Abstract
As engineering technologies advance, components of all high performance products have been miniaturized and meticulous. In order to store more data and place more components, significant efforts have been put into ensuring accuracy of data accessing operations and micro-fabrication processes in disk drive and semiconductor industries, respectively. Among all the key engineering factors, it was found that reduction of disk vibrations can help achieve the aforementioned goal as well as to improve product yield and competition in the market. As the present trend in disk drive industry is to pack more data track in disk’s radial direction and more data bits along disk’s circumferential direction in the same, smaller, and thinner disk space, to assure reliability and accuracy of reading and writing data from the disk at high rotating speed, dampening vibration response of the spinning disk is thought to be the key challenge an is the primary research focus of this thesis. In this research, parameter studies of several pair of stationary sector plates that sandwich the spinning annular disk were designed and validated through experimental measurements and numerical finite element studies. Reduction of the disk’s self-induced vibrations was characterized by the damping ratios of the disk natural modes observed in its response transfer functions made by Laser Doppler Vibrometer (LDV) and an impact hammer. Parameters being investigated by this research include the distance between the disk and the sector plates (0.35 mm, 0.75 mm, and 1.00 mm), span angle (60 o, 90 o, 180 o ) of the sector plates, and rotating speed (0 rpm to 14000 rpm) of the annular disk. The damping ratio was analyzed for disk’s (0,0) Mode, (0,2) Mode and (0,3) Mode individually. From this research, significant increase of the damping ratio was observed for disk’s (0,0), (0,2)B, (0,2)F, (0,3)B, (0,3)F Modes with 180 o sector plates placed 0.35mm both sides from the disk surface. It was also observed that the damping ratio increases with increasing spin speed of the disk. Last but not the least, the disk’s backward “B” nodal diameter modes were observed to render much higher damping with the designed sector plates than the corresponding forward “F” mode pairs. The new findings made by this thesis have significant engineering implications in vibration reduction applications in high precision disk drives, optical drives as well as wafers in semiconductor industries.