• Composites Research
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• v.13 no.6
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• pp.55-62
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• 2000

The strength test was done for the Carbon/Carbon rotor disk which is the critical part of a carbon/carbon brake system in an operating time. The loading fixture was designed for the static strength test of a single carbon/carbon brake disk using finite element analysis. To simulate the real dynamic system in a static condition, the friction surface of the rotor disk was fixed and static load was applied to the rotor slot in the circumferential direction. The described failure mechanism of the brake disk can be described as matrix cracking occurred first at the contact surface of the rotor slot, subsequent delamination from the cracked contact surface, and the final fracture at the notch of the rotor.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.716-720
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• 1996

In this work the surface damage mechanism of hard disk was investigated. Experiments were peformed to simulate the contact during start and stop. Evidence of significant surface damage appeared after 20,000 cycles. It was found that despite higher hardness, the slider showed more signs of damage than the disk. Optical microscopy showed that the surface was damaged by abrasive action as well as adhesion of wear debris.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.556-561
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• 2006

In this study, the failure of the automotive clutch disk was investigated. During the process of power transmission, clutch disk plates did repeated work of releasing and engaging the pressure plate. The effects of unbalance rotation in the abnormal vibration and torque amplitude under engaged state were measured from this experiment. In order to reduce the unbalance, a modified clutch disk shape was developed. With a three-dimensional model of the stopper pin, to predict fatigue fracture, finite element analysis was carried out and evaluated the improvement of the new clutch disk.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.322-326
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• 2001

Hard disk drive(HDD) consists of a head/slider system which flies over the magnetic disk at an extremely low height. As the density of HDD increases the flying height of the head needs to be decreased. This increases the chance for contact between the slider and the disk. This paper addresses some key issues related to surface failure characteristics of HDD. It is shown that flying behavior of the slider during contact-start-stop cycle can be analyzed based on different regimes of air film lubrication, experimental methods for identifying the underlying mechanisms and improving the reliability of HDD are discussed.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.2
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• pp.35-42
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• 2000

In recent years the recording density of hard disks has increased significantly largely due to the decreasing flying height. As a result of decreased flying height, the reliability issue become more critical. In this work the relationship between hard disk surface damage and data loss was investigated by using an actual hard disk drive. The purpose of this research was to identify the key factor which leads to data loss. It was shown that data loss is directly related to the physical damage of the Co-magnetic layer and there was no data loss when only carbon protective coating was damaged by the diamond tip.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.234-238
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• 2006

In this research, an analysis of damaged instance and forming fault for disc part in automotive steel wheel was performed. Rolled steel material, which had been used in the manufacturing of the damaged disc part, was prepared for tensile test, quantitative analysis of chemical component and acquirement of scanning electron microscope images. Although the results of mechanical properties and chemical component ratio for the material satisfied the suggested specification, some material inherent problem was found in the scanning electron microscope images. Finally, in an analysis of chemical component for the damaged disc part used in road condition, mismatching of chemical component ratio between the suggested specification and test result was found.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.31-35
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• 2004

The speed competition of optical disk drive has been accelerated with the fast advancement of its storage density and data transmission technology. The continuous increase of the spinning speed of CD meets the unexpected and catastrophic failure of disk during the operation. The effect of its thickness and outer radius of disk were investigated to reduce stresses and J-integral around the crack tip. The effect of its thickness was considered ahead of the crack tip. In the effect of outer radius of disk, linear elastic fracture mechanics was used to obtain the critical crack length, which indicates the onset length for unstable crack growth. This approach is so significant as to detect the growing crack by disk drive before the catastrophic failure, which will provide the standard size of its safety for high-speed disk drive.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.9
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• pp.167-174
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• 1998

In this work the surface damage of head and disk of a hard disk drive was analysed using an Atomic Force Microscope. The initial damage of the disk occurred by generation of extremely small wear particles. Also it was shown that wear particles tend to pile up near the front side of the slider. The surface damage mechanism of drag test and contact-start-stop test was found to be quite similar.

• Journal of the Korean Society for Nondestructive Testing
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• v.37 no.1
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• pp.29-36
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• 2017

Recently, KTX (Korean Train Express) train stoppage accidents were mainly caused by malfunctioning equipment, aging and cracking of railway vehicles, crack breakages of brake disks, and breakages of brake disks. Breakage of brake disk can cause large-scale casualties such as high-speed collision and concern about derailment by hitting lower axle and wheel. Therefore, in this study, a brake disk with solid and ventilation type, which is the brake disk of a KTX train was modeled, and a dynamometer system was constructed to operate the disk. A Rayleigh wave was used to inspect the surface of the brake disk. An ultrasonic inspection module was developed for the brake disk by using a local immersion method due to the difficulty involved in ultrasonic inspection using an existing immersion method. In addition, the surface defects of the brake disk were evaluated using a dynamometer mock-up system and an ultrasonic inspection module of the brake disk.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.1867-1879
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• 1997

DREAM-S is a distributed main-memory database system for the real-time processing of shared operational datra in ATM switching systems. DREAM-S has a client-server architecture in which only the server has the diskstorage, and provides the T-Tree index structure for efficient accesses to the data. We propose a recovery technique for the T-Tree index structre in DREAM-S. Although main-memory database system offer efficient access performance, the database int he main-memory may be broken when system failure such as database transaction failure or power failure occurs. Therfore, a recovery technique that recovers the database (including index structures) is essential for fault tolerant ATM switching systems. Proposed recovery technique relieves the bottleneck of the server processors disk operations by maintaining the T-Tree index structure only in the main-memory. In addition, fast recovery is guaranteed even in large number of client systems since the T-Tree index structure(s) in each system can be recovered cncurrently.