• 한국유체기계학회 논문집
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• 제5권2호
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• pp.43-49
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• 2002

In this paper, the steady-state performances analysis of a tilting pad gas bearing(TPGB) we analyzed by using finite element method for compressible Reynolds' equation. TPGB is used in a high-expansion-ratio expander running at a speed of 230,000 rpm. In order to solve the nonlinear finite element equations, the Newton-Raphson method is applied. The variations of the loading capacity, friction force and tilting angle of a single pad v.s. eccentricity direction of eccentricity and bearing number are investigated. The condition for the equilibrium of a pad, which is important for safe working of the bearing, is stated. The performances of the three pad bearing such as loading capacity, friction moment are predicted.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.1049-1052
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• 2008

내력벽시스템에 사용되는 연결보는 횡변위 조절을 위하여 효과적으로 사용되는 요소이나, 단면의 폭과 춤이 시스템에 의하여 제한되므로 연성능력을 향상시키기 위한 철근의 상세처리가 어럽다. 이러한 이유로 지진에 의하여 횡력이 발생할 경우 가장 먼저 연결보에 손상이 발생하게 될 것이므로, 본 연구에서는 연결보가 있는 내력벽 시스템의 성능을 평가하고자 하였다. 이러한 성능평가는 FEMA 400의 수정된 등가 선형의 절차에 의하여 수행되었다. 평가를 위한 모델은 15층이고 연결보의 강성은 변동이 없으며 질량을 변화하여 구조물의 주기를 변화하였다. 요구 스펙트럼 산정은 KBC 2005의 계수를 곱하지 않은 스펙트럼을 사용하였다. 성능 평가 결과로서, 토질 SD에 대하여 대부분의 모델에서 인명안전 수준에서 검토된 연결보의 제한 변위가 성능점 보다 작게 나타났다. 전반적으로 시스템의 주기가 짧아질수록 연결보의 손상도에 의하여 성능점이 감소되는 현상을 나타내었다.

• 한국지진공학회논문집
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• 제17권3호
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• pp.117-125
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• 2013

Seismic isolation has been considered and utilized in various industries as a way to prevent huge damage on to structures by large earthquakes in various industries. The laminated Laminated rubber bearings is are most frequently used in seismic isolation systems. The structural Structural safety could not be assured unless the performance of the rubber bearing is not guaranteed for the life time of the structure under the consideration that the bearing is a critical structural member to sustain vertical loads in the seismically isolated structure. However, there are few studies on the deterioration problems of rubber bearings during their service life. The long term performance of the rubber bearings was not considered in past designs of seismically isolated structures. This study evaluates the long term performance and creep characteristics of laminated natural rubber bearings that are used in seismically isolated buildings. For the this study, a set of accelerated thermal aging tests and creep tests are were performed on real specimens. The experimental results show that the natural rubber bearings would have a stable change rate of change for durability under severe environmental conditions for a long time.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 학술대회 논문집 전문대학교육위원
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• pp.216-220
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• 2006

This paper is presented for the measurement of the bearing stiffness for the spindle motors. BLDC Spindle Motors for the Hard Disk Drive are used by several kinds of the bearings, such as ball bearing, fluid dynamic bearing, and aero dynamic bearing. The spindle motors are attached the platters to read and write the data. Because the platter rotates at high end speed with the load and can be shocked from a suddenly moving, the bearing needs the rated stiffness with the pressure. By the way, it has not been realized to measure the real stiffness for each bearing types. In this paper, we proposed the method of measuring the stiffness for the bearings by using the magnet force. Experimental results show the performance to measure the bearing stiffness of the BLDC spindle motors for an HDD.

• 대한기계학회논문집A
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• 제22권1호
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• pp.33-43
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• 1998

High cutting speeds and feeds are essential requirements of a machine tool structure to accomplish its basic function which is to produce a workpiece of the required geometric form with an acceptable surface finish at as high a rate of production as is economically possible. Since the bearings in high speed spindle units are the main heat source of the total cutting system, in this work, the thermal characteristics of the spindle bearing system with a tilting axis were investigated using finite element methods to improve the performance of the spindle bearing system. Based on the theoretical results, a specially designed prototype spindle bearing system has been manufactured. Using the manufactured spindle bearing system, the thermal characteristics were measured. From the comparison of the experimental results with the theoretical ones, it was found that the finite element method predicted well the thermal characteristics of the spindle bearing system.

• 한국정밀공학회지
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• 제29권10호
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• pp.1050-1055
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• 2012

The bearing coupling section of machine tools is the most important factor to determine their static/dynamic stiffness. To ensure the proper performance of machine tools, the static/dynamic stiffness of the rotating system has to be predicted on the design stage. Various parameters of the bearing coupling section, such as the spring element, node number and preload influence the characteristics of rotating systems. This study focuses on the prediction of the static and dynamic stiffness of the rotating system with the bearing coupling section using the finite element (FE) model. MATRIX 27 in ANSYS has been adopted to describe the bearing coupling section of machine tools because the MATRIX 27 can describe the bearing coupling section close to the real object and is applicable to various machine tools. The FE model of the bearing couple section which has the sixteen node using MATRIX 27 was constructed. Comparisons between finite element method (FEM) predictions and experimental results were performed in terms of the static and dynamic stiffness.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.3-6
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• 2000

The magnetic bearing system are intrinsically unstable, and need the feedback control of electromagnetic forces with measured displacements. So the controller design plays an important role in constructing high performance magnetic bearing system. In case of magnetic bearing system, the order of identified model is high because of unknown dynamics included in closed loop systems - such as sensor dynamics, actuator dynamics - and non-linearity of magnetic bearings itself. In this paper the identification and robust control of flexible rotor supported by magnetic bearing are discussed. We measure and identify overall system that contains not only flexible rotor model but also magnetic bearing and time delay. The structured and unstructured uncertainties are modeled that cover variations of natural frequencies, uncertainties in sensor and actuator gains and unmodeled dynamics. And desired performances are specified with several weighting function. Using augmented system that includes identified model, uncertainties, and weighting functions, μ-synthesis is applied to flexible rotor supported with magnetic bearing. The flexible rotor was spin up over the first flexible critical speed.

• 한국구조물진단유지관리공학회 논문집
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• 제6권4호
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• pp.209-217
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• 2002

The effects on structures caused by the replacement of the bridge bearings are investigated in this study. The bearings of the bridge are seriously deteriorated because of the breakage of lower concrete and the corrosion of the bearing itself. Also, the negative reaction states are created at some bearings on the abutment. Then, the bridge has occurred excessive vibrations and severe noise and impact whenever heavy trucks pass the above joints. The existing bearings are replaced using the adjustable bearing. The height of the bearings is adjusted to minimize the level difference of above joint and also to induce the appropriate distribution of live loads The effects of replacing the bearings are investigated by measuring the behaviors of the bridge without and with replacing works. The results without replacing the bearing show that the distribution of displacements and stresses is distorted in comparison with the analytical results. Also the bridge without replacing the bearing shows that the impact and vibration from the heavy trucks are larger than those with replacing the bearing. Load carrying capacity of the bridge increase about 1.8 times through replacing the bearing. The above results show that the structural performance of the bridge is improved by replacing only bridge bearings.

• 콘크리트학회논문집
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• 제19권4호
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• pp.507-514
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• 2007

이 논문은 기존 내진설계와 비교하여 면진설계의 효용성과 경제적 효과에 대한 연구 결과를 정리한 것이며, 면진설계에 있어서는 납봉삽입적층고무베어링 (LRB)만을 사용한 경우와 비교하여 슬라이딩베어링과 LRB를 혼용한 면진시스템의 내진 거동을 함께 제시하였다. 연구 결과, 면진은 구조물에 대하여 지진동으로 인한 효과를 감소시키는데 매우 효과적이며, 층 가속도의 감소로 사용성을 증가시킬 수 있음이 입증되었다. 또한 층 가속도와 밑면 전단력의 감소라는 관점에서 슬라이딩베어링과 LRB를 혼용한 면진시스템이 LRB만을 사용한 경우보다 더 효과적임을 증명하였다. 하지만 경제적 효과 면에서는 증가된 성능에 비례하여 지불해야만 하는 비용도 커진다는 사실에 특별히 주의할 필요가 있는 것으로 나타났다.

• 전기학회논문지P
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• 제60권2호
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• pp.82-90
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• 2011

The small precision spindle motors in the high value-added products including the visible home appliances such as DLP projector require not only the energy conversion devices but also high efficiency, low vibration and sound operation. However, the spindle motors using the conventional ball bearing and sintered porous metal bearing have following problems, respectively: the vibration by the irregularity of balls and the short motor life cycle by the ball's abrasion and higher sound noises by dry contact between shaft and sleeve. In this paper, it is proposed that the spindle motor with a fluid dynamic bearing is suitable for the motor to drive the color wheel of the DLP(digital lightening processor) in the visible home appliances. The proposed spindle motor is composed of the fluid dynamic bearing with both the radial force and the thrust force. The fluid dynamic bearing is solved by the finite element analysis of the mechanical field with the Reynolds equations. The magnetic part of spindle motor, which is a type of Brushless DC Motor, is designed by the electro-magnetic field analysis coupled with the Maxwell equation. And the load capacity and the friction loss of fluid dynamic bearing are analyzed to bearing clearance variation by the fabrication error in designed motor. The design of the proposed motor is implemented by the load torque caused by the eccentricity and the unbalance of the fluid dynamic bearing when the motors are fabricated in error. The prototype of the motor with the fluid dynamic bearing is manufactured, and experiment results show the vibration, sound, and phase current at no load and color wheel load of the motors in comparison. The high performance characteristics with the low vibration, the low acoustic noise and the optimal mechanical structure are verified by the experimental results.