Flow induced vibration of magnetic head suspension in hard disk drive

Measurements of fluctuations in the flying height of a magnetic head-slider and in the strain of its suspension in a 14" hard disk drive reveal two dominant suspension vibration components. One is a 2 kHz bending mode, and the other is a 2.9 kHz torsional mode. The bending mode vibration causes the flying height fluctuations. The vortex street behind a section model of the suspension are visualized using the smoke-wire method. The frequency of the street is higher than the frequencies of the two modes. In a free jet, the amplitudes of the two components are both in proportion to the square of the flow velocity, and their frequencies remain constant. A natural vibration mode analysis of the suspension gives similar modes with similar frequencies. These results indicate the two components are forced vibration with the natural vibration frequencies of the suspension due to flow force acting on it. To predict the flow force, a computer program using the discrete vortex method is developed. The calculated drag coefficient is about 70% larger than the one obtained experimentally from the visualized vortex street behind the section model.