• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 가을 학술발표회 논문집
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• pp.131-137
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• 1996

To perform condition monitoring of P.C. Box girder bridge under ambient traffic, dynamic characteristics were identified using the results of load test an analysis. It was found that natural frequencies obtained from the measured acceleration data for the forced vibration part and free vibration part were nearly identical. Thus it can be concluded that dynamic parameters are properly determined under ambient traffic condition. Finite element model for analysis was calibrated using measured frequencies. Change of dynamic characteristics were predicted through analysis of the established finite element model with anticipated change.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 추계학술대회 논문집
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• pp.316-321
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• 1997

The purpose of this study is to reduce the vibration noise of differential gear by reducing torque fluctuation of drive pinion shaft which causes vibration noise of differential gear in rear wheel drive vehicles. For this we developed multi-degree of freedom analysis model in which mass moment of inertia and torsional spring combined, the validity of the simulation model was checked by the field test and we examined the influence of torsional vibration of driveline elements by performing forced vibration analysis of engine excitation torque. We studied the methods for reducing torsional vibration of driveline according to the design factor of propeller shaft and examined the effects reducing vibration differential gear by applying flexible coupling.

• 대한물리의학회지
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• 제12권4호
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• pp.29-37
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• 2017

PURPOSE: This study investigated the immediate effect of inspiratory muscle training with whole-body vibration on the pulmonary function of subacute stroke patients. METHODS: All participants (n=30) were allocated to the following groups: (1) the inspiratory muscle training group with whole-body vibration (n=10), wherein the patients received inspiratory muscle training with whole-body vibration comprising 3minutes of vibration per session and respiratory training of 30 times and 2 sessions for one day. (2) the inspiratory muscle training group with visual feedback (n=10), wherein the patients received inspiratory muscle training with visual feedback. (3) the inspiratory muscle training group (n=10), wherein the patients received inspiratory muscle training. RESULTS: After the experiment, the inspiratory muscle training group with whole-body vibration exhibited significantly higher forced vital capacity, forced expiratory volume at 1 second, peak inspiratory flow rate, maximal inspiratory pressure, and chest expansion (p<.05), compared to the other groups. Inspiratory muscle training group with whole-body vibration had significantly higher peak expiratory flow rate and maximal voluntary ventilation than the other groups (p<.05). CONCLUSION: These results show that pulmonary function, maximal inspiratory pressure, and chest expansion were significantly better in the inspiratory muscle training group with whole-body vibration than in the other groups. Thus, this treatment will help recovery of pulmonary function in stroke patients.

• International Journal of Fluid Machinery and Systems
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• 제4권2호
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• pp.289-306
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• 2011

In the development of very high head pumped storage projects, one of the critical problems is the strength of pumpturbine runners. Data obtained by stress measurements of high head pump-turbine runners indicated that dynamic stress due to the vibration of runner might be detrimental, possibly to cause fatigue failure, if the runner were designed without proper consideration on its dynamic behaviour. Numerous field stress measurements of runners and model tests conducted with hydrodynamic similarity revealed that the hydraulic excitation force developed by the interference of rotating runner blades with guide vane wakes sometimes would induce such heavy vibration of runner. Theoretical and experimental investigations on both the hydraulic excitation force and the natural frequencies of runner have been conducted to explore this forced vibration problem.

• 한국소음진동공학회논문집
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• 제26권1호
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• pp.104-109
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• 2016

The noncontact vibration exciter system using the electro-magnet for a thin plate is studied in this paper. Based on the Euler-Bernoulli beam theory, the equation of motion of thin plate is derived. The main purpose of this experiment is to match the input-frequency and response frequency of thin plate. The test equipment is configured to vibrate on both sides of the thin plate using the electro-magnet. Two frequencies(input frequency and response frequency) in our experiments show very good agreement. This study results will contribute to basic investigate of an alternative air-knife system for the steel industry.

• 한국자동차공학회논문집
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• 제17권1호
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• pp.114-119
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• 2009

The authors have investigated the NVH problems of drive system in full vehicle test. However it is difficult to define the NVH problems of driveline system. Since it is hard to measure the rotating part and it is vague that only the drive system induces the NVH problem. Vibration in a driveline is presented in this paper. In the experiment, the rear sub-frame and propeller shafts and axle were composed and mounted with rubber each other. For applying the vibration input instead of the torsional vibration effect of an engine, the shaker was taken. In particular, torsional vibration due to fluctuating forced vibration excitation across the joint between driveline and rear sub-frame was carefully examined. Accordingly, the joint response was checked from experiments and the FE-simulation using FRF (frequency response function) analysis was performed. All test results were signal processed and validated against numerical simulations. In present study, the new test bench for measuring the vibration signal and simulating the vehicle chassis system was proposed. The modal value and the mode shape of components were analyzed using the CAE model to identify the important components affecting driveline noise and vibration. It could be reached that the simplified test bench could be well established and be used for design guide and development of the vehicle chassis components.

• 항공우주시스템공학회지
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• 제18권1호
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• pp.37-45
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• 2024

본 논문에서는 쿼드로터형 드론의 제자리 비행 상태에서 제어부에 전달되는 수직 방향 진동을 저감하기 위한 수동적 진동 제어 방법에 따른 설계 방법을 제시하였다. 쿼드로터형 드론의 진동 해석을 위해 유한요소 기반 이산화 모델 및 번지 케이블을 이용한 지상진동시험 모사 모델을 구축하였다. 제자리 비행 상태에서의 하중을 부여하여 동특성 평가 및 공진 회피 설계를 위한 모드 해석을 수행하여 결과를 분석하였으며, 강제진동응답해석을 수행하여 제자리 비행 상태의 운용주파수 범위 내에서의 정상상 태응답을 도출하였다. 또한 감쇠 재료의 유무에 따른 진동 저감 효과를 비교하기 위해 동일한 조건내에서 제어부에 전달되는 진동을 유발할 수 있는 위치에 점성 감쇠 테이프를 적용하여 이에 따른 정상상태응답을 도출하고 감쇠 재료를 적용하였을 경우의 진동 저감 효과 및 부착 위치에 따른 진동 저감 효과를 평가하였다.

• 대한조선학회 특별논문집
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• 대한조선학회 2009년도 특별논문집
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• pp.59-64
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• 2009

The propeller induced forces acting on a hull are surface forces and bearing forces. The bearing forces are the forces acting directly on the propeller which are transferred to the hull through the propeller bearings. The surface forces are those which act by fluid pressure directly on the various hull surfaces. Because the surface force is main source to oscillate stern constructions and deckhouse, the estimation of surface force is very important to predict response of forced vibration of that. The estimation methods were statistical analysis method, theoretical analysis method and method through model test.

• Wind and Structures
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• 제4권2호
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• pp.85-100
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• 2001

The mechanism of wind-induced ovalling vibrations of cylindrical shells is numerically investigated by using a vortex method. The subject of this paper is limited to a two-dimensional structure in the subcritical regime. The aerodynamic stability of the ovalling vibrations in the second to fourth circumferential modes is discussed, based on the results of a forced-vibration test. In the analysis, two modal configurations are considered; one is symmetric and the other is anti-symmetric with respect to a diameter parallel to the flow direction. The unsteady pressures acting on a vibrating cylinder are simulated and the work done by them for one cycle of a harmonic motion is computed. The effects of a splitter plate on the flow around the cylinder as well as on the aerodynamic stability of the ovalling vibrations are also discussed. The consideration on the mechanism of ovalling vibrations is verified by the results of a free-vibration test.

• 한국소음진동공학회논문집
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• 제14권10호
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• pp.923-929
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• 2004

In this research, Forced Vibration Test(FVT) on a cable stayed bridge was conducted to examine the validity of the frequency domain pattern recognition method using signal anomaly index and artificial neuralnetwork. 7he considering structure, Samchunpo Bridge, located in Sachun-Shi, Kyungsangnam-Do, is a cable stayed bridge with the 436 meter span. The excitation force was induced by a sudden braking of a fully loaded truck. and vortical acceleration signals were acquired at 14 points. The initial 2-dimensional FE-model was developed from the design documents to prepare the training sets for the artificial neural network, and then the model calibration was performed with the field test data. As a result of the model calibration, we obtained the FFT spectrums from the model simulation, which was similar to those from the vibration test. These tests and the simulation data will be used for the structural identification using arbitrarily added masses to the bridge.