Analysis of Contact Characteristics of Small Rough Surfaces Taking Bulk Deformation and Meniscus Force Into Consideration

[+] 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, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552, Japanfwjd8106@mb.infoweb.ne.jp

J. Tribol 129(3), 453-460 (Jan 13, 2007) (8 pages) doi:10.1115/1.2736426 History: Received May 05, 2006; Revised January 13, 2007

We numerically investigated the characteristics of contact force, adhesion force, and contact stiffness between a smooth contact pad and a small rough surface, such as a current magnetic disk surface. The computer-generated asperity had an isotropic Gaussian distribution with a small asperity height and high asperity density. We took asperity contact, bulk deformation, and meniscus force of a lubricant layer at contacting asperity into consideration in the calculations. We evaluated the effects of asperity density, contact pad area, asperity radius, root mean square (RMS) asperity height, and lubricant thickness on external and internal contact forces, adhesion force, and contact stiffness as a function of the separation between the contact pad and disk in both approaching and separating processes. We found that contact and adhesion force tend to change suddenly at the start and end of contact and exhibits hysteresis in the approaching and separating processes when asperity density becomes large and RMS asperity height becomes small comparable with current head sliders and magnetic disks. We also found that contact stiffness is governed by bulk deformation and that the contact stiffness and adhesion force can be regarded as constant during contact when the asperity density increases, the RMS asperity height decreases, and the contact area increases.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Rough surface contact model with asperity and bulk deformation

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Figure 2

Meniscus model in toe-dipping regime

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Figure 3

Effect of asperity density on contact characteristics (σ=0.5nm, S=10μm×10μm, R=2.0μm, hl=1.0nm). (a) External contact force Fc, (b) ratio of adhesion force to its minimum value Fa∕∣Famin∣, (c) internal (real) contact force Fcr, and (d) contact stiffness kcr.

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Figure 4

Separations at start and end of contact and minimum external contact force as function of asperity density (σ=0.5nm, S=10μm×10μm, R=2.0μm, hl=1.0nm)

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Figure 5

Effect of a contact pad area on contact characteristics (σ=0.5nm, ρ=30μm−2, R=2.0μm, hl=1.0nm)

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Figure 6

Relationship between ratio of contact stiffness and contact pad area at each asperity density (R=2.0μm, hl=1.0nm)

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Figure 7

Effect of radius of curvature of asperity summit (S=20×20μm2, σ=0.5nm, ρ=30μm−2, hl=1.0nm)

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Figure 8

Effect of RMS asperity height on contact characteristics (S=20×20μm2, ρ=10μm−2, R=2.0μm, hl=1.0nm)

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Figure 9

Effect of lubricant thickness on contact characteristics (S=20×20μm2, σ=0.5nm, ρ=10μm−2, R=2.0μm)




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