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Magnetic Storage

A Lubrication Equation Incorporating Two-Dimensional Roughness Effects, With Emphasis on the Patterned Data Islands of a Recording Disk

[+] Author and Article Information
James White

6017 Glenmary Road,Knoxville, TN 37919

J. Tribol 134(1), 011901 (Feb 09, 2012) (12 pages) doi:10.1115/1.4005519 History: Received May 20, 2011; Revised December 02, 2011; Published February 08, 2012; Online February 09, 2012

Current industrial applications require a consideration of two-dimensional surface roughness effects in design and optimization of fluid bearings. Although the influence of striated surface roughness on fluid lubrication is now at a fairly mature level of understanding, the knowledge and understanding of two-dimensional roughness effects is not nearly at the same level as that achieved over the past several decades for one-dimensional striations. The subject of this paper includes the formulation of a practical “roughness averaged” lubrication equation that is appropriate for two-dimensional surface roughness and applicable over a wide range of Knudsen numbers. After derivation by multiple-scale analysis, the resulting lubrication equation is specialized to treat the patterned data islands located on a storage medium as a two-dimensional roughness pattern, and then used to determine the effect of this roughness on the air-bearing interface between recording head slider and disk. The roughness averaged lubrication equation is solved numerically by a variable-grid finite-difference algorithm, and computed results are included for several bearing geometries.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

The patterned data island disk orientation: (a) coordinate system (b) data island and recess roughness element

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Figure 2

The slider and disk orientation

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Figure 3

Wedge slider pressure contours as functions of the dimensionless slider coordinates (skew angle = 15 deg): (a) ɛ=0 (b) ɛ=0.5 (c) ɛ=1.0 (d) ɛ=1.5

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Figure 4

Net lift ratio as a function of dimensionless recession depth and roughness element island area ratio

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Figure 5

Femtosized vacuum cavity sliders: (a) symmetric slider (b) asymmetric slider

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Figure 6

Symmetric vacuum cavity slider pressure contours as functions of the dimensionless slider coordinates (skew angle = 0): (a) ɛ=0 (b) ɛ=0.5

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Figure 7

Symmetric vacuum cavity slider pressure contours as functions of the dimensionless slider coordinates (skew angle = 15 deg): (a) ɛ=0 (b) ɛ=0.5

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Figure 8

Contours of the k4 roughness averaging term as functions of the dimensionless slider coordinates for the symmetric vacuum cavity slider (skew angle = 0, ɛ=0.5)

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Figure 9

k4 profiles of the symmetric vacuum cavity slider as functions of the dimensionless slider coordinates near the slider trailing edge (skew angle = 0, ɛ=0.5): (a) two-dimensional contours (b) three-dimensional profile

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Figure 10

Asymmetric vacuum cavity slider pressure contours as functions of the dimensionless slider coordinates (skew angle = 15 deg): (a) ɛ=0 (b) ɛ=0.5

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