• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.3
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• pp.127-132
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• 2010

Eigensolutions associated with self-excited vibration of disc brake system can be obtained by complex eigenvalue analysis. The eigenvalue sensitivity to change in contact stiffness can be used to demonstrate stability criteria and eigenvalue veering. Dynamic instability on eigenvalue loci with respect to the variation of contact stiffness is found to be related to mode interaction between two adjacent modes. This modal interaction can be effectively shown by mode shape visualization. This paper presents the methodology to construct the mode shape of disc brake system where a disc and two brake pads are coupled with contact stiffness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.6 s.249
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• pp.615-621
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• 2006

Increased application of optical disks requires more improved dynamic stability of rotating disks. In this study, a new concept of controlling the processing conditions of injection molded disks was developed to improve vibration characteristics. The critical speed, which shows stiffness and dynamic stability of disk, is affected by the residual stress distribution; this varies as functions of distance from the gate and processing condition. The critical speed of disk was calculated with the initial stress taken into consideration, which was determined from injection molding simulation. Choosing melt temperature, mold temperature, filling speed and packing pressure as design parameters, critical speed is maximized with the method of response surface. It is shown that the stability of injection molded disk has been improved for the new condition obtained as a result of the study proposed.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.664-669
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• 2003

Recently, the recording density of hard disk drives has improved at an annual percentage rate of 100%. Therefore for faster access, higher disk rotational speeds will be required. The influence of the airflow produced by the rotation of a disk on the positioning accuracy has become a serious topic of research and the aerodynamic aspect of hard disk drives is now quite considerable with the increases in recording density and higher rotational speeds. Unsteady airflow in an actual hard disk drive is numerically simulated by using LES(Large Eddy Simulation) technique, we could predicted and aerodynamic mechanism that was related actuators' surroundings in HDD. At a result, with modifying the various shapes of the E-block and Damper, we estimated the characteristic of the influence of airflow in HDDs.

• Transactions of the Society of Information Storage Systems
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• v.8 no.1
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• pp.22-26
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• 2012

Optical disk drives (ODDs) are subjected to vibrations caused by the high-speed rotation of the optical disk, and these vibrations can be excessive and reduce the read/write performance. Elastic rubber mounts with cushioning materials are often used to minimize these problems. In this paper, the source of vibrations was identified by experimental modal tests and high-speed photography. Structural modifications were made based on a lumped parameter model and a finite element model.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.121-122
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• 2006

In the case of mechanical control systems, it is highly useful to be able to provide a compact model of the mechanical system to control engineers using the smallest number of variables, while still providing an accurate model. The reduced mechanical model can then be inserted into the complete mechanical control system models and used for system-level dynamic simulation. In this paper, a moment-matching based model order reduction (MOR) which reduces the number of degrees of freedom of an original finite element model via the Arnoldi process is considered to study the dynamic responses of a HDD actuator and suspension system.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.129-137
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• 2001

As the rotational speed and the track density are increased, the vibration of disk/spindle system becomes critical issue. In this work, we propose a simple inclined air bearing(20mm${\times}$20mm) system which is positioned very near to the rotating disk especially compact disc(CD) as a flexible disk, and we investigate suppressing effect about disk mode (0,0) both experimentally and numerically. We find dynamic stiffness and damping coefficients of bearing and apply to the disk vibration. The results show about 10 percent errors comparing to the experimental results. Also we investigate experimentally the reduction of disk vibration and power consumption with two different kinds of inclined bearing for normal disk drive system, which has tray and cover. We find inclined air bearing can decrease about 30 percents of the original disk vibration amplitude.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.309-314
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• 2004

The experimental loop was designed and installed to measure the disc positions, disc back stop load and differential pressure with flow velocity for 3 inch and 6 inch swing check valves. The tests were performed at various conditions of upstream flow disturbance source and distance from the tested check valves to investigate the effect of the upstream flow conditions on the disc stability of the swing check valves. The selected disturbance sources were elbow, globe valve, and orifice. The experimental results are presented herein.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.11
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• pp.742-748
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• 2000

This paper presents a numerical method to analyze the electromechanical-coupled field in the spindle motor of a computer hard drive and investigates dynamic response due to the electromechanical excitation, i.e. unbalanced magnetic force and centrifugal force for the rotational asymmetric motor. Magnetic field is calculated from Maxwells equation and voltage equation by introducing nonlinear time-dependent finite element analysis. Mechanical motion of rotor is calculated by solving Newton-Euler equation. Electromechanical excitation and dynamic response are characterized by analyzing the free response of a rotating rotor and Fourier analysis of the excitation force and resulting vibration of a rotor. It shows that centrifugal force produces the unbalanced magnetic force even in the rotational symmetric motor. It also shows that resonance produces quite considerable vibration even when the high excitation frequency with small amplitude matches with the natural frequency of the spindle motor.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.3
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• pp.569-574
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• 2008

In Because DTV comes to origin of car body shock or brake pedal flutter occurrence in car. This in development of measurement device that can examine this in driver protection dimension or at production early sending of goods visual point purpose of this study have. In this paper, I developed portable Brake Judder measurement system by use of the DTV.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1379-1388
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• 2008

In this paper, we present the equations of motion by which the natural vibration of a rotating annular disk can be accurately analyzed. These equations are derived from the theory of finite deformation and the principle of virtual work. The radial displacements of annular disk which is rotating at constant angular velocity are determined by non-linear equations formulated using 1-dimensional finite elements in radial direction. The equations of the in-plane vibrations at disturbed state are also formulated using 1-dimensional finite elements in radial direction along the number of nodal diameters. They are expressed as in functions of the radial displacements at the steady state and the disturbed displacements about the steady state. In-plane static deformation modes of the annular disk are used as the interpolation functions of 1-dimensional finite elements in radial direction. The natural vibrations of an annular disk with different boundary conditions are analyzed by using the presented model and the 3-dimensional finite element model to verify accuracy of the presented equations of motion. Its results are compared and discussed.