vacuum system and a thermal system. Especially, a cryogenic system in the thermal system simulates very low temperature of -196℃ under the high vacuum condition. In this paper, we propose the new cryogenic system can be applied to the future large thermal vacuum chamber.