• 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 Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.82-90
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• 1998

Machines that normally operate under fluid film lubricated condition also experience surface damage. This is largely due to the failure of the lubricant film which leads to boundary lubrication. Thus, it is important to have a good understanding of boundary lubrication behavior. In this paper the major tribological parameters that influence the boundary lubrication properties are evaluated. It is shown that disk roughness, hardness and normal load affect the friction and wear of metals in boundary lubrication. Also, the mechanism of surface damage is attributed to abrasion and wear particle interaction.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.365-373
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• 2002

For gas turbine engines, the safe life methodology has historically been used fur fatigue life management of failure critical engine components. The safe retirement limit is necessarily determined by a conservative life evaluation procedure, thereby many components which have a long residual life are discarded. The objective of this study is to introduce the damage tolerant design concept into the life management for aircraft engine component instead of conservative fatigue life methodology which has been used for both design and maintenance. Crack growth data were collected on a nickel base superalloy which have been subjected to combined static and cyclic loading at elevated temperatures. Stress analysis fur turbine disk was carried out. The program for computing creep-fatigue crack growth was developed. The residual lifes of turbine disk component under various temperatures and conditions using creep-fatigue crack growth data were estimated. As the result of analysis, it was confirmed that retirement fur cause concept was applicable to the evaluation of residual life of retired turbine disk which had been designed based on the conventional fatigue life methodology.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.6
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• pp.1784-1797
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• 1996

The disk/blade assembly of a turbine engine is made in the shape of a dovetail type or a fir-tree type. Since disk fillet regions or contact surfaces undergo high stress comcentration, fatigue cracks frequentrly occur in the disk/blade assembly. Therefore, it is necessary to analyze the stress distributions in the fir-tree type disk/balde assembly and predict the region of fatigue failure. The stress distributions of the disk/blade assembly were investigated by using the photoelastic method and the finite element method. Two dimensional photoelastic techniques were used to investigate the stress distributions of contact surfaces and fillet regions. TH stress distributions were obtained by the shear-difference method and were compared to the finite element results. It was found that maximum tensile stresses were higher in the fillet region thatn in the contact surfaces of the fir-tree models. The finite element results showed good agreement with the experimental results.

• Transactions on Control, Automation and Systems Engineering
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• v.3 no.3
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• pp.146-151
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• 2001

Optical disk drive has excellent advantage of random accessibility of which performance is measured by access time. However, due to the increased rotational velocity of the disk and constraints of mechanical structure, two-stage seek algorithm which executes coarse and fine seeks sequentially has been adopted in most commercial optical disk drives. Although the laser spot is moved to a target track by a single seek operation, the limited operation range of the fine actuator restricts the application of the fine seek algorithm below a few hundreds of tracks. Especially, excessive movement of the objective lens causes a failure in generation of track-cross pulse and results in an unstable seek operation. In this paper, a new control algorithm for extending the fine seek range is proposed with an appropriate control structure. The coarse actuator is utilized to reduce the misalignment between the objective lens and the laser beam axis, and the fine actuator is controlled to follow the reference velocity trajectory. The proposed algorithm is applied to a CD-ROM drive to show its feasibility and some experimental results are presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1157-1164
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• 2003

Dynamic Load/unload (L/UL) mechanism is an alternative to the contact start stop (CSS) technology which eliminates stiction and wear failure modes associated with CSS. Other benefits of L/UL include increased areal density due to smooth disk surfaces, thinner overcoats, and lower head flying height Improved shock resistance due to elimination of head slap, and reduced power consumption. Inertia latch mechanism becomes important for mobile disk drives because of non operating shock performance. Various types of latch designs have been introduced in hard disk drives to limit a rotary actuator from sudden uncontrolled motion. In this paper, a single spring inertia latch is introduced for a small form optical disk drive, which uses a rotary actuator for moving an optical pick-up. A new small inertia latch with single spring is designed to ensure both feasible and small size. The shock performance of the new inertia latch is experimentally verified.

• Journal of Digital Contents Society
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• v.16 no.1
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• pp.63-70
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• 2015

In this paper, we estimate the life cycle from acceleration life test about the hard disk of disk array of image storage of PACS. Webuil distribution was selected by the Anderson-Darling goodness-of-fit test with data of down time at $50^{\circ}C$ and $60^{\circ}C$. The equality test of shape parameter and scale parameter was conducted, so that the probability distribution estimated from data of down time at $50^{\circ}C$ and $60^{\circ}C$ was not statistically significant. The shape parameter was 1.0409, The characteristic life was 24603.5 hours at normal user condition($30^{\circ}C$) by the analysis of weibull-arrhenius modeling which included the acceleration factor of temperature, and The activation energy was 0.5011 eV through arrhenius modeling. The failure analysis of the failure samples of acceleration test and the samples of market return was conducted, so that the share percentage of failure mode was detail difference but the rank of share percentage was almost same. This study suggest the test procedure of acceleration test of hard disk drive in PACS using environment, and help the life estimation at manufacture and use.

• Composites Research
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• v.15 no.1
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• pp.41-52
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• 2002

This paper presents the thermo-elastic analysis for searching the behavior of carbon/carbon brake system during the braking period and the 3-D stress analysis to find the shape of the brake disk which is safe to the failure. The mechanical properties of the carbon/carbon brake disk were measured for both in-plane and out of plane directions. The mechanical properties were used as the input of the thermo-elastic analysis and 3-dimensional stress analysis for the brake disk. The gap between rotor clip and clip retainer is an important parameter in the loading transfer mechanism of the rotor disk. The change of gap was considered both the mechanical deformation and thermal deformation. Because the rotor clip and clip retainers were not contacted, they were excluded from the analysis model. Rotor disk was modeled by using the cyclic symmetry condition. The contact problems between rotor clip and key drum as well as between rotor disk and rotor were considered. From the results of the 3-D stress analysis, the stress concentration at the key hole of the brake disk was confirmed. The stress distributions were studied thor the variation of the rotation angle of the contact surface and the radius of curvature at the key hole part.

• KIPS Transactions on Computer and Communication Systems
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• v.12 no.4
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• pp.135-142
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• 2023

Recently, many companies are using public cloud services or building their own data center because digital transformation is expanding. The software-defined storage is a key solution for storing data on the cloud platform and its use is expanding worldwide. Software-defined storage has the advantage of being able to virtualize and use all storage resources as a single storage device and supporting flexible scale-out. On the other hand, since the size of an object is variable, an imbalance occurs in the use of the disk and may cause a failure. In this study, a method of redistributing objects by optimizing disk weights based on storage state information was proposed to solve the imbalance problem of disk use, and the experimental results were presented. As a result of the experiment, it was confirmed that the maximum utilization rate of the disk decreased by 10% from 89% to 79%. Failures can be prevented, and more data can be stored by optimizing the use of disk.

• Design & Manufacturing
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• v.7 no.1
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• pp.28-33
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• 2013

During the cold forming, due to high working pressure acting on the die surface, failure mechanics must be considered before die design. One of the main reasons of die failure in industrial application of metal forming technologies is wear. The mechanisms of wear are consisted of adhesion, abrasion, erosion and so on. Die wear affects the tolerances of formed parts, metal flow, and costs of process. The only way to control these failures is to develop a prediction method on die wear suitable in the design state in order to optimize the process. The wear system is used to analyse 'operating variables' and 'system structure'. In this study, with AISI D2, AISI 1020, AISI 304SS materials, a series of the wear experiments of pin-on-disk type to obtain the wear coefficients from Archard's wear model and the upsetting processes are carried out to observe the wear phenomenon during the cold forming process. The analysis of upsetting processes are performed by the rigid-plastic finite element method. The result of the analysis is used to investigate the die wear the processes, and the analysis simulated die wear profiles are compared with the experimental measured die wear profiles.