• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.201-207
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• 2015

Turbine-generator torsional response is caused by interaction between electrical transient air-gap torque and mechanical characteristics of turbine-generator shafts. If torsional shaft torque exceeds a certain threshold, the loss of fatigue life may occur and, in the end, it is possible to happen permanent shaft failure. Therefore, it is required to understand the torsional response for reliable operation and protection of turbine-generator shaft system. In this paper, we introduced multi-mass modeling method of turbine-generator shaft system using mechanical-electrical analogy and state-space equation to verify the transient torsional response based on ElectroMagnetic Transient Program (EMTP). These simple realization methods for turbine-generator shaft torsional response could be helpful to understand torsional interaction phenomena and develop the transient torque reduction countermeasures for turbine-generator shaft system.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.6
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• pp.19-25
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• 2019

We have developed a tool that uses finite element analysis (FEA) to rapidly evaluate a shaft-bearing system of machine tools. We extracted commercial data on suitable clamping units and defined the inner profile of the shaft to avoid needing direct user input to define the profile. We use a splitting algorithm to convert the shaft into beam elements with two diameters and length. To validate the tool, we used it to design and evaluate a shaft-bearing system and found that our tool automated the construction of an FE system model in a commercial FEA package as well as the static stiffness evaluation; both tasks were completed in seconds, demonstrating a significant reduction from the minutes normally required to complete these tasks manually.

• Journal of KSNVE
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• v.8 no.3
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• pp.450-456
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• 1998

A rotordynamic analysis is performed with a centrifuge rotor-bearing system for the raing speed of 100,000 rpm. The system is composed of a centrifuge rotor(or simply the rotor), flexible shaft, motor rotor and shaft, and two support rolling element bearings of the motor shaft. Design goals are to achieve wide separation margins of critical speeds and favorable unbalance responses of the rotor at the associated critical speeds. The latter requirements are especially important as the system crosses multiple numbers of critical speeds and as the system may not have enough separaton margins around the rating speed. As the system adopts an extra-flexible shaft, it is shown that the rotor has satisfactory small unbalance responses over higher criticals while having an unsatisfactory large one at the first critical. To supress this a bumper ring or guide bearing needs to be installed at a suitable location of the flexible shaft. It is also shown that even with the flexible shaft the dynamics of the motor must be incoporated into the full system model to accurately identify the fourth critical speed, which is close to the rating speed, and higher ones. The analysis is based on the finite element method.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.1
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• pp.63-69
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• 1998

A rotating shaft system subjected to seismic motions has been investigated for the various operating modes at start-up. During an earthquake excitation, the rotor may hit the stator of machines due to the excessive deformation of shaft, and thus the response of rotating shaft system of which foundation is supported by the vibration isolation devices has been simulated. In order to examine the transient response of the rotating shaft system at the start-up to both the various operating conditions and the seismic excitation simultaneously, nonlinear equations of motion are derived and solved numerically using Runge-Kutta method. The response of the rotating shaft system is calculated according to the operating modes as recommended by the machine and the system parameters such as the spring stiffness of isolation devices.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.48-53
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• 2019

A water jet propeller is a key component that generates propulsion during the start of a naval vessel. When failure or breakage occurs, the vessel cannot operate. Recently, a flow analysis and structural analysis were conducted to understand the cause of damage to a bolt on a water jet. In particular, the stress and strain acting on the fastening bolt (impeller shaft and tail shaft) were examined to determine the extent of misalignment between the impeller shaft and the tail shaft of the water jet propeller. The study determined that stress and strain were concentrated on the impeller shaft and the tail shaft bolt. The alignment of the propeller impeller shaft and the tail shaft increased significantly in response to the tail shaft bolt. Failure of the tail shaft bolt fastening can lead to misalignment between the impeller shaft and the tail shaft.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.3
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• pp.223-232
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• 2014

An inductive sensor system is proposed to detect the gear location and angular position of a geared shaft for automatic feeding of the shaft into the proper cutting position of the other end. The system consists of two set of coils, bridge circuit, signal condition circuit, and microprocessor. The coil sensors of the system measure changes of inductance along with the surface position of a geared shaft. The inductance changes are transformed to voltages by the bridge circuit, which are then conditioned and processed for the recognition of the gear. In order to incorporate with the experimental results with the sensor system, a finite element method (FEM) simulation for the magnetic field between the sensor and the shaft was carried out. The predicted results and the experiments revealed that the sensor system was appropriate for sensing the position of gear and the angular position of gear tooth of a geared shaft.

• Tribology and Lubricants
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• v.16 no.1
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• pp.39-45
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• 2000

In this paper, the effects of shaft and bearing flexibilities are investigated for the accurate modeling of a shaft-bearing system supported by ball bearings. Generally, rolling bearings are modeled by simple rigid pin-joint in the mechanical design. However, they can no longer be modeled by ideal boundary conditions in the advanced applications because the rigid pin-joint model cannot satisfy the current trends of mechanical design decreasing mass and reducing volume. Consequently the flexible support model of ball bearing is investigated using the static analysis module developed by A .B. Jones and T. A. Harris. A simple two-bearing system, supported by two deep groove ball bearings and radially loaded on the shaft midway between the bearings, is utilized to validate the coupled model of shaft-bearing system. Numerical computations using the model indicate that the shaft span length, locating/floating bearing arrangements and applied bearing size are significant factors in determining the mechanical behaviors. The flexible support model of ball bearing can be escaped to over-estimate in the bearing fatigue life. The proposed simple design formulation obtained by numerical simulations can approximately predict a rate of bearing life reduction as a function of shaft span length/shaft diameter (L/d).

• Journal of Biosystems Engineering
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• v.21 no.4
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• pp.399-405
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• 1996

In order to maintain a constant speed ratio between the tractor and attached seed planter, a feedback control unit to rotate the feed shaft of the planter in proportional to the ground speed of the tractor was designed. The fifth wheel was used as a ground speed sensor for the unit. Using this control unit a feed shaft driving system was developed and tested to estimate its performance both in laboratory and fields. The test results showed that the system rotates the feed shaft proportionally to the ground speed in the range of the normal planting speed of 0.5-0.8m/s with errors less than 5%.

• Journal of KSNVE
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• v.4 no.1
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• pp.23-31
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• 1994

When a shaft is misaligned, a high level of vibration is experienced. As a consequence, the system performance could be low with high level of noise generated. Even, a catastrophic damage of the rotating machinery may happen in the worst situation. The vibration caused by the shaft misalignment is not cured unless a correct alignment of the shaft is investigated. In this paper, a step by step approach for the turbine alignment has been demonstrated. It includes measurement tips of the coupling rim and face, calculation procedure of the bearing level, and the relevant values of the addition and subtration for shims in order to align the shaft level correctly. Then, as an application of the shaft alignment, the turbine system at the Pyung Tek focile electric power plant has been examined. Since the real system consists of high pressure, low pressure turbines and the generator, detailed alignment prolcedures of the multi stage shaft system has been demonstrated.

• Transactions on Control, Automation and Systems Engineering
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• v.2 no.4
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• pp.228-234
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• 2000

The aim of the work is to present a new method of estimating the existence of a mass unbalance and mass unbalance under a crack on a rotating shaft. This is an advanced new method for the detection of a mass unbalance and a new way to estimate the position of it under crack influence. As the first step, the shaft is physically modelled with a finite element method and the dynamic mathematical model is derived by using the Hamilton principle; thus, the system is represented by various subsystems. The equation of motion of the shaft with a mass unbalance and a crack are established by adapting the local mass unbalance and the stiffness change. this is a reference system for the given system. Based on a model for transient behavior induced from vabrations measured at the bearings, an elementary Estimator is designed to detect mass unblance on the shaft. Using the Estimator, a bank of the Estimator is established to estimate the estimate the position of the mass unbalance and arranged at a certain location on the shaft. The informations for the given system are the measurements of bearing displacements and velocity.