• 한국소음진동공학회논문집
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• 제23권10호
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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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.246-249
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• 2005

The TFT-LCD is extensively used from a small watch to a large TV display, and the demand is increasing rapidly. The size of R-LCD glass plate becomes more bigger, and the thickness become more thinner with high demands. As a result natural frequency of the TFT-LCD glass plate becomes more lower. The TFT-LCD glass plate will be moved by robot arm and may receive effect of vibration that occur at transfer. Natural frequency of the TFT-LCD glass plate is increased or decrease according to location that robot arm fixs glass plate. Purpose of a this study is finding support location that optimize the first natural frequency of TFT-LCD glass plate. The size optimization method of ANSYS 8.0 is used as the optimization tool search on the optimal support location of TFT-LCD glass plate. The considered number of support point is from 4 to 9.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.330-333
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• 2005

The paper presents a numerical solution to the problem of a hot rigid indenter siding over a thermoelastic Winkler foundation with a thermal contact resistance at constant speed. It is shown analytically that no steady-state solution can exist for sufficiently high temperature or sufficiently small normal load or speed regardless of the thermal contact resistance. However, the steady state solution may exist in the same situation if the thermal contact resistance is considered. This means that the effect of the large values of temperature difference and small value of force or velocity which occur at no steady state can be lessened due to the thermal contact resistance. When there is no steady-state the predicted transient behavior involves regions of transient stationary contact interspersed with regions of separation regardless of the thermal contact resistance. Initially, the system typically exhibits a small number of relatively large contact and separation regions, but after the initial transient the trailing edge of the contact area is only established and the leading edge loses contact, reducing the total extent of contact considerably. As time progresses, larger and larger number of small contact areas are established, until eventually the accuracy of the algorithm is limited by the discretization used.

• 한국소음진동공학회논문집
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• 제13권8호
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• pp.605-611
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• 2003

A simply supported pipe conveying fluid and two moving masses upon it constitute this nitration system. The equation of motion is derived by using Lagrange's equation. The influence of the velocities of two moving masses, the distance between two moving masses, and the velocities of fluid flow in the pipe have been studied on the dynamic behavior of a simply supported pipe by numerical method. The velocities of fluid flow are considered with in its critical values of a simply supported pipe without moving masses upon It. Their coupling effects on the transverse vibration of a simply supported pipe are inspected too. As the velocity of two moving masses increases, the deflection of a simply supported pipe is increased and the frequency of transverse vibration of a simply supported pipe is not varied. In case of small distance between two masses, the maximum deflection of the pipe occur when the front mass arrive at midspan. Otherwise as the distance get larger, the position of the front masses where midspan deflection is maximum moves beyond the midpoint of a simply supported pipe. The deflection of a simply supported pipe is increased by coupling of the velocities of moving masses and fluid flow.

• 한국정밀공학회지
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• 제21권8호
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• pp.120-128
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• 2004

The impulse between launch vehicle and atmosphere can generate a lot of noise and vibration during the process of launching a satellite. Structurally, the electronic equipment of a satellite consists of an aluminum case containing PCB. Each PCB has resistors and IC. Noise and vibration of the wide frequency band are transferred to the inside of fairing, subsequently creating vibration of the electronic equipment of the satellite. In this situation, random vibration can cause malfunctioning of the electronic equipment of the device. Furthermore, when the frequency of random vibration meets with natural frequency of PCB, fatigue fracture may occur in the part of solder joint. The launching environment, thus, needs to be carefully considered when designing the electronic equipment of a satellite. In general, the safety of the electronic equipment is supposed to be related to the natural frequency, shapes of mode and dynamic deflection of PCB in the electronic equipment. Structural vibration analysis of PCB and its electronic components can be performed using either FEM or vibration test. In this study, the natural frequency and dynamic deflection of PCB are measured by FEM, and the safety of the electronic components of PCB is evaluated according to the results. This study presents a unique method for finite element modeling and analysis of PCB and its electronic components. The results of FEA are verified by vibration test. The method proposed herein may be applicable to various designs ranging from the electronic equipments of a satellite to home electronics.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.786-791
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• 2006

Two stroke low speed diesel engines are mainly used for marine propulsion or power plant prime mover. These have many merits such as higher thermal efficiency, mobility and durability. However various annoying vibrations sometimes occur in ships or at the plant itself. Of these vibrations, torsional vibration is very important and it should be carefully investigated during the initial design stage for engine's safe operation. In this paper authors suggest a new estimation method of for shaft's can be calculated equivalently from accumulated fatigue cycles number due to torsional vibration. The 6S70MC-C($25,320ps{\times}91rpm$) engine for ship propulsion was selected as a case study, and the accumulated fatigue cycles numbers for shafting life time converted from the measured angular velocity and torsional vibration stress was calculated. This new method can be realized and confirmed in test model ship with two stroke low speed diesel engine.

• 소음진동
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• 제11권1호
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• pp.82-88
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• 2001

In a transmission or geared rotor system a coupled phenomenon of lateral and torsional vibrations may occur due to the gear meshing effect. Particularly, in high speed or low vibration and low noise applications of geared rotor systems a coupled rotordynamic analysis is required to precisely predict their dynamic characteristics. In this paper a generalized finite element model of a gear pair element is developed, which actively couples the lateral and torsional vibrations due to the gear meshing effect. In the modeling the generalized forces due to the transmission error. geometrical eccentricities. and unbalances in the gear system are also considered. Then. using the developed gear pair element model a coupled unforced rotordynamic analysis is performed with a prototype 800 RT turbo-chiller rotor-bearing system having a hull-pinion speed increasing gear. Results show that the torsional vibration characteristics experience some changes due to the gear meshing and lateral dynamic coupling effect, but that they have no adverse effect and the lateral ones have no practical changes in an operating speed range.

• 한국전기전자재료학회논문지
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• 제26권4호
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• pp.309-314
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• 2013

This paper dealt with the radiated electromagnetic wave detection of partial discharge (PD) in oil for insulation diagnostics of oil-immersed transformers. Three types of electrode system were fabricated to simulate the insulation defects that could occur in oil-immersed transformers. Frequency components of radiated electromagnetic wave in oil was measured by broadband bi-conical antennas of 300 MHz~2 GHz and a spectrum analyzer of 9 kHz~3 GHz. Frequency component of electromagnetic waves from PD in oil were highly distributed at 500 MHz. From the result, a narrow-band monopole antenna with the center frequency of 500 MHz was fabricated. We could detect PD signal in insulation oil without an influence of external noise by a measurement system which consists of the prototype monopole antenna, a LNA (Low Noise Amplifier), an oscilloscope and a spectrum analyzer.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.1185-1190
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• 2007

In this paper the vibration system is consisted of a rotating cantilever pipe conveying fluid. The equation of motion is derived by using the Lagrange's equation. Also, the equation of motion is derived applying a modeling method that employs hybrid deformation variables. Generally, the system of pipe conveying fluid becomes unstable by flutter. So, we studied about the influences of the rotating angular velocity, mass ratio and the velocity of fluid flow on the stability of a cantilever pipe by the numerical method. The influences of mass ratio, the velocity of fluid, the angular velocity of a cantilever pipe and the coupling of these factors on the stability of a cantilever pipe are analytically clarified. The critical fluid velocity$(u_{cr})$ is proportional to the angular velocity of the cantilever pipe. In this paper Flutter(instability) always occur in the second mode of the system.

• 한국소음진동공학회논문집
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• 제22권12호
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• pp.1250-1256
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• 2012

Resilient materials are used to reduce the floor impact sound in apartment buildings. Since an on-dol layer is installed in the resilient materials' upper part, thickness deformation can be occur in the resilient material. It is necessary to check a thickness deformation grade for a long period of time. In this research, we measured thickness deformation over 400th day to the resilient materials(EPP, EPS, EVA) which is used in Korea. Although there was a difference according to the kind of measurement test specimens, it became clear that thickness was decreases as to time increased. The thickness deformation grade of ten years after was calculated based on the thickness measurement result. Compare with the calculated result and result of ISO 20392. Larger thickness deformation occurred in the measurement result of these research findings compare with the ISO standard.