Improved Analysis of Unstable Bouncing Vibration and Stabilizing Design of Flying Head Slider in 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

Department of Mechanical and Control Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology, Tokyo 152-8550, Japanfwjd8106@mb.infoweb.ne.jp

J. Tribol 129(1), 65-74 (Aug 20, 2006) (10 pages) doi:10.1115/1.2401214 History: Received May 19, 2006; Revised August 20, 2006

This paper describes an improved analytical study of the bouncing vibration of a flying head slider in the near-contact region and gives quantitative designs guideline for realizing a stable flying head slider, based on the results of a parametric study. First, we numerically calculated the general characteristics of the contact and adhesion forces between a smooth contact pad and disk surface by considering asperity contact, the lubricant meniscus, and elastic bulk deformation. As a result, it was shown that the contact characteristics can be represented by a simple model with five independent parameters when the asperity density is large and the asperity height is small as in cases of current slider and disk surfaces. Then, we numerically computed the slider dynamics in a two degree of freedom slider model with nonlinear air-bearing springs by using the simplified contact characteristic model. As a result, we have obtained a self-excited bouncing vibration whose frequency, amplitude and touchdown/takeoff hysteresis characteristics agree much better with the experimental results compared with our previous analysis. From a parametric study for takeoff height, we could obtain design guidelines for realizing a stable head slider in a low flying height of 5nm or less.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Rough surface contact model: (a) model of contact between the slider pad and disk surface with asperity and bulk deformation; (b) meniscus in the toe-dipping regime

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Figure 2

Comparison of the external contact force and the contact stiffness between the present model and the GW model (S=20×20μm2, ρ=30μm−2, R=2.0μm, hl=1.0nm): (a) external contact force Fc; (b) contact stiffness kcr=−ΔFcr∕Δd

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Figure 3

External contact force Fc, internal contact force Fcr, and adhesion force Fm versus separation (S=15×15mm2; ρ=30mm−2, σ=0.5nm, hl=1nm)

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Figure 4

Effects of the contact pad area S and the asperity density ρ on the separation widths of the transient zone and the hysteresis of Fc between the approaching and separating processes (σ=0.5nm)

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Figure 5

2DOF analytical model of a flying head slider

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Figure 6

Model of the adhesion force Fm, the external contact force Fc, and the internal contact force Fcr as a function of the separation d

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Figure 7

Time histories of the displacements at the trailing and leading edges and the frequency spectrum of the trailing edge displacement (kf0=5.0×105N∕m, r=2.4, ζf=ζr=0.01, kc=5.0×106N∕m, μ=1.0, fm=10mN, ds=3.0nm, de=4.0nm, FH=7nm)

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Figure 8

Motion of the slider from the start of contact (1) to the highest bounce height (4) at the trailing edge under the condition of unstable bouncing vibration. During contact, the friction force does work on the slider

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Figure 9

Three different states of the slider under disturbances as a function of the nominal flying height FH (kf0=5.0×105N∕m, r=2.4, ζf=ζr=0.01, kc=5.0×106N∕m, μ=1.0, fm=10mN, ds=3.0nm, de=4.0nm)

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Figure 10

Effect of the adhesion force on the CFH (kf0=5.0×105N∕m, r=2.4, ζf=ζr=0.01, kc=106N∕m, μ=1.0, ds=3.0nm, de=4.0nm)

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Figure 11

Effect of the contact stiffness on the CFH (kf0=5.0×105N∕m, r=2.4, ζf=ζr=0.01, μ=1.0, fm=10mN, ds=3.0nm, de=4.0nm)

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Figure 12

Effect of the contact hysteresis on the CFH (kf0=5.0×105N∕m, r=2.4, ζf=ζr=0.01, kc=106N∕m, μ=1.0, fm=10mN, ds=3.0nm)

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Figure 13

Effect of the frictional coefficient on the CFH (kf0=5.0×105N∕m, r=2.4, ζf=ζr=0.01, kc=106N∕m, fm=10mN, ds=3.0nm, de=4.0nm)

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Figure 14

Effect of the front air-bearing stiffness and rear-to-front air-bearing stiffness ratio on the CFH (ζf=ζr=0.01, kc=106N∕m, μ=1.0, fm=10mN, ds=3.0nm, de=4.0nm)

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Figure 15

Effect of the front and rear air-bearing damping ratios on the CFH (kf0=5.0×105N∕m, r=2.4, kcr=106N∕m, μ=1.0, fm=10mN, ds=3.0nm, de=4.0nm)



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