• Title/Summary/Keyword: disk laser

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Visualization of the Flow Pattern Between Co-rotating Disks in HDD (HDD의 동시 회전 디스크 내부 유동 패턴의 가시화)

  • Kong Dae-Wee;Joo Won-Gu;Doh Deug-Hee
    • 한국가시화정보학회:학술대회논문집
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    • 2003.11a
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    • pp.67-70
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    • 2003
  • Hard disk drives (HDD) in computer are used extensively as data storage capacity. The trend in the computer industry to produce smaller disk drives rotating at higher speeds requires an improved understanding of fluid motion in the space between disks. Laser sheet and digital camera was used for 2-dimensional visualization of the unsteady flow between the center pair of two co-rotating disks in air with a cylindrical enclosure (or shroud). Geometric parameters are gap height (H) between disks, and gap distance (G) between disk tip and shroud. The lobe-structured boundary between inner region and outer region was detected by inserted particles, and the number of dominant vortices was determined clearly It is found from flow visualization that the number of vortex cells can be correlated with Reynolds number based on H which is defined as $Re_H={\Omega}RH/v$ ranging from $3.18\times10^3\;to\;1.43\times10^4$, and decreases as the disk speed increases. The lobe pattern by vortex cells is changed to a circular pattern for the wide gap than narrow one.

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Microstructural Observation of Phase Change Optical Disk by TEM (투과전자현미경을 이용한 상전이형 광디스크의 미세조직 관찰)

  • Kim, Soo-Chul;Kim, Gyeung-Ho
    • Applied Microscopy
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    • v.29 no.4
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    • pp.493-498
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    • 1999
  • With increasing demand for fast and reliable, yet economical data storage devices, the role of optical disk technology is becoming more important. In recent years, advanced laser technology combined with new materials has given the competitive edge over the traditional magnetic memory devices both in memory capacity and reliability of data retrieval. Continuing effort is being put into developing smaller and more complex structures for optical disks to increase their memory density. Characterization of such multilayered structure requires not only high spatial resolution for observation but also laborious specimen preparation. In this paper, the method of preparing optical disk specimens for TEM characterization is described in detail. The microstructural features in optical disks observed by TEM are also discussed.

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Visualization of the Flow Pattern Between Co-rotating Disks in Shroud (원통형 케이스 내의 동시회전 디스크 내부 유동패턴의 가시화)

  • Kong, Dae-Wee;Joo, Won-Gu
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1661-1665
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    • 2004
  • Hard disk drives (HDD) in computer are used extensively as data storage capacity. The trend in the computer industry to produce smaller disk drives rotating at higher speeds requires an improved understanding of fluid motion in the space between disks. Laser sheet and digital camera was used for 2-dimensional visualization of the unsteady flow between co-rotating disks in air with a cylindrical enclosure (or shroud). Geometric parameters are gap height (H) between disks, and gap distance (G) between disk tip and shroud. The lobe-structured boundary between inner region and outer region was detected by inserted particles, and the number of dominant vortices was determined clearly It is found from flow visualization that the number of vortex cells can be correlated with Reynolds number based on H which is defined as $Re_H={\Omega}RH/v$ ranging from $7.96{\times}10^2$ to $1.43{\times}10^4$, and decreases as the disk speed increases. The lobe pattern by vortex cells is changed to a circular pattern for the wide gap than narrow one.

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Scanning confocal microscope using a quad-detector (4분할 photodiode를 이용한 scanning confocal microscope)

  • 유석진;김수철;이진서;권남익
    • Korean Journal of Optics and Photonics
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    • v.8 no.2
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    • pp.165-168
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    • 1997
  • We have constructed a scanning confocal microscope using a 780 nm semiconductor laser, an actuator of a compact disk player and a quad-detector. This device detects heights and characteristics of a surface. The laser focus was located at the surface of a sample by using the error signal obtained by a quad-dector, and the current supplied to the actuator for lens was displayed as a height. The materials of a surface were classified according to reflected total intensities and was displayed by different color in a monitor. The device has very samll dimensions of 30 mm$\times$20 mm$\times$20 mm and scan field is 1.6 mm$\times$1.6mm. We obtained two images, one using only reflected light and the other using an error signal from a quad-detector and compared these two images.

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Experimental Study for the Mixing Effect of the Driven Bar on Rotating Flow in a Closed Cylinder (원통내 회전유동에서 회전봉의 형상이 혼합효과에 미치는 영향에 관한 실험적 연구)

  • Kim, Yu-Gon;Kim, Dong-Gyu
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.2
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    • pp.156-163
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    • 2001
  • The experiment is conducted on the rapidly rotating incompressible flow within a confined cylinder using LDV(Laser Doppler Velocimetry). The configurations of interest are the flows between a rotating upper disk with a bar and a stationary lower disk enclosed within a cylinder. The flow is considered to be an axisymmetric undisturbed basic flow. The results show that the flow is strongly dependent on the radius and the shape of bar but is negligibly affected by the Reynolds number in turbulent flow. It is observed that in the lid-driven case the main forms near the wall as the Reynolds number increases. The thin bar causes the second axial flow due to the suction effect and the thick bar causes the main flow to be pulled toward the surface of the bar. The step bar shows the dual effect of the two. 1:2 tilt bar shows that the main flow distributes wider than the other cases in which interference occurs due step bar.

Effect analysis in Laser Metal Deposition of SKD61 using AISI M2 power (AISI M2 파우더를 이용한 SKD61 재질의 레이저 메탈 디포지션 기초 특성 분석)

  • Kim, Won-Hyuck;Jung, Byung-Hun;Oh, Myeong-Hwan;Choi, Seong-Won;Kang, Dae-Min
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.14 no.3
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    • pp.50-56
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    • 2015
  • In this study, AISI M2 powder was selected primarily through various pieces of literature in order to improve the hardness and wear resistance. Among the laser metal deposition parameters, laser power was studied to improve the deposition efficiency in the laser metal deposition using a diode-pumped disk laser. An SKD61 hot work steel plate and AISI M2 powder were used as a substrate and powder for laser metal deposition, respectively. Experiments for the laser metal deposition were carried out by changing the laser power and track layer. The quality of the track surface and cross-section after applying the single-layer method was better than that obtained from applying the multi-layer method. As the laser power increased, the track thickness was increased, and the surface roughness deviation was decreased. In laser power condition of 1.6kW, the maximum hardness of the deposition track was 790Hv. This value was 40% better than the hardness of the SKD61 after heat treatment.

Application of Regression Analysis for Quality Control In Suspension Manufacturing

  • Ritthidetch, Thammasak;Masuchun, Ruedee;Chaikla, Amphawan;Julsereewong, Prasit;Tirasesth, Kitti
    • 제어로봇시스템학회:학술대회논문집
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    • 2004.08a
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    • pp.704-709
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    • 2004
  • This paper presents the laser processing to adjust the roll and pitch directions of the flex suspension assembly for hard disk drive production. The adjustment is accomplished using a number of laser beam projections that can be approximated using the regression model of the existing measured roll and pitch directions. Information derived from the analysis can be applied to control the quality of flex suspension assembly. The performances of the proposed technique were observed using the flex suspension assembly plant in Thailand as an illustrative case study. The experimental results are given to support the improving manufacturing yields and some economic benefits of the proposed technique.

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The Detection of Defects in Ferromagnetic Materials Using Magneto-Optical Sensor (자기광학센서를 이용한 강자성체 결함 탐상)

  • Kim, Hoon
    • Journal of Power System Engineering
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    • v.8 no.3
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    • pp.52-57
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    • 2004
  • A new non-destructive inspection technique has been developed. One characteristic of the technique is that defects are visualized by laser ray. Magnetic domains and domain walls of a magneto-optical sensor(MO sensor) are varied by the magnetic flux leaked by defects, and the variations are observed by the reflected light of the laser ray. The information of defect can remotely be inspected by this technique in a real time. This paper describes the results estimated on the 2-dimensional surface defects and opposite-side defects in a ferromagnetic material and the natural surface defect in a clutch disk wheel. The light region of a visible image and the magnitude of a reflected light increases as the input current of the magnetizer increases. The natural surface defect, that has not the width of crack's open mouth, can be also visualized like as 2-dimensional artificial defects.

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A Study of the Retina Image Controllability using a Sledge (망막 영상 조절 장치에 관한 연구)

  • 이숙희;이영춘;양연식
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.10a
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    • pp.273-276
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    • 1997
  • Seeing is an intelligent act. Retina is the most important part among the components of eye which is comprised of iris, pupil, lens, optic disk, and so forth. Because retina acts like a photo receiver to detect light from every object, if damaged, animals have a severe problem to live along with themselves and sometimes they lose their sight. In the ophthalmology, doctors use special instrument to see exact retina image of object and operate the surgery by rotating focus control knob. In this study, a basic test is done to achieve the auto focus control instrument. Specially made sledge and attenuator are installed on the optic bed to change the distance and laser power between the first reflective mirror and the second one. Control panel which is compiled by Visual C t t to control stepping motors ,laser power and photodiode are implemented with ADA-board.

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Simple Modeling for Laser Scribing (레이저 화선의 모델링)

  • Chung, Chulsup
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2002.10a
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    • pp.94-103
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    • 2002
  • Accurately controlling the shape of the read/write head structure is critical in the performance of a modern hard disk drive. The sliders investigated are composed of alumina and titanium carbide (AlTiC) and act as an air bearing when passing over the disks. Controlling the curvature of the slider is of primary importance. A laser scribing system that produces curvature by Inducing residual stress into the slider can be utilized. Predicting the curvature created by a pattern of scribes is of great importance to increase the control over the sliders' shape. Using finite element analysis a force system that produces stresses similar to the laser scribing is applied. The curvatures created by the force system are calibrated to experimental measurements.

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