INCREASING THE NATURAL FREQUENCIES OF CIRCULAR DISKS USING INTERNAL CHANNELS

This paper investigates a new design for computer disk drive disks that raises their natural frequencies. In this new design, a pattern of small, dense, internal channels or voids is distributed axisymmetrically about the midplane of the disk. These channels increase the natural frequencies of the disk by removing mass from the midplane of the disk while maintaining the coupling between the deflections of the upper and lower surfaces of the disk. This practice is commonly employed in I-beams and honeycombed sandwich panels, but the channeled geometry proposed here has not been previously considered or studied. This paper presents a detailed analytical model for a channeled disk, specifications for optimal channeled disk design, and experimental corroboration. Numerical results show that the natural frequencies of a properly channeled disk can be 10–100% higher than those of a uniform disk, depending on the size of the channels. The orientation of the channels does not significantly affect the natural frequencies, but, in the optimal design, the channels do not extend through the whole disk. Instead, they begin at an optimal, central, transition radius and radiate outward to the outer edge of the disk. Disks with this optimal channel design may be competitive with uniform thickness disks for disk drive applications in terms of both natural frequency and cost.