Research Papers

Simulating the Air Bearing Pressure and Flying Height in a Humid Environment

[+] Author and Article Information
Shuyu Zhang

 Samsung Information Systems America, 75 West Plumeria Drive, San Jose, CA 95134Sh.Zhang@samsung.com

Brian Strom, Sung-Chang Lee, George Tyndall

 Samsung Information Systems America, 75 West Plumeria Drive, San Jose, CA 95134

J. Tribol 130(1), 011008 (Dec 26, 2007) (4 pages) doi:10.1115/1.2805424 History: Received April 02, 2007; Revised September 04, 2007; Published December 26, 2007

For a hard disk drive operating in a humid environment, the water vapor in the slider’s air bearing is typically compressed beyond its saturation vapor pressure, causing the vapor to condense. Consequently, the air bearing pressure decreases and the slider’s flying attitude adjusts to balance the forces from the suspension. A method for calculating this air bearing response to humid air is presented. Using two air bearing designs, several test cases are analyzed to illustrate the air bearing response for various temperatures and humidity levels. The calculated flying heights agree with those measured in commercial hard disk drives.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Schematic representation of the coalescence of water molecules in a control volume due to the compression that occurs in the air bearing. Fs, Msφ, and Msθ stand for the suspension force/moments acting on the slider, and φ and θ represent directions in pitch and roll angles.

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Figure 2

Flowchart for calculating the air bearing pressure and FH in a given humidity condition

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Figure 3

ABS (pico slider) used in test and numerical models. Highest surfaces are dark gray; first etch is light gray; cavity etch is white; carbon pads are black.

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Figure 4

Air bearing pressure for ABS as shown in Fig. 3: (a) pressure at RH=0%; (b) pressure after the vapor condensation at RH of 70% and 60°C ambient; (c) water vapor pressure in air bearing after vapor condensation at RH of 70% and 60°C ambient

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Figure 5

Variation of flying attitude versus humidity at 60°C

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Figure 6

Comparison of FH changes measured in drive at a temperature 53°C and the corresponding changes in FH calculated by simulation

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Figure 7

FH sensitivity to relative humidity at temperatures

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Figure 8

FH sensitivity to humidity at various temperatures comparing measured data and simulation for a different ABS than that shown in Fig. 3. (a) FH change versus RH (%); (b) FH change versus partial water pressure (atm). The measurements come from a commercial disk drive.




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