• Journal of Fisheries and Marine Sciences Education
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• v.28 no.5
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• pp.1470-1477
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• 2016

This study has designed and evaluated the safety of watertight damper for Offshore Rigs. The watertight damper is an improved design for conventional DN 350 butterfly valve. Numerical analysis has been performed to investigate the safety factor and seat leakage of the designed 3-type disk dampers. The structure analysis results present the deformations, the equivalent stresses and the safety factor. It was confirmed that the designed disk, rib-disk and streamlined disk of watertight damper are safe enough in maximum operating pressure of 0.98MPa. The results show that the disk damper had the smallest maximum deformations and stress among 3-type disk dampers and the safety factor was 4.3. Therefore it is confirmed that the disk damper has the most excellent strength. Also linear static structural analysis was individually conducted for disk and body. The results show that the maximum disk deformation was larger than the body deformation, Therefore the disk damper is causes no seat leakage.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.3
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• pp.201-207
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• 2004

High speed rotating airflow inside a HDD chamber causes sub-micron scale disk vibration that could generate significant TMR problems in most of current HDD products. Many publications are presented for the reduction of airflow excitation. One of the most effective methods widely adopted in high-end HDD products is SqueezeAir Bearing Plate (SABP). However, because of its tight assembly clearance between the damper and disk, this method could not be easily implemented in volume production. This article presents a disk damper design that is modified to be feasible for volume production by virtue of a new airflow modeling method.

• Journal of Power System Engineering
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• v.20 no.6
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• pp.80-86
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• 2016

In this study, The watertight damper was designed to improve conventional DN 350A butterfly valve. The FSI(Fluid-Structure Interaction) analysis has performed to investigate the safety factor for the watertight damper. When watertight damper of disk was closed, the disk of pressure value is constant. However depending on the opening angle of disk, the flow velocity and pressure are changed. The maximum velocity was appeared at the end of disk on the small outlet area of duct. When the opening angel of disk is $90^{\circ}$, the maximum velocity was appeared at the center of ending disk. So we were found the opening angle of disk is bigger, the flow rate is increased and velocity is also increased from the result of FSI analysis. We can find the least deformation and stress when the opening angel of damper is $90^{\circ}$. When the $45^{\circ}$ opening angle of disk, the largest deformation and stress was found and the minimum safety factor 1.3 was calculated. As a result, we found that the structure of watertight damper is safe enough irrespective of opening angel.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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• pp.126-132
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• 2008

The vibration and disturbances from operating the compact disk layer have an effect on the play ability. As the excitation sources of the compact disk player, there are the vibration of the motors and gears, impact by mechanical parts and the external excitations. So, most of the compact disk player have a anti-vibrational system, which is included some rubber or oil dampers. In this study, the vibration characteristics of rubber damper which is used home compact disk player are investigated. The materials and shape of rubber damper are changed, and the transmissibility is measured. As a conclusion, the natural frequency is moved to higher frequency and the transmissibility is reduced by the increasing rubber stiffness. In comparison to butyl rubber damper, the transmissibility of silicon damper was increased by larger restitution elasticity. The hollow damper was effective to reduced the transmissibility.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.363-368
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• 2002

A practical implementation method of squeeze-film aeroelastic disk vibration damping and its practical design performance are presented to provide a solution method to meet the tight TMR(Track Mis-Registration) design budget of high-TPI HDDs. Most previous research results are mainly based on the component-level study in the 'open-cover state' which is far from the realistic operation HDD condition. In this study, the squeeze-film disk damping effect is widely investigated under the realistic drive-level condition of 'enclosed-cover state.' It is found that the proper aeroelastic gap(s) between disk(s) and adjacent surface(s) to give significant vibration reduction in the enclosed HDD operating conditions can be achieved not only by classical well-known squeeze-film damping gaps such as very small 0.0x-millimeter level gaps which are not practically implementable in mass-production HDDs, but also by a few 0.x millimeter which is possible for designing realistic HDD design. The various experimental results including drive-level PES are also presented to prove feasibility of the optimal disk damper design for 93kTPI HDDs.

• Journal of the Korean Institute of Gas
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• v.13 no.6
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• pp.1-8
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• 2009

This study pertains to damping device to reduce vibrational responses and shocks in multi-directions. To enhance the capability of disk spring damper which works for vertical vibration and shock, a multi-directional damper is proposed, which contains wedge system as well as disk spring stack. Wedge system converts horizontal load into vertical load. A mathematical model is proposed and investigated for the nonlinear behaviors of the disc spring damper containing wedge system. The results accord with the experimental results. Equivalent viscous damping in vertical and horizontal directions are found based upon energy dissipated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.340.2-340
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• 2002

A practical implementation method of squeeze-film aeroelastic disk vibration damping and its practical design performance are presented to provide a solution method to meet the tight TMR(Track Mis-Registration) design budget of high-TPI HDDs. Most previous research results are mainly based on the component-level study in the 'open-cover state' which is far from the realistic operations HDD condition. (omitted)

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.2038-2046
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• 1997

In this paper the instability of the system which has a disk and a mass-spring-damper system interacting through a medium having stiffness and damping is analyzed. To solve the equations of motion of this systme, it is assumed that the solution consists of the eigenfunctions which are the products of the Bessel functions and sine or cosine functions. The former represents the radial characteristics of the disk and the latter represents the circumferential characteristics. Using this assumed solution and the orthogonality of the eigenfunctions, the equations of motion can be transformed into a set of equations of motion with variables dependent only on the time. After this set is changed to the state equation, the eigenvalue problem can be made. Once the eigenvalues are calculated according to the angular velocity of the disk, the dynamic characteristics ofthis system is obtained. Because the thickness of the disk and the element characteristics of the mass-spring-damper system have important effects on the stability of the system, it will be understood how these factors affect the system and then a method to ameliorate the stability of the system with a disk will be presented.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.248-253
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• 2005

The recording density of a hard disk drive is increasing so rapidly that the storage capacity of a commercial HDD in PC reaches several hundred giga bytes recently. Many technologies related to the HDD, such as servo, media, actuator dynamics, thermo and fluid dynamics, etc. must be developed together to realize high recording density. Especially, researches in the airflow inside the HDD cavity become important as the rotational speed of a disk increases. Typical problem due to the airflow is the vibration of an actuator as the airflow collides with an I-block, suspensions and sliders, that is, FIV(Flow Induced Vibration). This problem is one of the significant sources of increasing TMR so that it must be resolved. In this research, a disk damper shape has been modified to minimize the effects of airflow on the actuator. Modified disk dampers which change flow field inside HDD cavity show good effects not only on the disk (tufter but also on the vibration of an actuator. Vibrations of E- block and slider have been measured with LDV and the airflow field inside the HDD cavity has been analyzed using a commercial package to verify these effects.

• Transactions of the Society of Information Storage Systems
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• v.2 no.1
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• pp.32-37
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• 2006

The recording density of a hard disk drive(HDD) has been increased so rapidly that the storage capacity of a commercial HDD for the personal computer already reaches several hundred giga-bytes recently. Many technologies related to the HDD, such as servo, media, actuator dynamics, thermo and fluid dynamics, etc. must be developed together to realize higher recording density. Especially, airflow inside the HDD cavity has been concerned as the rotational speed of the disk increases. Typical problem due to the airflow is the off-track vibration of a head stack assembly(HSA) as the airflow collides with the E-block, suspensions, and sliders, i.e., the flow induced vibration(FIV). This problem is one of the most significant sources of the track mis-registration(TMR) so that it must be resolved. In this study, disk damper shape is modified to minimize the influence of airflow on the HSA. Modified disk dampers, which change the flow field of the inside cavity of a HDD, show good effects not only on the disk vibration but also on the off-track vibration of a HSA. Vibrations of E-block and slider have been measured with LDV and the airflow field inside the HDD cavity has been analyzed with commercial CFD program to verify these effects.