• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.250-251
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• 2014

This paper investigates the stick-slip phenomena on spinning shaft. The modeling of the shaft is considered only torsional direction with nonlinear friction. The friction is adopted a negative friction-velocity slope. Based on the model, a nonlinear equation of motion is derived and analyze the stick-slip phenomena. In order to analyze the time dependent response, the nonlinear formulations are numerically solved by nonlinear Newmark method. The numerical results reveal the stick-slip phenomena on the spinning shaft system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.7
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• pp.510-517
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• 2015

The free vibration and stability analysis of a spinning composite shaft modelled as a thin-walled closed beam is performed for several design parameters, such as ply angle, aspect ratio, and spin speed. The governing equations of spinning shafts based on the Timoshenko beam theory are derived via Hamilton's variational principle. Coriolis acceleration and anisotropy of constituent materials are incorporated in the derivation. The equations of motion are then transformed to the standard form of an eigenvalue problem for free vibration and stability analysis. Analytical results both for uniform circular cylindrical shaft and rectangular cross-section shaft are obtained by using extended Galerkin method, and the results are compared with those from FEM ANSYS analysis for a verification.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1993.12a
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• pp.70-76
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• 1993

From the analysis of shaft-bearing indeterminate system, moment and misalingment angle which was generated in bearing were determined. And the influence of span length between bearings on the fatigue life was established. The equation to estimate the cage rotational speed was proposed, and this equation was verified by the measuring of cage speed and shaft speed. And accoding to quasi-static analysis, the spinning speed of ball was determined.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1083-1088
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• 2004

This paper deals with the vibration and stability of a circular cylindrical shaft, modeled as a tapered thin-walled composite beam and spinning with constant angular speed about its longitudinal axis, and subjected to an axial compressive force. Hamilton's principle and the assumed mode method are employed to derive the governing equations of motion. The resulting eigenvalue problem is analyzed, and the stability boundaries are presented for selected taper ratios and axial compressive force combinations. Taking into account the directionality property of fiber reinforced composite materials, it is shown that for a shaft featuring flapwise-chordwise-bending coupling, a dramatic enhancement of both the vibration and stability behavior can be reached. It is found that by the structural tailoring and tapering, bending natural frequencies, stiffness and stability region can be significantly increased over those of uniform shafts made of the same material. In addition, the particular case of a classical beam with internal damping effect is also included.

• Tribology and Lubricants
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• v.10 no.1
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• pp.62-68
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• 1994

The analysis of statically indeterminate bearing-shaft system was investigated. The moment loads and misalignment angles which were induced in the ball bearings were determined, and the influence of span length of this system on the moment loads and fatigue lives was identified. The sliding and spinning speeds between balls and raceways which affected the performance of ball bearing evaluated. The equation to estimate the cage speed of ball bearing under moment loads was proposed. This equation had been verified by the test results of measuring of cage speed, which was useful to the prediction of ball bearing under moment loads.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.697-698
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• 2013

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.784-789
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• 2000

Equations of motion are derived and solved using the finite element method substructure synthesis for the disk-spindle system with rigid spindle and flexible shaft. The disk is modeled as a flexible spinning disk by Kirchhoff plate theory and von Karman nonlinear strain. The spindle supporting the flexible disk is modeled as a rigid body to consider its complex geometry. The stationary shaft supporting the rotating disk-spindle-bearing system is modeled by Euler beam, and the ball bearings are modeled as the stiffness matrix with 5 degrees of freedom. Developed theory is applied to analyze the vibration characteristics of a 3.5" HDD and a 2.5" HDD, respectively, and modal tests are performed to verify the simulation results. This paper shows that the developed theory can be effectively applied to the rotating disk-spindle system with the spindle of complex shape.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.8
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• pp.583-591
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• 2014

The mathematical modeling on the free vibration and stability of a multi-stepped shaft of turbo compressor is performed in this study. The multi-stepped shaft is modeled as a non-uniform Timoshenko beam supported by anisotropic bearings. It is assumed that the shaft is spinning with constant speed about its longitudinal axis and subjected to a conservative axial force induced by front and rear impellers attached to the shaft. The structural model incorporates non-classical features such as transverse shear and rotary inertia. A structural coupling between vertical and lateral motions is induced by Coriolis acceleration terms. The governing equations are derived via Hamilton's variational principle and the equations are transformed to the standard form of an eigenvalue problem. The implications of combined gyroscopic effect, conservative axial force, bearing stiffness and damping are revealed and a number of pertinent conclusions are outlined. In this study analytical results are compared with those from ANSYS finite element analysis and experimental modal testing.

• Tribology and Lubricants
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• v.39 no.6
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• pp.268-272
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• 2023

This study explores the characteristics of tilting pad journal bearings used in the high-speed rotating shaft systems of centrifugal compressors. A centrifugal compressor is a high-speed rotating machine that is widely used to compress gases or vapors employed in various industrial applications. It transfers the centrifugal force of a fast-spinning impeller to the fluid and compresses it under high pressure. Many high-speed rotating shaft systems, which require high stability, use tilting pad journal bearings. The characteristics of these bearings can vary depending on several properties, and identifying the appropriate characteristics is essential to optimize the design on a case-to-case basis. In this study, the authors perform a time-dependent analysis of the properties of tilting pad journal bearings and the rotordynamics of the rotating shaft system using COMSOL Multiphysics software. Specifically, the authors analyze the characteristics of the tilting pad journal bearings by performing a parametric sweep using parameters such as pad clearance, maximum tilting angle, preload, number of pads, and pad pivot offset. The authors then use the results of the bearing-characteristics analysis to evaluate the vibration of the rotating shaft and verify its operation within a desirable range. The understanding gained from this study will allow us to determine the optimal properties of these bearings and the limiting operational speed using COMSOL Multiphysics software.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.3 s.96
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• pp.251-258
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• 2005

The free vibration of a spinning flexible disk-spindle system supported by hydro dynamic bearings (HDB) in an HDD is analyzed by FEM. The spinning flexible disk is described using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. It is discretized by annular sector element. The rotating spindle which includes the clamp, hub, permanent magnet and yoke, is modeled by Timoshenko beam including the gyroscopic effect. The flexible supporting structure with a complex shape which includes stator core, housing, base plate, sleeve and thrust pad is modeled by using a 4-node tetrahedron element with rotational degrees of freedom to satisfy the geometric compatibility. The dynamic coefficients of HDB are calculated from the HDB analysis program, which solves the perturbed Reynolds equation using FEM. Introducing the virtual nodes and the rigid link constraints defined in the center of HDB, beam elements of the shaft are connected to the solid elements of the sleeve and thrust pad through the spring and damper element. The global matrix equation obtained by assembling the finite element equations of each substructure is transformed to the state-space matrix-vector equation, and the associated eigen value problem is solved by using the restarted Arnoldi iteration method. The validity of this research is verified by comparing the numerical results of the natural frequencies with the experimental ones. Also the effect of supporting structures to the natural modes of the total HDD system is rigorously analyzed.