Experimental and theoretical investigation of bouncing vibrations of a flying head slider in the near-contact region

We experimentally and theoretically investigated in detail bouncing vibrations of a flying head slider in the near-contact region between the head and disk surface. By changing the Z-height in the experiment, we evaluated the effect of the pitch static angle on the ambient pressure at which unstable bouncing vibration starts and stops. We found that the touch-down and take-off pressure hysteresis decreased as the pitch static angle increased even though the flying height at the trailing edge decreased slightly. From detailed measurement of the slider dynamics at the threshold of the bouncing vibration, we found that the trailing edge of the slider was first attracted to the disk. As the pitch static angle decreased, the magnitude of the first drop of the trailing edge increased and the bouncing vibration amplitude increased more rapidly. We also measured the mode of the bouncing vibration by using two laser Doppler vibrometers simultaneously. By using an improved two-degree-of-freedom slider model, in which the small micro-waviness and the shearing force of the lubricant were taken into account, we could analyze the touch-down/take-off hysteresis, mode, and destabilization process of the bouncing vibration similar to the experimental results. We also theoretically found that either self-excited bouncing vibration. with lower pitch frequency or forced vibration with higher pitch frequency was generated, depending on the magnitudes of the micro-waviness and the disturbance.