Modification of mode shapes of rotating disk by non-uniform gap between disk and shroud

摘要

Experiments on disk flutter of hard disk drives with non-uniform gap between disks and a shroud were conducted. In this experiments, polyester tapes were partly attached on the shroud so that the shroud gap was changed along the circumference of the disks. Three non-axisymmetric normal modes of the disk were measured, and these amplitude had extremal values at the circumferential position where the shroud gap was narrowest. These vibration modes should not appear if the shroud gap is uniform. Numerical simulation with non-uniform shroud gap was performed, and normal modes of a rotating disk were computed. The mode shapes of these normal modes well matched those of the measured vibration modes. Therefore, it is thought that mode amplitude at a specified point can be decreased by aerodynamic damping force.