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Research Papers: Magnetic Storage

High Velocity Oblique Impact and Coefficient of Restitution for Head Disk Interface Operational Shock

[+] Author and Article Information
Raja R. Katta

Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801

Andreas A. Polycarpou1

Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801polycarp@illinois.edu

Jorge V. Hanchi, Robert M. Crone

 Seagate Technology LLC, Minneapolis, MN 55416

1

Corresponding author.

J. Tribol 131(2), 021903 (Mar 05, 2009) (9 pages) doi:10.1115/1.3078770 History: Received June 06, 2008; Revised December 16, 2008; Published March 05, 2009

With the increased use of hard disk drives (HDDs) in mobile and consumer applications combined with the requirement of higher areal density, there is enhanced focus on reducing head disk spacing, and consequently there is higher susceptibility of slider/disk impact damage during HDD operation. To investigate this impact process, a dynamic elastic-plastic finite element model of a sphere (representing a slider corner) obliquely impacting a thin-film disk was created to study the effect of the slider corner radius and the impact velocity on critical contact parameters. To characterize the energy losses due to the operational shock impact damage, the coefficient of restitution for oblique elastic-plastic impact was studied using the finite element model. A modification to an existing physics-based elastic-plastic oblique impact coefficient of restitution model was proposed to accurately predict the energy losses for a rigid sphere impacting a half-space. The analytical model results compared favorably to the finite element results for the range from low impact angles (primarily normal impacts) to high impact angles (primarily tangential impacts).

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Elastic-plastic CM-based impact model for homogeneous glass: (a) δ versus t, and (b) contours of max δ

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Figure 2

Finite element model mesh used for the impact analysis; sphere radius R=10 μm

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Figure 3

Oblique impact von Mises stress field for R=10 μm, Vy=0.5 m/s, and Vx=10 m/s; (a) overall view and (b) zoomed in view

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Figure 4

Normal impact von Mises stress field for R=10 μm and Vy=0.5 m/s; (a) overall view and (b) zoomed in view

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Figure 5

Oblique impact: contact parameters for R=10 μm, Vy=0.5 m/s, and Vx=10 m/s: (a) displacement δ (designated as Y-Disp) and (b) contact pressure pm

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Figure 6

Normal impact: contact parameters for R=10 μm and Vy=0.5 m/s; (a) displacement δ (designated as Y-Disp) (b) contact pressure pm

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Figure 7

Tangential surface traction: R=10 μm, Vy=0.5 m/s, and μ=0.2; (a) oblique impact and (b) normal impact

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Figure 8

Maximum penetration δ comparison for CM-based (normal), FEA normal, and FEA oblique impact models (R=10 μm)

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Figure 9

Schematic of oblique impact process showing the different velocity components

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Figure 10

Comparison of analytical normal impact models with FEA results for R=10 μm

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Figure 11

Coefficient of restitution e and its components (ex, ey) as a function of the impact angle θ (R=10 μm, μ=0.2)

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Figure 12

Proposed analytical model, Eq. 6 for ex as a function of impact angle θ when gross slip occurs: (a) R=10 μm and (b) R=25 μm

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Figure 13

Proposed analytical model for ex compared with FEA results when μ=0.2: (a) R=25 μm and (b) R=50 μm

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Figure 14

Proposed analytical model for ex compared with FEA results applicable in practical disk drive impact range when Vx=10 m/s; (a) R=10 μm and (b) R=25 μm

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