• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.473-485
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• 1994

Vibration control of concrete slab mounting precision instrument is needed to make the working vibration environments in frequency domain as well as time domain. In order to take the vibration control countermeasures, signal and system analyses of the concrete slab are processed. Through them the dynamic responses of concrete slab are obtained in frequency domain, and frequency response functions are acquired by exciting the concrete slab and measuring dynamic responses at various points across its surface. The dynamic characteristics of concrete slab are determined by experimental modal analysis. Based on modal parameters from a set of frequency response function measured, it is possible to investigate the effects of potential design modifications and reduce the dynamic response of concerned point by moving or suppressing an objectionable modal resonance conditions through structural dynamics modification.

• Journal of the Korea Convergence Society
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• v.5 no.1
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• pp.1-8
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• 2014

The purpose of this paper was to evaluate the fatigue life to apply the vibration fatigue analysis considering the stiffness change of the spot welding due to fatigue damage accumulation. For this, the mechanical and fatigue properties of base and spot welded standard specimens were obtained through the tensile and constant amplitude fatigue test. The transfer function of the spot-welded structure was obtained from the frequency response analysis and fatigue analyisis was performed under the condition of PSD=0.11. A vibration fatigue analysis that considered changes in the frequency response due to the fatigue damage that is, failure of some wleding point was conducted on spot-welded structure. The fatigue life of the spot-welded structure was determined by combining the transfer function, the S-N curve of the tensile-shear spot-welded joint and the input PSD.

• Explosives and Blasting
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• v.21 no.1
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• pp.69-76
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• 2003

Test blasting has been performed with V-cut to investigate the characteristics. Blasting vibrations were measured at two directions, the proceed direction and side direction. Propagation characteristics were determined by regression analysis; square root scaled distance and cube root scaled distance with maximum charge per delay of the blast. Testing result, The cross point was 62m in the allowable vibration velocity of 3mm/sec and 46m In 5mm/sec. Also, vibration level with measuring point was highest and decayed fastest, adapting to cube root scaled distance, for the proceed direction on ground.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1193-1199
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• 2010

Spot welding is the primary method of joining sheet metals in the automotive industry. As automobiles are subjected to fatigue loading, some spot welds may fracture before the whole system has failed. This local fracture of spot welds may lead to change in the dynamic response and consequently affect fatigue behavior of an automobile. Therefore, this change in dynamic response should be taken into consideration to assess the fatigue life of structures subjected to spectrum loading, such as automobiles. In this study, vibration fatigue analysis was performed by taking into consideration the change in the dynamic response due to accumulated damage at spot-welded parts. Fatigue tests were carried out on tensile-shear spot-welded specimens under constant amplitude loading condition. And the fatigue life of spot welds under spectrum loading was predicted using vibration fatigue analysis method based on finite element analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.190-195
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• 1995

초음파 세정기에 의한 세정 성능의 향상을 위한 연구로서, 세정조 내에서의 초음파 전파 현상을 이론적으로 밝히고, 수치해석에 의해 실제 상황의 음압 분포를 구하였으며, 실험에 의해 세정액 내 음압 분포를 확인하였다. 세정액 내의 음압 분포는 세정기 진동판으로부터의 거리에 따라 반파장 간격으로 극대점 또는 극소점이 반복된다. 이에 근거하여 세정 성능 향상 대책이 제시될 수 있게 되었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.2
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• pp.21-29
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• 2002

The M-AUSMPW+ scheme that can capture shock waves exactly with monotonic characteristic is developed by analyzing the cause of oscillation in shock regions. Firstly shock-capturing characteristics of general FVS including the AUSM-type schemes are investigated in detail, according to the different between a cell-interface and a sonic transition position. The cause of oscillation is the improper numerical dissipation that could not represent the real physics. The M-AUSMPW+ could capture shocks exactly without oscillatory behaviors in considering the sonic transition position and an cell-interface position

• Journal of KSNVE
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• v.7 no.6
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• pp.899-908
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• 1997

본 글에서는 소형 압축기 셸과 같은 비교적 복잡한 기계 구조물의 간접적 입력 측정에 대한 결과 및 직접 측정과의 비교를 기술하였고 다수 응답의 동시 측정에 따른 문제점을 해결코자 기준점을 이용한 전달함수의 측정 방법을 제시 하였다. 하부 빈 셸에 대한 실험 결과, 압축기의 셸과 같은 비교적 복잡한 구조물에 대해서도 간접 입력 측정을 상당한 신뢰성을 갖고 시도할 수 있으며 특히 공진점이나 영점 부근에서의 추정 오차는 측정점의 갯수를 증대시킴으로써 크게 개선 시킬수 있음을 보여주었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.1
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• pp.61-66
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• 2012

In this study, to find the effect of nonequilibrium condensation on the oscillation of the terminating shock wave in transonic flows, an NACA0014 airfoil flow with nonequilibrium condensation is analyzed using the total variation diminishing (TVD) numerical scheme. Transonic free stream Mach numbers of 0.81-0.87 are tested with variations in the stagnation relative humidity. For the same free stream Mach number and attack angle of ${\alpha}=0^{\circ}$, an increase in the stagnation relative humidity attenuates the strength of the terminating shock and reduces the oscillation of the terminating shock wave. Furthermore, for the same stagnation relative humidity, the larger the free stream Mach number becomes, the shorter the period of the oscillation shock wave is. The excursion distance of the oscillation shock increases with the free stream Mach numbers for the same stagnation relative humidity. Finally, it is found that for the same shock location, the strength of the oscillating shock facing upstream is stronger than that facing downstream.

• Proceedings of the KIEE Conference
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• 2008.09a
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• pp.144-146
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• 2008

운전 중인 전력용 변압기의 고장 원인 중 진동에 의한 기계적 결함이 대부분을 차지하고 있다. 이러한 원인을 규명하기 위하여 한전 대전전력관리처 산하 변전소를 순회하면서 운전 중인 전력용 변압기에 대하여 진동 현상을 측정하였다. 측정 점은 변압기 한 면에 규칙 배열된 $5{\times}5$ 이다. 측정 점에 대한 진동 현상을 2D와 3D로 나타내어 분석하였다. 분석 결과와 전력용변압기의 경년, 설치 조건, 부하 정도에 따라 나타나는 현상을 분석하였다. 이 결과를 근거로 하여 전력용 변압기의 진동 기준을 정립하는데 기초로 활용하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.1105-1110
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• 2001

본 논문은 머리진동 측정용 바이트 바의 동적 특성에 관한 연구이다. 머리진동의 관심주파수 영역은 0.5Hz~30Hz 범위의 주파수이며 기구학적 이론들을 이용하여 측정된 선형 가속도로부터 머리의 각각속도를 계산하는 과정을 소계한다. 본 논문에서는 9개의 선형가속도를 이용하여 각각속도를 구하는 방법에 대한 검증뿐 아니라 나아가 센서의 측정점의 Offset 영향을 고려한 이론식을 제시한다.