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Research Papers

Failure of Brittle and Ductile Hard Disks Due to High Shock Levels

[+] Author and Article Information
Jianfeng Xu

Center for Magnetic Recording Research, University of California, San Diego 9500 Gilman Drive, La Jolla, CA 92093john@talkelab.ucsd.edu

Izhak Etsion

Department of Mechanical Engineering, Technion, Haifa 32000, Israeletsion@technion.ac.il

Frank E. Talke

Center for Magnetic Recording Research, University of California, San Diego 9500 Gilman Drive, Mail Code 0401, La Jolla, CA 92093ftalke@ucsd.edu

J. Mech. Des 131(11), 111007 (Oct 13, 2009) (8 pages) doi:10.1115/1.4000238 History: Received March 20, 2009; Revised August 28, 2009; Published October 13, 2009

The failure due to accidental drop of magnetic recording disks made of brittle or ductile materials is of great interest in the design of small form factor hard disk drives. In this study, fracture of glass disks (brittle material) and plastic deformation of aluminum disks (ductile material) at very high shock levels caused by accidental drop are investigated using finite element analysis. It is found that failure inception for both disk types occurs at the inside perimeter of the disk. For glass disks, cracks are found to propagate toward the outer perimeter of the disk along distinct radial lines associated with the largest bending moment of the disk. The critical shock level at which failure originates increases with an increase in the clamp diameter, a reduction in the disk diameter, and an increase in the thickness of the disk. Some experimental results are presented to validate the numerical model.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

The structure of a state-of-the-art hard disk drive

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Figure 2

Typical stress-strain curves for brittle and ductile materials

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Figure 3

Finite element model of a disk drive

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Figure 4

Schematic side view of the model

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Figure 5

Finite element model of the disk clamp

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Figure 6

Point force applied by the slider on the disk

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Figure 7

Shock load versus time as applied to the two rails of the disk enclosure

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Figure 8

A schematic of the experimental setup

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Figure 9

An experimental drop test acceleration profile of the disk enclosure

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Figure 10

Displacement of the disk obtained (a) from the drop test experiment and (b) from the numerical model.

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Figure 11

Failure of a 27.4 mm diameter glass disk in response to a shock level of 4500 G when slider-disk contact is present: (a) failure inception and (b) crack propagation

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Figure 12

Failure of a 27.4 mm diameter glass disk in response to a shock level of 4500 G when slider-disk contact is absent: (a) failure inception and (b) crack propagation

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Figure 13

Critical shock level versus disk thickness (other design parameters are kept constant)

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Figure 14

Critical shock level versus clamping force (other design parameters are kept constant)

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Figure 15

Critical shock level versus clamp outer diameter (other design parameters are kept constant)

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Figure 16

Finite element models for hard disk drives with different form factors

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Figure 17

Critical shock level versus disk form factor

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Figure 18

Bending of a flat circular plate (outer edge free, inner edge clamped) (31)

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