• Title/Summary/Keyword: Rigid Bearing

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The characteristics of the behaviour of plate girder bridges according to the boundary conditions. (경계조건에 따른 판형교 장대레일의 거동 특성)

  • Min Kyung-Ju;Jung Ue Ha;Kim Young-Kook
    • Proceedings of the KSR Conference
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    • 2003.05a
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    • pp.356-363
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    • 2003
  • The CWR of the plate girder bridges in non-ballast causes the additional axial force on the rail and the bearing due to the temperature axial force and the interaction between the CWR and bridges. This study shows the remarkable improvement of reducing the axial force of the CWR on the non-ballast bridge, compared to conventional methods. New method, which is differently designed in terms of longitudinal semi-rigid bearing, reduces the axial force on the bearing by making the girder act both directions. This method is applicable to most cases of bridges regardless of the restriction of length, and useful to reduce the abrasion and damage of the track material.

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A Design and Control of an Active Magnetic Bearing System (능동형 자기 베어링 시스템의 설계 및 제어)

  • 김종문;최영규
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.53 no.2
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    • pp.82-89
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    • 2004
  • In this paper, an active magnetic bearing(AMB) system is designed and controlled using a digital Proportional-Integral-Derivative(PID) control concept. The plant dynamics consisting of actuator and rigid rotor dynamics are described. A digital PID controller with a global control and a local control concept is designed and implemented using digital signal processor. Some experiments are conducted with each global control and local control concept. These include start-up test, impulse test, whirl response, and generator load test. The experimental results and comparison between those of a global control and a local control indicate that the global control of concept has impressive static and dynamic control performance for the prototype considered. From the whirl test, the developed system set can be controlled within about $\pm10\mu\textrm{m}$ gap variation at the rotational speed of 6000rpm and generate the AC power of frequency of $60\textrm{Hz}$, voltage of 100V and current of 0.8$\textit{A}$.

Controller Design and Experiment to Levitate a Rotor in an Active Magnetic Bearing System (능동 자기 베어링 시스템의 제어기 설계 및 연구)

  • Chang, Yu;Shim, Sung-Hyo;Yang, Joo-Ho
    • Journal of Power System Engineering
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    • v.6 no.4
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    • pp.73-80
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    • 2002
  • 이 논문은 MIMO 능동 자기 베어링 시스템에 있어서의 병진 및 회전(기울기)운동을 하는 횡축형 강체 로터의 동적 거동을 모델링하고, 로터 양 끝단의 간섭효과를 고려한 제어방법을 제안한다. 제어기는 DSP 보드를 이용하였으며, 설계된 제어기의 타당성을 시뮬레이션 및 실험을 통하여 검증하였다.

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The Process Design for Hot Forging of Bearing Hub Considering Flow Line (단류선을 고려한 베어링 허브의 열간 단조 공정설계)

  • Byun H. S.;No G. Y.;Kim B. M.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2005.05a
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    • pp.428-431
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    • 2005
  • This paper describes the process design for hot forging of bearing hub. Forging processes of bearing hub are simulated using the rigid-plastic finite element method. In the process called closed die forging without flash, the design of blocker geometry is of critical importance. Forging processes designs are take advantage of computer aided Process planning and experts. But that is difficult to predict metal flow line. So the preform is designed by the expert, and modified through predict metal flow line by CAE. This paper is to approach preform design considered defect such as metal flow and unfitting etc. at the finisher process.

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Seismic bearing capacity of shallow footings on cement-improved soils

  • Kholdebarin, Alireza;Massumi, Ali;Davoodi, Mohammad
    • Earthquakes and Structures
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    • v.10 no.1
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    • pp.179-190
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    • 2016
  • A single rigid footing constructed on sandy-clay soil was modeled and analyzed using FLAC software under static conditions and vertical ground motion using three accelerograms. Dynamic analysis was repeated by changing the elastic and plastic parameters of the soil by changing the percentage of cement grouting (2, 4 and 6 %). The load-settlement curves were plotted and their bearing capacities compared under different conditions. Vertical settlement contours and time histories of settlement were plotted and analyzed for treated and untreated soil for the different percentages of cement. The results demonstrate that adding 2, 4 and 6 % of cement under specific conditions increased the dynamic bearing capacity 2.7, 4.2 and 7.0 times, respectively.

A Simulation for the Critical Speeds of a Geared Rotor System with Time Varying Mesh Stiffnesses and Bearing Flexibilities. (시 변화 물림 강성도와 베어링 유연도를 고려한 기어-로터의 위험 속도 시뮬레이션)

  • 최명진
    • Journal of the Korea Society for Simulation
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    • v.8 no.3
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    • pp.39-48
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    • 1999
  • A finite element model of geared rotor system with flexible bearings were used to simulate the critical speeds and to investigate the effects of bearing coefficients on the dynamic behaviors of the systems. The finite element model includes the effects of tooth mesh stiffness, gyroscopic moment, rotary inertia, shear, and torque of the shaft. The gear mesh was modelled as a pair of rigid disks connected by a spring of time varying stiffness. The time varying mesh stiffness results in the abrupt change of the critical speeds of spur geared systems. As the bearing stiffness increases, critical speeds increase rapidly in case of stiff shafts, compared with flexible shafts.

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Seismic performance evaluation of RC bearing wall structures

  • Rashedi, Seyed Hadi;Rahai, Alireza;Tehrani, Payam
    • Computers and Concrete
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    • v.30 no.2
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    • pp.113-126
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    • 2022
  • Reinforced concrete bearing walls (RCBWs) are one of the most applicable structural systems. Therefore, vulnerability analysis and rehabilitation of the RCBW system are of great importance. In the present study, in order to the more precise investigation of the performance of this structural resistant system, pushover and nonlinear time history analyses based on several assumptions drawing upon experimental research were performed on several models with different stories. To validate the nonlinear analysis method, the analytical and experimental results are compared. Vulnerability evaluation was carried out on two seismic hazard levels and three performance levels. Eventually, the need for seismic rehabilitation with the basic safety objective (BSO) was investigated. The obtained results showed that the studied structures satisfied the BSO of the seismic rehabilitation guidelines. Consequently, according to the results of analyses and the desired performance, this structural system, despite its high structural weight and rigid connections and low flexibility, has integrated performance, and it can be a good option for earthquake-resistant constructions.

Rotordynamic Analysis and Operation Test of Turbo Expander with Hydrostatic Bearing (정압베어링을 적용한 터보팽창기의 회전체 동역학 해석 및 구동시험)

  • Lee, Donghyun;Kim, Byungock;Jung, Junha;Lim, Hyungsoo
    • Tribology and Lubricants
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    • v.38 no.2
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    • pp.33-40
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    • 2022
  • In this study, we present rotor dynamic analysis and operation test of a turbo expander for a hydrogen liquefaction plant. The turbo expander consists of a turbine and compressor wheel connected to a shaft supported by two hydrostatic radial and thrust bearings. In rotor dynamic analysis, the shaft is modeled as a rigid body, and the equations of motion for the shaft are solved using the unsteady Reynolds equation. Additionally, the operating test of the turbo expander has been performed in the test rig. Pressurized helium is supplied to the bearings at 8.5 bar. Furthermore, we monitor the shaft vibration and flow rate of the helium supplied to the bearings. The rotor dynamic analysis result shows that there are two critical speeds related with the rigid body mode under 40,000 rpm. At the first critical speed of 36,000 rpm, the vibration at the compressor side is maximum, whereas that of the turbine is maximum at the second critical speed of 40,000 rpm. The predicted maximum shaft vibration is 3 ㎛, whereas sub-synchronous vibration is not presented. The operation test results show that there are two critical speeds under the rated speed, and the measured vibration value agrees well with predicted value. The measured flow rate of the helium supplied to the bearing is 2.0 g/s, which also agrees well with the predicted data.

PID Control of a Synchronous Rotor System Vibration with Active Air Bearing (능동 공기 베어링에 의한 로터계 동기진동의 PID제어)

  • Gwon, Dae-Gyu;Lee, Yeong-Chun;Lee, Seong-Cheol
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.8
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    • pp.32-39
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    • 2001
  • This paper presents the synchronous vibration control of a rotor system using an Active Air Bearing(AAB). In order to suppress the synchronous vibration, it is necessary to actively control the air film pressure or the air film thickness. In this study, active pads are used to control the air film thickness. Active pads are supported by the pivots containing piezoelectric actuators and their radial positions can be actively controlled by applying voltage to the actuators. Disturbances and various kinds of external force can cause the shaft vibration as well as the change of the air film thickness. The dynamic behaviors of a rotary system supported by two tilting-pad gas bearings and its active stabilization using the tilting-pads as actuators are investigated numerically. The PID controller is applied to the tilting-pad gas bearing system with three pads, two of which contain piezoelectric actuators. To test the vapidity of the theoretical method, the performance of this control method is evaluated through experiments. The experimental results show the effectiveness of the control system for suppressing the unbalanced response of the rigid modes.

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Optimal Weight Design of Rotor-Bearing Systems Considering Whirl Natural Frequency and Stability (선회 고유진동수와 안정성을 고려한 회전자-베어링 시스템의 중량 최적설계)

  • 이동수;손윤호;최동훈
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.3
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    • pp.639-646
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    • 1995
  • The objective of this study is to minimize the weight of a damped anisotropic roto-bearing system considering whirl natural frequency and stability. The system is modeled as an assemblage of rigid disks, flexible shafts and discrete bearings. The system design variables are the crosssectional areas of shaft elements and the properties of bearings. To analyze the system, the polynomial method which is derived by rearranging the calculations performed by a transfer matrix method is adopted. For the optimization, the optimization software IDOL (Integrated Design Optimization Library) which is based on the Augmented Lagrange Multiplier (ALM) method is employed. Also, an analytical design sensitivity analysis of the system is used for high accuracy and efficiency. To demonstrate the usefulness of the proposed optimal design program incorporating analysis, design sensitivity analysis, and optimization modules, a damped anisotropic rotor-bearing system is optimized to obtain 34$ weight reduction.