• Proceedings of the KSME Conference
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• 2001.06b
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• pp.601-606
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• 2001

Free vibration analysis was performed for a spinning disk/spindle system mounted on a flexible baseplate. A simplified model was presented considering the effects of the baseplate flexibility on a disk/spindle system, and the equations of motion were derived by the assumed mode method and Lagrange's equation. From the results of the tree vibration analysis, the variations of the natural frequencies were investigated by changing rotating speed, baseplate thickness. They were attributed to the coupling between the flexible modes of the spinning disk/spindle system and the baseplate. This simplified model was used to predict the dynamic characteristics of a small size disk drive. The validity of the simplified model was verified by experiments and FE analysis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.3
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• pp.206-214
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• 1991

Flow field in a hard disk drive has been predicted numerically. Theoretical model was constructed based on a commercially available hard disk drive with 40 Mega byte capacity. Since the gap between disk tip and shroud is not homogeneous in real hard disk drive, three kinds of gap size have been tested as computational model. The discussion has been made on the circumferential velocity, radial velocity, and pressure fields. As a result, the average shear stress on the disk surface was reduced as the gap size decreased. This means that the shroud should be designed compactly to reduce power consumption of the spindle motor.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.946-949
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• 2002

Particulate contamination is known to be a significant cause of failures of removable storage media. In this work, The effect of particles on the surface damage of removable hard disk media was investigated. The particles of different materials and size were introduced to the head-disk interface using a particle injection system. It was found that the particles of particulate size and property serious damaged the media. This study showed that cleaning pad is effective for reducing particle contamination, except for the particles of specific size and property. As a means to removed the particles of specific size, the concept of using a stepped taper at the leading edge of the slider is proposed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.1
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• pp.30-38
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• 1987

One of the important characteristics of a disk valve is the thrust force. This thrust force has close relationship to the clearance between valve and valve seat in the disk valve. When the clearance is very small, it is very important to analyze the thrust force. This paper deals with the variation of the thrust force by comparing the experimental ed results and theoretical results in accordance with d the valve clearance. In case of the theoretical problems, the pressure gradient of the radial flow in a narrowly spaced disks was calculated by Sui Lin and Pai-Mow Lee already. Therefore, the thrust force of the disk valve was computed by utilizing this pressure gradient in the radial flow. In the experiment, the hydraulic oil which has high viscosity was used. Making the comparative study of the calculated results and the experimental results, the characteristics of the thrust force in the disk valve were investigated. The results obtained are as follows: 1. When the disk valve clearance was comparatively small, the experimental values had fairly good agreement with the calculated values independently of inlet pressure and valve size. 2. When the disk valve size was constant in the wide range of the disk valve clearance, the lower the inlet pressure was, the better the agreement between the experimental values and the calculated values was. 3. In case of the small clearance, the thrust force was depended on the outer diameter of the disk valve. In opposite case the thrust force was constant as the disk valve size varied.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.179-183
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• 2005

Particles in the HDD can cause serious damages such as scratches and thermal asperity(TA) at the head/disk interface(HDI). Accordingly, particles cause data loss including physical and electrical damages. To improve the reliability of head-disk interface, understanding the damage characteristics at the HDI due to particle interactions is required. The materials such as $A1_2O_3$, TiC and aluminum were used in this experiment. The size and hardness of particles injected into the HDI are closely relevant to surface damage caused the data loss on the disk and head. In this paper, a variety of scratches were analyzed using scanning electron microscope(SEM) and atomic force microscope(AFM). In order to analyze defects of very small size on the disk, optical surface analyzer(OSA) was also used.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.4
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• pp.183-188
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• 2003

Particulate contamination is known to be a significant cause of failures of removable storage media. In this work, the effect of particles on the surface damage of removable hard disk media was investigated. The particles of different materials and size were introduced to the Head Disk Interface (HDI) using a particle injection system. It was round that the particles of particulate size and property serious damaged the media. This study showed that cleaning pad is effective for reducing particle contamination, except fer the particles of specific size and property. As a means to remove the particles of specific sire. the concept of using a stepped taper at the leading edge of the slider is proposed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.669-672
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• 1999

In this paper, we studied the properties of small-size disk-type ultrasonic motor using travelling wave for the application to the precise control robotic joint motor and fabricated it. The diameter of the ultrasonic motor fabricated was 13mm. Also, the piezoelectric vibrator was constructed by piezoelectric ceramic and elastic material. The piezoelectric ceramic was composed to PZ-PT-PMN which was shown the high electromechanical stability under high vibration level and stainless steel was used as the elastic material in which configuration was disk-type. To conform the capability of application to robotic motor, we measured the change of rotational speed according to applied voltage and applied frequency. As the results, the small-size disk-type ultrasonic motor was able to fabricate, and the revolution speed was 350 (rpm) when input voltage was 55 (Vrms) and applied frequency 160.4 IkHz] under pre-load.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.1
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• pp.61-69
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• 1998

Vapor Axial Deposition (VAD), one of optical fiber preform fabrication processes, is performed by deposition of submicron-size silica particles that are synthesized by combustion of raw chemical materials. In this study, flow field is assumed to be a forced uniform flow perpendicularly impinging on a rotating disk. Similarity solutions obtained in our previous study are utilized to solve the particle transport equation. The particles are approximated to be in a polydisperse state that satisfies a lognormal size distribution. A moment model is used in order to predict distributions of particle number density and size simultaneously. Deposition of the particles on the disk is examined considering convection, Brownian diffusion, thermophoresis, and coagulation with variations of the forced flow velocity and the disk rotating velocity. The deposition rate and the efficiency directly increase as the flow velocity increases, resulting from that the increase of the forced flow velocity causes thinner thermal and diffusion boundary layer thicknesses and thus causes the increase of thermophoretic drift and Brownian diffusion of the particles toward the disk. However, the increase of the disk rotating speed does not result in the direct increase of the deposition rate and the deposition efficiency. Slower flow velocity causes extension of the time scale for coagulation and thus yields larger mean particle size and its geometric standard deviation at the deposition surface. In the case of coagulation starting farther from the deposition surface, coagulation effects increases, resulting in the increase of the particle size and the decrease of the deposition rate at the surface.

• Korean Journal of Optics and Photonics
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• v.8 no.4
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• pp.255-259
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• 1997

In this paper, the result of a performance study on a home-built spinning disk type confocal microscope is presented. The confocal microscope was fabricated with a Nipkow disk made of the made of the microfilm. The throughput of the disk was 0.5%, allowing the observation of specimen with higher reflectivities only. A laser diode at 692.7nm was used as the light source. The topographic structures of a PC ROM and the CD ROM were observed with sufficient reliability, while the effect of the convolution of the beam size with the finite object size was found dominant. Also the shadowing effect by the etched pattern was observed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3386-3394
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• 1994

An experimental study has been performed on the flow over a rotating disk, where the diameter of the disk is 500 mm and the maximum vertical deviation of the upper surface is $50 \mu{m}$ for the whole range of the angular velocity up to 3400 rpm. The flow visualization experiment for the wall jet flow induced by impinging circular jet is carried out using schlieren system and measurements are made by 3-hole and 5-hole pitot tubes. Schlieren photographs show that as the rotating speed increases the wall jet flow becomes more stable and the size of the largest eddies becomes smaller. Measurements for impinging jet flow on the stationary disk verify the accuracy of the present experiment, and those for free rotating disk flow display the existence of transition region from laminar to turbulent flows. Measurements for impinging jet flow on the rotating disk exhibit the interaction between the wall jet and the viscous pumping effect, which explains the decay in size of turbulent eddies illustrated by the schlieren photographs.