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RESEARCH PAPERS

Experimental and Numerical Investigation of Dynamic Instability in the Head Disk Interface at Proximity

[+] Author and Article Information
Rohit Ambekar

Department of Mechanical Engineering, University of California, Berkeley, CA 94704rohit@cml.berkeley.edu

Vineet Gupta

Department of Mechanical Engineering, University of California, Berkeley, CA 94704vineet@cml.berkeley.edu

David B. Bogy

Department of Mechanical Engineering, University of California, Berkeley, CA 94704dbogy@cml.berkeley.edu

J. Tribol 127(3), 530-536 (Mar 23, 2005) (7 pages) doi:10.1115/1.1924429 History: Received March 01, 2004; Revised March 23, 2005

As the flying height decreases to achieve greater areal density in hard disk drives, different proximity forces act on the air bearing slider, which results in fly height modulation and instability. Identifying and characterizing these forces has become important for achieving a stable fly height at proximity. One way to study these forces is by examining the fly height hysteresis, which is a result of many constituent phenomena. The difference in the touchdown and takeoff rpm (hysteresis) was monitored for different slider designs, varying the humidity and lubricant thickness of the disks, and the sliders were monitored for lubricant pickup while the disks were examined for lubricant depletion and modulation. Correlation was established between the observed hysteresis and different possible constituent phenomena. One such phenomenon was identified as the Intermolecular Force from the correlation between the lubricant thickness and the touchdown velocity. Simulations using 3D dynamic simulation software explain the experimental trends.

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Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) 18 nm (pico) slider; (b) 7 nm CML (pico) slider. (Note: The ABS of 5nm design is very similar to 7 nm design.)

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Figure 2

Velocity profile for hysteresis tests

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Figure 3

Hysteresis observed at zero humidity for 18 nm slider

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Figure 4

Dependence on ambient humidity for 18 nm slider

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Figure 5

Effect of lubricant pickup for 18 nm slider

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Figure 6

Effect of lubricant thickness on touchdown rpm for 7 nm slider

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Figure 7

Variation of touchdown rpm as a function of lubricant thickness for various slider designs (experimental results)

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Figure 8

Multilayer model for modeling intermolecular forces

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Figure 9

Variation of intermolecular forces (simulations)

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Figure 10

Fly height diagram (simulations)

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Figure 11

Variation of touchdown rpm as a function of lubricant thickness for various slider designs (simulation results)

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