• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.912-918
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• 2004

Main vibration problems of a transaxle type forklift truck are caused by the resonance of engine excitation force and natural mode shade of major components such as engine-mount system, mast, and main frame. But, it is well known that the reduction of vibration is very difficult because of the limitation of structural modifications. In this paper, the vibration characteristics of engine-mast system including engine mount were firstly identified by the experimental and simplified numerical methods. And also, the free and forced vibration characteristics of a whole forklift truck were surveyed with modal test and ODS(operation deflection shape) measurement. Based on these results, the reliable finite element model was developed. Finally, various countermeasures were considered and applied to a real forklift truck and then its effects were confirmed.

• 정보저장시스템학회논문집
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• 제8권1호
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• pp.22-26
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• 2012

Optical disk drives (ODDs) are subjected to vibrations caused by the high-speed rotation of the optical disk, and these vibrations can be excessive and reduce the read/write performance. Elastic rubber mounts with cushioning materials are often used to minimize these problems. In this paper, the source of vibrations was identified by experimental modal tests and high-speed photography. Structural modifications were made based on a lumped parameter model and a finite element model.

• International Journal of Automotive Technology
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• 제8권1호
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• pp.75-82
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• 2007

This paper presents practical work on the reduction of gear whine noise. In order to identify the source of the gear whine noise, transfer paths are searched and analyzed by operational deflection shape analysis and experimental modal analysis. It was found that gear whine noise has an air-borne noise path instead of structure-borne noise path. The main sources of air-borne noise were the two global modes caused by the resonance of an axle system. These modes created a vibro-acoustic noise problem. Vibro-acoustic noise can be reduced by controlling the vibration of the noise source. The vibration of noise source is controlled by the modification of structure to avoid the resonance or to reduce the excitation force. In the study, the excitation force of the axle system is attenuated by changing the tooth profile of the hypoid gear. The modification of the tooth profile yields a reduction of transmission error, which is correlated to the gear whine noise. Finally, whine noise is reduced by 10 dBA.

• 대한기계학회논문집
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• 제10권5호
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• pp.601-610
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• 1986

본 연구에서는 음향학적 고찰로써 최근 디지를 처리기술의 발달에 따른 근접 한 2점의 음압으로 부터 테니스 라켓의 공기입자속도를 근사적으로 구하기 위하여 두 개의 마이크로폰을 이용하여 계산된 음향인텐시티는 구물의 오무드 해석법에 의해 구 해진 테니스 라켓의 동적 특성과 비교 검토함으로써 진동과 음의 발생기구를 구명하고 측정계의 비접촉에 의한 테니스 라켓의 동적 거동을 규명하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 봄 학술발표회 논문집
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• pp.414-421
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• 1998

The content of this paper consists of two related subjects. One is the assessment of damages in the existing structure and the other is the evaluation of seismic capacity of the structure with damage. A method is presented for damage assessment of existing structures using the modal data measured at limited points by the inverse medal perturbation technique. For efficient damage assessment, the number of the unknown probable damaged members is reduced for each damage identification by grouping the members in the large structure. The aseismic capacity is evaluated for the structure using the results of damage assessment. An example analysis is carried out for a building structure subjected to different earthquake excitations.

• 전산구조공학
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• 제4권4호
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• pp.97-106
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• 1991

주-부 구조물의 진동 특성을 파악하기 위한 새로운 방법인 frequency window method를 다중 지지되고 구조물간의 커플링이 강한 주-부 구조물을 해석하였다. 다항식의 합으로 표현된 특성 방정식과 이 식의 해는 기존의 고유치 해석 방법의 결과와는 다른 새로운 것으로 frequency window method의 주된 장점으로는 공진과 커플링 현상을 정량적으로 파악할 수 있는 피라미터의 정의, 전체 주-부 구조물의 모드특성을 나타내는 해석적인 식과 반복 기법의 도입으로 인한 해석 결과의 정확성등이 있다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.964-968
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• 2003

Hermetic rotary compressor is one of the most Important components for air conditioning system since it has a great effect on both the performance and the noise and vibration of He system. Noise and vibration of rotary compressor is occurred due to gas pulsation during compression process and unbalanced dynamic force. In order to reduce noise and vibration. it is necessary to identify sources of noise and vibration and effectively control then. Many approaches have been tried to identify noise sources of compressor. However, compressor noise source identification has proven to be difficult since the characteristics of compressor noise are complicated due to the interaction of the compressor parts and gas pulsation. In this work, Statistical Energy Analysis has been used to trace the energy flow in the compressor and identify transmission paths from the noise source to the sound field.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.797-801
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• 2003

The Statistical Energy Analysis is based on the power flow and the energy conservation between sub-systems, which enable the prediction of acoustic and structural vibration behavior in mid-high frequency ranges. This paper discusses the identification of SEA coupling loss factor parameters from experimental measurements of small reverberation chamber sound pressure levels and structural accelerations. As structural subsystems, steel plates with and without damping treatment are considered. Calculated CLFs were verified by both transmission loss values for air-borne CLF case and running SEA commercial software As a result, CLFs have shown a good agreement with those computed by software. Acoustical behavior of air-borne noise and structure-borne noise has been examined. which shows reasonable results, too.

• Smart Structures and Systems
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• 제21권2호
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• pp.235-248
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• 2018

An efficient method utilizing the multi-stage improved differential evolution algorithm (MSIDEA) as an optimization solver is presented here to detect the multiple-damage of structural systems. Natural frequency changes of a structure are considered as a criterion for damage occurrence. The structural damage detection problem is first transmuted into a standard optimization problem dealing with continuous variables, and then the MSIDEA is utilized to solve the optimization problem for finding the site and severity of structural damage. In order to assess the performance of the proposed method for damage identification, an experimental study and two numerical examples with considering measurement noise are considered. All the results demonstrate the effectiveness of the proposed method for accurately determining the site and severity of multiple-damage. Also, the performance of the MSIDEA for damage detection compared to the standard differential evolution algorithm (DEA) is confirmed by test examples.

• 한국공작기계학회논문집
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• 제16권6호
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• pp.140-145
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• 2007

To improve productivity of a metal cutting process, it is required to monitor machining stability in real time. Since cutting environment is harsh against sensing conditions due to vibration, chip, and cutting fluid, etc., it is necessary to develop a robust and reliable sensing system for the practical application. In this work, a chatter monitoring system was developed and its effectiveness was proved. Spindle displacement caused by cutting was selected as a main monitoring parameter. A cylindrical capacitive displacement sensor was adopted. Chatter frequencies were identified through modal analysis. To quantify chatter vibrations, chatter correlation coefficient was introduced. The identification of the monitoring system showed a good agreement with the result of experiment.