• Title/Summary/Keyword: flexible disk

Search Result 114, Processing Time 0.026 seconds

Effect of viscous damping force subjected to a rotating flexible disk (점성감쇠력이 회전탄성원판에 미치는 영향)

  • Kong, Dae-Wee;Joo, Won-Gu
    • Proceedings of the KSME Conference
    • /
    • 2001.06e
    • /
    • pp.185-190
    • /
    • 2001
  • Rotating disks are used in various machines such as floppy disks, hard disk, turbines and circular sawblades. The problems of vibrations of rotating disks are important in improving these machines. Many investigators have dealt with these problem. Specially, vibrations of a rotating flexible disk taking into account the effect of air is difficult problem in simulation. The governing equation of a rotating flexible disk coupled to the surrounding fluid is investigated by a simple mathematical model. And several important parameters concerned with the stability of a rotating flexible disk are defined. Coupling strength between air and rotating flexible disk is proportional to square of disk radius directly and square root of the all of bending rigidity, disk density and thickness inversely. Lift-to-damping coefficient has relation to the onset of disk flutter.

  • PDF

Experimental and Numerical Study on an Air-Stabilized Flexible Disk Rotating Close to a Rigid Rotating Disk (회전원판 근처에서 회전하는 유연디스크에 대한 실험 및 수치해석)

  • Gad, Abdelrasoul M.M.;Rhim, Yoon-Chul
    • Transactions of the Society of Information Storage Systems
    • /
    • v.5 no.1
    • /
    • pp.19-35
    • /
    • 2009
  • The present work is an experimental and analytical study on a flexible disk rotating close to a rigid rotating disk in open air. In the analytical study, the air flow in the gap between the flexible disk and the rigid disk is modeled using Navier-Stokes and continuity equations while the flexible disk is modeled using the linear plate theory. The flow equations are discretized using the cell centered finite volume method (FVM) and solved numerically with semi-implicit pressure-linked equations (SIMPLE algorithm). The spatial terms in the disk equation are discretized using the finite difference method (FDM) and the time integration is performed using fourth-order Runge-Kutta method. An experimental test-rig is designed to investigate the dynamics of the flexible disk when rotating close to a co-rotating, a counter-rotating and a fixed rigid disk, which works as a stabilizer. The effects of rotational speed, initial gap height and inlet-hole radius on the flexible disk displacement and its vibration amplitude are investigated experimentally for the different types of stabilizer. Finally, the analytical and experimental results are compared.

  • PDF

Numerical Simulations for Suppressing Transverse Vibration of a very Flexible Rotating Disk using Air Bearing Concept (고속 회전 유연 디스크의 진동 저감용 공기 베어링 해석)

  • Lee Sung-ho;Rhim Yoon-chul
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
    • /
    • 2004.11a
    • /
    • pp.175-185
    • /
    • 2004
  • Rotating disks are used in various machines such as data storage device, gyroscope, circular saw, etc. Transverse vibration of a rotating disk is very important for the performance of these machines. This work proposes a method to suppress transverse vibration of a very flexible rotating disk in non-contacting manner. A system considered in this study is a very flexible rotating disk with a thrust bearing pad which is located underneath the rotating disk. The pressure force generated in the gap between the rotating disk and the thrust pad pushes the rotating disk in the direction of axis of rotation while the centrifugal force and the elastic recovery force push the rotating disk in reverse direction. The balance between these forces suppresses the transverse vibration of the rotating disk. A coupled disk-fluid system is analyzed numerically. The finite element method is used to compute the pressure distribution between the thrust pad and the rotating disk while the finite difference method is used to compute the transverse vibration of a rotating disk. Results show that the transverse vibration of the rotating disk can be suppressed effectively for certain combination of air bearing and operating parameters.

  • PDF

Behavior Analysis and Empirical Relation for a Flexible Disk with High Speed Rotation (고속회전 유연디스크의 거동해석과 경험식)

  • Lee, Ho-Ryul;Rhim, Yoon-Chul
    • Transactions of the Society of Information Storage Systems
    • /
    • v.2 no.4
    • /
    • pp.245-250
    • /
    • 2006
  • Organizations such as broadcasting stations and libraries which deal with huge amount of information require high-capacity storage systems for archiving their materials and information. It is necessary and urgent for the storage people to develop a compact, high capacity, and low-cost data storage systems. Even though the Blue-ray technology is commercialized and now it is on the market, demand for the compact and low-cost system is still increasing. A flexible disk system has been introduced recently to satisfy above mentioned requirements. The system uses multiple of thin disks and is expected to achieve technical requirements. However, decreasing the disk thickness makes it difficult to read and write data because it decreases the disk rigidity so that the transverse vibration of the rotating disk increases easily due to both the interaction with surrounding air and the vibration characteristics of thin flexible disk itself. In this study, flat-type stabilizer is proposed to suppress the transverse vibration of a $95{\mu}m$-thick polycarbonate disk. Characteristics of disk vibration have been studied through the results of numerical analysis from the fluid mechanics point of view. Numerical simulation is verified through the experiment by measuring the gap between the rotating disk and the stationary flat stabilizer. The axial deflections of the disk are computed for various rotating speeds and reference gap sizes and then a method of regression is applied to those data. As a result, an empirical relation is proposed for the steady deformation shape of the rotating disk.

  • PDF

Finite Element Analysis of Vibration of HDD Disk-Spindle System with Rigid Complex Spindle and Flexible Shaft (복잡한 형상의 강체 스핀들과 유연축을 고려한 HDD 디스크-스핀들 계의 고유진동 유한요소해석)

  • Lee, Sang-Hoon;Jang, Gun-Hee
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2000.11a
    • /
    • pp.784-789
    • /
    • 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.

  • PDF

Vibration Analysis of the Shaft-duplicate Disk System (축-이중 원판계의 진동해석)

  • Chun, Sang-Bok;Lee, Chong-Won
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.21 no.6
    • /
    • pp.896-906
    • /
    • 1997
  • The effect of duplicate flexible disks on the vibrational modes of a flexible rotor system is investigated by using an anlytical method based on the assumed modes method. The rotor model to be analyzed consists of duplicate disks on a flexible shaft. In modeling the system, centrifugal stiffening and disk flexibility effects are taken into account. To demonstrate the effectiveness of the method, a hard disk drive spindle system commonly used in personal computers and a simple flexible rotor system with two disks are selected as examples. In particular, the dynamic coupling between the vibrational modes of the shaft and the duplicate disks is investigated with the shaft rotational speed varied.

GYROSCOPIC EFFECT ON MODE SPLITTING IN ROTATING DISK: HDD SPINDLE SYSTEM VIBRATIONS

  • Lee, Chong-Won
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 1997.10a
    • /
    • pp.43-49
    • /
    • 1997
  • A rotating rigid disk, attached on a flexible shaft or supported by a torsional spring, experiences precessional whirling due to gyroscopic moment loading. It is well known in rotor dynamics area that, as the rotational speed increases, the precessional mode of the rotating rigid disk starts splitting into two: forward and backward precessional modes. On the other hand, it is also well known in disk vibration area that a rotating flexible disk also shows another kind of mode splitting phenomenon due to the rotation, resulting in forward and backward traveling waves. When rotating multiple flexible disks are coupled in vibration with the supporting Flexible shaft, the associated mode splitting should be compatible with the two seemingly different vibration analysis methods. This paper investigates the possibility of fusing the precessional and traveling wave mode splittings so that the bending coupled disk vibrations in HDD spindle systems can be better understood.

  • PDF

A Study on the Torque Transmitting Capability of a Disk Coupling by Finite Element Analysis (유한요소해석을 이용한 디스크 커플링의 토크전달 능력에 대한 연구)

  • Seo, Won Sang;Kim, Sung Muk;Kim, Jong-Bong
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.30 no.11
    • /
    • pp.1171-1177
    • /
    • 2013
  • In this study, the torque transmitting capability of a flexible disk coupling was investigated. Flexible disc coupling is used to transmit power between two axes, and there exist mis-alignments such as angle of deviation and end play between two shafts. A disk is an important part in the flexible disk coupling because the disk has to transmit power between two mis-aligned shafts. To investigate the effect of mis-alignment on load carrying capacity, finite element analyses were carried out. Analyses were carried out for two types of disk; i.e., circular and square disks. The rotational and bending stiffness of disk plates was predicted to investigate the effect of mis-alignment on stress. As a result, it was shown that the mis-alignment can cause severe decrease in load-carrying capacity. And, the square disk showed better performance than the circular disk.

A Study on the Behavior of a Spinning Flexible Disk near a Curved Wall (곡률이 있는 벽면근처에서 고속회전하는 유연디스크의 거동 해석)

  • Lee, Ho-Ryul;Rhim, Yoon-Chul
    • Transactions of the Society of Information Storage Systems
    • /
    • v.2 no.3
    • /
    • pp.201-207
    • /
    • 2006
  • Information storage devices have been studied to increase the storage capacity and the data transfer rate as well as to decrease the access time and their physical sizes. Optical information storage devices have been achieved high-capacity by reducing optical spot size remarkably due to the development of Blue-ray technology. Optical information storage devices usually use 1.2mm-thick polycarbonate(PC) media to get high enough stiffness. However, it would be better if we can decrease the thickness of a disk for achieving thinner device while keeping the capacity as large as possible. Decreasing the thickness of the storage media makes it difficult to read and write data because it increases the transverse vibration of the rotating disk due to the interaction with surrounding air and the vibration characteristics of thin flexible disk itself, Therefore, a special design based on the fluid mechanics is required to suppress the transverse vibration of the disk in non-contact manner so that the optical pickup can read/write data successfully. In this study, a curved wall is proposed as a stabilizer to suppress the transverse vibration of a $95{\mu}m$-thick PC disk. The characteristics of disk vibration due to a curved wall have been studied through numerical and experimental analysis from the fluid mechanics point of view. The proposed shapes are possible candidates as stabilizers to suppress the transverse vibration of a flexible disk which rotates at high speed.

  • PDF

A study on the Flexible Disk Grinding Process with Variable Control Stages (절삭속도제어 구간에 따른 유연성 디스크 연삭가공에 관한 연구)

  • 신관수
    • Journal of the Korean Society of Manufacturing Technology Engineers
    • /
    • v.9 no.1
    • /
    • pp.81-87
    • /
    • 2000
  • A variable cutting speed control model was developed to be implemented for the flexible disk grinding process Control algorithm was based on the error referred by the discrepancy between current disk angle and intended one that are pro-posed to produce desired resulting depth of cut. Controller was implemented in two different aspect One was to initiate the control law from the beginning while the other was to activate as soon as the disk start to produce ground surface i.e. The beginning of the between edges stage. Several performance analysis were conducted comparing various process parameters such as cutting force disk angle depth of cut and disk speed with respect to process transition time Tentative results revealed that controller implemented from the earlier stages of the process showed better performance than the other revealed that controller implemented from the earlier stages of the process showed better performance that the other.

  • PDF