• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1654-1663
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• 1994

Even if the ball bearing was conservatively designed considering the dynamic capacity and the rating life, sometimes the bearing was early failed on account of the misalignment and the lubricant contaminations etc. Misalignment was generated when bearing-shaft system transmitted large power and when the bearing was inadequately mounted. It was possible to predict the fatigue life of ball bearing under the misalignment considering the motions of ball, cage and raceway, and the factors of the effect on fatigue life. Misalignment affected on ball bearing as radial and moment load and the relationships between misalignment and moment were obtained. In this paper, the analysis of the load distributions between ball and raceway, and the prediction of fatigue life of deep groove ball bearing under radial and moment loads were carried out. And, the new formulation of equivalent dynamic load considering the effects of moment load was proposed.

• Journal of the Korean Solar Energy Society
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• v.38 no.2
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• pp.1-13
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• 2018

This paper deals with the NREL (National Renewable Energy Laboratory) 5-MW reference wind turbine. The controller which include MPPT (Maximum power point tracking) control algorithm and tower load reduction control algorithm was designed by MATLAB Simulink. This paper propose a tower damper algorithm to improve the existing tower damper algorithm. To improve the existing tower damper algorithm, proposed tower damper algorithm were applied the thrust sensitivity scheduling and PI control method. The thrust sensitivity scheduling was calculated by thrust force formula which include thrust coefficient table. Power and Tower root moment DEL (Damage Equivalent Load) was set as a performance index to verify the load reduction algorithm. The simulation were performed 600 seconds under the wind conditions of the NTM (Normal Turbulence Model), TI (Turbulence Intensity)16% and 12~25m/s average wind speed. The effect of the proposed tower damper algorithm is confirmed through PSD (Power Spectral Density). The proposed tower damper algorithm reduces the fore-aft moment DEL of the tower up to 6% than the existing tower damper algorithm.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.3
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• pp.17-26
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• 2004

In this paper, power transmission systems converts the shaft power of a Turbo-shaft Engine with Free Power Turbine into the generator power and be composed of a method being supplied in the thrust motor driving a propellers. Being used this, Gas turbine engine works to flat rating about 110 kw (147 shp) that the thrust motor be extremely supplied from the engine of 317shp. In this test equipment, the engine is installed with the flywheel being able to the damping function when happen to the varying load between gas turbine engine output-shaft and generator. Then if the flywheel of inertial moment be not considered, the generator and motor not get the required power from the engine for raising the load. Also it is certified that the engine works the abnormal operation. Hence the flywheel of inertial moment is determined the required range to do the performance analysis with the dynamic transient from the given and tested engine data. This system is able to get the required power after a mounting test with the redesigned flywheel.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.385-389
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• 2004

Test facilities for the wind turbine performance monitoring and mechanical load measurements are installed in Vestas 100 kW wind turbine in Wollyong test site, Jeju island. The monitoring system consists of Garrad-Hassan T-MON system, telemetry system for blade load measurement, various sensors such as anemometer, wind vane, strain gauge, power meter, and etc. The experimental procedure for the measurement of wind turbine loads, such as edgewise(lead-lag) bending moment, flapwise bending moment, and tower base bending moment, has been established. Strain gauges are on-site calibrated against load cell prior to monitoring the wind turbine loads. Using the established monitoring system, the wind turbine is remotely monitored. From the measured load data, the load analysis has been performed to obtain the load power spectral density and the fatigue load spectra of the wind turbine.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.7B
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• pp.951-956
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• 2001

A weather radar usually extracts the necessary information from the return Doppler spectrum moment estimates. Phase stability is a very important factor in obtaining accurate and reliable information in a Doppler weather radar system since the system phase noise may seriously degrade the weather spectrum moment estimation quality. These spectrum moment estimates are commonly obtained using the pulse pair method which is simple to implement and fast enough to process an enormous amount of weather radar data in real time. Therefore, an analytical method is developed in this paper to analyze and quantify the phase noise effects on the pulse pair spectrum moment estimates in terms of the phase noise power and broadness.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.542-545
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• 2005

This paper proposes an algorithm for the moment of inertia estimation. The algorithm finds the moment of inertia observing the position error signal, which contains an error information of moment of inertia, generated by speed observer. Moreover, the proposed algorithm is easily realized in the observer -based speed detection method. The experimental results are also presented to confirm the performance of moment of inertia estimation method. The results show that the moment of inertia converges to the actual value with the proposed method.

• Journal of Power System Engineering
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• v.8 no.4
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• pp.57-63
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• 2004

Conventionally, 2WS is used for vehicle steering, which can only steering front wheel. In case of trying to high speed lane change or cornering through this kind of vehicle equipped 2WS, it may occur much of Yaw moment. On the other hand, 4WS makes decreasing of Yawing Moment, outstandingly, so it is possible to support vehicle movement stable. And conventional ABS and TCS can only possible to control the longitudinal movement of braking equipment and drive which can only available to control of longitudinal direction. There after new braking system ESP was developed, which controls both of longitudinal and lateral, with adding of the function of controlling Active Yaw Moment. On this paper, we show about not only designing of improved braking and steering system through establishing of the integrated control system design of 4WS and ESP but also designing of the system contribute to precautious for advanced vehicle stability problem.

• Journal of Biosystems Engineering
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• v.27 no.5
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• pp.371-380
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• 2002

The objectives of this study were to analyze gear rattle in a power drive line using its dynamic model and to derive design guidelines to eliminate it. A 72 degrees of freedom model of power driveline of an agricultural tractor was developed and proved to be valid fer predicting the collision characteristics of gears in mesh, which may determine whether or not the gear rattle will occur. Using the model the effects on the rattle of drag torque, backlash, mass moment of inertia, transmitting torque were analyzed. Increasing drag torque or decreasing mass moment of inertia reduced gear rattle. The gears transmitting power do not develop rattles. It was also found that a large amount of rattle is likely to be developed by the change gears placed at the end of idle shafts. Increasing the drag torque to such change gears may be the most effective way of reducing the gear rattle in a tractor driveline.

• Steel and Composite Structures
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• v.16 no.2
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• pp.221-231
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• 2014

The purpose of this study was to evaluate the cyclic behavior of steel column-tree moment connections used in steel moment resisting frames. These connections are composed of shop-welded stub beam-to-column connection and field bolted beam-to-beam splice. In this study, the effects of beam splice length on the seismic performance of column-tree connections were experimentally investigated. The change of the beam splice location alters the bending moment and shear force at the splice, and this may affect the seismic performance of column-tree connections. Three full-scale test specimens of column-tree connections with the splice lengths of 900 mm, 1,100 mm, and 1,300 mm were fabricated and tested. The splice lengths were roughly 1/6, 1/7, 1/8 of the beam span length of 7,500 mm, respectively. The test results showed that all the specimens successfully developed ductile behavior without brittle fracture until 5% radians story drift angle. The maximum moment resisting capacity of the specimens showed little differences. The specimen with the splice length of 1,300 mm showed better bolt slip resistance than the other specimens due to the smallest bending moment at the beam splice.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.5
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• pp.742-749
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• 2003

Failure of a pipeline due to local wall thinning is getting more attention in the nuclear power plant industry. Although guidelines such as ANSI/ASME B31G and ASME Code Case N597 are still useful fer assessing the integrity of a wall thinned pipeline, there are some limitations in these guidelines. For instance, these guidelines consider only pressure loading and thus neglect bending loading. However, most Pipelines in nuclear power plants are subjected to internal pressure and bending moment due to dead-weight loads and seismic loads. Therefore, an assessment procedure for locally wall thinned pipeline subjected to combined loading is needed. In this paper, three-dimensional finite element(FE) analyses were performed to simulate full-scale pipe tests conducted for various shapes of wall thinned area under internal pressure and bending moment. Maximum moments based on true ultimate stress(${\alpha}$$\sub$u,t/) were obtained from FE results to predict the failure of the pipe. These results were compared with test results, which showed good agreement. Additional finite element analyses were performed to investigate the effect of key parameters, such as wall thinned depth, wall thinned angle and wall thinned length, on maximum moment. Also, the effect of internal pressure on maximum moment was investigated. Change of internal pressure did not show significant effect on the maximum moment.