• Journal of Welding and Joining
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• v.19 no.3
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• pp.298-304
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• 2001

Turbine blade is subject to force of three types ; the torsional force by torsional mount, the centrifugal force by the rotation of rotor and the cyclic bending force by steam pressure. The cyclic bending force was a main factor on fatigue strength. SEM fractography in root of turbine blade showed micro-clack width was not dependent on stress intensity factor range. Especially, fatigue did not exist on SEM photograph in root of turbine blade. To clear out the fracture mechanism of turbine blade, nanofractography was needed on 3-dimensional crack initiation and crack growth with high magnification. Fatigue striation partially existed on AFM photograph in root of turbine blade. Therefore, to find a fracture mechanism of the torsion-mounted blade in nuclear power plant, the relation between stress intensity factor range and surface roughness measured by AFM was estimated, and then the load amplitude ΔP applied to turbine blade was predicted exactly by root mean square roughness.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.10
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• pp.895-901
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• 2013

Last blades of LP turbine in nuclear power plant are the highly damaged part and suffered from nozzle steam impulses during the turbine operation. Nozzle impulse is known as a common cause of damage or failure in the turbine blade and results from steam flow distortions due to uneven steam flow patterns between the stationary blade vanes. If impulse force was continuously acting on the blade for a long time, crack or wear will occur in weak parts such as root. So, it is important to know variation of nozzle impulse during the blade moving. But there is no way to measure and estimate the magnitude and direction of nozzle impulse. Therefore, this study was performed to know the variation of nozzle impulse force according to the positions of the blade and to obtain blade equivalent force and torque. This results can be used for blade stress estimation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.12
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• pp.1164-1171
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• 2012

Recently, researches related to the green energy generation systems have increased significantly. Among them wind turbines are the most spread practical green energy generation systems. In order to enhance the power generation capacity of the wind turbine blade, the length of wind turbine blade has increased. It might cause undesirable excessive dynamic loads. Therefore dynamic characteristics of a wind turbine blade system should be identified for a safe design of the system. In this study, the equations of motion of a wind turbine blade system undergoing gravitational force are derived considering wind force and pitch angle. Effects of wind speed, variation of pitch angle of the wind turbine blade, rotating speed, and the blade length on its stability characteristics are investigated.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.39-42
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• 2008

In the case of the general helicopter among rotorcraft, length of the rotor blade for thrust-generation is longer than that of fuselage and tail rotor is required in order to compensate moment of the fuselage. For those reasons, enough space for take-off and landing should be secured and an accessibility for building is low. Also, the accidents caused by tail rotor occur frequently. However, the case of counter-rotating has merits that tail rotor is unnecessary as well as length of the rotor blade can be shortened but has a weakness that the weight of body is increased. In the present study, aerodynamic force measurement on single rotor system equipped with NACA0012 airfoil, which has aspect ratio of 6 and chord length of 35.5 mm, was carried out. And measurement was conducted with blade which has a half size of the former blade by using single motor counter-rotating. Aerodynamic force measurement was acquired by using 6-component balances and coefficients of thrust and power were derived along the pitch angle varying from 0$^{\circ}$ to 90$^{\circ}$ with the increment of 10$^{\circ}$. Those aerodynamic force data will be utilized for the design and production of brand-new counter-rotating rotor blade system which has same thrust with single blade system and provides a good accessibility to building by reducing its blade length.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.258-265
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• 2001

Turbine blade is subject to force of three type ; torsional force by torsion-mount, centrifugal force by rotation of rotor and cyclic bending force by steam pressure. Cyclic bending force of them is main factor on fatigue fracture. In the X-ray diffraction method, the change in the values related to plastic deformation and residual stress near the fracture surface mat be determined, and information of internal structure of material can be obtained. Therefore, to find a fracture mechanism of torsion-mounted blade in nuclear plant, based on the information from the fracture surface obtained by fatigue test, the correlation of X-ray parameter and fracture mechanics parameter was determined, and then the load applied to actual broken turbine blade parts was predicted. Failure analysis is performed by finite element method and Goodman diagram on torsion-mounted blade.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.489-493
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• 2000

Turbine blade has trouble of cracking at root region. Fracture surface of blade root is surveyed by SEM and AFM to clear relation between fracture mechanical parameter and surface parameter (striation width and surface roughness). Service stress is predicted by maximum height roughness $R_{max}$, on fractured surface and stress analysis on turbine blade. It is to thought that turbine blade is fractured by abnormal condition such as incorrect fittings between pin and pin hole but isn't fractured by normal service conditions such as steam pressure, centrifugal force and torsional force.

• Journal of the Korean Society of Visualization
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• v.9 no.2
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• pp.40-47
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• 2011

Tilt-rotor aircraft can be used in various fields because they have the capabilities of the vertical take-off and landing and the high-speed cruise flight. In the present study, the flow analysis of a tilt-rotor aircraft is conducted at various tilt angles. The lift and drag forces of the tilt-rotor aircraft are obtained and the wakes by the rotor-blade are visualized. The result shows that the rotor-blade affects the lift force in a hovering mode and the main wing has an influence on the lift force in a cruise mode. Additional thrust is required at the tilt angle of around 40 degree due to the least lift force. The drag force is dependent on the rotor-blade at overall tilt angles. The minus drag force appears between the tilt angles of 90 degree and 55 degree. Also, the drag force is dramatically increased at the other tilt angles. The wake by rotor-blade affects the flow around the fuselage of the tilt-rotor aircraft at the tilt angles of 75 degree and 60 degree.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.77-81
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• 1999

The predictions of metal flow forging load optimal die angle and preform size are not so easy in turbine blade forging. First of all the quality of final product is influenced by side force which is one of the significant factors. in this study slab method is applied to determine optimal die angle minimizing side force and the position of preform Finally drawing of die design is obtained in optimal die angle with developing tool that is composed of Visual Basic.

• Journal of Institute of Convergence Technology
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• v.6 no.1
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• pp.37-41
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• 2016

The serpentine internal passage is located in turbine blade and it shows the variety heat transfer distribution. Especially, the Coriolis force, which is induced by blade rotation, makes different heat transfer distribution of the leading and trailing surfaces of serpentine internal passage. The different heat transfer is one of the reasons why the serpentine cooling passage shows low cooling performance in the rotating condition. So, this study tried to design the advanced the serpentine passage to consideration of the Coriolis force. The design concept of advanced serpentine cooling is maximizing cooling performance using the Coriolis force. So, the flow turns from leading surface to trailing surface in advanced serpentine passage to match the direction of Coriolis force and rotating force. We performed numerical analysis using CFX and compared the existing and advanced serpentine internal passage. This design change is induced the high heat transfer distribution of whole advanced serpentine internal passage surfaces.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2259-2265
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• 2000

A dynamic modeling of a rotating pretwist blade which interacts with the fluid is proposed in this study. The hybrid deformation variable modeling method is employed to derive the equations of motion. The external force and moment induced by the fluid (with fixed configurations of the blade) are obtained by fluid flow analysis and tabulated in a database. This database is efficiently utilized to save the computational effort to calculate the dynamic response of the blade. The numerical results show that the fluid affects the transient response as well as frequency characteristics of the system.