• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.674-678
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• 2007

기술수준의 발달로 인해 건물이 대형화 고층화됨에 따라 높은 양정의 펌프를 사용하고 있으며, 배관계통을 대부분 전자식 밸브를 채택하여 입상급수라인의 수충격 현상이 대두되어 수충격 현상제어를 위한 여러 방법들이 시행되고 있다. 본 연구는 수충격 현상을 제어하는 방법 중 수충격 방지기를 이용하여 입상급수라인의 수충격 현상의 제어를 효과적으로 제어할 수 있었다. 향후 본 연구를 계속 진행 시켜나감에 따라 수충격 현상의 제어에 큰 성과를 거둘수 있을 것으로 판단된다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.145-151
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• 2008

URN(Underwater Radiated Noise) is one of the important performances of the battle ship related to the stealth. The main source of the URN is the structure-borne noise on the hull. And the pipe vibration transmitted to the hull is the main source of the structure-borne noise when the speed of the ship is lower than CIS(Cavitation Inception Speed). In this paper, the vibration isolator(rubber mount) for the pipe system is described in order to reduce the structure-borne noise transmitted to the hull. The vibrations on the sea-water conveying pipes and their supports are measured in order to know how much vibration occurs on those positions. Based on these test results, the improved design of the rubber mount is suggested by the parametric study and is verified numerically with the pipe and hull model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.472-473
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• 2008

In this research, the finite element model is formulated taking into consideration of the effects of the fluid flow in a pipe. The characteristic of vibration is presented using mass, damping and stiffness matrix in the finite element equation of this pipe system. The displacement distribution of pipe system caused by fluid force is discussed. The method for optimizing the location of mount and the value of mount stiffness to reduce the vibration of pipe system is introduced.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1371-1374
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• 2007

A few intake stations have vibration problems caused by pipes. The vibration transffered from pipes excites building severely. Therefore, the crack is generated on building wall and people who work at intake station are damaged. In this paper, the vibration is measured and analysis is carried out for pipes at intake station in order to identify the usefulness and effectiveness of the solution proposed for pipe resonance avoidance. According to the result of analysis, bellows is reduced the vibration of pipes.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.681-686
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• 2008

In this paper, we estimated the degree of pipe thinning by using two accelerometers. It uses measured velocity of flexural wave traveling along the pipes. If the thickness of the wall decreases because of pipe thinning, flexural stiffness of the pipes decreases and accordingly, traveling velocity of flexural wave decreases. Thus, if we install two vibration sensors outside of the pipes and measures traveling velocity of flexural waves regularly, we can estimate and monitor the degree of pipe thinning quickly. In order to test the method we experimented with pipes, and get the result that group velocity varies according to the degree of pipe thinning. It verified this method can be used to monitor the pipe thinning.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1437-1441
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• 2007

This paper formulates the finite element model is formulated taking into consideration of the effects of the fluid flow in a pipe. The characteristic of vibration is presented using mass, damping and stiffness matrix in the finite element equation of this pipe system. The displacement distribution of pipe system caused by fluid force is discussed. The variation of vibration of a pipe system according the change of mount stiffness is discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.156-162
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• 2006

Pipe thinning is one of the major issues for the structural fracture of pipes of nuclear power plants. Therefore a method to inspect a large area of piping systems quickly and accurately is needed. In this paper, we proposed the method for monitoring pipe thinning. Our basic idea come from that a group velocity of impact wave is different as wall thickness. If the group velocity is measured, wall thickness can be estimated. To obtain the group velocity, time-frequency analysis is used. This is because an arrival time difference can be measured easily in time-frequency domain rather than time domain. To test the performance of this technique, experiments have been performed for a plate and U type pipe. Results show that the proposed technique is quite powerful in the monitoring pipe thinning.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.588-592
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• 2002

There was the transient vibration on $H_2$ piping system for cooling the generator in a power plant. We found it was resulted from resonance between the natural vibration of the piping system and exciting force from the turbine rotor by measurement and simulation test. We verified it would be changed the mode shape of the piping system by several simulation test for the structural modification of the piping system. Therefore we concluded that the change of natural vibration mode depends on deeply changing effective length of pipe and reducing supports.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.12 s.117
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• pp.1224-1230
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• 2006

Pipe thinning is one of the major issues for the structural fracture of pipes of nuclear power plants. Therefore a method to inspect a large area of piping systems quickly and accurately is needed. In this paper, we proposed the method for monitoring pipe thinning. Our basic idea come from that a group velocity of impact wave is different as wall thickness. If the group velocity is measured, wall thickness can be estimated. To obtain the group velocity, time -frequency analysis is used. This is because an arrival time difference can be measured easily in time-frequency domain rather than time domain. To test the performance of this technique, experiments have been performed for a plate and U type pipe. Results show that the proposed technique is quite powerful in the monitoring pipe thinning.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.4
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• pp.381-385
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• 2008

This paper suggests a non-contact sensor for measuring bending vibration of a non-metallic cylinder in two orthogonal directions simultaneously. Recent research shows that a solenoid can pick up bending vibrations of a nonmetallic cylinder based on the reversed Lorentz force mechanism if an electrically conductive patch is attached to the cylinder. In this work, pairs of specially designed patches are used to make two independent paths for the current induced by bending vibrations, which enables the measurement of bending vibrations along two orthogonal directions simultaneously. The working performance of the developed sensor was verified by using two accelerometers.