• 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 Korea Committee for Ocean Resources and Engineering Conference
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• 2000.04a
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• pp.7-12
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• 2000

As the offshore oil fields are moved to the deep ocean, the oil production systems of FPSO(Floating production storage and offloading system) are building these days and so it is the most important to estimate the drift motion and damping effects the drift motion importantly. The components of damping consist of viscous, wave radiation effect and wave drift damping. It is need to estimate the wave drift damping exactly among them. The wave drift damping means the change rate of mean wave drift force with respect to the ship and ocean structures speed. In order to calculate this, the 3-Dimensional panel method used to translating and pulsating Green function is adopted. The calculation is carried out for series 60(CB = 0.7) vessel and the results are compared with other theoretical ones.

• 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.

• Proceedings of the Korean Reliability Society Conference
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• 2002.06a
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• pp.205-210
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• 2002

엔지니어링 플라스틱은 제품의 경량화 및 기계적 특성을 향상시키기 위해 다양한 분야에서 사용이 증가하고 있다. 엔지니어링 플라스틱이 접촉부재의 부품으로 교체될 때는 접촉부재와의 마멸 및 마찰 특성이 시스템 전체의 신뢰성에 큰 영향을 끼치게 된다. 또한 접촉부재의 일반적인 역할이 마찰력에 따른 동력의 전달 및 진동 감쇠와 같으므로 엔지니어링 플라스틱의 교체에 따른 시스템의 효율을 고려해야만 한다. 따라서 본 논문에서는 접촉부재를 엔지니어링 플라스틱으로 교체함에 따른 마멸 및 마찰 특성을 분석하여 접촉부재에서의 신뢰성을 분석해 보고, 접촉부재에서의 진동 감쇠 특성을 분석하여 엔지니어링 플라스틱의 교체에 관한 최적의 재료를 선정해 보고자 한다. 이를 통해, 여러 종류의 시스템에서 엔지니어링 플라스틱의 접촉부재 교체에 따른 신뢰성 향상 방안 및 최적화를 위한 기초 자료를 제공하고자 한다.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.508-511
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• 2008

The most landing gear use oleo-pneumatic shock strut to absorb the impact energy during touchdown. The shock strut is composed of the oil damper and the gas spring, especially the oil damper provides resistance force which is proportional to the square of landing speed. In case of high landing speed, the abnormal peak load can be occurred and transferred to the airframe structure. To prevent this, the pressure-relief valve is used to limit the damping force under the specific level. In this paper, it is presented the design process to find optimal damping and analysis results using pressure-relief valve.

• Transactions of The Korea Fluid Power Systems Society
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• v.5 no.1
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• pp.20-26
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• 2008

Various types of hydraulic shock absorbers are widely used in many fields because of its numerous advantages. However, in order to design adequate damping characteristics, accurate flow data near the orifices are required essentially. In this paper, a commercial computational fluid dynamics(CFD) code, FLUENT is adopted to investigate the flow characteristics near orifices of a shock absorber. Static pressure and velocity vector distributions, fluid path lines are presented for compression/tension strokes and various piston speeds. In order to validate the result of analysis, the numerically obtained damping forces are compared with those of analytical estimations obtained by modified Bernoulli equation. The results reported herein will provide better understanding of the detailed flow fields within shock absorber, and the CFD analysis method proposed in this paper can be used in the design of other types of hydraulic shock absorber.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.998-999
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• 2014

This paper proposes a method for damping force modeling of magnetorheological (MR) damper featuring bypass hole. After describing configuration and of the MR damper, a damping force modeling of the MR damper is derived based on Bingham model of MR fluid. MR damper consists of piston, accumulator, gap, bypass hole and coil. Damping force is consists of spring force induced by accumulator, viscous force induced at gap and bypass hole, and controllable force induced at gap.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.8
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• pp.767-773
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• 2004

Semi-active control systems have attracted a great deal of attention in recent years, because they offer the adaptability of active devices without requiring large Power sources. One of the most Promising semi-active devices proposed for structural control is magneto-rheological fluid dampers (MR damper). In this paper, an MR damper having the capacity of about 1 ton was designed and fabricated. and series of tests were performed to grasp the fundamental Performance characteristics of it. It was also applied to a 6-story steel structure under random excitation and 3-different seismic excitations for the confirmation of its validity on structural vibration absorption. Through this study, the techniques and know-hows for MR damper production were acquired.

• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.257-266
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• 2004

A three node triangular element with drilling rotations incorporating improved higher-order zig-zag theory(HZZT) is developed to accurately assess the stress distribution through thickness of the laminated plate and analyze the vibration of pretwisted composite plates with embedded damping layer. Shear force matching conditions are enforced along the interfaces between the embedded damping patch and the border patch. The natural frequencies and model loss factors are calculated for cantilevered pretwisted composite blade with damping core with the present triangular element, and compared to experiments and MSC/NASTRAN using a layered combination of plate and solid elements.

• Computational Structural Engineering
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• v.4 no.4
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• pp.10-13
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• 1991

현대의 건물은 초고층화 되어가기 때문에 바람이나 지진에 의한 건물의 과다진동이 일어나며 이것은 기초분리(base isolation) 방법 또는 제진장치를 설치함으로써 해결할 수가 있다. 기초분리 방법은 지진 다발 지역에서 지진에 의한 피해를 감소시키기 위하여 주로 이용되며 제진장치는 지진은 물론 바람을 받는 고층건물, 타워, 다리 등의 대형 구조물의 제진에 사용이 되며 병원, 컴퓨터센터, 그리고 반도체 공장 등 정밀한 작업이 이루어지는 곳에서의 국부적인 제진에 적용이 되고 있다. 제진장치는 수동제진장치와 능동제진장치로 대별이 되며 원리는 질량을 이용한 건물의 감쇠력을 증대시키는 데 있다. 능동제진장치를 이용한 시스템은 과다한 설치비와 운영비 뿐만 아니라 강한 바람이나 지진이 왔을 때 전력 중단이 되어 작동이 되지 않을 때가 있으므로 현재로서는 수동제진장치가 많이 이용이 되고 있다. 따라서 현재 강한 바람이나 지진에 대한 건물전체의 거동은 수동제진장치에 의하여 대처하고 약한 바람과 지진 등에 대한 국부적인 제진에는 능동제진장치를 이용하는 복합제진시스템(hybrid vibration control system)이 제시되고 있다.