• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.3
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• pp.186-193
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• 2003

Floor vibrations in residence and office buildings are typically induced by heel drop and walking movement of occupants. The criteria of most vibration provisions have been developed based on the vibration caused by heel drop impact rather than walking. There may be considerable differences between the vibration characteristics induced by walking and heel drop. The effect of walking vibration was not well reflected on current provisions. In this paper, shaking table test was performed to investigate the human perception level against the vibrations due to walking and heel drop. This study attempts to compare the human Perception level of two different vibration sources. Also, this study investigates the effect of damping on a Perception level under heel drop and walking vibration.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.1
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• pp.187-195
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• 2003

The performance of shock absorber is directly related to the car behaviour and performance, both for handling and ride comfort. The displacement sensitive shock absorber has two modes of damping force (i.e. soft and hard) according to the position of piston. In this study, a mathematical nonlinear dynamic model is introduced to predict the performance of displacement sensitive shock absorber. Especially in this paper, the transient zone is considered and the simulation result is well fit with experimental data. And the vehicle dynamic characteristic of displacement sensitive shock absorber is presented using quarter car simulation model. The simulation results of frequency response are compared with passive shock absorber.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.156-162
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• 2003

The shock absorber is a part having a direct influence on the ride comfort, stability and dynamic load prediction of a vehicle. Thus, a rationally modeled shock absorber should be required in the dynamic analysis of vehicles. This thesis presents a modified model, based on Worden's hyperbolic tangent function, in order to fit experimental data on the velocity-damping force of a shock absorber. The hyperbolic tangent function correctly indicates the characteristics of a shock absorber, and has the advantage of containing physical causality. To evaluate the method, comparative evaluations of the linear model, the 5th polynomial model and Worden's model were carried out. The function presented in this paper is not only simple but also makes it possible to estimate the function coefficients easily and visually. In addition, it has the advantage of containing physical causality. Lastly, it effectively models the damping force of a shock absorber.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1994.04a
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• pp.34-38
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• 1994

진동계측, 충격실험 및 진동해석등을 통하여 대형 다기능 공작기계(planomiller) 구조의 진동특성을 규명하고자 하였다. 정상적인 기존 모델에 대해 다양한 운전조건에서의 진동을 계측하여 그 주파수 특성으로부터 실험과 해석의 대상 주파수대역을 선정하고 주된 진동의 성분과 수준을 조사하여 향후 유사공작기계의 개발시 비교평가의 기준으로 삼고자 하였다. 또한 정지상태의 공작기계 구조물에 대한 충격시험을 통하여 실험 주파수응답함수를 구하고 이로부터 공작기계가 가지는 기본적인 고유진동수와 진동모드, 동강성 수준등을 파악하였다. FEM 모델에 대한 진동해석을 수행하여 실험결과와 비교함으로써 이러한 대형공작기계의 동특성 규명에 대한 해석적 예측의 가능성을 검토하였는데 특히 하부지지조건, 습동면 접촉부의 연결조건 및 감쇠력등이 동특성에 미치는 영향을 고찰하였다.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.6
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• pp.167-177
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• 2003

In this study, a mathematical nonlinear dynamic model is introduced to predict the damping force of automotive shock absorber. And 11 design parameters were proposed for the sensitivity analysis of damping force. Design parameters consist of 5 piston valve design parameters, 5 body valve design parameters and 1 initial pressure of reservoir chamber air. All of these design parameters are main design parameters of shock absorber in the procedure of shock absorber design. The simulation results of this paper offer qualitative information of damping force variation according to variation of design parameters. Therefore, simulation results of this paper can be usefully use in the design procedure of shock absorber

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.257-260
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• 2004

This study aims to evaluate factors of ceiling structure influencing to the floor impact sound. For this reasons, we measured the vibration of ceiling and the floor impact sound by ceiling structure. The main results from this study are that ceiling structure makes worse to non-ceiling structure for an effect of air layer in heavy-weight floor impact sound. But it has an effect on light-weight floor impact sound about $2\sim8dB$.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.11
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• pp.11-16
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• 1997

In the stroke sensitive shock absorber, the oil path is formed along the internal cylinder surface to make the oil flow during the piston's upper-lower reciprocation movement. In constrast with the conventional shock absorbesr which show one dynamic characteristic curve, stroke sensitive shock absorber shows two kinds of dynamic characteristics according to the stroke. In this study, in order to obtain more precise information about design and damping performance analysis, the analysis on the damping force generation process and dynamic behaviour characteristics of stroke sensitive shock absorber are performed by considering the valve characteristics.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2003.07a
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• pp.149-155
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• 2003

우리나라의 농가에서 운반용으로 사용되고 있는 동력경운기와 트랙터 등의 트레일러는 현가장치와 방진장치가 없는 것이 대부분이다. 이런 트레일러를 비포장 된 과수원 등의 농장에서 과채류를 포장되지 않은 상태로 적재물이 트레일러의 바닥에 깔린 채 소량을 적재한 상태로 저속으로 운송될 때 충격, 진동, 마찰 등으로 많은 수송 손실이 예상된다. 이런 수송손실을 줄이기 위해서는 트레일러에 전달되는 진동을 줄여야 한다. (중략)

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3185-3194
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• 1994

In this study, an impact model and impact response analysis method was suggested for the impacts between arbitrary shaped bodies. Unlike the impacts between geometrically simple structures, there is no rules to analyze the impacts between general elastic structures First of all, it has been attempted to explain the impoot between arbitrary elastic structures as the elastic deformation of a virtual contact spring in the vicinity of contact points. The contact stiffness and the exponent are determined from the Hertz's contact theory and F. E. analysis. In order to evaluate the validities and limitations of the proposed methods, an impact tester and the miniature of container, missile and isolators have been provided and tested experimentally. All the experiments were performed with various impact conditions. The results obtained by the proposed methods were directly compared with the measured values in terms of maximum contract force, contact duration, the shape of contact force and the structure responses. The computed contact force and responses, using this proposed methods, were very close to the measured results, unless any plastic deformations were presented.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.5 s.248
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• pp.550-559
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• 2006

This paper presents designs and performance investigations of two bypass-type MR (magneto-rheological) shock dampers for high impulsive force systems, one of which is with single rod and the other with double rod. First of all, on the basis of the Bingham properties of the MR fluid and the magnetic field analysis of the magnetic circuit, the MR shock dampers are designed and manufactured. After experimental investigations on their magnetic field-dependent damping forces and responses characteristics, dynamic models of the proposed dampers are formulated and compared. Then, a simple 1 degree-of-freedom mass-drop system is constructed, and the effective and practical control algorithm is designed by considering dynamic characteristics of the shock control system. The shock control performances of the proposed MR shock dampers are verified through the comparison study of experiment results with simulation ones.