• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 추계학술대회 논문집
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• pp.527-534
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• 2000

Characteristics of local vibration modes of a corrugated panel are investigated by finite element analysis and modal testing. Structural modification model in the corrugation is proposed to increase the resonance frequency. This model decreases the fall by the local resonance in the transmission loss of the corrugated pallet and improves sound insulation performance. Damping effect of tile foam filled ill tile core cavity is also estimated by experiment The results of tile study offer useful information how to predict the severe local resonances in corrugations and how to prevent their undesirable effect ell the sound insulation and the vibration transmission.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.457-462
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• 2009

In a high speed train, aluminium extruded panel is widely used in floor, side wall and roof structures for high bending stiffness and weight reduction. However, with some inevitable reasons, aluminium extruded panel shows inferior sound insulation performance compared with the flat panel having same weight. Especially, occurrence of local resonance modes in the particular frequency band, is one of the main reason in the deterioration of the sound insulation performance. Local resonance modes are generated in the structure which consists of periodic unit structure, such as the aluminium extruded panel. The local resonance frequency is determined by the specification of the unit structure. In this study, we predict the local resonance frequency band on the aluminium extruded panel used for the high speed train, and investigate how the design modification in the unit structure influences the local resonance frequency band and panel bending stiffness. The purpose of the study is to provide the design information for the effective unit structure in order to improve the sound insulation performance of the aluminium extruded panel.

• 한국철도학회논문집
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• 제4권3호
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• pp.87-93
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• 2001

Characteristics of the local vibration modes of an aluminium extruded panel are investigated by the finite element analysis and modal testing. Practical methods to increase the damping of the local resonances are proposed. Effects by filling urethan foam in the core cavity and by coating tar on the panel surface are compared by experiments. Modified panel structures to shift the local resonance frequency band are proposed. The results of the study are utilized to predict the severe local resonances in the aluminium extruded panels and prevent their undesirable effect on the sound insulation.

• Journal of the Optical Society of Korea
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• 제12권4호
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• pp.314-318
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• 2008

We investigate the conditions of the complete tunneling of light across a composite barrier made of multiple layers involving metamaterials. It is shown that complete tunneling phenomena are related to the resonance transmission properties of local modes formed in barrier layers and that there are two distinctive kinds of local barrier modes involved in actual complete tunneling: the degenerate inner-barrier mode and the full barrier mode. Complete tunneling occurs via two successive mode couplings: from the incident plane wave to the plane wave in the transmission layer through the direct mediation of these two kinds of local barrier modes.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2006년도 전기학술대회논문집
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• pp.39-40
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• 2006

Diesel power plant(DPP) with the medium speed diesel engine is operated under the very severe condition in aspect of load and operating time as compared with the marine diesel generator set. So, minimized vibration level have to be insured for the more stable operation of engine and generator. The vibration of generator set mainly comes from the resonance between the rigid modes by resilient mount or distortion modes by structural stiffness and the excitation forces of engine. Then, avoidance of resonance with structural modification is generally well known. In this paper, the first order vibration in non-resonance range and local vibration modes were investigated by impact test, response/ODS(operational deflection shape) measurement and 3D finite element analysis for the additional reduction of vibration. The proposed countermeasures were actually applied and their final effects were verified through the in-situ measurement.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.2185-2190
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• 2008

In a high speed train, multi-layered panels for floor, side wall and roof are important sound insulating part. As these multi-layered panels require high bending strength vs. weight, corrugated steels or aluminium honeycomb panel are generally used. However, with some inevitable factors, these panels show lower sound insulation performance than that of the plate with the same weight. Transmission loss(TL) often severely decreases in a particular frequency range because of the decrease of the critical frequency, occurrence of local resonance modes and cavity resonance modes, which are not shown in a plate. In this study, frequency range and cause of the TL drop are investigated on the corrugated and honeycomb panels.

• 한국해양공학회지
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• 제34권5호
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• pp.325-333
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• 2020

As regulations concerning ship vibration and noise are becoming stricter, considerable attention is being drawn to prediction technologies for ship vibration and noise. In particular, the resonance and lock-in phenomena caused by vortex-induced vibration (VIV) have become considerably important with increases in the speed and the size of ships and ocean structures, which are known to cause structural problems. This study extends the fluid-structure interaction (FSI) analysis method to predict resonances and lock-in phenomena of high modes and VIV of ship rudders. Numerical stability is secured in underwater conditions by implementing added mass, added damping, and added stiffness by applying the potential theory to structural analysis. An expanded governing equation is developed by implementing displacements and twist angles of high modes. The lock-in velocity range and resonant frequencies of ship rudders obtained using the developed FSI method agree well with the experimental results and the analytic solution. A comparison with local vibration guidelines published by Lloyd's Register shows that predictions of resonances and lock-in phenomena of high modes are necessary in the shipbuilding industry due to the possible risks like fatigue failure.

• 소음진동
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• 제10권4호
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• pp.662-668
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• 2000

Sound transmission characteristics are investigated on the aluminium extruded panels used for railway vehicles. An equivalent orthotropic plate model and mass law are applied to predict the sound transmission loss. An extruded panel specimen used in the floor of railway vehicles is manufactured and is tested to measure sound transmission loss by two reverberant chamber method. Predicted transmission loss I compared with measured values and the effect of local resonance on the transmission characteristics is identified. The results are applied to design the extruded panel having better sound insulation performance.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1995년도 추계학술대회논문집; 한국종합전시장, 24 Nov. 1995
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• pp.185-190
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• 1995

In recent years, many researcher have been interested in the stability of a thin beam. Among them, Pai and Nayfeh[1] had investigated the nonplanar motion of the cantilever beam under lateral base excitation and chaotic motion, but this study is associated with internal resonance, i.e. one to one resonance. Also Cusumano[2] had made an experiment on a thin beam, called Elastica, under bending loads. In this experiment, he had shown that there exists out-of-plane motion, involving the bending and the torsional mode. Pak et al.[3] verified the validity of Cusumano's experimental works theoretically and defined the existence of Non-Local Mode(NLM), which is came out due to the instability of torsional mode and the corresponding aspect of motions by using the Normal Modes. Lee[4] studied on a thin beam under bending loads and investigated the routes to chaos by using forcing amplitude as a control parameter. In this paper, we are interested in the motion of a thin beam under torsional loads. Here the form of force based on the natural forcing function is used. Consequently, it is found that small torsional loads result in instability and in case that the forcing amplitude is increasing gradually, the motion appears in the form of dynamic double potential well, finally leads to complex motion. This phenomenon is investigated through the poincare map and time response. We also check that Harmonic Balance Method(H.B.M.) is a suitable tool to calculate the bifurcated modes.

• 대한기계학회논문집A
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• 제40권12호
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• pp.1061-1066
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• 2016

주름 강판의 주름은 강판의 중량당 굽힘 강성을 획기적으로 증가시킨다. 그러나 주름 강판은 같은 중량을 갖는 평판보다 낮은 차음 성능을 보인다. 특히, 특정한 주파수대역에서는 투과손실이 크게 감소한다. 이 문제의 주 요인은 주름단위에서의 국부적 공진으로 알려져 있다. 특정 주파수대역에서 다수의 국부적 공진모드가 발생하고 모드밀도가 급속히 증가한다. 본 연구에서는 음 투과손실과 모드 밀도 사이의 관계를 검토한다. 최종적으로, 중량의 증가 없이 주름 강판의 차음 성능을 향상시키기 위한 모드 밀도의 측면에서의 설계전략을 제시한다.