• 한국소음진동공학회논문집
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• 제13권1호
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• pp.26-32
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• 2003

The vibrational system of this study is consisted of a rotating cantilever pipe and the flow in the pipe. The equation of motion is derived by using Lagrange equation. The influences of the rotating angular velocity and the velocities of fluid flow in the pipe have been studied on the dynamic characteristics of a rotating cantilever pipe by numerical method. The tip-amplitude of axial vibration and maximum tip-deflection of axial direction of cantilever pipe are directly proportional to the velocity of fluid and rotating angular velocity of pipe In the steady state. respectively The bending tip-amplitude of cantilever pipe is inversely proportional to the velocity of fluid in the steady state. When the rotating angular velocity is 5 rad/s, the velocity of fluid increase with increasing the natural frequency of axial vibration at second mode and third mode, but the natural frequency axial direction of first mode is decreased. The natural frequency of lateral direction is decreased due to increase of the rotating angular velocity. It identifies that the Influence of velocity of fluid give much variation lower mode of vibration in lateral direction. And the Influence of velocity of fluid give much variation higher mode of vibration in axial direction.

• 한국항공우주학회지
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• 제42권9호
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• pp.723-730
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• 2014

이차유동을 이용한 초음속 동축류 추력편향 제어기법에 대한 실험적 연구가 진행되었다. 쉴리렌 유동가시화 및 로드셀을 이용한 고정확도의 다분력 시험장치를 통하여 이차원 초음속(마하수 2.0) 유동의 추력편향 특성이 관찰되었다. 추력편향각은 부유동의 압력이 점차 커지면서 일시 감소 후 다시 증가하는 V-자형 추세를 보이고 있음이 관찰되었다. 추력편향 유동의 성능을 나타내는 성능계수들의 분석이 이루어졌으며, 보다 높은 성능지표를 나타내는 본 시스템의 운용조건이 제시되었다.

• 한국재료학회지
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• 제17권5호
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• pp.289-292
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• 2007

Although piezoelectric bimorph that is using as the sensor in medical and industrial measurement has large displacement, it has problems including efficiency in generating force, energy convergence, and response. Its application is being limited based on the change in resonance frequency with temperature. In this study, to overcome the disadvantages, PZT piezoelectric ceramics was prepared and produced a parallel type piezoelectric bimorphs. In addition, by using the finite element method. the configuration of piezoelectric bimorph was designed and the displacement of the bimorph based on applied electric pressure and the wave pattern were measured. By analyzing the resonance characteristics of the bimorph in the temperature range of $-60{\sim}80^{\circ}C$, an attempt was made to study the operational characteristics and temperature reliability of vortex flowmeter sensor. As a result, the resonance frequency of the bimorph was gradually increased with the temperature from $-60{\sim}80^{\circ}C$. The deflection of the bimorph was found to strongly depend on both the applied electric field waveform and the environmental temperature.

• 한국정밀공학회지
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• 제28권1호
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• pp.31-39
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• 2011

This paper presents design and control of a quarter-vehicle magneto-rheological (MR) suspension system for ECS (electronic control suspension). In order to achieve this goal, MR shock absorber is designed and manufactured based on the optimized damping force levels and mechanical dimensions required for a commercial mid-sized passenger vehicle. After experimentally evaluating dynamic characteristics of the manufactured MR shock absorber, the quarter-vehicle MR suspension system consisting of sprung mass, spring, tire and the MR shock absorber is constructed in order to investigate the ride comfort and driving stability. After deriving the equations of the motion for the proposed quarter-vehicle MR suspension system, the skyhook controller is then implemented for the realization of quarter-vehicle MR suspension system. In order to present control performance of MR shock absorber for ECS, ride comfort and driving stability characteristics such as vertical acceleration of sprung mass and tire deflection are experimentally evaluated under various road conditions and presented in both time and frequency domain.

• 대한기계학회논문집B
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• 제30권8호
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• pp.722-730
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• 2006

In this study, the flow characteristics of a FPN (Fountain Pen Nano-Lithography) using active membrane pumping are investigated. The FPN has integrated chamber, micro channel, and high capacity reservoir for continuous ink feed. The most important aspect in this probe provided control of fluid injection using active membrane pumping in chamber. The flow rates in channel by capillary force are theoretically analyzed, including the control of the mass flow rates by the deflection of the membrane. The above results are compared with the numerical simulations that calculated by commercial code, FLUENT. The velocity of the fluid in micro channel shows linear behaviors. And the mass flows are proportional to the second order function of the pumping pressure that is imposed to the membrane.

• 도시과학
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• 제11권2호
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• pp.19-24
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• 2022

Conventional RC beams for crossing small and medium-sized rivers do not have a cross-sectional area, so the floating debris is accumulated and disasters such as damage to bridges occur. To improve this, the PSC method was invented. However, this also had problems such as transverse curvature, increase in dead weight due to cross-sectional shape, and negative moment generated during serialization, so it was necessary to develop a new type of girder. Therefore, it was intended to propose a LIT(Leton Interaction Thrust) girder bridge that is safer and has better performance than the conventional PSC girder with improved section efficiency. Unlike existing girder bridges, the LIT girder has the feature that the change in the strands of the entire girder occurs only in the vertical direction when the first tension is applied because the tendon arrangement is symmetrical by applying the raised portion. In addition, slab continuation generates a secondary moment that is advantageous to the continuous point, effectively controlling the negative moment and preventing the corrosion of the tendon. The dimensions of the cross section were determined, and the arrangement of the strands was designed to conduct structural analysis and detailed analysis. As a result of the structural analysis, the stress of the girder showed results within the allowable compressive stress, and the deflection showed the result within the allowable deflection. showed results. In addition, a detailed analysis was performed to examine the stress distribution around the girder body and the anchorage area and the stress distribution of the embossed portion, and as a result, the stress of the girder body due to the tension force showed a stable level.

• 한국정밀공학회지
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• 제27권11호
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• pp.46-56
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• 2010

The present research works investigated into the low velocity impact characteristics of DP 780 high strength steel sheet with 1.7 mm in thickness subjected to free boundary condition using three-dimensional finite element analysis. Finite element analysis was carried out via ABAQUS explicit code. Hyper-elastic model and the damping factor were introduced to improve an accuracy of the FE analysis. An appropriate FE model was obtained via the comparison of the results of the FE analyses and those of the impact tests. The influence of the impact energy and nose diameter of the impact head on the force-deflection curves, impact time, absorption characteristics of the impact energy, deformation behaviours, and stress-strain distributions was quantitatively examined using the results of FE analysis. The results of the FE analysis showed that the absorption rate of impact energy lies in the range of the 70.7-77.5 %. In addition, it was noted that the absorption rate of impact energy decreases when the impact energy increases and the nose diameter of the impact head decreases. The local deformation of the impacted region was rapidly increased when the impact energy was larger than 76.2 J and the nose diameter was 20 mm. A critical impact energy, which occur the instability of the DP780, was estimated using the relationship between the plastic strain and the impact energy. Finally, characteristics of the plastic energy dissipation and the strain energy density were discussed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1198-1201
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• 2005

A new foxtail actuator driven by V-shape beam deflection using electrostatic force has been designed, fabricated and characterized for nano-resolution manipulators. The proposed foxtail mechanism was implemented using a pair of electrostatic actuators and a pair of holding actuators, which was analyzed based on the electromechanically coupled motion of voltage - displacement relation. The proposed actuator was fabricated onto Silicon-on-Insulator (SOI) wafer and its stepping characteristics were measured by micro optical interferometer consisting of integrated micromirror and optical fiber. The fabricated foxtail microactuator was successfully operated from 1nm to 76nm, and the magnitude of step displacement was controllable up from 26nm/cycles to 53nm/cycle by changing the voltage.

• 한국철도학회논문집
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• 제9권2호
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• pp.160-168
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• 2006

The major objective of this study is to investigate the effects and application of external post-tensioning method far steel plate girder bridge. It analyzed the mechanical behaviors of steel plate girder bridge with applying external post-tensioning on the finite element analysis, field test and laboratory test fur the lateral dynamic characteristics. As a result, the reinforcement of steel plate girder bridge the external post-tensioning method are obviously effective for the lateral dynamic response which is non-reinforced. The analytical and experimental study are carried out to investigate the post-tension force decrease lateral acceleration and deflection on steel plate girder bridge for serviceability. And the external post-tensioning method reduce dynamic maximum displacement(about $10{\sim}24%$), the increase of dynamic safety is predicted by adopting external post-tensioning method. From the dynamic test results of the servicing steel plate girder bridge, it is investigated that the change degree of natural frequency is very low with applying the external post-tensioning method The servicing steel plate girder bridge with external post-tensioning has need of the reasonable reinforcement measures which could be reducing the effect of lateral dynamic behavior that degradation phenomenon of structure by an unusual response characteristic and a drop durability.

• 제어로봇시스템학회논문지
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• 제8권3호
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• pp.199-207
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• 2002

In this paper, a self-tuning gain-scheduled skyhook control for semi-active suspension systems is investigated. The dynamic characteristics of a continuously variable damper including electro-hydraulic pressure control valves is analyzed. A 2-d.o.f. time-varying quarter-car model that permits variations in sprung mass and suspension spring coefficient is considered. The self-tuning skyhook control algorithm proposed in this paper requires only the measurement of body acceleration. The absolute velocity of the sprung mass and the relative velocity of the suspension deflection are estimated by using integral filters. The skyhook gains are gain-scheduled in such a way that the body acceleration and the dynamic tire force are optimized. An ECU prototype is discussed. Experimental results using a 1/4-ear simulator are discussed. Also, a suspension ECU prototype targeting real implementation is provided.