| Summary: | 碩士 === 國立中正大學 === 機械系 === 90 === Increasing the data storage capacity of an optical disk accompanied by the demands of high data access rates and high positioning accuracy of head/write heads has recently become a stringent necessity. With the increased demands in performance, the optical disk drive needs to be high speed and more stable. However, considerable vibration problems become apparent as the increase of the optical disk rotating speed. For a high-speed disk drive, the flutter instability caused by fluid-structure interactions becomes apparent and leads to track misregistration. The purpose of this research is to predict the fluid-induced disk response using finite element method when the disk drive is rotating in high-speed. Three top covers with different shapes of an optical disk drive have been chosen to investigate the aerodynamic effect of the shapes on the disk stability. Results show that the cover shape influences velocity fields of the rotating flow and then alters the characteristics of secondary recirculating vortex. Furthermore, coupling advection effects between streamlines affect the distribution of fluid pressure on the optical disk. All the effective pressure frequencies of three different top covers are close to the nature frequency corresponding to the first axisymmetric mode of the disk and leads to the disk self-excited vibration. Nevertheless altering the shape can improve the disk response caused by the effective pressure almost 50% when compared to the original shape of the top cover. Eventually, an optimization procedure combined with the algorithm developed here seems to be feasible to determine the top cover shape that can convert the energized pressure into a stabilized one. Then the high-speed optical drives can operate more stable.
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