• Title/Summary/Keyword: Equilibrium Position

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A study on the dynamic characteristics of an epicyclic gear trains supported with journal bearing (저널베어링으로 지지된 유성기어열의 동특성에 관한 연구)

  • Lee, Jeong-Han;Ryu, Hyeong-Tae;Cheon, Gil-Jeong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.22 no.1
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    • pp.198-205
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    • 1998
  • In this paper, the dynamic characteristics of a star type epicyclic gear train have been analyzed. Nonlinear stiffness of a gear pair were obtained considering the bending and shear deformation, Hertz contact deformation, as well as tooth fillet deformation. Nonlinear stiffness coefficients and damping coefficients around the static equilibrium position were obtained by perturbation method. The loci of the planet gears and sun gear were estimated. Tooth meshing forces and bearing reaction forces were calculated. The effects of bearing clearance and oil viscosity on the gear behavior were also analyzed.

A Study on the Analysis of Multi-let Spread Mooring Systems (다점지지 계류시스템의 정적해석에 대한 연구)

  • Sin, Hyeon-Gyeong;Kim, Deok-Su
    • Journal of Ocean Engineering and Technology
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    • v.9 no.2
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    • pp.53-60
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    • 1995
  • A multi-leg spread mooring system for floating offshore structures is important, but the multi-leg static analysis is complicated due to the nonlinear behavior of each line and the effect of current which affects each line differently. The pretensioned position of the multi-leg mooring system obtained from the static equilibrium condition changes into a different position due to external loads and current. In this paper, the new position and the static tension at each line are caculated. The relation between the initial static equilibrium position and the new position due to the external loads is expressed in terms of the Taylor's series expansion. The Runge-Kutta $4^{th}$ method is employed in analyzing the 3-dimensional static cable nonlinear equations.

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Study on the Oil-free Turbocharger Supported by Air Foil Bearing (공기 포일 베어링으로 지지되는 무급유 터보 과급기 회전체 설계에 대한 연구)

  • Lee, Yong-Bok;Kim, Tae-Ho;Kim, Chang-Ho;Lee, Nam-Soo
    • 유체기계공업학회:학술대회논문집
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    • pp.453-458
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    • 2002
  • The feasibility study on supporting a turbocharger rotor on air foil bearing is investigated. Based on finite difference method and Newton-Raphson method, the static equilibrium position of a turbocharger rotor is predicted. And using finite difference method and perturbation method, dynamic characteristics of air foil bearings are calculated. Rotordynamic analysis is performed by finite element method, with collaboration of calculated stiffness and damping of foil bearing. The effect of compliance and clearance of bump foil bearing on the oil-free turbocharger is investigated in terms of rotordynamics. And the critical speeds, eccentricity ratio, vibration amplitude, and stability are considered. It is demonstrated that foil bearings offer a rlausible replacement for oil-lubricated bearings in turbocharger.

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Investigation on the Strength and Vibration Safety of the Oxidizer Turbopump (산화제 터보펌프의 구조 강도 및 진동 안전성에 관한 연구)

  • Jeon, Seong-Min;Kim, Jin-han;Yang, Soo-Seok;Lee, Dae-Sung
    • The KSFM Journal of Fluid Machinery
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    • v.5 no.3
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    • pp.25-32
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    • 2002
  • Structural and dynamic analyses of inducer and impeller for an oxidizer turbopump are peformed to investigate the safety level of strength and vibration at a design point. Due to high rotational speed of turbopump, effects of centrifugal forces are carefully considered in the structural analysis. Hydrodynamic pressure is also considered as an external force applied to inducer and impeller blades. A three-dimensional Finite Element Method (FEM) is used for linear and nonlinear structural analyses with modified Newton-Raphson iteration method. After the nonlinear trim solution is obtained from the structural analysis, dynamic characteristics are obtained as a function of rotational speed from the linearized eigenvalue analysis at an equilibrium position. According to the results of numerical analysis, the safety margins of strength and vibration resonances are sufficient enough for safe operation within the requited life cycle.

A Study on the Oil-free Turbocharger Supported by Air Foil Bearing (공기 포일 베어링으로 지지되는 무급유 터보 과급기 회전체 설계에 대한 연구)

  • Lee Yong-Bok;Kim Tae-Ho;Kim Chang-Ho;Sa Jong-Sung;Lee Nam-Soo
    • The KSFM Journal of Fluid Machinery
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    • v.6 no.1
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    • pp.51-56
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    • 2003
  • The feasibility study on the oil-free turbocharger supported by air foil bearings is investigated. Using the perturbation method, dynamic characteristics of air foil bearings are calculated based on the static equilibrium position of a turbocharger rotor is predicted. With collaboration of calculated stiffness and damping of foil bearing, rotordynamic analysis is performed using the finite element method. The effects of bump compliance and bearing clearance on rotordynamic characteristics of the oil-free turbocharger such as the critical speeds, eccentricity ratio, vibration amplitude and stability are investigated.

Static equilibrium and linear vibration analysis of a high speed electric train system (고속전철 시스템의 정적평형 및 선형진동 해석)

  • 김종인;유홍희;황요하
    • Journal of the Korean Society for Railway
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    • v.2 no.4
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    • pp.1-8
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    • 1999
  • A formulation to perform static equilibrium and linear vibration analysis is presented in this paper. The formulation employs minimum number of equations of motion which are derived by using a partial velocity matrix. The static equilibrium analysis is performed first, then the linear vibration analysis is performed at the static equilibrium position. By using the formulation presented in this paper, static equilibrium and linear vibration analysis of a high speed electric train system are performed. A single bogie system, a power car vehicle, and a train system which consists of five vehicles are analyzed, respectively. Natural frequencies and a few lowest mode shapes of the two are identified in this paper.

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Impact Behavior Analysis of Mechanical Monoleaflet Heart Valve Prostheses in the Opening Phase

  • Cheon, Gill-Jeong;Chandran, K.B.
    • Journal of Biomedical Engineering Research
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    • v.13 no.3
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    • pp.235-244
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    • 1992
  • In this paper, fluttering behavior of mechanical monoleaflet tilting disc heart valve prostheses during the opening phase was analyzed taking into consideration the impact between the occluder and the guiding strut at the fully open position. The motion of the valve occluder was modeled as a rotating system, and equations were derived by employing the moment equilibrium principle. Forces due to lift, drag, gravity and buoyancy were considered as external forces acting on the occluder. The 4th order Runge-Kutta method was used to solve the governing equations. The results iimonstrated that the occludes reaches steady equilibrium position only after damped vibration. Fluttering frequency varies as a function of time after opening and is in the range of 8-84 Hz. Valve opening appears to be affected by the orientation of the valve relative to gravitational force. The opening velocities are in the range of 0.65-1.42m/sec and the dynamic loads by impact of the occludes and the strut are in the range of 90-190 N.

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Dynamic Behavior Analysis of Mechanical Bileaflet Heart Valve Prosthesis (기계식 이엽심장밸브의 동적거동 해석)

  • 천길정
    • Journal of Biomedical Engineering Research
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    • v.12 no.3
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    • pp.149-156
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    • 1991
  • In this paper, fluttering behavior of mechanical bileaflet heart valve prosthesis was analyzed taking into consideration of the impact between valve plate and stopper Vibration system of the valve was modeled as a rotating system, and equations are induced by moment equilibrium equations. Lift force, drag force, gravity and buoyancy were considered as external forces acting on the valve plate/ The 4th order Runge-Kutta method was used to solve the equations. Valve plate does not come to the static equilibrium position at a stretch, but come to that position after under damping vibration. Damping ratio increases as the cardiac optput increases, and the mean damping ratio is in the range of 0.16~40.25. Fluttering frequency does not have any specific value, but varies as a function of time. It is in the range of 10~40Hz. Valve opening appears to be affected by the orientation of the of the valve relative to gravitational forces.

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Steady-state Equilibrium Analysis of a Multibody System Driven by Constant Generalized Speeds (일정 일반속력으로 구동되는 다물체계의 정상상태의 평형해석)

  • Choi, D.H.;Park, J.H.;Yoo, H.H.
    • Proceedings of the KSME Conference
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    • pp.465-470
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    • 2001
  • This paper presents an algorithm which seeks steady-state equilibrium positions of constrained multibody systems driven by constant generalized speeds. Since the relative coordinates are employed, the constraint equations at cut joints are incorporated into the formulation. The proposed algorithm leads to nonlinear equations that need to be solved iteratively. This algorithm should satisfy both types of conditions: the force equilibrium equations and the kinematic constraint equations. To verify the effectiveness of the proposed algorithm, two numerical examples are solved and the results are compared with those of a commercial program. This method, compared to the conventional method of using dynamic analysis, has the advantage of computational efficiency and stability.

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Design and Control of an Active Magnetic Bearing for Linear Motors (리니어 모터를 위한 능동 자기 베어링의 설계 및 제어)

  • 양광원;허경무
    • Proceedings of the IEEK Conference
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    • pp.119-122
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    • 2001
  • This paper deals with new type of active magnetic bearing (AMB) for the linear motors. We adopted optical sensing mechanism for the gap sensing. Using the laser and the PSD (Position Sensitive Device), the absolute rotor position is obtained independent of the profile of the guide rail. With this measurement, the rotor can be controller to follow the straight beam of the laser. Another advantage of optical sensing mechanism might be the elimination of the possible interference between the proximity sensor and the electro-magnet. By adopting the push-full actuating mechanism, the bearing stiffness is increased near the equilibrium position. For the simplicity, distributed control system is constructed. Eight independent PID control algorithm is used with the full order observer. Several simulation md test results are presented.

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