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TECHNICAL PAPERS

Experimental and Theoretical Investigation of Bouncing Vibrations of a Flying Head Slider in the Near-Contact Region

[+] Author and Article Information
Kyosuke Ono

Storage Technology Research Center, Central Research Laboratory, Hitachi Ltd., 2880 Kozu, Odawara-shi, Kanagawa-ken, 256-8510, Japankyosuke.ono.jk@hitachi.com

Masami Yamane

 Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8552, Japan

J. Tribol 129(2), 246-255 (Nov 15, 2006) (10 pages) doi:10.1115/1.2464131 History: Received January 06, 2006; Revised November 15, 2006

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.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Outline of experimental setup

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Figure 2

Air-bearing surface configuration of the sliders used for experiments: (a) Slider A and (b) Slider B

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Figure 3

Structure of the slider and suspension, and measurement points

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Figure 4

RMS values of bouncing vibrations of slider A and B as a function of decreasing and increasing ambient pressure, and calculated nominal flying height (FH) of each slider: (a) Slider A and (b) Slider B

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Figure 5

Frequency characteristics of bouncing vibrations just after touch-down and just before take-off of slider A: (a) after touch-down and (b) before take-off

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Figure 6

Frequency characteristics of bouncing vibrations just after touch-down and just before take-off of slider B: (a) after touch-down and (b) before take-off

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Figure 7

Repeatability of slider motion at three trials of touch down: (a) destabilization process of slider A at TD pressure of 0.41atm. and (b) destabilization process of slider B at TD pressure of 0.38atm.

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Figure 8

Two-LDV system for measurement of slider motion at two close points

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Figure 9

Measured three-dimensional motion of unstable bouncing vibration just before take-off (slider A): (a) motions at points B and C and (b) motions at points C and D

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Figure 10

Variation of pitch static angle θ by changing Z-height: (a) side view of slider and suspension and relationship between Z-height (ZH) and pitch static angle θ, and (b) calculated variation of θ and FH as a function of ZH (slider A)

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Figure 11

Effect of Z-height on the characteristics of touch-down and take-off pressure (slider A)

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Figure 12

Time history of the trailing edge at the touch-down point (slider A)

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Figure 13

2-DOF analytical model of a flying head slider and a disk surface

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Figure 14

Contact characteristics

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Figure 15

Calculated hysteresis characteristics of bouncing vibration during decreasing and increasing of nominal flying height (σ=0.1nm, β=0.2, fm=10mN, Fμ=50mN)

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Figure 16

Calculated time history and frequency spectrum of trailing-edge motion (σ=0.1nm, β=0.2, fm=10mN, Fμ=50mN): (a) Time histories of trailing edge and center of mass and (b) Frequency spectrum of trailing edge

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Figure 17

Calculated time history of trailing edge at the touch-down points (σ=0.1nm, β=0.2, Fμ=50mN): (a) fm=10mN and (b) fm=20mN

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Figure 18

Calculated effect of initial conditions on slider dynamics at FH=6nm (f1=96kHz, f2=149kHz, σ=0.4nm, β=0.2). (i) Time history and (ii) Frequency spectrum: (a) Initial height zp0=6nm and (b) zp0=50nm.

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Figure 19

Calculated effect of initial conditions on slider dynamics at FH=6nm (f1=96kHz, f2=149kHz, σ=0.1nm, β=0.2). (i) Time history and (ii) Frequency spectrum: (a) Initial height zp0=6nm and (b) zp0=50nm.

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