• Title/Summary/Keyword: Asymmetric Spinning

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The Trend of New Technology in Metal Spinning (Metal 스피닝의 신기술 동향)

  • Lee, Tae-Ho
    • Journal of the Korean Society of Propulsion Engineers
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    • v.16 no.1
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    • pp.79-85
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    • 2012
  • This study investigates mainly on the technical development trend through the published papers, such as asymmetric metal spinning, metal spinning in heat treatment conditions and free mandrel spinning. Although the classical spinning, so called conventional, shear, tube spinning, uses the axisymmetric shaped mandrel(which is same inner shape of the final product), in new technologies the mandrel can be asymmetric one, spinning can be done without mandrel and also spinning is done with heat treatment together.

Finite Element Forced Response of a Spinning Flexible HDD Disk-spindle System Considering the Asymmetry Originating from Gyroscopic Effect and Fluid Dynamic Bearings (자이로스코픽 효과와 유체 동압 베어링에 의한 비대칭성을 고려한 회전 유연 디스크-스핀들 시스템의 유한요소 강제 진동 해석)

  • Park, Ki-Yong;Jang, Gun-Hee;Seo, Chan-Hee
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.10
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    • pp.915-922
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    • 2010
  • This paper presents an efficient method for determining the forced response of a spinning flexible disk-spindle system supported by fluid dynamic bearings(FDBs) in a computer hard disk drive(HDD). The spinning flexible disk-spindle system is represented by the asymmetric finite element equations of motion originating from the asymmetric dynamic coefficients of the FDBs and the gyroscopic moment of a spinning disk-spindle system. The proposed method utilizes only the right eigenvectors of the eigenvalue problem to transform the large asymmetric finite element equations of motion into a small number of coupled equations, guaranteeing the accuracy of their numerical integration. The results are then back-substituted into the equations of motion to determine the forced response. The effectiveness of the proposed method was verified by comparing it with the responses from the classical methods of mode superposition with the general eigenvalue problems, and mode superposition with modal approximation. The proposed method was shown to be effective in determining the forced response represented by the asymmetric finite element equations of motion of a spinning flexible disk-spindle system supported by FDBs.

New Technology of Metal Spinning (Metal 스피닝의 신기술 동향)

  • Lee, Tae-Ho
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.04a
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    • pp.265-271
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    • 2011
  • This paper investigates mainly on the technical development trend such as asymmetric technology and the metal spinning in heat treatment conditions. Although the classical spinning, so called conventional, shear, tube spinning, uses the axisymmetric shaped mandrel(which is same inner shape of the final product), new technology does not use it. and also spinning can be done with free mandrel.

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An Elastohydrodynamic Lubrication of Elliptical Contacts : Part II - The Effect of Spin Motion (타원접촉의 탄성유체윤활 : 제2보 - 스핀운동의 영향)

  • Park, Tae-Jo
    • Tribology and Lubricants
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    • v.23 no.2
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    • pp.49-55
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    • 2007
  • A numerical analysis of elastohydrodynamic lubrication of elliptical contacts with both rolling and spinning has been carried out. A finite difference method with non-uniform grid systems and the Newton-Raphson method are applied to solve the problems. The velocity vectors resulting from combined spinning and rolling/sliding motion lead to asymmetric pressure distributions and film shapes. Pressure distributions, film contours and variations of the minimum and central film thicknesses are compared with various spin-roll ratios. Reduction of the minimum film thickness under spinning is remarkable whereas the central film thickness is relatively less. The spin motion have large effect on variations of the minimum film thickness with load parameter which are small in pure rolling/sliding cases. Therefore present numerical scheme can be used in the analysis of general elliptical contact EHL problems and further studies are required.

Finite Element Modal Analysis of a Spinning Flexible Disk-spindle System Supported by a Flexible Base Plate in a HDD (유연한 베이스 플레이트로 지지되는 회전 유연 HDD 디스크-스핀들계의 유한 요소 진동 해석)

  • 한재혁;장건희
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.571-577
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    • 2003
  • This research proposes a finite element method to determine the natural vibration characteristics of the spinning disk-spindle system in a HDD including the flexibility of supporting structure. Finite element equations of each substructure are derived with the introduction of consistent variables to satisfy the geometric compatibility at the internal boundaries. The natural frequencies and modes from the global asymmetric matrix equations of motion are determined by using the implicit restarted Arnoldi iteration method. The validity of the proposed method is verified by the experimental modal testing. It also shows that the flexibility of base plate plays an important role to determine the natural frequencies of the spinning disk-spindle system in a HDD.

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REMOVAL OF DISSOLVED OXYGEN USING PVDF HOLLOW FIBER MEMBRANE CONTACTOR

  • Lee, Ki-Sub;Park, You-In;Yeon, Sun-Hwa;Sung, Kyung-Soo;Rhim, Ji-Won;Lee, Kew-Ho
    • Proceedings of the Membrane Society of Korea Conference
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    • 2003.07a
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    • pp.133-135
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    • 2003
  • The removal of dissolved oxygen(DO) from water was studied using a poly(vinyliene fluoride)(PVDF) hollow fiber membrane contactor(HFMC) with the vacuum degassing process(VDP), Asymmetric porous PVDF hollow fiber membranes (HFM) for membrane contactor were prepared by a wet phase inversion method. In spinning of these PVDF hollow fibers, dimethy lacetamide (DMAc), LiCl and pure water were used as a solvent, a pore-forming additive and internal/external coagulant, respectively. The characteristics of the structure(pore size, porosity etc.) of the prepared PVDF HFMs as a function of concentration of pore-forming additive in polymer dope solution were studied. Also, the removal efficiency of DO from water according to flow rates of water, using PVDF HFMC with VDP, was studied. The performance of the asymmetric porous PVDF HFMC and a symmetric porous PP HFMC commercialized were compared. As a result, the asymmetric porous PVDF HFMC showed higher removal efficiency of DO than that of a symmetric porous PP HFMC.

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Preparation of Asymmetric Folyethersulfone Hollow Fiber Membranes for Flue Gas Separation (온실기체 분리용 폴리이서설폰 비대칭 중공사 막의 제조)

  • Kim Jeong-Hoon;Sohn Woo-Ik;Choi Seung-Hak;Lee Soo-Bok
    • Membrane Journal
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    • v.15 no.2
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    • pp.147-156
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    • 2005
  • It is well-known that polyethersulfone (PES) has high $CO_2$ selectivity over $N_2\;(or\;CH_4)$ and excellent pressure resistance of $CO_2$ plasticization among muy commercialized engineering plastics[1-4]. Asymmetric PES hollow fiber membranes for flue gas separation were developed by dry-wet spinning technique. The dope solution consists of PES, NMP and acetone. Water and water/NMP mixtures are used in outer and inner coagulants, respectively. Gas permeation rate (i.e., permeance) and $CO_2/N_2$ selectivity were measured with pure gas, respectively and the micro-structure of hollow fiber membranes was characterized by scanning electron microscopy. The effects of polymer concentration, ratio of NMP to acetone, length of air gap, evaporation condition and silicone coating were investigated on the $CO_2/N_2$ separation properties of the hollow fibers. Optimized PES hollow fiber membranes exhibited high permeance of $25\~50$ GPU and $CO_2/N_2$ selectivity of $30\~40$ at room temperature and have the apparent skin layer thickness of about $0.1\;{\mu}m$. The developed PES hollow fiber membranes, would be a good candidate suitable for the flue gas separation process.

DYNAMIC CHARACTERISTICS OF SPINNING DISK VIBRATION INFLUENCED BY CENTRIFUGAL AIRFLOW (광자기 기록 장치에서의 디스크 진동과 회전 공기 유동 특성에 관한 연구)

  • 김수경;송인상;손희기
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1998.04a
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    • pp.206-210
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    • 1998
  • A study on dynamic characteristics of rotating disks in magneto optical disk drives is presented. Natural frequencies of rotating disks are investigated experimentally and numerically. The frequency response and critical speeds of the ASMO disk are discussed. The characteristics of airflow around the disk and their effects on disk vibrations are also investigated. It is found that the numerical calculation of the natural frequencies of rotating disks agrees well with the experimental results. The airflow around the disk in the cartridge affects the characteristics of the disk vibrations to reduce the modal frequencies of the disk. The experiment shows that negative vertical offsets of the disk in the cartridge possibly increase the vibration amplitudes. As being influenced by the geometry of the cartridge, the rotation of the disk causes an asymmetric airflow in the presence of window.

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Vortex Pairing and Jet-Spreading in an Axisymmetric Jet under Helical Fundamental and Axisymmetric Subharmonic Forcing (헬리컬 기본교란과 축대칭 분수조화교란을 이용한 원형제트에서의 보텍스 병합 및 제트확산)

  • Cho, Sung Kwon;Yoo, Jung Yul;Choi, Haecheon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.11
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    • pp.1610-1624
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    • 1998
  • An axisymmetric jet is forced with two helical fundamental waves of identical frequency spinning in opposite directions and an additional axisymmetric sub harmonic wave. The subharmonic component rapidly grows downstream from subharmonic resonance with the fundamental, significantly depending on the initial phase difference. The variations of the subharmonic amplitude with the initial phase difference show cusp-like shapes. The amplification of the sub harmonic results in 'vortex pairing of helical modes'. Furthermore, azimuthal variation of the amplification induces an asymmetric jet cross-section. When the initial subharmonics is imposed with an initial phase difference close to a critical value, the jet-cross section evolves into a three-lobed shape. One lobe is generated by the enhanced vortex pairing and the other two lobes are generated by the delayed vortex pairing. Thus, it is confirmed that the initial phase difference between the fundamental and the subharmonic plays an important role in controlling the jet cross-section.

Modification of Silica Nanoparticles with Bis[3-(triethoxysilylpropyl)]tetrasulfide and Their Application for SBR Nanocomposite (Bis[3-(triethoxysilylpropyl)]tetrasulfide에 의한 실리카 입자의 표면개질 반응과 SBR 나노 복합체 응용)

  • Ryu, Hyun Soo;Lee, Young Seok;Lee, Jong Cheol;Ha, KiRyong
    • Polymer(Korea)
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    • v.37 no.3
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    • pp.308-315
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    • 2013
  • In this study, we performed surface modification of silica nanoparticles with bis[3-(triethoxysilylpropyl)]tetrasulfide (TESPT) silane coupling agent to study the effects of treatment temperature, treatment time, and amount of TESPT used on the silanization degree with Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), elemental analysis (EA) and solid state $^{13}C$ and $^{29}Si$ cross-polarization magic angle spinning (CP/MAS) nuclear magnetic resonance spectroscopy (NMR). We found peak area of isolated silanol groups at $3747cm^{-1}$ decreased, but peak area of $-CH_2$ asymmetric stretching of TESPT at $2938cm^{-1}$ increased with the amount of TESPT from FTIR measurements. We also used universal testing machine (UTM) to study mechanical properties of styrene butadiene rubber (SBR) nanocomposites with 20 phr (parts per hundred of rubber) of pristine and TESPT modified silicas, respectively. The tensile strength and 100% modulus of modified silica/SBR nanocomposite were enhanced from 5.65 to 9.38MPa, from 1.62 to 2.73 MPa, respectively, compared to those of pristine silica/SBR nanocomposite.